CN112358659A - Polysaccharide nano-fibril reinforced flame-retardant starch composite foam and preparation method thereof - Google Patents

Polysaccharide nano-fibril reinforced flame-retardant starch composite foam and preparation method thereof Download PDF

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CN112358659A
CN112358659A CN202011347118.3A CN202011347118A CN112358659A CN 112358659 A CN112358659 A CN 112358659A CN 202011347118 A CN202011347118 A CN 202011347118A CN 112358659 A CN112358659 A CN 112358659A
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polysaccharide
starch
mixed solution
nanofibril
ultrasonic
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刘大刚
单佳琦
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Nanjing University of Information Science and Technology
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Nanjing University of Information Science and Technology
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/28—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof by elimination of a liquid phase from a macromolecular composition or article, e.g. drying of coagulum
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/0061—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof characterized by the use of several polymeric components
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2201/00—Foams characterised by the foaming process
    • C08J2201/04—Foams characterised by the foaming process characterised by the elimination of a liquid or solid component, e.g. precipitation, leaching out, evaporation
    • C08J2201/048—Elimination of a frozen liquid phase
    • C08J2201/0484—Elimination of a frozen liquid phase the liquid phase being aqueous
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2303/00—Characterised by the use of starch, amylose or amylopectin or of their derivatives or degradation products
    • C08J2303/02—Starch; Degradation products thereof, e.g. dextrin
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2305/00—Characterised by the use of polysaccharides or of their derivatives not provided for in groups C08J2301/00 or C08J2303/00
    • C08J2305/08—Chitin; Chondroitin sulfate; Hyaluronic acid; Derivatives thereof
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2403/00—Characterised by the use of starch, amylose or amylopectin or of their derivatives or degradation products
    • C08J2403/02—Starch; Degradation products thereof, e.g. dextrin
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2405/00—Characterised by the use of polysaccharides or of their derivatives not provided for in groups C08J2401/00 or C08J2403/00
    • C08J2405/08—Chitin; Chondroitin sulfate; Hyaluronic acid; Derivatives thereof

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  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
  • Polysaccharides And Polysaccharide Derivatives (AREA)
  • Compositions Of Macromolecular Compounds (AREA)

Abstract

The invention discloses a flame-retardant starch composite foam enhanced by polysaccharide nano-fibrils and a preparation method thereof, wherein the composite foam is prepared by mixing and freezing the polysaccharide nano-fibrils and starch; wherein the polysaccharide nano-fibril accounts for 0-50% of the mass of the starch, and the solid content of the mixed solution is 3.5% -5.0%; the polysaccharide is selected from one of chitin and chitosan; the chitin nanofibrils have the diameter of 60nm and the length of micron order; the diameter of the chitosan nanofibril is 80-120 nm, and the length of the chitosan nanofibril is micrometer. The invention has the advantages of beneficial mechanical myocardial infarction, controllable orientation and regulation, flexible performance selection, easy control of the preparation process, lower cost and the like.

Description

Polysaccharide nano-fibril reinforced flame-retardant starch composite foam and preparation method thereof
Technical Field
The invention belongs to the field of natural high polymer materials, relates to a foam material, and particularly relates to a polysaccharide nanofibril reinforced flame-retardant starch composite foam and a preparation method thereof.
Background
Most of the commonly used raw materials for preparing the foam are petroleum-based high molecular materials, and are prepared by chemical reactions, such as polymerization reaction and the like, the foam prepared by using the petroleum-based raw materials is not easy to degrade, can cause a plurality of pollution problems, and the raw materials can not be regenerated; the existing widely applied polyurethane foam has high content of organic solvent, which can cause serious VOC pollution; the foam in the prior art is difficult to realize green full degradation without pollution.
There are many different ways to prepare a foam material with a porous structure, including a dual surfactant templating method, a colloidal crystal templating method, a polymer templating method, a biostimulation method, an emulsion templating method, an SCFs method, a freeze-drying method, an BFs method, a phase separation method, a selective leaching method, a replication method, a zeolization method, a sol-gel control method, a post-treatment method, a natural formation method, and the like. The freeze-drying technique, also known as ice crystal templating or ice detachment induced self-assembly (ISSa) process, has proven to be a new, low cost, simple and versatile method of preparing bio-foam materials with controlled structure in the prior art, which has many advantages, the first being the use of green templates, with aqueous solutions, ice crystals as templates (or so-called "porogens" and "pore formers"), which is particularly beneficial for biological applications. Secondly, impurities cannot be brought to the sample in the freeze drying process, and the purity of the sample is kept. Third, by changing the conditions during freezing, a variety of porous structures can be constructed, including a large number of pore morphologies and nanostructures (from two-dimensional to three-dimensional structures). Composite nanofibrillar foams and aerogels are becoming increasingly popular due to the advantages of being green, degradable, etc., as compared to foams and aerogels synthesized from polymer or carbon-based materials from petroleum-based products.
Disclosure of Invention
The invention aims to fill the vacancy of utilizing a natural polymer material to reinforce a flame-retardant starch foam in the prior art, solve the problems of non-renewable raw materials, environmental pollution and the like in the prior art, provide an environment-friendly and fully-degradable reinforced starch composite foam, and selectively enhance or weaken the mechanical property in a certain direction, wherein the orientation of the reinforced starch composite foam is controllable.
To achieve the above object, the present invention provides a polysaccharide nanofibril reinforced flame retardant starch composite foam having the following features: prepared by mixing and freezing polysaccharide nanofibrils and starch; wherein the polysaccharide nanofibrils account for 0-50% of the Starch (ST) by mass, and the solid content of the mixed solution is 3.5-5.0%; the polysaccharide is selected from one of chitin and chitosan; the chitin nanofibrils (CTF) have the diameter of 60nm and the length of micrometer order; the diameter of the chitosan nanofibril (CSF) is 80-120 nm, and the length of the CSF nanofibril is micrometer.
The invention provides a preparation method of a flame-retardant starch composite foam reinforced by polysaccharide nano-fibrils, which is characterized in that: the method comprises the following steps:
step one, preparing polysaccharide nanofibril suspension: adding polysaccharide solid powder into a container, adding deionized water, stirring uniformly, standing, removing upper layer impurities, stirring uniformly, and circulating through a high-pressure homogenizer to obtain polysaccharide nanofibril suspension;
preparation of gelatinized starch solution: and (3) putting the solid starch granules into a container, adding deionized water, and continuously stirring under a heating condition to obtain a transparent starch solution which is uniformly gelatinized.
Step two, adding the polysaccharide nanofibril suspension into the gelatinized starch solution, and uniformly stirring and mixing to obtain a starch/polysaccharide mixed solution; and (3) evaporating and concentrating the starch/polysaccharide mixed solution, and then performing defoaming treatment to obtain a starch/polysaccharide mixed solution stock solution.
Pouring the stock solution of the starch/polysaccharide mixed solution into a Polytetrafluoroethylene (PTFE) container, sealing, directly freezing the PTFE container filled with the stock solution, or wrapping and insulating to expose at least one surface, and freezing.
Preferably, when the PTFE container is square, only the lower surface exposed when wrapped is in contact with cold air, so that the resulting syntactic foam has a higher compressive strength in the freezing direction (bottom-up); when the PTFE container is a cylinder, heat insulation wrapping is not carried out, and direct freezing is carried out, so that the obtained composite foam has higher compressive strength (after heat insulation wrapping is carried out, a threaded structure is easily formed on the surface of the foam, and the compressive strength is reduced to a certain degree).
And step four, taking out the frozen PTFE container, uncovering the PTFE container, putting the PTFE container into a freeze dryer, and freeze-drying the PTFE container for 120 hours, and taking out the PTFE container to obtain the starch polysaccharide composite foam.
Further, the present invention provides a method for preparing a polysaccharide nanofibril reinforced flame retardant starch composite foam, which may further have the following characteristics: wherein, in the step one, the chitosan polysaccharide is chitosan with acetyl degree more than or equal to 95%.
