CN109369851B - Preparation method of starch-based foaming buffer material - Google Patents
Preparation method of starch-based foaming buffer material Download PDFInfo
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- CN109369851B CN109369851B CN201811295192.8A CN201811295192A CN109369851B CN 109369851 B CN109369851 B CN 109369851B CN 201811295192 A CN201811295192 A CN 201811295192A CN 109369851 B CN109369851 B CN 109369851B
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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
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F251/00—Macromolecular compounds obtained by polymerising monomers on to polysaccharides or derivatives thereof
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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
- C08J2351/00—Characterised by the use of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Derivatives of such polymers
- C08J2351/02—Characterised by the use of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Derivatives of such polymers grafted on to polysaccharides
Abstract
The invention relates to the technical field of foaming materials, in particular to a preparation method of a starch-based foaming buffer material, which comprises the following steps: mixing 11-17 parts of inorganic strong base, 29-34 parts of acrylic acid, 12-24 parts of acrylamide, 6-15 parts of starch, 0.4-0.6 part of initiator, 0.4-0.6 part of plasticizer and 0.4-0.6 part of cross-linking agent by weight to form a first composite humidity-controlling material; reacting the first composite humidity-controlling material with starch, potassium persulfate, glycerol and N, N-methylene-bisacrylamide to form a second composite humidity-controlling material; and heating and foaming the second composite humidity-controlling material to form the starch-based foaming buffer material. The prepared buffer material can effectively adjust the humidity of a closed space and has good moisture absorption/release performance. Meanwhile, the platform has higher stress and smaller buffer coefficient, and has excellent buffering and energy absorbing functions.
Description
Technical Field
The invention relates to the technical field of foaming materials, in particular to a preparation method of a starch-based foaming buffer material.
Background
Along with the improvement of the living standard of people, the development of the logistics industry is faster and faster, and the products are usually damaged and fail due to the action of mechanical loads such as vibration and impact in the circulation process, so that the products need to be protected by adopting a buffer packaging technical measure. The key to the cushioning protection is to select a suitable cushioning packaging material. The buffering packaging material is a protective material which can absorb a large amount of impact energy and prevent the product from being damaged by vibration and impact. The cushioning packaging materials are various in types, and the foaming material is one type with excellent comprehensive performance and most extensive application. The foam material has good buffering performance and energy absorption performance, and is often used as a buffering packaging material for transporting and packaging products such as instruments, valuables, precision instruments, electronic components and the like. However, the existing foaming material only has the functions of buffering and absorbing energy, and the failures of products such as electronic elements, instruments and meters are caused by vibration and impact and also related to the humidity of the environment.
Therefore, a method for preparing a cushioning material having both an excellent cushioning and energy absorbing function and a good moisture absorbing/releasing performance is needed.
Disclosure of Invention
The invention aims to provide a preparation method of a starch-based foaming buffer material, so that the prepared buffer material has an excellent buffering and energy absorbing function and better moisture absorbing/releasing performance.
The technical problem to be solved by the invention is realized by adopting the following technical scheme.
The invention provides a preparation method of a starch-based foaming buffer material, which comprises the following steps: mixing inorganic strong base, acrylic acid and acrylamide to form a first composite humidity-regulating material;
reacting the first composite humidity-controlling material with starch, an initiator, a plasticizer and a cross-linking agent to form a second composite humidity-controlling material;
heating and foaming the second composite humidity-controlling material to form a starch-based foaming buffer material;
the starch-based foaming buffer material is prepared from the following raw materials in parts by weight: 11-17 parts of inorganic strong base, 29-34 parts of acrylic acid, 12-24 parts of acrylamide, 6-15 parts of starch, 0.4-0.6 part of initiator, 0.4-0.6 part of plasticizer and 0.4-0.6 part of cross-linking agent.
According to the method, the starch with low cost and wide sources is used as the raw material, and is polymerized with the high-water-absorptivity monomer to prepare the starch-based foaming buffer material, and the material can effectively adjust the humidity of a closed space and has good moisture absorption/release performance. Meanwhile, the starch-based foaming buffer material has high platform stress, small buffer coefficient and excellent buffering and energy absorbing functions.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
FIG. 1 is a graph showing moisture absorption and desorption rates of starch-based foaming buffer materials for respective mass ratios of acrylic acid-sodium acrylate to acrylamide;
FIG. 2 is an SEM image of starch-based foamed conditioning materials of different mass ratios of acrylic acid-sodium acrylate to acrylamide;
FIG. 3 is a graph of a static compression test of a starch-based foaming buffer material with a mass ratio of acrylic acid-sodium acrylate to acrylamide;
FIG. 4 is a static compression test chart of the starch-based foaming buffer material and the konjac glucomannan-based foaming buffer material;
FIG. 5 is a graph showing the energy absorption curves of the starch-based foaming buffer material and the konjac glucomannan-based foaming buffer material;
FIG. 6 is a graph of the buffer coefficients of a starch-based foam buffer material and a konjac glucomannan-based foam buffer material;
FIG. 7 is an SEM image of starch-based foaming buffer materials with different starch contents;
FIG. 8 is a stress-strain curve of starch-based foamed conditioning material with different starch contents;
FIG. 9 is a graph of moisture pick-up and release rates for starch-based foams of varying starch content.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below. Those whose specific conditions are not specified in the embodiment or examples are carried out according to the conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
The following will specifically explain a method of manufacturing a starch-based foam cushion material according to an embodiment of the present invention.
