Preparation method of modified chitin whisker reinforced and toughened PBAT micro-foamed composite material
By introducing PBAT segments onto the surface of chitin whiskers and synergistically working with chain extenders, the problems of low strength and poor foaming performance of PBAT materials were solved, achieving efficient biodegradability and excellent mechanical properties.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- GUIZHOU MATERIAL IND TECH INSTITUE
- Filing Date
- 2023-09-01
- Publication Date
- 2026-08-04
AI Technical Summary
Existing PBAT materials have low strength and are difficult to uniformly disperse traditional reinforcing agents, resulting in decreased biodegradability and poor foaming performance.
Modified chitin whiskers were used as reinforcing agents. By introducing PBAT segments on their surface, compatibility was improved, and the melt strength and viscosity were increased in synergy with chain extenders.
It has achieved improvements in the biodegradability and mechanical properties of PBAT materials, as well as improvements in foaming quality, resulting in significant reinforcement and toughening effects.
Smart Images
Figure BDA0004427732920000051 
Figure BDA0004427732920000091
Abstract
Description
Technical Field
[0001] This invention belongs to the field of polymer materials, specifically relating to a method for preparing a modified chitin whisker-reinforced and toughened PBAT microfoamed composite material. Background Technology
[0002] Plastics, rubber, and synthetic fibers, as synthetic polymers, are widely used in people's production and daily lives. However, these materials are often discarded into the natural environment after use, causing serious pollution to soil, rivers, and oceans due to their difficulty in degradation. To address this problem, countries worldwide have begun to focus on the research and development of biodegradable materials. Biodegradable materials can be broken down by microorganisms, and under composting conditions, they can even be completely degraded within weeks, transforming into nutrients that plants can absorb. Foamed materials have attracted attention due to their advantages such as lightweight, cushioning, and insulation. If biodegradable plastics can be organically combined with foamed materials to develop biodegradable plastic foamed materials, it will not only significantly reduce material costs and broaden their application range, but also provide new solutions for environmental protection and sustainable development. This is of great significance for achieving resource recycling and reducing plastic pollution. Therefore, biodegradable plastic foamed materials have attracted great attention from academia and industry.
[0003] Polybutylene terephthalate (PBAT) is a biodegradable polyester that combines the degradation properties of aliphatic polyesters with the mechanical properties of aromatic polyesters. PBAT exhibits excellent toughness, with an elongation at break of 600%-800%, thus possessing great potential to replace traditional petroleum-based flexible foam materials. However, PBAT has relatively low strength, and traditional reinforcing agents such as glass fiber, carbon fiber, and basalt fiber are made from non-degradable materials. These reinforcing agents cannot be effectively broken down by microorganisms during biodegradation, contradicting the goal of biodegradability. Using traditional reinforcing agents to reinforce PBAT negates its sustainability advantages as a biodegradable material, and these reinforcing agents are difficult to disperse uniformly in the PBAT matrix, resulting in ineffective reinforcement. Therefore, finding sustainable and environmentally friendly alternative reinforcing agents is crucial. These alternatives should be compatible with biodegradable materials and produce environmentally friendly decomposition products during degradation, reducing potential risks to the environment and health. On the other hand, PBAT molecular chains have a linear structure, resulting in low melt strength and weak melt viscoelasticity. At higher foaming temperatures, the melt strength and viscosity of the entire system decrease sharply, leading to cell collapse and poor foaming quality. Therefore, improving the foaming performance of PBAT has become a key focus for those skilled in the art. Summary of the Invention
[0004] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.
[0005] In view of the problems existing in the above and / or prior art, the present invention is proposed.
[0006] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a modified chitin whisker-reinforced and toughened PBAT microfoamed composite material.
[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for preparing a modified chitosan whisker-reinforced and toughened PBAT microfoamed composite material, comprising,
[0008] Chitosan whiskers (CHW) were mixed with 1,4-butanediol (BDO) and dispersed evenly. Then, 1,6-adipic acid (AA) and terephthalic acid (TPA) were added to obtain the reaction system.