Further, the present invention provides a method for preparing a polysaccharide nanofibril reinforced flame retardant starch composite foam, which may further have the following characteristics: wherein, in the first step, the dosage ratio of the polysaccharide to the deionized water is 20 g: 1500 mL.
Further, the present invention provides a method for preparing a polysaccharide nanofibril reinforced flame retardant starch composite foam, which may further have the following characteristics: wherein in the preparation process of the polysaccharide nanofibril suspension in the step one, the standing time is 24 hours; the number of cycles of the high-pressure homogenizer was 20.
Further, the present invention provides a method for preparing a polysaccharide nanofibril reinforced flame retardant starch composite foam, which may further have the following characteristics: wherein in the preparation process of the gelatinized starch solution in the step one, the heating condition is 80-100 ℃ water bath; the stirring time is 30-60 min.
Further, the present invention provides a method for preparing a polysaccharide nanofibril reinforced flame retardant starch composite foam, which may further have the following characteristics: and in the second step, after defoaming, carrying out ultrasonic treatment in an ultrasonic cleaning instrument.
Further, the present invention provides a method for preparing a polysaccharide nanofibril reinforced flame retardant starch composite foam, which may further have the following characteristics: wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min.
Further, the present invention provides a method for preparing a polysaccharide nanofibril reinforced flame retardant starch composite foam, which may further have the following characteristics: wherein, in the third step, the freezing temperature is-50 ℃ to-20 ℃, and the freezing time is 24 hours.
Further, the present invention provides a method for preparing a polysaccharide nanofibril reinforced flame retardant starch composite foam, which may further have the following characteristics: wherein, in the fourth step, the freeze drying time is 120 h.
The invention has the beneficial effects that: the present invention provides a flame retardant starch composite foam reinforced with polysaccharide nanofibrils and a method for preparing the same, wherein the mechanical properties of the foam produced by starch control are very low and the material is very brittle, but adding polysaccharide nanofibrils to starch can produce a foam with excellent structural integrity and properties, and also polysaccharide nanofibrils are difficult to independently form a porous structural foam with excellent mechanical properties due to their inherent stiffness characteristics. The chitin nanofibrils, the chitosan nanofibrils and the starch are of polysaccharide molecular structures, and the chitin nanofibrils, the chitosan nanofibrils and the starch have good biocompatibility. For the nanofibrils, gelatinized starch can be used as an excellent binder, and for the gelatinized starch, chitin and chitosan nanofibrils can be used as an excellent plasticizer. Therefore, the nano-fibrils and the gelatinized starch are blended, so that a better strengthening effect can be obtained. The chitin and the chitosan are natural high molecular materials rich in nitrogen, the starch is a natural charring agent, and the combination of the chitin and the chitosan can improve the flame retardant property of the starch composite foam. The flame-retardant starch composite foam reinforced by chitin and chitosan nano-fibril is a novel potential green sustainable material, accords with the energy-saving and environment-friendly concept of modern society, and expands the application of the flame-retardant starch composite foam in the fields of high polymer material tissue engineering, flame-retardant resin and the like on the basis of improving the mechanical property and the flame-retardant property of the flame-retardant starch composite foam.
Compared with the prior art, the invention has the following advantages: the invention uses green pollution-free starch as raw material, uses two natural polysaccharide nanofibrils as plasticizer, namely chitin nanofibrils and chitosan nanofibrils, and the prepared starch polysaccharide nanofibrils composite foam is environment-friendly and fully degradable, the mechanical property is greatly improved, the orientation of the composite foam can be regulated and controlled by applying heat insulation design operation in the freezing process, and the mechanical property in a certain direction can be selectively enhanced or weakened in the macroscopic aspect; on the other hand, the preparation method is characterized in that the preparation method comprises the steps of blending and compounding, stirring and concentrating by a water bath heating method to a specific solid content, pouring the solid content into a container, and freeze-drying the solid content.
The composite material of STCTF and STCSF is a novel potential green sustainable material, accords with the energy-saving and environment-friendly concept of modern society, and has wide application prospect in a plurality of engineering fields, including the fields of building, traffic, energy and flame-retardant resin.
Drawings
FIG.1 is a microscopic electron micrograph of STCTF and STCSF syntactic foams of different solids contents prepared in examples 4, 9, 14, 19 of the present invention;
FIG.2 is a stress-strain plot of STCTF and STCSF syntactic foams of varying solids content and varying filament ratios prepared in examples 4, 9, 14, 19 and examples 11, 12, 13, 14, 15 of the present invention;
FIG.3 is a graph of the Young's modulus, resiliency and maximum stress values of all foam samples prepared in examples 1-21 of the present invention as a function of the solid and fibril content of the samples;
FIG.4 is a layout drawing of various insulation patterns, a resultant foam object drawing, a syntactic foam microscopic orientation drawing, and a stress-strain drawing of the mechanical properties of the reactive syntactic foam of a foam sample made using a 3X 3cm square PTFE cell of example 9 of this invention;
FIG.5 is a design layout, resulting foam object, syntactic foam microscopic orientation, and stress strain plot of the mechanical properties of the reacted syntactic foam for various thermal insulation modes of foam samples made with cylindrical PTFE capsules of 3.5cm diameter and 5.4cm height according to example 9 of this invention;
FIG. 6 is a comparative graph of the results of horizontal flame retardancy tests conducted on foam samples prepared using 1X 10cm cartridges of examples 1-21 of the present invention and a microscopic electron microscope image of the burned surface of the samples.
Detailed Description
The present invention is further illustrated by the following specific examples.
Example 1
The embodiment provides a preparation method of a polysaccharide nanofibril reinforced flame-retardant starch composite foam, which comprises the following steps:
step one, preparing polysaccharide nanofibril suspension and gelatinized starch solution. Wherein the polysaccharide is chitin or chitosan respectively.
Preparation of chitin nanofibril suspension (CTF): taking 20g of chitin solid powder, adding 1500mL of deionized water into a beaker, uniformly stirring, standing for 24 hours, removing upper-layer impurities, uniformly stirring, circulating for 20 times by using a high-pressure homogenizer to obtain a uniformly dispersed chitin nanofibril suspension, and then placing the suspension in an ultrasonic cleaning instrument for ultrasonic treatment, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min.
Preparation of chitosan nanofibril suspension (CSF): taking 20g of chitosan solid powder with deacetylation degree of more than or equal to 95 percent, adding 1500ml of deionized water, stirring uniformly, standing for 24 hours, removing upper-layer impurities, stirring uniformly, circulating for 20 times by using a high-pressure homogenizer to obtain uniformly dispersed chitosan nanofibril suspension, then placing the suspension in an ultrasonic cleaning instrument for ultrasonic treatment, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min.
Preparation of gelatinized starch Solution (ST): and (3) putting 10g of solid starch granules into a beaker, adding 200ml of deionized water, and continuously stirring for 30-60 min under the condition of 80-100 ℃ water bath to obtain a transparent uniformly gelatinized starch solution, wherein the rotating speed of the stirrer is 400 revolutions per minute.
And step two, preparing a starch polysaccharide nanofibril mixed solution.
Preparation of starch chitin nanofibril mixed solution (ST/CTF): adding the prepared chitin nanofibril suspension containing 1g of chitin into the gelatinized starch solution, mixing and stirring the mixed solution at the temperature of 80-100 ℃, wherein the stirring speed is 400 revolutions per minute, the mixed solution is evaporated and concentrated until the solid content is 3.5%, cooling to the normal temperature, performing vacuum defoaming operation, and finally placing the mixed solution in an ultrasonic cleaner for ultrasonic treatment to obtain an ST/CTF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch were present in a proportion of 10% and the mixed solution had a solids content of 3.5%, thus this group of samples was named as STCTF10 (3.5%).
