CN113845764A - Heat-resistant modified polylactic acid material and preparation method thereof - Google Patents
Heat-resistant modified polylactic acid material and preparation method thereof Download PDFInfo
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- CN113845764A CN113845764A CN202111141175.0A CN202111141175A CN113845764A CN 113845764 A CN113845764 A CN 113845764A CN 202111141175 A CN202111141175 A CN 202111141175A CN 113845764 A CN113845764 A CN 113845764A
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- 239000000463 material Substances 0.000 title claims abstract description 75
- 238000002360 preparation method Methods 0.000 title abstract description 9
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- 239000002109 single walled nanotube Substances 0.000 claims abstract description 32
- RNFJDJUURJAICM-UHFFFAOYSA-N 2,2,4,4,6,6-hexaphenoxy-1,3,5-triaza-2$l^{5},4$l^{5},6$l^{5}-triphosphacyclohexa-1,3,5-triene Chemical compound N=1P(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP=1(OC=1C=CC=CC=1)OC1=CC=CC=C1 RNFJDJUURJAICM-UHFFFAOYSA-N 0.000 claims abstract description 31
- 239000003063 flame retardant Substances 0.000 claims abstract description 31
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- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 10
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- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L67/00—Compositions of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Compositions of derivatives of such polymers
- C08L67/04—Polyesters derived from hydroxycarboxylic acids, e.g. lactones
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
- C08G63/06—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from hydroxycarboxylic acids
- C08G63/08—Lactones or lactides
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/78—Preparation processes
- C08G63/82—Preparation processes characterised by the catalyst used
- C08G63/84—Boron, aluminium, gallium, indium, thallium, rare-earth metals, or compounds thereof
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- C—CHEMISTRY; METALLURGY
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- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/78—Preparation processes
- C08G63/82—Preparation processes characterised by the catalyst used
- C08G63/85—Germanium, tin, lead, arsenic, antimony, bismuth, titanium, zirconium, hafnium, vanadium, niobium, tantalum, or compounds thereof
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- C08J3/00—Processes of treating or compounding macromolecular substances
- C08J3/24—Crosslinking, e.g. vulcanising, of macromolecules
- C08J3/246—Intercrosslinking of at least two polymers
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- C08J2367/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
- C08J2367/04—Polyesters derived from hydroxy carboxylic acids, e.g. lactones
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- C08J2479/00—Characterised by the use of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing nitrogen with or without oxygen, or carbon only, not provided for in groups C08J2461/00 - C08J2477/00
- C08J2479/04—Polycondensates having nitrogen-containing heterocyclic rings in the main chain; Polyhydrazides; Polyamide acids or similar polyimide precursors
- C08J2479/08—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
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Abstract
The invention belongs to the technical field of high polymer materials, and particularly relates to a heat-resistant modified polylactic acid material and a preparation method thereof. The polylactic acid material comprises the following components in parts by weight: 50-80 parts of lactide, 2-4 parts of catalyst, 10-30 parts of chitosan, 10-26 parts of single-walled carbon nanotube, 10-20 parts of polyimide, 3-9 parts of flame retardant and 0.5-1 part of toughening agent. The invention has the advantages of wide raw material source, excellent processing performance, good high temperature resistance and excellent mechanical performance.
Description
Technical Field
The invention belongs to the technical field of high polymer materials, and particularly relates to a heat-resistant modified polylactic acid material and a preparation method thereof.
Background
Polylactic acid is an environment-friendly plastic from biomass, has the advantages of excellent biocompatibility, biodegradability, processability and the like, has the reputation of 'green plastic', and is more and more concerned by people. However, polylactic acid still has the problems of brittleness, low toughness, poor heat resistance and the like, and the notch impact strength value is lower than 4KJ/m2This severely limits the wide application of polylactic acid materials in various fields. Therefore, research on modification of polylactic acid materials is becoming a hot spot, and in particular, various toughening modifications are being performed on the polylactic acid materials.