The invention provides a method for preparing a composite humidity-controlling material, which comprises the steps of mixing inorganic strong base, acrylic acid and acrylamide to form a first composite humidity-controlling material;
reacting the first composite humidity-controlling material with starch, an initiator, a plasticizer and a cross-linking agent to form a second composite humidity-controlling material;
heating and foaming the second composite humidity-controlling material to form a starch-based foaming buffer material;
the starch-based foaming buffer material is prepared from the following raw materials in parts by weight: 11-17 parts of inorganic strong base, 29-34 parts of acrylic acid, 12-24 parts of acrylamide, 6-15 parts of starch, 0.4-0.6 part of initiator, 0.4-0.6 part of plasticizer and 0.4-0.6 part of cross-linking agent.
In some embodiments, the inorganic strong base may be 11 to 17 parts, or 12 to 15 parts, or 13 to 14 parts by weight of the raw materials of the starch-based foaming buffer material; the acrylic acid can be 29-34 parts, or 29-33 parts, or 30-32 parts; the acrylamide can be 12-24 parts, or 15-22 parts, or 17-20 parts; the starch can be 6-15 parts, 6-12 parts or 8-12 parts; the initiator can be 0.4-0.6 part, or 0.4-0.5 part, or 0.5-0.6 part; the plasticizer can be 0.4-0.6 part, or 0.4-0.5 part, or 0.5-0.6 part; the cross-linking agent can be 0.4-0.6 part, or 0.4-0.5 part, or 0.5-0.6 part.
The inventor creatively mixes and cross-links starch with inorganic strong base, acrylic acid and acrylamide to form a material, and then foams the material to improve the buffering and energy absorbing performance and the moisture absorbing/releasing performance of the material, and the reason may be that: acrylate, acrylamide and starch formed by neutralizing acrylic acid are polymerized under the action of an initiator, molecular chains are mutually crosslinked under the action of a crosslinking agent to form a three-dimensional network structure, and then foaming is carried out, so that the material formed by foaming has a rough surface and a large specific surface area, and functional groups can be fully contacted with water molecules, and the material has good moisture absorption and release performance.
According to some embodiments, the inorganic strong base is sodium hydroxide or potassium hydroxide, preferably the inorganic strong base is sodium hydroxide. The sodium hydroxide can better react with the acrylic acid to generate stable acrylic acid-sodium acrylate mixed solution.
According to some embodiments, the initiator is potassium persulfate, the crosslinking agent is N, N-methylene bisacrylamide, and the plasticizer is glycerol, and by using the plasticizer such as glycerol, the interaction force among starch molecular chains can be weakened, the mobility of the starch molecular chains can be increased to reduce the formation of crystals, and the elasticity and the extensibility of the starch molecular chains can be enhanced, so that the mechanical properties can be improved. Meanwhile, glycerin is further selected as a plasticizer in the crosslinking reaction process, and the plasticizer has good permeability and strong capability of forming hydrogen bonds with starch, so that the plasticizer has a good effect of improving mechanical properties, and further the final material has specific apparent density, porosity, specific surface area and surface roughness, and the characteristics are favorable for improving the moisture absorption/desorption performance and the buffering and energy absorption functions of the material.
According to some embodiments, the starch-based foamed buffer material is prepared from the following raw materials in parts by weight: 15-25 parts of sodium hydroxide, 29-60 parts of acrylic acid, 12-24 parts of acrylamide, 6-15 parts of starch, 0.4-0.6 part of potassium persulfate, 0.4-0.6 part of glycerol, 0.4-0.6 part of N, N-methylene-bisacrylamide and 23-31 parts of water.
According to some embodiments, the preparation method of the starch-based foaming buffer material specifically comprises the following steps:
s1, mixing inorganic strong base, acrylic acid and acrylamide to form the first composite humidity conditioning material.
Specifically, an inorganic strong alkali solution is dripped into acrylic acid, then the acrylic acid and the amine acrylate are mixed, and the mixture is stirred until the amine acrylate is completely dissolved, so that the first composite humidity-controlling material, namely the (acrylic acid + sodium acrylate) -acrylamide composite humidity-controlling material, is obtained. Wherein the inorganic strong alkali solution is a NaOH solution with the concentration of 28-40%, and the dropping process is carried out in a cold water bath under electromagnetic stirring. The dosage of the inorganic strong base, the acrylic acid and the acrylamide are mixed according to the proportion of the raw materials.