Preparation of starch chitosan nanofibril mixed solution (ST/CSF): adding the prepared chitosan nanofibril suspension containing 1g of chitosan into the gelatinized starch solution, mixing and stirring the mixed solution at the temperature of 80-100 ℃, wherein the stirring speed is 400 r/min, the mixed solution is evaporated and concentrated until the solid content is 3.5%, cooling to normal temperature, carrying out vacuum defoaming operation, and finally placing in an ultrasonic cleaner for ultrasonic treatment to obtain ST/CSF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch ratio were 10% and the mixed solution had a solids content of 3.5%, thus this group of samples was named STCSF10 (3.5%).
Step three and step four, preparing the starch polysaccharide nanofibril composite foam.
Preparing the starch chitin nanofibril composite foam: pouring the prepared ST/CTF stock solution into PTFE small boxes with the diameters of 3 multiplied by 3cm, 3.5cm, 5.4cm and 1 multiplied by 10cm for sealing, performing heat insulation orientation design in different directions on the PTFE small boxes with the diameters of 3 multiplied by 3cm, 3.5cm and 5.4cm, which are filled with the stock solution, namely tightly wrapping the surfaces of the small boxes by using heat insulation EPE pearl cotton, performing blank control, namely not performing any heat insulation orientation design, not performing the orientation design on the PTFE small boxes with the diameters of 1 multiplied by 10cm, and then putting all the small boxes into a refrigerator with the temperature of minus 50 ℃ to minus 20 ℃ for freezing for 24 hours. And taking the frozen PTFE small box out of the refrigerator, opening the cover, putting the box into a freeze dryer, freeze-drying the box for 120 hours, taking the box out to obtain the starch chitin composite foam, and storing the prepared STCTF foam sample in the dryer.
Preparing the starch chitosan nanofibril composite foam: pouring the prepared ST/CSF stock solution into PTFE small boxes with the diameters of 3 multiplied by 3cm, 3.5cm and the heights of 5.4cm and 1 multiplied by 10cm for sealing, performing heat insulation orientation design in different directions on the PTFE small boxes with the diameters of 3 multiplied by 3cm, 3 multiplied by 3cm and 3.5cm and the heights of 5.4cm, namely tightly wrapping the surfaces of the small boxes by using heat insulation EPE pearl cotton, performing air-white comparison, namely not performing any heat insulation orientation design, not performing the orientation design on the PTFE small boxes with the diameters of 1 multiplied by 10cm, and then completely freezing the small boxes in a refrigerator with the temperature of minus 50 ℃ to minus 20 ℃ for 24 hours. And taking the frozen PTFE small box out of the refrigerator, uncovering the box, putting the box into a freeze dryer, freeze-drying the box for 120 hours, taking the box out to obtain the starch chitosan composite foam, and storing the prepared STCSF foam sample in the dryer.
Wherein, the orientation design of the heat insulation: the heat insulation mode of the PTFE square box with the size of 3 multiplied by 3cm is divided into the following modes: firstly, the lower surface conducts heat, and the rest surface is wrapped by EPE pearl wool; secondly, one side of the side surface conducts heat, and the rest side is wrapped by EPE pearl wool; the upper part and the lower part are wrapped by EPE pearl cotton, and the middle part conducts heat; the middle of the bag is wrapped by EPE pearl wool, and the heat is conducted up and down; fifthly, direct freezing is carried out without heat insulation design, and the heat insulation modes are respectively named as OD1, OD2, OD3, OD4 and None. The PTFE cylindrical box with the diameter of 3.5cm and the height of 5.4cm has the following heat insulation modes: the lower part conducts heat, and the rest is wrapped by EPE pearl wool; secondly, conducting heat at the upper part, and wrapping the rest by EPE pearl wool; the upper part and the lower part are wrapped by EPE pearl cotton, and the middle part conducts heat; the middle part is wrapped by EPE pearl wool, and the upper part and the lower part conduct heat; fifthly, direct freezing is carried out without heat insulation design, and the heat insulation modes are respectively named as OD6, OD7, OD8, OD9 and None.
Example 2
The present example provides a method for preparing a polysaccharide nanofibril reinforced flame retardant starch composite foam. The difference between the embodiment and the embodiment 1 is that in the step two, the prepared chitin nanofibril suspension containing 2g of chitin is added into the gelatinized starch solution, the mixed solution is mixed and stirred at 80-100 ℃, the stirring speed is 400 rpm, the mixed solution is evaporated and concentrated until the solid content is 3.5%, after cooling to normal temperature, vacuum defoaming operation is performed, and finally the mixed solution is placed in an ultrasonic cleaner for ultrasonic treatment to obtain an ST/CTF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch ratio were 20% and the mixed solution had a solids content of 3.5%, thus this group of samples was named as STCTF20 (3.5%); and the other difference is that the prepared chitosan nanofibril suspension containing 2g of chitosan is added into the gelatinized starch solution in the second step, the mixed solution is mixed and stirred at the temperature of 80-100 ℃, the stirring speed is 400 r/min, the mixed solution is evaporated and concentrated until the solid content is 3.5%, after being cooled to the normal temperature, the mixed solution is subjected to vacuum defoaming operation, and finally the mixed solution is placed into an ultrasonic cleaner for ultrasonic treatment to obtain ST/CSF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch ratio were 10% and the mixed solution had a solids content of 3.5%, thus this group of samples was named STCSF20 (3.5%).
Example 3
The present example provides a method for preparing a polysaccharide nanofibril reinforced flame retardant starch composite foam. The difference between the embodiment and the embodiment 1 is that in the step two, the prepared chitin nanofibril suspension containing 3g of chitin is added into the gelatinized starch solution, the mixed solution is mixed and stirred at the temperature of 80-100 ℃, the stirring speed is 400 rpm, the mixed solution is evaporated and concentrated until the solid content is 3.5%, after cooling to the normal temperature, vacuum defoaming operation is performed, and finally the mixed solution is placed in an ultrasonic cleaner for ultrasonic treatment to obtain an ST/CTF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch ratio were 30% and the mixed solution had a solids content of 3.5%, thus this group of samples was named as STCTF30 (3.5%); and the other difference is that the prepared chitosan nanofibril suspension containing 3g of chitosan is added into the gelatinized starch solution in the second step, the mixed solution is mixed and stirred at the temperature of 80-100 ℃, the stirring speed is 400 r/min, the mixed solution is evaporated and concentrated until the solid content is 3.5%, after being cooled to the normal temperature, the mixed solution is subjected to vacuum defoaming operation, and finally the mixed solution is placed into an ultrasonic cleaner for ultrasonic treatment to obtain ST/CSF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch ratio were 30% and the mixed solution had a solids content of 3.5%, thus this group of samples was named STCSF30 (3.5%).
Example 4
The present example provides a method for preparing a polysaccharide nanofibril reinforced flame retardant starch composite foam. The difference between the embodiment and the embodiment 1 is that the prepared chitin nanofibril suspension containing 4g of chitin is added into the gelatinized starch solution in the step two, the mixed solution is mixed and stirred at the temperature of 80-100 ℃, the stirring speed is 400 rpm, the mixed solution is evaporated and concentrated until the solid content is 3.5%, after being cooled to normal temperature, vacuum defoaming operation is carried out, and finally the mixed solution is placed in an ultrasonic cleaner for ultrasonic treatment to obtain an ST/CTF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch ratio were 40% and the mixed solution had a solids content of 3.5%, thus this group of samples was named as STCTF40 (3.5%); and the other difference is that the prepared chitosan nanofibril suspension containing 4g of chitosan is added into the gelatinized starch solution in the second step, the mixed solution is mixed and stirred at the temperature of 80-100 ℃, the stirring speed is 400 r/min, the mixed solution is evaporated and concentrated until the solid content is 3.5%, after being cooled to the normal temperature, the mixed solution is subjected to vacuum defoaming operation, and finally the mixed solution is placed into an ultrasonic cleaner for ultrasonic treatment to obtain ST/CSF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch ratio were 40% and the mixed solution had a solids content of 3.5%, thus this group of samples was named STCSF40 (3.5%).