PLA belongs to polyester, has poor hydrophilicity, has slow degradation rate under natural conditions, can improve the hydrophobicity, the crystallinity and the like of PLA materials, and the degradation rate of the polymer can be controlled according to the molecular weight of the copolymer, the types and the mixture ratio of comonomers and the like. Common modifying materials include polyethylene glycol (PEG) with good hydrophilicity, polyglycolic acid (PGA), poly epsilon-caprolactone (PCL) with good drug permeability and the like. Research shows that as the content of PEG increases, the glass transition temperature decreases and the elongation rate increases, and when the content reaches a certain degree (such as the mass fraction of PEG reaches 7.7 percent), the copolymer has yield tension and overcomes the brittleness of PLA. The change from brittleness to toughness indicates that the PEG modified PLA is a biodegradable material with controllable comprehensive performance.
Polylactic acid has poor temperature resistance, the heat distortion temperature of non-annealed PLA is usually lower than 60 ℃, the polylactic acid has higher brittleness and is not easy to process and form, which causes great difficulty for practical production and application; the traditional polylactic acid is generally hard and brittle and has insufficient strength, and the mechanical strength of the traditional polylactic acid is difficult to be considered. There is a need for a polylactic acid with good high temperature resistance and excellent mechanical properties, and the processability of the polylactic acid is improved.
Disclosure of Invention
In view of the above problems, the present invention proposes a heat-resistant modified polylactic acid material and a method for preparing the same to overcome or at least partially solve the above problems.
The technical scheme for realizing the purpose is as follows:
the invention provides a heat-resistant modified polylactic acid material which comprises the following components in parts by weight: 50-80 parts of lactide, 2-4 parts of catalyst, 10-30 parts of chitosan, 10-26 parts of single-walled carbon nanotube, 10-20 parts of polyimide, 3-9 parts of flame retardant and 0.5-1 part of toughening agent; the crystallinity is 45-68% by volume fraction.
Optionally, the polylactic acid material has a thermal deformation temperature of not less than 118 ℃, a crystallization temperature of 115-125 ℃, and a density of more than 1.2g/cm3The tensile strength is more than 160MPa, and the lowest notch impact strength is 115KJ/m2。
Optionally, the catalyst comprises alumina and titania.
Optionally, the flame retardant comprises pseudo-boehmite, sodium lignosulfonate and ethylenediamine.
Optionally, the toughening agent comprises at least one of an ethylene-methyl acrylate-glycidyl methacrylate random copolymer, a hydrogenated polystyrene-polybutadiene-polystyrene triblock copolymer, natural rubber and polycaprolactone plastic.
Optionally, the mass ratio of the toughening agent to the single-walled carbon nanotube polylactic acid is 1: 50-95.
Optionally, the polyimide is polyimide containing an asymmetric indole structure.
A method for preparing a heat-resistant modified polylactic acid material, which comprises the following steps:
mixing lactide, a catalyst, chitosan and the single-walled carbon nanotube, and dispersing and molding to obtain single-walled carbon nanotube polylactic acid;
blending and molding the single-walled carbon nanotube polylactic acid, the polyimide, the flame retardant and the toughening agent in a molten state to obtain a blank;
and irradiating, stretching, cooling and solidifying the blank to obtain the polylactic acid material.
Optionally, the melting and the drawing are each performed above a glass transition temperature of the billet.
Optionally, the cooling solidification is performed below the glass transition temperature of the blank.
One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages: the polyimide and the single-walled carbon nanotube polylactic acid are subjected to synergistic compounding, the catalyst comprises aluminum oxide and titanium dioxide, and the mechanical stress can be improved and the temperature resistance can be provided by melt blending or heating; the crystallinity of the polylactic acid blending material can be increased to 45-68% through stretching treatment, so that the heat resistance of the material is greatly improved; has excellent mechanical properties; is convenient for processing.
The foregoing description is only an overview of the technical solutions of the present invention, and the embodiments of the present invention are described below in order to make the technical means of the present invention more clearly understood and to make the above and other objects, features, and advantages of the present invention more clearly understandable.
Drawings
Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:
FIG. 1 is a microscopic structure of polylactic acid material in the example;
FIG. 2 is a flow chart of the preparation of polylactic acid material in the example.
Detailed Description
The present invention will be described in detail below with reference to specific embodiments and examples, and the advantages and various effects of the present invention will be more clearly apparent therefrom. It will be understood by those skilled in the art that these specific embodiments and examples are for the purpose of illustrating the invention and are not to be construed as limiting the invention.