S2, reacting the first composite humidity conditioning material with starch, potassium persulfate, glycerol and the N, N-methylene-bisacrylamide to form a second composite humidity conditioning material.
Specifically, the starch and the first composite humidity-controlling material are mixed and stirred uniformly and then gelatinized, and the intermolecular hydrogen bonds of the starch are destroyed by heating, so that the crystalline structure of the starch is destroyed, which is beneficial to better dissolving the starch in the liquid to improve the viscosity of the mixed liquid and then better performing the crosslinking reaction. Wherein the pasting process is carried out in the stirring process, and the rotating speed is 400-500 r/min. The gelatinization temperature is 60-68 ℃, preferably 62-68 ℃, and more preferably 64-66 ℃; the gelatinization time is 25-45 min, preferably 30 min.
And (3) placing the gelatinized mixed solution at room temperature, mixing and stirring the gelatinized mixed solution with an initiator and a plasticizer uniformly, and then adding a cross-linking agent for cross-linking reaction to form a second composite humidity-controlling material, namely the starch- (acrylic acid + sodium acrylate) -acrylamide composite humidity-controlling material. Preferably, the crosslinking reaction is carried out under stirring, and the crosslinking reaction time is 40-60 min, preferably about 45 min.
And S3, heating and foaming the second composite humidity control material to form the starch-based foaming buffer material.
Specifically, the second composite humidity-controlling material is injected into a mold, and is placed in a microwave oven together with the mold for foaming, wherein the power of the microwave oven is preferably 65-75W, more preferably 70W, and the foaming time is 50-60 seconds.
Some embodiments of the invention also provide application of the starch-based foaming buffer material prepared by the preparation method in packaging materials, and the starch-based foaming buffer material can be used for manufacturing packaging bags, especially transportation packaging bags for products such as instruments, valuables, precision instruments, electronic components and the like, so that the starch-based foaming buffer material has better buffer performance, has a better humidity absorption function and avoids the products from losing efficacy due to environmental humidity.
The features and properties of the present invention are described in further detail below with reference to examples.
Example 1
1) Preparing a first composite humidity-controlling material, namely acrylic acid-sodium acrylate-acrylamide solution:
6.8g of NaOH was dissolved in 12g of water, and the dissolved NaOH was slowly dropped into 13.5g of Acrylic Acid (AA) by a dropper while stirring it with a cold water bath and with an electromagnet, and then the ratio of (acrylic acid + sodium acrylate): quantitative Acrylamide (AM) was weighed out in a mass ratio of 32.3g to 9.6g, and added to the above acrylic acid (sodium) solution, and the mixture was stirred until AM was completely dissolved. Wherein, the acrylic acid and the sodium acrylate refer to a mixed solution obtained by dripping NaOH solution.
2) Preparing a second composite humidity-controlling material, namely a starch-based composite humidity-controlling material:
weighing 6g of corn starch, adding the corn starch into the mixed solution, stirring and mixing uniformly, and gelatinizing for 40min in a water bath at the temperature of 68 ℃ and at the rotating speed of 410 r/min; after being taken out to room temperature, 0.24g of potassium persulfate and 0.24g of glycerol are added, mechanical stirring is carried out for 15min, and 0.24g N-N methylene bisacrylamide is added for continuous stirring for 40 min.
3) Starch-based buffering foaming material with humidity adjusting function
Placing a certain amount of the composite humidity-controlling material prepared in the step 2) into a mold by using an injector, then placing the mold into a microwave oven, and modulating the microwave heating time to be 50s and the power to be 75w to foam the gelatinous composite humidity-controlling material, thereby obtaining the starch-based buffer foaming material with the humidity-controlling function.
Example 2
1) Preparing a first composite humidity-controlling material, namely acrylic acid-sodium acrylate-acrylamide solution:
4.4g of NaOH was dissolved in 9.2g of water, and the dissolved NaOH was slowly dropped into 11.6g of Acrylic Acid (AA) by a dropper while stirring it with a cold water bath and with an electromagnet, and then, as a solution (acrylic acid + sodium acrylate): quantitative Acrylamide (AM) was weighed out in a mass ratio of 25.2g to 4.8g, and added to the above acrylic acid (sodium) solution, and the mixture was stirred until AM was completely dissolved. Wherein, the acrylic acid and the sodium acrylate refer to a mixed solution obtained by dripping NaOH solution.
2) Preparing a second composite humidity-controlling material, namely a starch-based composite humidity-controlling material:
weighing 2.4g of corn starch, adding into the mixed solution, stirring and mixing uniformly, and gelatinizing for 26min in a water bath at the temperature of 62 ℃ and at the rotating speed of 490 r/min; after being taken out to room temperature, 0.17g of potassium persulfate and 0.17g of glycerol are added, mechanical stirring is carried out for 15min, and 0.17g N-N methylene bisacrylamide is added for further stirring for 58 min.