Example 5
The present example provides a method for preparing a polysaccharide nanofibril reinforced flame retardant starch composite foam. The difference between the embodiment and the embodiment 1 is that in the step two, the prepared chitin nanofibril suspension containing 5g of chitin is added into the gelatinized starch solution, the mixed solution is mixed and stirred at 80-100 ℃, the stirring speed is 400 rpm, the mixed solution is evaporated and concentrated until the solid content is 3.5%, after cooling to normal temperature, vacuum defoaming operation is performed, and finally the mixed solution is placed in an ultrasonic cleaner for ultrasonic treatment to obtain an ST/CTF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch ratio were 50% and the mixed solution had a solids content of 3.5%, thus this group of samples was named as STCTF50 (3.5%); and the other difference is that the prepared chitosan nanofibril suspension containing 5g of chitosan is added into the gelatinized starch solution in the second step, the mixed solution is mixed and stirred at the temperature of 80-100 ℃, the stirring speed is 400 r/min, the mixed solution is evaporated and concentrated until the solid content is 3.5%, after being cooled to the normal temperature, the mixed solution is subjected to vacuum defoaming operation, and finally the mixed solution is placed into an ultrasonic cleaner for ultrasonic treatment to obtain ST/CSF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch ratio were 50% and the mixed solution had a solids content of 3.5%, thus this group of samples was named STCSF50 (3.5%).
Example 6
The present example provides a method for preparing a polysaccharide nanofibril reinforced flame retardant starch composite foam. The difference between the embodiment and the embodiment 1 is that in the step two, the prepared chitin nanofibril suspension containing 1g of chitin is added into the gelatinized starch solution, the mixed solution is mixed and stirred at the temperature of 80-100 ℃, the stirring speed is 400 rpm, the mixed solution is evaporated and concentrated until the solid content is 4.0%, after being cooled to the normal temperature, the vacuum defoaming operation is carried out, and finally the mixed solution is placed in an ultrasonic cleaner for ultrasonic treatment to obtain an ST/CTF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch were 10% and the mixed solution had a solids content of 4.0%, thus this group of samples was named as STCTF10 (4.0%); and the other difference is that the prepared chitosan nanofibril suspension containing 1g of chitosan is added into the gelatinized starch solution in the second step, the mixed solution is mixed and stirred at the temperature of 80-100 ℃, the stirring speed is 400 r/min, the mixed solution is evaporated and concentrated until the solid content is 4.0%, after being cooled to the normal temperature, the mixed solution is subjected to vacuum defoaming operation, and finally the mixed solution is placed into an ultrasonic cleaner for ultrasonic treatment to obtain ST/CSF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch were present in a proportion of 10% and the mixed solution had a solids content of 3.5%, thus this group of samples was named STCSF10 (4.0%).
Example 7
The present example provides a method for preparing a polysaccharide nanofibril reinforced flame retardant starch composite foam. The difference between the embodiment and the embodiment 1 is that in the step two, the prepared chitin nanofibril suspension containing 2g of chitin is added into the gelatinized starch solution, the mixed solution is mixed and stirred at the temperature of 80-100 ℃, the stirring speed is 400 rpm, the mixed solution is evaporated and concentrated until the solid content is 4.0%, after being cooled to normal temperature, vacuum defoaming operation is carried out, and finally the mixed solution is placed in an ultrasonic cleaner for ultrasonic treatment to obtain an ST/CTF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch ratio were 20% and the mixed solution had a solids content of 4.0%, thus this group of samples was named as STCTF20 (4.0%); and the other difference is that the prepared chitosan nanofibril suspension containing 2g of chitosan is added into the gelatinized starch solution in the second step, the mixed solution is mixed and stirred at the temperature of 80-100 ℃, the stirring speed is 400 r/min, the mixed solution is evaporated and concentrated until the solid content is 4.0%, after being cooled to the normal temperature, the mixed solution is subjected to vacuum defoaming operation, and finally the mixed solution is placed into an ultrasonic cleaner for ultrasonic treatment to obtain ST/CSF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch ratio were 20% and the mixed solution had a solids content of 4.0%, thus this group of samples was named STCSF20 (4.0%).
Example 8
The present example provides a method for preparing a polysaccharide nanofibril reinforced flame retardant starch composite foam. The difference between the embodiment and the embodiment 1 is that in the step two, the prepared chitin nanofibril suspension containing 3g of chitin is added into the gelatinized starch solution, the mixed solution is mixed and stirred at the temperature of 80-100 ℃, the stirring speed is 400 rpm, the mixed solution is evaporated and concentrated until the solid content is 4.0%, after being cooled to normal temperature, vacuum defoaming operation is carried out, and finally the mixed solution is placed in an ultrasonic cleaner for ultrasonic treatment to obtain an ST/CTF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch ratio were 30% and the mixed solution had a solids content of 4.0%, thus this group of samples was named as STCTF30 (4.0%); and the other difference is that the prepared chitosan nanofibril suspension containing 3g of chitosan is added into the gelatinized starch solution in the second step, the mixed solution is mixed and stirred at the temperature of 80-100 ℃, the stirring speed is 400 r/min, the mixed solution is evaporated and concentrated until the solid content is 4.0%, after being cooled to the normal temperature, the mixed solution is subjected to vacuum defoaming operation, and finally the mixed solution is placed into an ultrasonic cleaner for ultrasonic treatment to obtain ST/CSF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch ratio were 30% and the mixed solution had a solids content of 4.0%, thus this group of samples was named STCSF30 (4.0%).
Example 9
The present example provides a method for preparing a polysaccharide nanofibril reinforced flame retardant starch composite foam. The difference between the embodiment and the embodiment 1 is that in the step two, the prepared chitin nanofibril suspension containing 4g of chitin is added into the gelatinized starch solution, the mixed solution is mixed and stirred at the temperature of 80-100 ℃, the stirring speed is 400 rpm, the mixed solution is evaporated and concentrated until the solid content is 4.0%, after being cooled to normal temperature, vacuum defoaming operation is carried out, and finally the mixed solution is placed in an ultrasonic cleaner for ultrasonic treatment to obtain an ST/CTF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch ratio were 40% and the mixed solution had a solids content of 4.0%, thus this group of samples was named as STCTF40 (4.0%); and the other difference is that the prepared chitosan nanofibril suspension containing 4g of chitosan is added into the gelatinized starch solution in the second step, the mixed solution is mixed and stirred at the temperature of 80-100 ℃, the stirring speed is 400 r/min, the mixed solution is evaporated and concentrated until the solid content is 4.0%, after being cooled to the normal temperature, the mixed solution is subjected to vacuum defoaming operation, and finally the mixed solution is placed into an ultrasonic cleaner for ultrasonic treatment to obtain ST/CSF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch ratio were 40% and the mixed solution had a solids content of 4.0%, thus this group of samples was named STCSF40 (4.0%).
Example 10
The present example provides a method for preparing a polysaccharide nanofibril reinforced flame retardant starch composite foam. The difference between the embodiment and the embodiment 1 is that in the step two, the prepared chitin nanofibril suspension containing 5g of chitin is added into the gelatinized starch solution, the mixed solution is mixed and stirred at the temperature of 80-100 ℃, the stirring speed is 400 rpm, the mixed solution is evaporated and concentrated until the solid content is 4.0%, after being cooled to the normal temperature, the vacuum defoaming operation is carried out, and finally the mixed solution is placed in an ultrasonic cleaner for ultrasonic treatment to obtain an ST/CTF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch ratio were 50% and the mixed solution had a solids content of 4.0%, thus this group of samples was named as STCTF50 (4.0%); and the other difference is that the prepared chitosan nanofibril suspension containing 5g of chitosan is added into the gelatinized starch solution in the second step, the mixed solution is mixed and stirred at the temperature of 80-100 ℃, the stirring speed is 400 r/min, the mixed solution is evaporated and concentrated until the solid content is 4.0%, after being cooled to the normal temperature, the mixed solution is subjected to vacuum defoaming operation, and finally the mixed solution is placed into an ultrasonic cleaner for ultrasonic treatment to obtain ST/CSF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch were present in a proportion of 50% and the mixed solution had a solids content of 4.0%, thus this group of samples was named as STCTF50 (4.0%).