Throughout the specification, unless otherwise specifically noted, terms used herein should be understood as having meanings as commonly used in the art. Accordingly, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. If there is a conflict, the present specification will control.
Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.
It should be further noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
In order to solve the technical problems, the technical scheme in the embodiment of the invention has the following general idea:
the invention provides a heat-resistant modified polylactic acid material which comprises the following components in parts by weight: 50-80 parts of lactide, 2-4 parts of catalyst, 10-30 parts of chitosan, 10-26 parts of single-walled carbon nanotube, 10-20 parts of polyimide, 3-9 parts of flame retardant and 0.5-1 part of toughening agent.
The lowest notched impact strength of the present invention is 115KJ/m2While the notched impact strength is from the conventional 80KJ/m2Increased to 175J/m2. The elongation at break is improved to 50-148%, and the toughness is improved while the rigidity of the material is improved.
As an optional embodiment, the polylactic acid material has the heat distortion temperature of not less than 118 ℃, the density of more than 1.2g/cm3, the tensile strength of more than 160MPa and the lowest notch impact strength of 116KJ/m2。
In the embodiment of the application, the thermal deformation temperature is increased from the traditional 80-90 ℃ to 118 ℃ or higher, the density of the polylactic acid is reduced, and the mechanical property of the polylactic acid is effectively ensured.
A method for preparing a heat-resistant modified polylactic acid material, as shown in fig. 2, the method comprising:
s1, mixing lactide, a catalyst, chitosan and the single-walled carbon nanotube, and dispersing and molding to obtain single-walled carbon nanotube polylactic acid;
s2, blending and molding the single-walled carbon nanotube polylactic acid, the polyimide, the flame retardant and the toughening agent in a molten state to obtain a blank;
and S3, irradiating, stretching, cooling and solidifying the blank to obtain the polylactic acid material.
In the embodiment of the application, the carbon nanotube polylactic acid, the polyimide, the flame retardant and the toughening agent are blended in a molten state, and a corresponding compatilizer or a corresponding cross-linking agent can be added for reaction.
In the embodiment of the application, the crystallinity of the polylactic acid blending material can be increased to 45-68% through stretching treatment, and the increase of the crystallinity is beneficial to improving the mechanical strength and the heat-resistant stability of the material and can greatly improve the heat-resistant performance of the material; has excellent mechanical performance.
In the embodiment of the application, the fact that the crystallization enthalpy of the modified polylactic acid is obviously improved and the half-crystal period is obviously reduced under the same cooling speed is found; the cold crystallization and subsequent melting behavior of polylactic acid at different temperatures are studied, the polymer matrix of the embodiment of the invention has better crystallization capacity, the addition of the single-walled carbon nanotube provides a large number of heterogeneous nucleation points, the matrix induces faster crystallization after the attached crystallization on the carbon tube, and the synergistic effect of the added polyimide and the plasticizer promotes the increase of the crystallization temperature. While an increase in crystallinity results in an increase in enthalpy of crystallization.
Generally, the addition of nucleating agent accelerates annealing crystallization of the material to refine polymer spherulites, larger spherulites are easy to become stress concentrators, so that the reduction of the spherulite size results in a large increase in impact strength, and crystallization can improve the barrier property of polylactic acid. The single-walled carbon nanotube can improve the crystallinity, improve the impact strength of the material, and simultaneously improve the brittleness, so that the polylactic acid has higher impact strength.
According to an exemplary embodiment of the invention, it is provided that the melting and the drawing are each carried out above the glass transition temperature of the blank.
The temperature at which a high polymer is converted from a high elastic state to a glassy state refers to the temperature at which an amorphous polymer (including an amorphous part in a crystalline polymer) is converted from the glassy state to the high elastic state or from the latter to the former, and is the lowest temperature at which a macromolecular chain segment of the amorphous polymer freely moves, generally represented by Tg.
As an alternative embodiment, the crystallization temperature in the cooling solidification is 115 ℃ to 125 ℃, and the cooling solidification is carried out below the glass transition temperature of the blank.