3) Starch-based buffering foaming material with humidity adjusting function
Placing a certain amount of the composite humidity-controlling material prepared in the step 2) in a mould by using an injector, then placing the mould in a microwave oven, modulating the microwave heating time to be 58s and the power to be 65w, and foaming the gelatinous composite humidity-controlling material to obtain the starch-based buffer foaming material with the humidity-controlling function.
Example 3
1) Preparing a first composite humidity-controlling material, namely acrylic acid-sodium acrylate-acrylamide solution:
6g of NaOH was dissolved in 11.2g of water, and the dissolved NaOH was slowly dropped into 12.8g of Acrylic Acid (AA) by a dropper while stirring it with a cold water bath and with an electromagnet, and then, as a solution (acrylic acid + sodium acrylate): a fixed amount of Acrylamide (AM) was weighed out in a mass ratio of 30g to 8g, and added to the above acrylic acid (sodium) solution, and the mixture was stirred until AM was completely dissolved. Wherein, the acrylic acid and the sodium acrylate refer to a mixed solution obtained by dripping NaOH solution.
2) Preparing a second composite humidity-controlling material, namely a starch-based composite humidity-controlling material:
weighing 4.5g of corn starch, adding into the mixed solution, stirring and mixing uniformly, and gelatinizing for 28min in a water bath at the temperature of 66 ℃ and at the rotating speed of 460 r/min; after being taken out to room temperature, 0.21g of potassium persulfate and 0.21g of glycerol are added, mechanical stirring is carried out for 15min, and 0.21g N-N methylene bisacrylamide is added for continuous stirring for 50 min.
3) Starch-based buffering foaming material with humidity adjusting function
Placing a certain amount of the composite humidity-controlling material prepared in the step 2) in a mould by using an injector, then placing the mould in a microwave oven, and modulating the microwave heating time to be 53s and the power to be 72w to foam the gelatinous composite humidity-controlling material, thereby obtaining the starch-based buffer foaming material with the humidity-controlling function.
Influence of mass ratio of (acrylic acid + sodium acrylate) to acrylamide on performance of buffer foaming material
Example 4
1) Preparing a first composite humidity-controlling material, namely acrylic acid-sodium acrylate-acrylamide solution:
5.36g of NaOH was dissolved in 10g of water, and the dissolved NaOH was slowly added dropwise to 12g of Acrylic Acid (AA) by a dropper while stirring it with a cold water bath and an electromagnet, and then the ratio of (acrylic acid + sodium acrylate): acrylamide (AM) ═ 23.83 g: 9.53g of acrylamide was weighed out in a predetermined amount by mass ratio and added to the above acrylic acid (sodium) solution, and the mixture was stirred until AM was completely dissolved. Wherein, the acrylic acid and the sodium acrylate refer to a mixed solution obtained by dripping NaOH solution.
2) Preparing a second composite humidity-controlling material, namely a starch-based composite humidity-controlling material:
weighing 3g of corn starch, adding the corn starch into the mixed solution, stirring and mixing uniformly, and gelatinizing for 30min in a water bath at the temperature of 65 ℃ and at the rotating speed of 450 r/min; after being taken out to room temperature, 0.2g of potassium persulfate and 0.2g of glycerol are added, mechanical stirring is carried out for 15min, and 0.2g N-N methylene bisacrylamide is added for continuous stirring for 45 min.
3) Starch-based buffering foaming material with humidity adjusting function
Placing a certain amount of the composite humidity-controlling material prepared in the step 2) in a mould by using an injector, then placing the mould in a microwave oven, and modulating the microwave heating time to be 50s and the power to be 70w to foam the gelatinous composite humidity-controlling material, thereby obtaining the starch-based buffer foaming material with the humidity-controlling function.
Example 5
1) Preparing a first composite humidity-controlling material, namely acrylic acid-sodium acrylate-acrylamide solution:
5.36g of NaOH was dissolved in 10g of water, and the dissolved NaOH was slowly dropped into 12g of Acrylic Acid (AA) by a dropper while stirring it with a cold water bath and with an electromagnet, and then the ratio of (acrylic acid + sodium acrylate): quantitative Acrylamide (AM) was weighed out in a mass ratio of 25.95g to 7.41g, and added to the above acrylic acid (sodium) solution, and the mixture was stirred until AM was completely dissolved. Wherein, the acrylic acid and the sodium acrylate refer to a mixed solution obtained by dripping NaOH solution.
2) Preparing a second composite humidity-controlling material, namely a starch-based composite humidity-controlling material:
weighing 3g of corn starch, adding the corn starch into the mixed solution, stirring and mixing uniformly, and gelatinizing for 30min in a water bath at the temperature of 65 ℃ and at the rotating speed of 450 r/min; after being taken out to room temperature, 0.2g of potassium persulfate and 0.2g of glycerol are added, mechanical stirring is carried out for 15min, and 0.2g N-N methylene bisacrylamide is added for continuous stirring for 45 min.
3) Starch-based buffering foaming material with humidity adjusting function
Placing a certain amount of the composite humidity-controlling material prepared in the step 2) in a mould by using an injector, then placing the mould in a microwave oven, and modulating the microwave heating time to be 50s and the power to be 70w to foam the gelatinous composite humidity-controlling material, thereby obtaining the starch-based buffer foaming material with the humidity-controlling function.