Example 11
The present example provides a method for preparing a polysaccharide nanofibril reinforced flame retardant starch composite foam. The difference between the embodiment and the embodiment 1 is that in the step two, the prepared chitin nanofibril suspension containing 1g of chitin is added into the gelatinized starch solution, the mixed solution is mixed and stirred at the temperature of 80-100 ℃, the stirring speed is 400 rpm, the mixed solution is evaporated and concentrated until the solid content is 4.5%, after being cooled to the normal temperature, the vacuum defoaming operation is carried out, and finally the mixed solution is placed in an ultrasonic cleaner for ultrasonic treatment to obtain the ST/CTF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch ratio were 10% and the mixed solution had a solids content of 4.5%, thus this group of samples was named as STCTF10 (4.5%); and the other difference is that the prepared chitosan nanofibril suspension containing 1g of chitosan is added into the gelatinized starch solution in the second step, the mixed solution is mixed and stirred at the temperature of 80-100 ℃, the stirring speed is 400 r/min, the mixed solution is evaporated and concentrated until the solid content is 4.5%, after being cooled to the normal temperature, the mixed solution is subjected to vacuum defoaming operation, and finally the mixed solution is placed into an ultrasonic cleaner for ultrasonic treatment to obtain ST/CSF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch ratio were 10% and the mixed solution had a solids content of 3.5%, thus this group of samples was named STCSF10 (4.5%).
Example 12
The present example provides a method for preparing a polysaccharide nanofibril reinforced flame retardant starch composite foam. The difference between the embodiment and the embodiment 1 is that in the step two, the prepared chitin nanofibril suspension containing 2g of chitin is added into the gelatinized starch solution, the mixed solution is mixed and stirred at the temperature of 80-100 ℃, the stirring speed is 400 rpm, the mixed solution is evaporated and concentrated until the solid content is 4.5%, after being cooled to the normal temperature, the vacuum defoaming operation is carried out, and finally the mixed solution is placed in an ultrasonic cleaner for ultrasonic treatment to obtain the ST/CTF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch ratio were 20% and the mixed solution had a solids content of 4.5%, thus this group of samples was named as STCTF20 (4.5%); and the other difference is that the prepared chitosan nanofibril suspension containing 2g of chitosan is added into the gelatinized starch solution in the second step, the mixed solution is mixed and stirred at the temperature of 80-100 ℃, the stirring speed is 400 r/min, the mixed solution is evaporated and concentrated until the solid content is 4.5%, after being cooled to the normal temperature, the mixed solution is subjected to vacuum defoaming operation, and finally the mixed solution is placed into an ultrasonic cleaner for ultrasonic treatment to obtain ST/CSF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch ratio were 20% and the mixed solution had a solids content of 4.5%, thus this group of samples was named STCSF20 (4.5%).
Example 13
The present example provides a method for preparing a polysaccharide nanofibril reinforced flame retardant starch composite foam. The difference between the embodiment and the embodiment 1 is that in the step two, the prepared chitin nanofibril suspension containing 3g of chitin is added into the gelatinized starch solution, the mixed solution is mixed and stirred at the temperature of 80-100 ℃, the stirring speed is 400 rpm, the mixed solution is evaporated and concentrated until the solid content is 4.5%, after being cooled to the normal temperature, the vacuum defoaming operation is carried out, and finally the mixed solution is placed in an ultrasonic cleaner for ultrasonic treatment to obtain the ST/CTF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch ratio were 30% and the mixed solution had a solids content of 4.5%, thus this group of samples was named as STCTF30 (4.5%); and the other difference is that the prepared chitosan nanofibril suspension containing 3g of chitosan is added into the gelatinized starch solution in the second step, the mixed solution is mixed and stirred at the temperature of 80-100 ℃, the stirring speed is 400 r/min, the mixed solution is evaporated and concentrated until the solid content is 4.5%, after being cooled to the normal temperature, the mixed solution is subjected to vacuum defoaming operation, and finally the mixed solution is placed into an ultrasonic cleaner for ultrasonic treatment to obtain ST/CSF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch ratio were 30% and the mixed solution had a solids content of 4.5%, thus this group of samples was named STCSF30 (4.5%).
Example 14
The present example provides a method for preparing a polysaccharide nanofibril reinforced flame retardant starch composite foam. The difference between the embodiment and the embodiment 1 is that in the step two, the prepared chitin nanofibril suspension containing 4g of chitin is added into the gelatinized starch solution, the mixed solution is mixed and stirred at the temperature of 80-100 ℃, the stirring speed is 400 rpm, the mixed solution is evaporated and concentrated until the solid content is 4.5%, after being cooled to the normal temperature, the vacuum defoaming operation is carried out, and finally the mixed solution is placed in an ultrasonic cleaner for ultrasonic treatment to obtain the ST/CTF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch ratio were 40% and the mixed solution had a solids content of 4.5%, thus this group of samples was named as STCTF40 (4.5%); and the other difference is that the prepared chitosan nanofibril suspension containing 4g of chitosan is added into the gelatinized starch solution in the second step, the mixed solution is mixed and stirred at the temperature of 80-100 ℃, the stirring speed is 400 r/min, the mixed solution is evaporated and concentrated until the solid content is 4.5%, after being cooled to the normal temperature, the mixed solution is subjected to vacuum defoaming operation, and finally the mixed solution is placed into an ultrasonic cleaner for ultrasonic treatment to obtain ST/CSF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch ratio were 40% and the mixed solution had a solids content of 4.5%, thus this group of samples was named STCSF40 (4.5%).
Example 15
The present example provides a method for preparing a polysaccharide nanofibril reinforced flame retardant starch composite foam. The difference between the embodiment and the embodiment 1 is that in the step two, the prepared chitin nanofibril suspension containing 5g of chitin is added into the gelatinized starch solution, the mixed solution is mixed and stirred at the temperature of 80-100 ℃, the stirring speed is 400 rpm, the mixed solution is evaporated and concentrated until the solid content is 4.5%, after being cooled to the normal temperature, the vacuum defoaming operation is carried out, and finally the mixed solution is placed in an ultrasonic cleaner for ultrasonic treatment to obtain the ST/CTF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch ratio were 50% and the mixed solution had a solids content of 4.5%, thus this group of samples was named as STCTF50 (4.5%); and the other difference is that the prepared chitosan nanofibril suspension containing 5g of chitosan is added into the gelatinized starch solution in the second step, the mixed solution is mixed and stirred at the temperature of 80-100 ℃, the stirring speed is 400 r/min, the mixed solution is evaporated and concentrated until the solid content is 4.5%, after being cooled to the normal temperature, the mixed solution is subjected to vacuum defoaming operation, and finally the mixed solution is placed into an ultrasonic cleaner for ultrasonic treatment to obtain ST/CSF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch ratio were 50% and the mixed solution had a solids content of 4.5%, thus this group of samples was named STCSF50 (4.5%).