The polylactic acid has the characteristics of heat resistance, softening resistance, high impact strength and the like, keeps the special biodegradation performance, and solves the defect of high-temperature thermal deformation; the polylactic acid material is crystallized at the optimized high temperature of 120 ℃, and the high temperature resistant effect is generated due to the regular arrangement of molecular chains after the polylactic acid material is crystallized, wherein the polylactic acid material is produced at a temperature higher than the conventional crystallization temperature. The cooling solidification is carried out below the glass transition temperature of the blank, which is beneficial to maintaining the crystallinity and the molecular arrangement in the polylactic acid material.
In the process of balling the polylactic acid, the ice bath mode is adopted, so that the polylactic acid is not adhered and agglomerated.
As an alternative embodiment, the catalyst comprises alumina and titania.
As an alternative embodiment, the flame retardant comprises pseudo-boehmite, sodium lignosulfonate and ethylenediamine.
In the embodiment of the application, the flame retardant can meet the flame retardant performance required by the material, and the flame retardant is matched with titanium dioxide, so that molten drops generated by combustion are reduced, the increase of char formation amount is promoted, and flame propagation is prevented.
As an alternative embodiment, the toughening agent includes at least one of an ethylene-methyl acrylate-glycidyl methacrylate random copolymer, a hydrogenated polystyrene-polybutadiene-polystyrene triblock copolymer, natural rubber, and polycaprolactone plastic.
The toughening agent selected in the invention has better compatibility with polylactic acid, can improve the strength of the polylactic acid, improve the brittleness of the polylactic acid and improve the shock resistance of the polylactic acid material, and the active functional group in the toughening agent reacts with the end group of the polylactic acid to improve the stability of the material.
As an optional embodiment, the mass ratio of the toughening agent to the single-walled carbon nanotube polylactic acid is 1: 50-95.
The flame retardant and the single-wall nano carbon are subjected to synergistic compounding, so that the flame retardant can be well combined with the surface of polylactic acid, the crosslinking and carbon forming rate of the polylactic acid is improved, a carbon layer is formed on the surface of the polylactic acid, and the flame retardant property of the polylactic acid material is further improved; in addition, the polylactic acid material and the polyimide are compounded and added, so that polylactic acid molecules can be regularly arranged, the dispersity and compatibility of polylactic acid and polyimide are further enhanced, and the prepared polylactic acid material has good toughness and thermal stability.
As an alternative embodiment, the polyimide is a polyimide containing an asymmetric indole structure. Preferably, the structural formula of the polyimide containing the asymmetric structure and the asymmetric indole structure is shown as follows,
n is a positive integer.
The polyimide containing the asymmetric indole structure is subjected to synergistic compounding with a flame retardant and single-walled nanocarbon due to the asymmetry of the polyimide, can be well combined with the surface of polylactic acid, improves the crosslinking and carbonizing rate of the polylactic acid, forms a carbon layer on the surface of the polylactic acid, and improves the crystallization temperature of the polyactic acid. The polylactic acid material has extremely excellent heat resistance, and can make up or eliminate the defect of low heat resistance of-C-O-group on the polylactic acid molecular chain to a certain extent, so that the melting point of the prepared polylactic acid material is about 50-80 ℃ higher than that of the traditional polylactic acid product.
The conventional asymmetric polyimide can reduce the crystallinity and influence the mechanical strength and the thermal stability of the polyimide, because the molecular symmetry is reduced and the molecular chain diffusion speed is influenced, so that the crystallization speed is very slow, the crystallinity is reduced, and the crystallinity and the thermal resistance of the polyimide can not be improved by adding the polyimide conventionally; the blend is crystallized at a temperature of more than 115 ℃, and the prepared polylactic acid has a thermal deformation temperature of not less than 118 ℃ and a density of more than 1.2g/cm3The tensile strength is more than 160MPa, the flame retardant grade can reach UL-94V-0 grade, and the lowest notch impact strength is 115KJ/m2While the notched impact strength is from the conventional 80KJ/m2Increased to 175J/m or higher in the present invention2. The elongation at break is increased to 50-148%, the rigidity of the material is improved, the toughness is improved, the thermal deformation temperature is increased, the density of the polylactic acid material is reduced, and the impact-resistant toughening effect is very obvious.