Example 6
1) Preparing a first composite humidity-controlling material, namely acrylic acid-sodium acrylate-acrylamide solution:
5.36g of NaOH was dissolved in 10g of water, and the dissolved NaOH was slowly added dropwise to 12g of Acrylic Acid (AA) by a dropper while stirring it with a cold water bath and an electromagnet, and then the ratio of (acrylic acid + sodium acrylate): a fixed amount of Acrylamide (AM) was weighed out in a mass ratio of 27.29g to 6.07g, and added to the above acrylic acid (sodium) solution, and the mixture was stirred until AM was completely dissolved. Wherein, the acrylic acid and the sodium acrylate refer to a mixed solution obtained by dripping NaOH solution.
2) Preparing a second composite humidity-controlling material, namely a starch-based composite humidity-controlling material:
weighing 3g of corn starch, adding the corn starch into the mixed solution, stirring and mixing uniformly, and gelatinizing for 30min in a water bath at the temperature of 65 ℃ and the rotating speed of 450 r/min; after being taken out to room temperature, 0.2g of potassium persulfate and 0.2g of glycerol are added, mechanical stirring is carried out for 15min, 0.2g N is added, and stirring is continued for 45 min.
Example 7
1) Preparing a first composite humidity-controlling material, namely acrylic acid-sodium acrylate-acrylamide solution:
5.36g of NaOH was dissolved in 10g of water, and the dissolved NaOH was slowly added dropwise to 12g of Acrylic Acid (AA) by a dropper while stirring it with a cold water bath and an electromagnet, and then the ratio of (acrylic acid + sodium acrylate): a fixed amount of Acrylamide (AM) was weighed out in a mass ratio of 28.23g to 5.13g, and added to the above acrylic acid (sodium) solution, and the mixture was stirred until AM was completely dissolved. Wherein, the acrylic acid and the sodium acrylate refer to a mixed solution obtained by dripping NaOH solution.
2) Preparing a second composite humidity-controlling material, namely a starch-based composite humidity-controlling material:
weighing 3g of corn starch, adding the corn starch into the mixed solution, stirring and mixing uniformly, and gelatinizing for 30min in a water bath at the temperature of 65 ℃ and the rotating speed of 450 r/min; after being taken out to room temperature, 0.2g of potassium persulfate and 0.2g of glycerol are added, mechanical stirring is carried out for 15min, 0.2g N is added, and stirring is continued for 45 min.
3) Starch-based buffering foaming material with humidity adjusting function
Placing a certain amount of the composite humidity-controlling material prepared in the step 2) in a mould by using an injector, then placing the mould in a microwave oven, and modulating the microwave heating time to be 50s and the power to be 70w to foam the gelatinous composite humidity-controlling material, thereby obtaining the starch-based buffer foaming material with the humidity-controlling function.
The moisture control properties and static compression properties of the starch-based cushioning foams of examples 4-7 were tested by the following methods. The moisture absorption/release rate of the foaming material can be tested according to GB/T20313-2006 Standard of the cultural relic protection industry of the people's republic of China. Placing a certain mass of foamed material into a vacuum drying oven (DZF-6050, Shanghai sperm macro laboratory equipment Co., Ltd.), drying at 85 deg.C for more than 12 hr, cooling to room temperature, weighing, and recording the mass as m0. The sample was then placed in a constant temperature and humidity chamber (TEMI880, jiangsu huai an zhongya test equipment ltd) at a temperature of 25 ℃ and a humidity of 80% RH, and the sample was periodically taken out from the constant temperature and humidity chamber and weighed. Continuously measuring for 30min until the mass change of two adjacent times is less than 0.01g, and recording the sample mass as ma(ii) a Taking out the sample after fully absorbing moisture, placing into another constant temperature and humidity box with temperature of 25 deg.C and humidity of 30% RH, continuously weighing for 30min until the mass change of two adjacent times is less than 0.01g, and recording the sample mass as md(ii) a Thus, the moisture absorption rate U of the foamaAnd moisture release rate UdThe calculation can be performed according to formula (1) and formula (2), respectively:
the moisture absorption/release equilibrium humidity is measured by placing a certain amount of foaming material in a constant temperature and humidity box (25 ℃, 50% RH) for pretreatment for 12 h; respectively placing 2L glass containers in two constant temperature and humidity chambers with the temperature of 25 ℃ and the relative humidity of 80% and 30% for pretreatment for 2h to balance the temperature and the humidity in the glass containers; a high-precision hygrometer (JB913, Med instruments and meters Co., Ltd.) and the pretreated foam material were placed in two glass containers, respectively, and immediately sealed, and curves of changes in the readings of the hygrometers in the two glass containers with time were recorded. When the humidity-time curve tends to be stable, recording the humidity at the moment, namely the moisture absorption/moisture release equilibrium humidity. Static compression performance test: according to the pretreatment conditions specified in GB/T8168-2008 packaging buffer material static compression test method, the sample is pretreated for 24 hours by placing the foaming material under the conditions of 25 ℃ temperature and 50% RH humidity. The pretreated specimen was placed in an universal material testing machine (RGL-214, Riger instruments, Inc., Shenzhen) and a load was applied to the specimen at a speed of 12 mm/min. And recording load-displacement data, drawing a stress-strain curve of the sample, and analyzing the mechanical property and the energy absorption property of the sample. The test results are shown in table 1.