[0009] The reaction system was heated to 180–200°C, a catalyst was added, and esterification was carried out under a nitrogen atmosphere for 6–8 hours.
[0010] Then the temperature is raised to 230-240℃ and polycondensed at 80-120 Pa for 3-4 hours until the viscosity of the reactants no longer increases, thus obtaining the PBAT / CHW composite.
[0011] The PBAT / CHW complex was purified, and the precipitate was washed, centrifuged and dried to obtain PBAT-grafted modified chitin nanofibers CHW-g-PBAT.
[0012] The dried PBAT, CHW-g-PBAT and chain extender are melt-blended to obtain the modified chitin whisker-reinforced and toughened PBAT composite material.
[0013] The modified chitosan whisker-reinforced and toughened PBAT microfoamed composite material is obtained by adding chitosan whisker-reinforced and toughened PBAT composite material and foaming agent into an injection molding machine and then using chemical microfoaming injection molding.
[0014] As a preferred embodiment of the preparation method described in this invention, the chitin whiskers are high-rigidity organic whisker reinforcements prepared by sulfuric acid hydrolysis using natural shrimp and crab shell powder as raw material, with a whisker diameter of 20-100 nm and an aspect ratio of 20:1-50:1.
[0015] As a preferred embodiment of the preparation method described in this invention, the chitin whiskers (CHW) contain 1-3 wt% of the total mass of acid and alcohol (BDO+AA+TPA), the molar ratio of 1,6-adipic acid (AA) to terephthalic acid (TPA) is 40:60-60:40, and the molar ratio of alcohol to acid (BDO:AA+TPA) is 1:1-1.6:1.
[0016] In a preferred embodiment of the preparation method described in this invention, the catalyst is one or more of tetrabutyl titanate, tetraethyl titanate, or tetraisopropyl titanate, and the molar ratio of the catalyst to acid AA+TPA is 1-5:1000.
[0017] In a preferred embodiment of the preparation method described in this invention, the PBAT / CHW complex is purified and the precipitate is washed, wherein the purification solvent is chloroform and the washing solvent is chloroform.
[0018] As a preferred embodiment of the preparation method described in this invention, the dried PBAT, CHW-g-PBAT and chain extender are melt-blended, wherein the chain extender is any one or more combinations of epoxy compound, dianhydride, diisocyanate, phosphite or dioxazoline; the melt-blending instrument is a circulating twin-screw internal mixer, the temperature of the circulating twin-screw internal mixer is 160-190℃, and the time is 5-20 min.
[0019] As a preferred embodiment of the preparation method described in this invention, the weight parts of PBAT, CHW-g-PBAT and chain extender are as follows: PBAT is 95-99.9 parts, CHW-g-PBAT is 0.1-5 parts, and chain extender is 1-5 parts.
[0020] As a preferred embodiment of the preparation method described in this invention, the chitosan whisker-reinforced and toughened PBAT composite material and the foaming agent are added to the injection molding machine, wherein the foaming agent is one of azodicarbonamide AC, sodium bicarbonate and 4,4'-oxobis(benzenesulfonyl)hydrazine hydrazine (OBSH); the weight ratio of chitosan whisker-reinforced and toughened PBAT composite material particles to foaming agent is 100:1 to 100:5.
[0021] As a preferred embodiment of the preparation method described in this invention, the method employs chemical micro-foaming injection molding, wherein the injection temperature is 160–190°C, the injection speed is 120–200 mm / s, the injection pressure is 100–200 MPa, and the mold retraction distance is 0.6–2 mm.
[0022] Another objective of this invention is to overcome the shortcomings of the prior art and provide a modified chitin whisker-reinforced and toughened PBAT microfoamed composite material.