The invention researches the influence of the synergistic effect of adding the single-walled carbon nanotube, the polyimide and the plasticizer in the polylactic acid on the crystallization behavior of the polylactic acid, and the prepared polylactic acid has excellent flame retardance, toughness and thermal stability, is not easy to agglomerate in the using process and can be widely applied.
As an optional implementation mode, the heat distortion temperature of the polylactic acid material is not lower than 118 ℃, the high-temperature resistance of the polylactic acid material is good, and the density of the polylactic acid material is more than 1.2g/cm3The tensile strength is more than 160MPa, the flame retardant grade can reach UL-94V-0 grade, and the lowest notch impact strength is 115KJ/m2The above.
The polylactic acid material of the present invention will be described in detail with reference to examples and experimental data.
Example 1
A heat-resistant modified polylactic acid material comprises the following components in parts by weight: 50g of lactide, 2g of catalyst, 10g of chitosan, 10g of single-walled carbon nanotube, 10g of polyimide, 3g of flame retardant and 0.5g of toughening agent. The polyimide is polyimide containing an asymmetric indole structure, wherein the chemical general formula is as follows:
n is 8.
The catalyst comprises alumina. The toughening agent comprises an ethylene-methyl acrylate-glycidyl methacrylate random copolymer. The mass ratio of the toughening agent to the single-walled carbon nanotube polylactic acid is 1: 50. The polyimide is polyimide containing an asymmetric indole structure. Adding chitosan (with the molecular weight of 30 ten thousand and the deacetylation degree of 60%) into a reaction container, adding lactide, a catalyst, the chitosan and the single-walled carbon nanotube, mixing, stirring and dispersing for 3 hours, heating a reaction product to 120 ℃, and drying for 2 hours; adding the obtained high molecular weight polylactic acid (with the molecular weight of 20 ten thousand KDa) into a miniature internal mixer, heating to the melting temperature of 165 ℃, internally mixing for 0.5h at the melting temperature of the polylactic acid, adding polyimide, a flame retardant and a toughening agent into the polylactic acid, compression molding the obtained blend into a 6 x 22 x 100mm (used for preparing an impact sample bar) parison in a compression molding machine, wherein the compression molding temperature is 210 ℃, the pressure is 16MPa, the time is 10min, and cooling the sample to room temperature by ice water quenching. Carrying out electron irradiation, carrying out secondary crosslinking reaction, then stretching the parison on a temperature-controlled stretching equipment tester, wherein the stretching temperature is 70 ℃, the stretching speed is 70mm/min, the strain is 300%, and after the preset strain is reached, cooling and solidifying are carried out in the room-temperature air environment to obtain the polylactic acid material. The sample after the stretching treatment was cut and processed and then subjected to an impact test.
Example 2
A heat-resistant modified polylactic acid material comprises the following components in parts by weight: 80g of lactide, 4g of catalyst, 30g of chitosan, 26g of single-walled carbon nanotube, 20g of polyimide, 9g of flame retardant and 1g of toughening agent.
The melting and the drawing are each performed at a temperature equal to or higher than the glass transition temperature of the material. The crystallization temperature in the cooling solidification is 155 ℃, and the cooling solidification catalyst comprises alumina. The toughening agent comprises a hydrogenated polystyrene-polybutadiene-polystyrene triblock copolymer. The mass ratio of the toughening agent to the single-walled carbon nanotube polylactic acid is 1: 95. The polyimide is polyimide containing an asymmetric indole structure.