TABLE 1
Comparative examples 1 to 4
10g of water and 5.36g of NaOH are prepared into a solution, the prepared NaOH solution is slowly dripped into 12g of Acrylic Acid (AA) by a dropper under the conditions of cold water bath and electromagnetic stirring, and then the weight ratio of (acrylic acid + sodium acrylate) is respectively as follows: acrylamide (AM) ═ 2:1, 3: 1. 4: 1. 5: weighing a certain amount of acrylamide according to the mass ratio of 1, adding the acrylamide into the acrylic acid (sodium) solution, and continuously stirring until the AM is completely dissolved.
Weighing 0.1g of KGM, adding the KGM into the mixed solution, stirring for 10min to uniformly mix the KGM in the solution, adding N, N-methylene-bisacrylamide, and continuing stirring for 10 min. Adding span and stirring for 10min, and finally adding potassium persulfate and stirring for 10 min.
The prepared composite humidity controlling material is placed in a microwave oven, the microwave heating time is adjusted to be 1 minute, the power is adjusted to be 122.5w, and the gelatinous composite humidity controlling material is foamed.
The comparative examples 1 to 4 were also subjected to the performance test according to the above test method, and the results are shown in table 2.
TABLE 2
By comparing the data in tables 1 and 2, it can be seen that the moisture absorption and release rate of the starch-based foaming buffer material is higher than that of the konjac glucomannan-based foaming material, and the moisture absorption and release rate of the starch-based foaming buffer material can reach about 70% and 56% respectively.
Further, the re-supplementation only has a mass ratio of 6.5: 1, and the starch-based foaming buffer material prepared by the method with the other conditions being the same as the example 7. The above test results show that fig. 1 is a graph of moisture absorption and desorption rates of the foam cushioning material in different mass ratios of acrylic acid-sodium acrylate to acrylamide in the examples of the present invention. In fig. 1, a is a curve of moisture absorption rate, and b is a curve of moisture release rate. It can be seen from fig. 1 that the moisture absorption and desorption rate of the material increases as the mass ratio increases. This is because the content of the hydrophilic group sodium carboxylate and the hydroxyl group increases with an increase in the mass ratio, and the water absorption performance increases; wherein, three groups of amide group, hydroxyl and sodium carboxylate can generate synergistic action, which can improve the moisture absorption and release performance of the material; with the increase of the mass ratio, the viscosity of the system is increased, and the foam holes of the gel are more uniform during microwave foaming, so that the absorption and release performance of the material is increased; the surface area of the material is rough, and if the specific surface area is large, the contact between the functional groups and water molecules is increased, so that the moisture absorption and release performance of the material is improved. Scanning electron microscope analysis is performed on the starch-based foaming buffer materials of examples 4-7 through a scanning electron microscope, so as to obtain a graph shown in fig. 3, wherein the graph shown in fig. 3 is an SEM image of the starch-based foaming humidity-controlling material with different mass ratios of acrylic acid-sodium acrylate to acrylamide, and the corresponding ratios are as follows: (a)2.5: 1; (b)3.5: 1; (c)4.5: 1; (d)5.5: 1.
From FIG. 2 and Table 1, it can be seen that when the mass ratio of acrylic acid-sodium acrylate to acrylamide is 4.5:1, the cells of the starch-based foaming humidity-controlling material are most uniform and regular because: along with the increase of the mass ratio of the acrylic acid-sodium acrylate to the acrylamide, the viscosity of the humidity-regulating material is increased, so that bubbles can be effectively wrapped, the number of foam holes is increased, and the foaming of the starch-based humidity-regulating material is facilitated; however, when the mass ratio of acrylic acid-sodium acrylate to acrylamide is too large, the viscosity of the humidity control material system is too high, a large amount of bubbles cannot grow, and the power provided by water evaporation is smaller than the surface tension and the resistance provided by starch, so that the cells are difficult to grow, the number of the cells is reduced, and the foaming effect is poor.
Further, fig. 3 is a static compression test chart of the starch-based foaming buffer material of the mass ratio of acrylic acid-sodium acrylate to acrylamide. Fig. 4, fig. 5 and fig. 6 are the mechanical property diagrams of the starch-based foaming buffer material and the konjac glucomannan-based foaming buffer material.