[0023] Beneficial effects of this invention:
[0024] (1) This invention selects biodegradable and high-modulus chitin whiskers as a reinforcing agent. Chitin whiskers have high modulus and are biodegradable, making them a highly efficient and environmentally friendly nanofiber reinforcing agent that enables PBAT-based reinforced composites to achieve complete biodegradation. Through surface modification technology, PBAT segments with the same composition as the PBAT matrix are introduced onto the surface of the chitin whiskers. This design enables the chitin whiskers to have good compatibility with the matrix, thereby achieving full dispersion in the matrix. The PBAT segments grafted onto the surface of the chitin whiskers can achieve bonding and molecular chain entanglement with the PBAT matrix, which helps to solve key problems such as the difficulty in uniformly dispersing the reinforcing filler in composites and the weak interfacial bonding force between the filler and the matrix. Chitin whiskers uniformly distributed in the PBAT matrix can more effectively transfer shear stress through various means such as load transfer, pull-out effect, crack deflection, and crack bridging. This design achieves the dual effects of reinforcement and toughening, enabling the grafted and modified chitin whiskers to improve the mechanical properties of PBAT-based composites more effectively than traditional reinforcing agents.
[0025] (2) The chitin whiskers grafted and modified in this invention can entangle with the molecular chains of the matrix PBAT, increase the intermolecular forces, and reduce the mobility of the molecular chains. This helps to appropriately increase the melt viscosity of PBAT and prevent the foaming process from cracking and merging. In addition, the chitin whiskers can also work together with the chain extender to increase the branching degree of the PBAT molecular chains, transforming them from a linear structure to a three-dimensional structure, thereby increasing the melt strength of PBAT and improving its foaming performance.
[0026] (3) The chitin whiskers grafted and modified in this invention can be used as a reinforcing agent to strengthen and toughen PBAT resin, and can also work synergistically with chain extenders to improve the melt viscosity and melt strength of the PBAT matrix, thereby improving its foaming performance. Detailed Implementation
[0027] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.
[0028] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.
[0029] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.
[0030] The chitin whiskers are derived from natural shrimp and crab shells. The preparation method is as follows: commercially available chitin powder is purified by acid hydrolysis in sulfuric acid solution. The purified product is centrifuged, the supernatant is removed, and the precipitate is collected. The precipitate is repeatedly washed with deionized water by centrifugation, and then dialyzed in a dialysis bag, with the deionized water being changed several times until the pH of the solution inside and outside the dialysis bag is 7. The dialyzed product is ultrasonically dispersed and then freeze-dried to obtain chitin nano-whisker powder.
[0031] Unless otherwise specified, all other materials used in the embodiments of this invention were purchased from the market.
[0032] Performance testing method in the embodiments of this invention:
[0033] Tensile strength and elongation at break tests: Tested according to GB / T1040.2-2006, tensile rate 50 mm / min, 5 samples per group, and average value is taken.
[0034] Density test: Apparent density was tested according to GB / T1033.1-2008. Five samples were tested in each group, and the average value was taken.
[0035] Cell structure characterization: After immersing the sample in liquid nitrogen for 5 hours, it was removed, broken, and gold was sputtered onto the fracture surface. The cell structure was observed under a scanning electron microscope (SEM) at a test voltage of 20 kV. The SEM images were processed using Image-Pro Plus software, from which the average diameter of the cells could be calculated. Based on the number of cells n in the SEM image, the image area A (cm2) and the density ρ0 of the unfoamed sample and ρ1 of the foamed sample were determined. The cell density N was estimated using the following formula:
[0036]
[0037] Example 1
[0038] (1) Chitosan whiskers (CHW) with a total mass of 1 wt% of dicarboxylic acid and diol and 1.3 mol of 1,4-butanediol (BDO) were mixed and the CHW was uniformly dispersed by a high-energy ultrasonic probe. Then, 0.5 mol of 1,6-adipic acid (AA) and 0.5 mol of terephthalic acid (TPA) were added. The reaction system was heated to 180 °C and 0.002 mol of tetrabutyl titanate was added as a catalyst. Esterification was carried out for 7 h under a nitrogen atmosphere. Then, the temperature was raised to 230 °C and polycondensation was continued for 4 h under 80 Pa. Polycondensation was stopped when the viscosity of the reactants did not continue to increase, and the PBAT / CHW composite was obtained.