Adding chitosan (with the molecular weight of 30 ten thousand and the deacetylation degree of 70 percent) into a reaction container, adding lactide, a catalyst, the chitosan and the single-walled carbon nanotube, mixing, stirring and dispersing for 4 hours, heating a reaction product to 122 ℃, and drying for 2.5 hours; adding the obtained high molecular weight polylactic acid (with the molecular weight of 20 ten thousand KDa) into a miniature internal mixer, heating to the melting temperature of 155 ℃, internally mixing for 0.6h at the melting temperature of the polylactic acid, adding polyimide, a flame retardant and a toughening agent into the polylactic acid, compression molding the obtained blend into a 6 x 22 x 100mm (used for preparing an impact sample bar) parison in a compression molding machine, wherein the compression molding temperature is 220 ℃, the pressure is 18MPa, the time is 12min, and cooling the sample to the room temperature by ice water quenching. Carrying out electron irradiation, carrying out secondary crosslinking reaction, then stretching the parison on a temperature-controlled stretching equipment tester, wherein the stretching temperature is 70 ℃, the stretching speed is 70mm/min, the strain is 280%, and after the preset strain is reached, cooling and solidifying are carried out in the room-temperature air environment to obtain the polylactic acid material. The sample after the stretching treatment was cut and processed and then subjected to an impact test.
Example 3
A heat-resistant modified polylactic acid material comprises the following components in parts by weight: 65g of lactide, 3g of catalyst, 20g of chitosan, 18g of single-walled carbon nanotube, 15g of polyimide, 6g of flame retardant and 0.8g of toughening agent.
The catalyst comprises alumina. The toughening agent comprises elastomers such as natural rubber or polycaprolactone plastic. The mass ratio of the toughening agent to the single-walled carbon nanotube polylactic acid is 1: 68. The polyimide is polyimide containing an asymmetric indole structure. The crystallization temperature in the cooling solidification is 120 ℃, and the cooling solidification is carried out below the glass transition temperature of the blank.
Adding chitosan (with the molecular weight of 30 ten thousand and the deacetylation degree of 65 percent) into a reaction container, adding lactide, a catalyst, the chitosan and the single-walled carbon nanotube, mixing, stirring and dispersing for 3.2 hours, heating a reaction product to 122 ℃, and drying for 2 hours; adding the obtained high molecular weight polylactic acid (with the molecular weight of 20 ten thousand KDa) into a miniature internal mixer, heating to the melting temperature of 175 ℃, carrying out internal mixing for 0.5h at the melting temperature of the polylactic acid, adding polyimide, a flame retardant and a toughening agent into the polylactic acid, molding the obtained blend into a 6 x 22 x 100mm (used for preparing an impact sample bar) parison in a molding press, wherein the molding temperature is 210 ℃, the pressure is 18MPa, the time is 19min, and cooling the sample to room temperature by ice water quenching. Carrying out electron irradiation, carrying out secondary crosslinking reaction, then stretching the parison on a temperature-controlled stretching equipment tester, wherein the stretching temperature is 70 ℃, the stretching speed is 70mm/min, the strain is 285%, and after the preset strain is reached, cooling and solidifying are carried out in the room-temperature air environment to obtain the polylactic acid material. The sample after the stretching treatment was cut and processed and then subjected to an impact test.
Example 4
A heat-resistant modified polylactic acid material comprises the following components in parts by weight: 70 parts of lactide, 3.5 parts of catalyst, 26 parts of chitosan, 14 parts of single-walled carbon nanotube, 18 parts of polyimide, 4 parts of flame retardant and 0.6 part of toughening agent. Otherwise, the preparation method was the same as in example 3.
Comparative example 1
A heat-resistant modified polylactic acid material comprises the following components in parts by weight: 70 parts of lactide, 3.5 parts of catalyst, 26 parts of chitosan, 14 parts of lactide and the like in mass instead of the single-walled carbon nanotube, 18 parts of conventional polyimide without an asymmetric indole structure, 4 parts of flame retardant and 0.6 part of toughening agent. The crystallization temperature was 106 ℃ and the crystallinity 25%. Otherwise, the preparation method was the same as in example 3.
Comparative example 2
A heat-resistant modified polylactic acid material comprises the following components in parts by weight: 70 parts of lactide, 3.5 parts of catalyst, 26 parts of chitosan, 14 parts of single-walled carbon nanotube, 18 parts of lactide and the like, and the like are used for replacing polyimide, 4 parts of flame retardant and 0.6 part of toughening agent. The crystallization temperature was 95 ℃ and the degree of crystallinity was 31%. Otherwise, the preparation method was the same as in example 3.
Comparative example 3
The cooling solidification is directly carried out without electron irradiation and stretching, the crystallization temperature is 100 ℃, the crystallinity is 30 percent, and the preparation method is the same as the comparative example 1.