As can be seen from the results in fig. 3 and table 1, the stress-strain curve of the starch-based foaming buffer in the mass of acrylic acid-sodium acrylate and acrylamide is divided into 3 stages: an elastic phase, a yield plateau phase and a dense phase. And (3) an elastic stage: when the strain is small, the foaming material is in a linear elastic region and generates elastic deformation, and the strength characteristic of a pore structure is mainly reflected; a yield plateau stage: as the pressure increases, the material begins to plastically deform and enter the yield plateau region, and during a relatively long deformation, as the strain increases, the stress remains substantially constant, indicating that the material is able to continue to absorb energy at a nearly constant stress plateau. From fig. 4 it is seen that the yield plateau phase is around 10% -70% strain; a densification stage: continuing to pressurize, the foam enters a densification stage, which indicates that the voids of the cushioning packaging material are nearly compacted and the stress rises sharply. This stage indicates that the voids of the cushioning packaging material are nearly compacted and the stress rises sharply. It can be seen from fig. 3 that when the mass ratio is 5.5:1, the yield platform of the foam material tends to be flat, the stress is large, and the buffering effect is good. With the increase of the mass ratio, the viscosity of the system is increased, which is beneficial to the uniform growth of cells, so that the buffering performance of the material is increased.
From fig. 4, 5 and 6, it can be seen that the mechanical properties of the starch-based foaming material are better than those of the konjac glucomannan-based foaming material. From fig. 4, it can be seen that the platform stress of the starch-based foam material is 0.534MPa, which is greater than that of the konjac glucomannan-based foam material, and the buffer platform is also wider than that of the konjac glucomannan-based foam material. The buffering efficiency is an important parameter for judging whether the buffering packaging material is reasonable, but the buffering coefficient C, namely the reciprocal of the buffering efficiency, is commonly used for measuring the buffering performance of the sample. A smaller buffer coefficient C, i.e. a higher buffer efficiency, indicates more energy absorbed per unit volume of the sample, so that a minimum value of the buffer coefficient generally indicates an optimum use of the sample. From fig. 5, it can be seen that the buffer coefficient of the starch-based foaming buffer material is 3.2, the buffer coefficient of the konjac glucomannan-based foaming material is 4.1, and from fig. 6, the absorption energy of the starch-based foaming buffer material is greater than that of the konjac glucomannan-based foaming material under the same stress, so that the mechanical property of the starch-based foaming buffer material is better.
Effect of starch content on the Properties of cushioning foams
Examples 8 to 10:
examples 8 to 10 differ from example 4 only in the use of starch contents of 2g, 4g and 5g in this order.
Analyzing the starch-based foaming buffer materials obtained in the embodiments 8, 4 and 9-10 by a scanning electron microscope to obtain fig. 8, wherein the starch content corresponding relationship in fig. 8 is as follows: (a)2g of starch; (b)3g of starch; (c)4g of starch; (d)5g of starch.
As can be seen from FIG. 7, when the starch content is 3g, the cells of the starch-based foaming conditioning material are most uniform and regular. The reason is that more starch granules are gelatinized and expanded along with the increase of the starch content, so that the viscosity of the humidity-adjusting material is increased, air bubbles can be effectively wrapped, the number of foam holes is increased, and the foaming of the starch-based humidity-adjusting material is facilitated; however, when the starch content is too high, too many starch molecular chains are entangled to form a bulk structure, so that the viscosity of the humidity-controlling material system is too high, a large amount of bubbles cannot grow, the number of foam cells is reduced, and the foaming effect is poor. When the starch content is 2g, the cells of the starch-based foaming humidity-controlling material are large, and the foaming humidity-controlling material has a retraction phenomenon.
Further, the stress-strain curves of the starch-based foaming conditioning materials with different starch contents are shown in FIG. 8. As can be seen from FIG. 8, with the increase of the starch content, the plateau stress of the starch-based foaming humidity-controlling material increases first and then decreases, and when the starch content is 3g, the yield stress of the starch-based foaming material reaches 0.646MPa, the yield stress plateau is wider, the buffer coefficient is the smallest, and the usability of the material is the best. The gelatinization degree of the starch granules is improved after heating and gelatinization, so that the viscosity of a system is continuously improved, and when microwave foaming is carried out, foam holes are more regular and more uniform in distribution, so that the foam holes are not easily compressed, the yield stress of the material is increased, and the buffer coefficient is reduced; however, when the starch is excessive, molecular chains are tangled to form a bulk structure, the viscosity of the system is too high, a large amount of bubbles cannot grow, the number of bubbles is reduced, the foaming effect is poor, the yield stress is reduced, the buffer coefficient is increased, and the buffer performance is poor. Further, moisture absorption and desorption rate curves of the starch-based foaming materials with different starch contents are shown in FIG. 9. As can be seen from fig. 9, the moisture absorption and release rates of the starch-based foam materials are all decreased as the starch content is increased. This is because starch is mainly used to provide a skeleton with a cross-linked network structure, and when the amount of starch is too large, the formed polymer network skeleton is large, the number of polymer branches is large, and the network space of the starch-based foaming humidity-controlling material is small, which is not beneficial to moisture absorption and desorption, so the moisture absorption and desorption rate of the starch-based foaming material is reduced. When the starch content is 2g, the moisture absorption and release of the starch-based foaming humidity control material reaches 67.91% and 52.16% respectively, but when the starch content is 2g, the viscosity of the system is too small, the foam pores are large during foaming, the foaming humidity control material has a retraction phenomenon, and the buffer performance is poor; when the starch content is 3g, the moisture absorption and release rates of the starch-based foaming humidity-controlling material are 66.23 and 51.34, respectively, which are not different from the moisture absorption and release rates of the starch-based foaming humidity-controlling material when the starch content is 2g, and the buffering performance is the best when the starch content is 3g, so that the starch content is 3 g.