Example 16
The present example provides a method for preparing a polysaccharide nanofibril reinforced flame retardant starch composite foam. The difference between the embodiment and the embodiment 1 is that in the step two, the prepared chitin nanofibril suspension containing 1g of chitin is added into the gelatinized starch solution, the mixed solution is mixed and stirred at the temperature of 80-100 ℃, the stirring speed is 400 rpm, the mixed solution is evaporated and concentrated until the solid content is 5.0%, after being cooled to the normal temperature, the vacuum defoaming operation is carried out, and finally the mixed solution is placed in an ultrasonic cleaner for ultrasonic treatment to obtain an ST/CTF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch were 10% and the mixed solution had a solids content of 5.0%, thus this group of samples was named as STCTF10 (5.0%); and the other difference is that the prepared chitosan nanofibril suspension containing 1g of chitosan is added into the gelatinized starch solution in the second step, the mixed solution is mixed and stirred at the temperature of 80-100 ℃, the stirring speed is 400 r/min, the mixed solution is evaporated and concentrated until the solid content is 5.0%, after being cooled to the normal temperature, the mixed solution is subjected to vacuum defoaming operation, and finally the mixed solution is placed into an ultrasonic cleaner for ultrasonic treatment to obtain ST/CSF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch were present in a proportion of 10% and the mixed solution had a solids content of 5.0%, thus this group of samples was named STCSF10 (5.0%).
Example 17
The present example provides a method for preparing a polysaccharide nanofibril reinforced flame retardant starch composite foam. The difference between the embodiment and embodiment 1 is that in the step two, the prepared chitin nanofibril suspension containing 2g of chitin is added into the gelatinized starch solution, the mixed solution is mixed and stirred at 80-100 ℃, the stirring speed is 400 rpm, the mixed solution is evaporated and concentrated until the solid content is 5.0%, after cooling to normal temperature, vacuum defoaming operation is performed, and finally the mixed solution is placed in an ultrasonic cleaner for ultrasonic treatment to obtain an ST/CTF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch ratio were 20% and the mixed solution had a solids content of 5.0%, thus this group of samples was named as STCTF20 (5.0%); and the other difference is that the prepared chitosan nanofibril suspension containing 2g of chitosan is added into the gelatinized starch solution in the second step, the mixed solution is mixed and stirred at the temperature of 80-100 ℃, the stirring speed is 400 r/min, the mixed solution is evaporated and concentrated until the solid content is 5.0%, after being cooled to the normal temperature, the mixed solution is subjected to vacuum defoaming operation, and finally the mixed solution is placed into an ultrasonic cleaner for ultrasonic treatment to obtain ST/CSF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch ratio were 20% and the mixed solution had a solids content of 5.0%, thus this group of samples was named STCSF20 (5.0%).
Example 18
The present example provides a method for preparing a polysaccharide nanofibril reinforced flame retardant starch composite foam. The difference between the embodiment and the embodiment 1 is that in the step two, the prepared chitin nanofibril suspension containing 3g of chitin is added into the gelatinized starch solution, the mixed solution is mixed and stirred at the temperature of 80-100 ℃, the stirring speed is 400 rpm, the mixed solution is evaporated and concentrated until the solid content is 5.0%, after being cooled to normal temperature, vacuum defoaming operation is carried out, and finally the mixed solution is placed in an ultrasonic cleaner for ultrasonic treatment to obtain an ST/CTF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch ratio were 30% and the mixed solution had a solids content of 5.0%, thus this group of samples was named as STCTF30 (5.0%); and the other difference is that the prepared chitosan nanofibril suspension containing 3g of chitosan is added into the gelatinized starch solution in the second step, the mixed solution is mixed and stirred at the temperature of 80-100 ℃, the stirring speed is 400 r/min, the mixed solution is evaporated and concentrated until the solid content is 5.0%, after being cooled to the normal temperature, the mixed solution is subjected to vacuum defoaming operation, and finally the mixed solution is placed into an ultrasonic cleaner for ultrasonic treatment to obtain ST/CSF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch ratio were 30% and the mixed solution had a solids content of 5.0%, thus this group of samples was named STCSF30 (5.0%).
Example 19
The present example provides a method for preparing a polysaccharide nanofibril reinforced flame retardant starch composite foam. The difference between the embodiment and the embodiment 1 is that in the step two, the prepared chitin nanofibril suspension containing 4g of chitin is added into the gelatinized starch solution, the mixed solution is mixed and stirred at the temperature of 80-100 ℃, the stirring speed is 400 rpm, the mixed solution is evaporated and concentrated until the solid content is 5.0%, after being cooled to the normal temperature, the vacuum defoaming operation is carried out, and finally the mixed solution is placed in an ultrasonic cleaner for ultrasonic treatment to obtain an ST/CTF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch ratio were 40% and the mixed solution had a solids content of 5.0%, thus this group of samples was named as STCTF40 (5.0%); and the other difference is that the prepared chitosan nanofibril suspension containing 4g of chitosan is added into the gelatinized starch solution in the second step, the mixed solution is mixed and stirred at the temperature of 80-100 ℃, the stirring speed is 400 r/min, the mixed solution is evaporated and concentrated until the solid content is 5.0%, after being cooled to the normal temperature, the mixed solution is subjected to vacuum defoaming operation, and finally the mixed solution is placed into an ultrasonic cleaner for ultrasonic treatment to obtain ST/CSF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch ratio were 40% and the mixed solution had a solids content of 5.0%, thus this group of samples was named STCSF40 (5.0%).
Example 20
The present example provides a method for preparing a polysaccharide nanofibril reinforced flame retardant starch composite foam. The difference between the embodiment and the embodiment 1 is that in the step two, the prepared chitin nanofibril suspension containing 5g of chitin is added into the gelatinized starch solution, the mixed solution is mixed and stirred at 80-100 ℃, the stirring speed is 400 rpm, the mixed solution is evaporated and concentrated until the solid content is 5.0%, after being cooled to normal temperature, vacuum defoaming operation is performed, and finally the mixed solution is placed in an ultrasonic cleaner for ultrasonic treatment to obtain an ST/CTF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch ratio were 50% and the mixed solution had a solids content of 5.0%, thus this group of samples was named as STCTF50 (5.0%); and the other difference is that the prepared chitosan nanofibril suspension containing 5g of chitosan is added into the gelatinized starch solution in the second step, the mixed solution is mixed and stirred at the temperature of 80-100 ℃, the stirring speed is 400 r/min, the mixed solution is evaporated and concentrated until the solid content is 5.0%, after being cooled to the normal temperature, the mixed solution is subjected to vacuum defoaming operation, and finally the mixed solution is placed into an ultrasonic cleaner for ultrasonic treatment to obtain ST/CSF mixed solution stock solution, wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min. The nanofibrils in the starch ratio were 50% and the mixed solution had a solids content of 5.0%, thus this group of samples was named STCSF50 (5.0%).
Example 21
And (3) putting 10g of solid starch powder in a beaker, adding 200ml of deionized water, and continuously stirring for 30-60 min under the condition of 80-100 ℃ water bath to obtain a transparent uniformly gelatinized starch solution, wherein the rotating speed of the stirrer is 400 revolutions per minute. Pouring the prepared gelatinized starch solution into PTFE small boxes of 3 × 3 × 3cm, 3.5cm in diameter and 5.4cm and 1 × 1 × 10cm for sealing, performing heat insulation orientation design in different directions on the PTFE small boxes of 3 × 3 × 3cm in diameter and 3.5cm in diameter and 5.4cm in height filled with the stock solution, namely tightly wrapping the surfaces of the small boxes by using heat insulation EPE pearl cotton, performing blank control, namely not performing any heat insulation orientation design, not performing the orientation design on the PTFE small boxes of 1 × 1 × 10cm filled with the samples, and then completely freezing the small boxes in a refrigerator at the temperature of-50 ℃ to-20 ℃ for 24 hours. And taking the frozen PTFE small box out of the refrigerator, uncovering the box, putting the box into a freeze dryer, freeze-drying the box for 120 hours, taking the box out to obtain pure starch foam (ST), and storing the prepared ST foam sample in the dryer.