The polylactic acid materials synthesized in the examples were tested:
the thermal stability of the polylactic acid material is measured by adopting a TG 209F3 thermogravimetric analyzer produced by Germany Netzsch company, wherein the heating rate is 20 ℃/min and the temperature range is 40-800 ℃ under the nitrogen atmosphere; the glass transition temperature of the material was tested using a model Q400 static thermodynamic analyzer manufactured by TA instruments, usa, with the static force set at 0.05N; the mechanical properties of the polymer are tested by adopting an IBTC-300S type micro in-situ mechanical test system produced by Kaire test and control system (Tianjin) Co.
Table 1 mechanical and thermal properties of the polylactic acid material.
Table 1 shows the mechanical and thermal test data of the polylactic acid materials of examples 1-4 and comparative examples 1-2, in examples 1-4, the polylactic acid prepared by the synergistic combination of flame retardant, polyimide and single-wall nano carbon and crystallization at the temperature of more than 115 ℃ has the heat distortion temperature of not less than 118 ℃ and the density of more than 1.2g/cm3The tensile strength is more than 160MPa, the flame retardant grade can reach UL-94V-0 grade, and the lowest notch impact strength is 115KJ/m2The above; comparative exampleThe crystallization temperature is too low, the synergistic effect of polyimide and single-wall nano carbon is lacked, the density is high, the secondary degradation effect is poor, the heat resistance is poor, and the use experience of a user is influenced.
Description of the attached drawings 1:
fig. 1 is a micrograph of the polylactic acid material in example 1, from which the arrangement and crystallization state of grains can be observed, and the morphological structure of the polylactic acid material is microscopically analyzed, which is convenient for analysis, popularization and application.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (10)
1. A heat-resistant modified polylactic acid material is characterized by comprising the following components in parts by weight: 50-80 parts of lactide, 2-4 parts of catalyst, 10-30 parts of chitosan, 10-26 parts of single-walled carbon nanotube, 10-20 parts of polyimide, 3-9 parts of flame retardant and 0.5-1 part of toughening agent; the crystallinity, in volume fraction, is 45 to 68%.
2. The polylactic acid material as claimed in claim 1, wherein the polylactic acid material has a heat distortion temperature of not less than 118 ℃, a crystallization temperature of 115 ℃ and 125 ℃, and a density of more than 1.2g/cm3The tensile strength is more than 160MPa, and the lowest notch impact strength is 115KJ/m2。
3. The polylactic acid material of claim 1, wherein the catalyst comprises alumina and titanium dioxide.
4. The polylactic acid material of claim 1, wherein the flame retardant comprises pseudo-boehmite, sodium lignosulfonate, and ethylenediamine.
5. The polylactic acid material of claim 4, wherein the toughening agent comprises at least one of an ethylene-methyl acrylate-glycidyl methacrylate random copolymer, a hydrogenated polystyrene-polybutadiene-polystyrene triblock copolymer, natural rubber, and polycaprolactone plastic.
6. The polylactic acid material according to claim 1, wherein the polyimide is a polyimide containing an asymmetric indole structure.
7. A method for preparing a heat-resistant modified polylactic acid material according to any one of claims 1 to 6, wherein the method comprises the following steps:
mixing lactide, a catalyst, chitosan and the single-walled carbon nanotube, and dispersing and molding to obtain single-walled carbon nanotube polylactic acid;
blending and molding the single-walled carbon nanotube polylactic acid, the polyimide, the flame retardant and the toughening agent in a molten state to obtain a blank;
and irradiating, stretching, cooling and solidifying the blank to obtain the polylactic acid material.
8. The method of claim 7, wherein said melting and said drawing are each performed above a glass transition temperature of said blank.
9. The polylactic acid material as claimed in claim 6, wherein the mass ratio of the toughening agent to the single-walled carbon nanotube polylactic acid is 1: 50-95.
10. The method of claim 7, wherein the cooling solidification occurs below a glass transition temperature of the blank.
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| CN115322543B (en) * | 2022-08-10 | 2024-05-17 | 浙江旺林生物科技有限公司 | Polylactic acid/polycaprolactone/plant carbon black composite material and preparation method thereof |
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