In conclusion, the starch with lower cost and wider source compared with konjac glucomannan is used as the raw material, and is polymerized with the high-water-absorptivity monomer and then soaked under the microwave condition to obtain the starch-based foaming buffer material with adjustable humidity, and the moisture absorption and release capacity of the material can reach 70% and 56% respectively. Meanwhile, the platform stress of the starch-based humidity-regulating foaming material prepared by the invention is improved by 0.134MPa and the buffer coefficient is small by 0.9 compared with that of the konjac glucomannan-based humidity-regulating material.
The embodiments described above are some, but not all embodiments of the invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Claims (14)
1. A preparation method of a starch-based foaming buffer material is characterized by comprising the following steps of;
mixing inorganic strong base, acrylic acid and acrylamide to form a first composite humidity-regulating material;
reacting the first composite humidity-controlling material with starch, an initiator, a plasticizer and a cross-linking agent to form a second composite humidity-controlling material;
heating and foaming the second composite humidity-controlling material to form the starch-based foaming buffer material;
the starch-based foaming buffer material is prepared from the following raw materials in parts by weight: 11-17 parts of inorganic strong base, 29-34 parts of acrylic acid, 12-24 parts of acrylamide, 6-15 parts of starch, 0.4-0.6 part of initiator, 0.4-0.6 part of plasticizer and 0.4-0.6 part of cross-linking agent.
2. The method for preparing the starch-based foaming buffer material according to claim 1, wherein the inorganic strong base is sodium hydroxide or potassium hydroxide;
the initiator is potassium persulfate;
the plasticizer is glycerol;
the cross-linking agent is N, N-methylene bisacrylamide.
3. The method for preparing starch-based foaming buffer material according to claim 2, wherein the inorganic strong base is sodium hydroxide.
4. The preparation method of the starch-based foaming buffer material according to claim 3, characterized in that the raw materials for preparing the starch-based foaming buffer material are as follows in parts by weight: 11-17 parts of sodium hydroxide, 29-34 parts of acrylic acid, 12-24 parts of acrylamide, 6-15 parts of starch, 0.4-0.6 part of initiator, 0.4-0.6 part of plasticizer, 0.4-0.6 part of cross-linking agent and 23-31 parts of water.
5. The method for preparing the starch-based foaming buffer material according to claim 1, wherein the mixing of the inorganic strong base, the acrylic acid and the acrylamide specifically comprises:
and dropwise adding an inorganic strong base solution prepared from the inorganic strong base into the acrylic acid, and mixing the solution and the acrylamide at normal temperature until the acrylamide is completely dissolved.
6. The method for preparing the starch-based foaming buffer material according to claim 5, wherein the concentration of the inorganic strong alkali solution is 28-40% by mass.
7. The method for preparing the starch-based foaming buffer material according to claim 5, wherein the process of dripping the inorganic strong alkali solution is carried out under cold water bath and electromagnetic stirring.
8. The method for preparing the starch-based foaming buffer material according to claim 5, wherein the reacting the first composite humidity controlling material with the starch, the initiator, the plasticizer and the cross-linking agent specifically comprises:
and uniformly mixing the starch and the first composite humidity-controlling material, gelatinizing, mixing with the initiator, the plasticizer and the cross-linking agent at room temperature, and reacting.
9. The method for preparing the starch-based foaming buffer material according to claim 8, wherein the mixture of the starch and the first composite humidity-controlling material after gelatinization is uniformly mixed with the initiator and the plasticizer at room temperature, and then is mixed with a cross-linking agent for reaction.
10. The preparation method of the starch-based foaming buffer material according to claim 8, wherein the gelatinization temperature is 60-68 ℃; the gelatinization time is 25-45 min.
11. The method for preparing the starch-based foaming buffer material according to claim 10, wherein the gelatinization temperature is 62-68 ℃.
12. The method for preparing the starch-based foaming buffer material according to claim 10, wherein the gelatinization temperature is 64-66 ℃.
13. The method for preparing the starch-based foaming buffer material according to claim 5, wherein the heating foaming of the second composite humidity control material is carried out by placing the second composite humidity control material in a mold and heating foaming in a microwave oven.
14. The method for preparing the starch-based foaming buffer material according to claim 13, wherein the microwave heating time is 50-60 s and the power is 65-75 w.
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