Performance testing of the examples:
microscopic electron micrographs of STCTF and STCSF syntactic foams of different solids contents prepared in examples 4, 9, 14, 19 are shown in fig.1, in which a-h represent STCTF40 (3.5%), STCSF40 (3.5%), STCTF40 (4.0%), STCSF40 (4.0%), STCTF40 (4.5%), STCSF40 (4.5%), STCTF40 (5.0%) and STCSF40 (5.0%), respectively. It can be seen from the figure that 3.5% of STCTF40 had 42.86% of the pores distributed in the range of 30-40 μm (FIG.1a inset), and 5.0% of STCTF had 52.78% of the pores distributed in the range of 10-20 μm (FIG.1g inset); 3.5% STCSF40 had 44.44% of the pore distribution in the 50-70 μm range (FIG.1b inset), and 5.0% STCS40 had 41.94% of the pore distribution in the 10-30 μm range (FIG.1h inset), and it can be seen that the solids content increased and the pore size changed in the direction of smaller pore size. Because the solute proportion in the mixed solution system is increased when the solid content is increased, the ice crystals are extruded and surrounded by a large amount of solute in the freezing process, the nucleation growth of the ice crystals is prevented, a large amount of small ice crystals with small size are formed and distributed in the system, and a larger number of pores with smaller pore diameter are left after sublimation.
Stress-strain plots for STCTF and STCSF syntactic foams of different solids content and different filament ratios prepared in examples 4, 9, 14, 19 and examples 11, 12, 13, 14, 15 as shown in fig.2, the mechanical properties of both STCTF and STCSF become stronger as the total solids content increases when the filament content is fixed (fig.2a,2b), which is related to a denser and regular pore structure at higher solids content (fig.1), and as can be seen from the microscopic electron microscopy image of fig.1, the syntactic foam has a higher pore density and smaller pore size as the total solids content increases, so the higher the solids content, the greater the number of pores, the more stress tolerant pore structure, and hence the mechanical strength of the syntactic foam is proportional to the solids content. The influence effect of the fibril content of different nano fibril contents on the mechanical property of the composite foam is different, and the mechanical property of the STCTF is increased along with the increase of the CTF content under the condition of 4.5 percent of solid content (FIG.2 c); the stress value of STCSF increases and then decreases with increasing CSF content (fig.2 d).
The Young's modulus, the resilience and the maximum stress value of all the foam samples prepared in examples 1-21 have different changes with the solid content and the fibril content of the samples as shown in FIG. 3. the addition of two types of nanofibrils, CSF and CTF, has a certain effect on the mechanical property enhancement of the starch foam, except that, at a high fibril ratio, the increase of the CSF content is in inverse proportion to the Young's modulus (FIG.3) and the compressive stress of the composite foam, the CTF is in direct proportion, and when the solid content and the fibril content are both increased, the enhancement effect of the CTF is more remarkable. The mechanical property of the STCSF can reach a larger compressive stress when the proportion of the filament is lower and the solid content is higher, and the mechanical property can reach 185kPa at the maximum when the proportion of the filament with the solid content of 5.0 percent and the proportion of the filament with the solid content of 10 percent, namely the mechanical property of the STCSF10(5.0 percent) is the best; while STCTF achieves a higher compressive stress at higher filament ratios and a maximum compressive stress of 236kPa at a filament ratio of 5.0% solids to 50%, i.e., STCTF50 (5.0%) has the best mechanical properties.
The electrostatic interaction between ST and CSF is stronger than the repulsive force in a mixed solution system, so solute molecules have different interactions and are dispersed unevenly, and the large gaps are easily formed by extruding and separating ice crystals in the freezing process. Compared with STCSF, the system of STCTF is more stable, solute molecules repel each other, the dispersion is uniform, the ice crystal is difficult to separate the solute molecules in the growth process, only small ice crystals can be formed to fill in the ice crystal, a plurality of uniformly distributed small holes can be formed after sublimation, and the CTF contains a large amount of acetamido groups, has certain hydrophobicity, and is difficult to drive fibrils to be arranged in the process of forming the ice crystal, so that the front and back difference is small when the orientation design is carried out on the fibrils (fig.4, fig. 5). Therefore, the influence of STCSF on mechanical properties is mainly studied by performing orientation design aiming at the characteristic that STCSF can amplify the change of mechanical properties caused by anisotropic conduction of heat.
Design layout of various insulation patterns, formed foam object pattern, syntactic foam micro-orientation pattern, and stress-strain pattern reflecting the mechanical properties of syntactic foam of the foam samples made with square PTFE cartridges of 3X 3cm in example 9 As shown in FIG.4, the insulation design OD1 conducts heat only from the bottom surface which is first contacted with cold air, rapidly forms ice crystals and grows upward along the temperature gradient direction (FIG.4I), after freeze-drying, ice crystals sublimate leaving large gaps to form a longitudinally oriented structure (FIG.4A), and therefore more stress needs to be applied in the longitudinal direction to cause corresponding strain (FIG.4 a). The thermal insulation design OD2 conducts heat only from the right side, the right side is firstly contacted with cold air flow, a temperature gradient (FIG.4II) beneficial to ice crystal growth from right to left is formed, after freeze drying, a transverse orientation structure (FIG.4B) is formed due to the pore channels and gaps formed by ice crystal sublimation, and the transverse layer structure enables more strain to occur when a specific stress is applied in the longitudinal direction to a certain extent, so that a smaller stress value (FIG.4b) can be seen in a stress-strain diagram of OD 2. The thermal insulation design OD3 wraps the upper part and the lower part with thermal insulation foam, foam in the middle is reserved for heat conduction, the thermal insulation design enables heat to be uniformly distributed (FIG.4III), the surface of the formed composite foam is smooth and has no obvious large gaps and pore passages (FIG.4C), the whole system is more isotropic, and compared with the composite foam without any thermal insulation design, the mechanical properties of the composite foam and the composite foam are similar and have no obvious difference (FIG.4 c). The insulation design OD4 was made by wrapping the foam around the perimeter with insulating foam such that the top and bottom surfaces were in direct contact with the cold air, thus creating two opposite heat conduction directions, where the two forces met at about the middle, macroscopically, the sides were compression cracked (fig.4 iv), and microscopically, two differently oriented interfaces (fig.4d), although this structure also showed good mechanical properties (fig.4d), but the presence of the fractured layer resulted in a composite foam that was not integral.
Design planning plots for various insulation patterns, resulting foam plots, syntactic foam microscopic orientation plots, and stress strain plots reflecting the mechanical properties of syntactic foams for the foam samples of example 9 made with cylindrical PTFE cells of 3.5cm diameter and 5.4cm height are shown in fig.5, which are similar to square molds in that the faces in direct contact with the cold air are not significantly oriented, except that the faces surrounded by the insulation material will be given a staggered thread orientation, probably because the freezing rate of the faces in direct contact with the cold air is faster, ice crystals quickly nucleate and freeze, while where they are surrounded, ice crystal nucleation is slow and directional growth occurs after nucleation, influenced by the appearance (cylindrical) of the mold, with straight voids that would have formed in the plane becoming tortuous rows of voids, referred to herein as thread structures. The same as OD4, the formation of OD9 orientation is unsatisfactory, probably because the upper and lower parts contact with cold air simultaneously to form two reverse cold flow conduction directions, and the middle part is wrapped by a heat insulating material to form a buffer zone, the buffer zone only slows down the growth rate of ice crystal but does not change the growth direction of ice crystal, so when two cold flows collide with each other, because the directions are opposite, two forces extrude and pile each other, the original thread structure is extruded and damaged to form a fracture layer (FIG.5 IV) due to the action of the upper and lower forces, and the fracture layer junction can be seen from an electron microscope image of OD9, the gap is wider, and the structure is incomplete (FIG. 5D). The observation results of the stress-strain curve show that compared with the square foam, the thermal insulation orientation design has no critical effect on the improvement of the mechanical property of the cylindrical foam, but reduces the mechanical property (fig.5a-e), which is probably related to the thread structure formed on the cylindrical foam in the longitudinal direction with high probability, and the stress which can be borne by the longitudinal thread structure in the longitudinal direction is reduced due to the formation of the longitudinal thread structure.
Flame retardancy tests were carried out in examples 1 to 21 using prepared foam samples packed in 1X 10cm small boxes, and the flame retardancy grade of the foams was determined according to the flame retardancy level method test method (GB/T2108-1996) using the horizontal flame retardancy method (ISO 1210). The test results are shown in fig. 6. Flame retardant grades include four grades (symbol FH indicates horizontal burning): FH-1: after the ignition source is removed, the flame is extinguished or the combustion front does not reach the marking of 25 mm; FH-2: after the ignition source is removed, the combustion front crosses the 25mm mark line but does not reach the 100mm mark line, and in the combustion grade FH-2 grade, the combustion length should be written into a grading mark, such as FH-2-70 mm; ③ FH-3: after the ignition source is removed, the combustion front crosses the 100mm mark line, the combustion speed is not more than 40mm/min, and in the combustion grade FH-3 grade, the linear combustion speed is written into a grading mark, such as FH-3-30 mm/min; fourthly, FH-3: the same as FH-3 stages, except that the linear burn rate is greater than the specified value, should be written into the staging marks, such as FH-4-60 mm/min. As can be seen from FIG. 6, the burning rate of the pure starch foam material is 180mm/min, and the burning of the foam with the length of 100mm is finished in less than 1min (flaming burning), and an expanded carbon layer is formed on the surface after burning. With the addition of the chitosan nanofibrils, namely STCSF50, the combustion speed is greatly reduced, but the combustion speed is still in flaming combustion, the combustion speed is 66mm/min, the reduction of the combustion speed is attributed to the formation of a compact carbon layer during combustion, the exchange rate of oxygen is greatly reduced, and the combustion speed is influenced, but the flame retardant grade is not improved because a large channel structure is easily formed in the freeze drying process due to the strong electrostatic action between ST and CSF, and air backflow is formed inside the material during combustion due to the formation of the large channel structure, so that the flame retardant is not facilitated. However, the starch composite foam added with chitin nanofibrils, namely STCTF50, has self-extinguishment within 5 seconds after the fire source is removed, the combustion grade is raised to FH-2, the structural integrity of the combustion interface can be seen by microscopic electron microscopy images, the excellent flame retardant effect of STCTF50 is mainly due to the fact that the good biocompatibility and interfacial viscosity between the STCTF and the starch enable the STCTF and the starch to form a regular and compact small-pore structure after freeze drying, the existence of air in the small-pore structure greatly reduces the thermal conductivity due to insufficient size to form air backflow when the starch burns, and the reduction of the thermal conductivity causes the material to fail to reach the heat required by combustion, so that the material self-extinguishes. Therefore, chitin nanofibrils reinforced flame retardant starch foam is a more preferred flame retardant material.

Claims (10)

1. A polysaccharide nanofibril reinforced flame retardant starch syntactic foam characterized by:
prepared by mixing and freezing polysaccharide nanofibrils and starch;
wherein the polysaccharide nano-fibril accounts for 0-50% of the mass of the starch, and the solid content of the mixed solution is 3.5% -5.0%;
the polysaccharide is selected from one of chitin and chitosan;
the chitin nanofibrils have the diameter of 60nm and the length of micron order;
the diameter of the chitosan nanofibril is 80-120 nm, and the length of the chitosan nanofibril is micrometer.
2. The method of claim 1, wherein the polysaccharide nanofibril-reinforced flame retardant starch composite foam is prepared by:
the method comprises the following steps:
step one, preparing polysaccharide nanofibril suspension: adding polysaccharide solid powder into a container, adding deionized water, stirring uniformly, standing, removing upper layer impurities, stirring uniformly, and circulating through a high-pressure homogenizer to obtain polysaccharide nanofibril suspension;
preparation of gelatinized starch solution: putting solid starch granules into a container, adding deionized water, and continuously stirring under a heating condition to obtain a transparent uniformly gelatinized starch solution;
step two, adding the polysaccharide nanofibril suspension into the gelatinized starch solution, and uniformly stirring and mixing to obtain a starch/polysaccharide mixed solution; evaporating and concentrating the starch/polysaccharide mixed solution, and then performing defoaming treatment to obtain a starch/polysaccharide mixed solution stock solution;
pouring the stock solution of the starch/polysaccharide mixed solution into a polytetrafluoroethylene container, sealing the container, directly freezing the polytetrafluoroethylene container filled with the stock solution, or wrapping and insulating the container to expose at least one surface, and then freezing;
and step four, taking out the frozen PTFE container, uncovering the PTFE container, putting the PTFE container into a freeze dryer, and freeze-drying the PTFE container for 120 hours, and taking out the PTFE container to obtain the starch polysaccharide composite foam.
3. The method of preparing a polysaccharide nanofibril reinforced flame retardant starch composite foam according to claim 1, wherein:
wherein, in the step one, the chitosan polysaccharide is chitosan with acetyl degree more than or equal to 95%.
4. The method of preparing a polysaccharide nanofibril reinforced flame retardant starch composite foam according to claim 1, wherein:
wherein, in the first step, the dosage ratio of the polysaccharide to the deionized water is 20 g: 1500 mL.
5. The method of preparing a polysaccharide nanofibril reinforced flame retardant starch composite foam according to claim 1, wherein:
wherein in the preparation process of the polysaccharide nanofibril suspension in the step one, the standing time is 24 hours; the number of cycles of the high-pressure homogenizer was 20.
6. The method of preparing a polysaccharide nanofibril reinforced flame retardant starch composite foam according to claim 1, wherein:
wherein in the preparation process of the gelatinized starch solution in the step one, the heating condition is 80-100 ℃ water bath; the stirring time is 30-60 min.
7. The method of preparing a polysaccharide nanofibril reinforced flame retardant starch composite foam according to claim 1, wherein:
and in the second step, after defoaming, carrying out ultrasonic treatment in an ultrasonic cleaning instrument.
8. The method of claim 7, wherein the polysaccharide nanofibril-reinforced flame retardant starch composite foam is prepared by:
wherein the ultrasonic power of the ultrasonic treatment is 200W, and the ultrasonic time is 10 min.
9. The method of preparing a polysaccharide nanofibril reinforced flame retardant starch composite foam according to claim 1, wherein:
wherein, in the third step, the freezing temperature is-50 ℃ to-20 ℃, and the freezing time is 24 hours.
10. The method of preparing a polysaccharide nanofibril reinforced flame retardant starch composite foam according to claim 1, wherein:
wherein, in the fourth step, the freeze drying time is 120 h.
CN202011347118.3A 2020-11-26 2020-11-26 Polysaccharide nano-fibril reinforced flame-retardant starch composite foam and preparation method thereof Pending CN112358659A (en)

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Publication number Priority date Publication date Assignee Title
CN106693041A (en) * 2016-12-16 2017-05-24 武汉工程大学 Asymmetric wettable chitosan/starch compound sponge and preparation method thereof
CN108295319A (en) * 2018-03-08 2018-07-20 山东省药学科学院 A kind of hydrophilic composite material and preparation method of medical nano fiber reinforcement type and purposes
CN111187451A (en) * 2020-02-11 2020-05-22 陕西科技大学 Degradable starch fiber composite foam material and preparation method thereof

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Publication number Priority date Publication date Assignee Title
CN106693041A (en) * 2016-12-16 2017-05-24 武汉工程大学 Asymmetric wettable chitosan/starch compound sponge and preparation method thereof
CN108295319A (en) * 2018-03-08 2018-07-20 山东省药学科学院 A kind of hydrophilic composite material and preparation method of medical nano fiber reinforcement type and purposes
CN111187451A (en) * 2020-02-11 2020-05-22 陕西科技大学 Degradable starch fiber composite foam material and preparation method thereof

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Application publication date: 20210212