[0039] (2) The PBAT / CHW complex was purified by chloroform as solvent. The precipitate was collected, washed with chloroform, and centrifuged. The purified product was dried in a vacuum drying oven at 40℃ for 24h to obtain PBAT-grafted modified chitin nanowhiskers (CHW-g-PBAT).
[0040] (3) Combine the dried PBAT (99 parts), CHW-g-PBAT (1 part), and chain extender (epoxy chain extender) PBAT composite material was obtained by melt blending 43,701 parts of ADR using a circulating twin-screw internal mixer.
[0041] (4) Chitosan whisker-reinforced and toughened PBAT composite material and azodicarbonamide were added to an injection molding machine at a weight ratio of 100:2 and chemical micro-foaming injection molding was used with a mold opening distance of 1.6 mm to obtain PBAT micro-foamed composite material.
[0042] Tests showed that the tensile strength of the prepared PBAT composite material was 30 MPa, and the elongation at break was 850%; the density of the prepared PBAT microfoamed composite material was 0.94 g / cm³. 3 The cell size is 35.3 μm and the cell density is 6.8 × 10⁻⁶. 7 pcs / cm 3 The tensile strength of the PBAT microfoamed composite material is 26 MPa, and the elongation at break is 660%.
[0043] Example 2
[0044] The preparation method of PBAT-grafted modified chitin nanocrystals (CHW-g-PBAT) is the same as in Example 1.
[0045] The dried PBAT (99.9 parts), CHW-g-PBAT (0.1 parts), and chain extender (epoxy chain extender) were then added. ADR 43703 parts) were melt-blended in a circulating twin-screw internal mixer to obtain PBAT composite material;
[0046] PBAT composite material and azodicarbonamide were added to an injection molding machine at a weight ratio of 100:2, and chemical microfoaming injection molding was used with a mold opening distance of 1.6 mm to obtain PBAT microfoamed composite material.
[0047] Tests showed that the tensile strength of the prepared PBAT composite material was 26 MPa, and the elongation at break was 760%; the density of the prepared PBAT microfoamed composite material was 0.92 g / cm³. 3 The cell size is 38.2 μm and the cell density is 5.3 × 10⁻⁶. 7 pcs / cm 3 The PBAT microfoamed composite material has a tensile strength of 24 MPa and an elongation at break of 670%.
[0048] Example 3
[0049] The preparation method of PBAT-grafted modified chitin nanocrystals (CHW-g-PBAT) is the same as in Example 1.
[0050] The dried PBAT (97 parts), CHW-g-PBAT (3 parts), and chain extender (epoxy chain extender) were added. ADR43701 parts) were melt-blended in a circulating twin-screw internal mixer to obtain PBAT composite material;
[0051] PBAT composite material and azodicarbonamide were added to an injection molding machine at a weight ratio of 100:2, and chemical microfoaming injection molding was used with a mold opening distance of 1.6 mm to obtain PBAT microfoamed composite material.
[0052] Tests showed that the tensile strength of the prepared PBAT composite material was 36 MPa, and the elongation at break was 900%; the density of the prepared PBAT microfoamed composite material was 0.94 g / cm³. 3 The cell size is 21.7 μm, and the cell density is 9.2 × 10⁻⁶. 7 pcs / cm 3 The tensile strength of the PBAT microfoamed composite material is 28 MPa, and the elongation at break is 680%.
[0053] Example 4
[0054] The preparation method of PBAT-grafted modified chitin nanocrystals (CHW-g-PBAT) is the same as in Example 1.
[0055] The dried PBAT (95 parts), CHW-g-PBAT (5 parts), and chain extender (epoxy chain extender) were added. ADR43703 parts) were melt-blended in a circulating twin-screw internal mixer to obtain PBAT composite material;
[0056] PBAT composite material and azodicarbonamide were added to an injection molding machine at a weight ratio of 100:2, and chemical microfoaming injection molding was used with a mold opening distance of 1.6 mm to obtain PBAT microfoamed composite material.
[0057] Tests showed that the tensile strength of the prepared PBAT composite material was 45 MPa, and the elongation at break was 820%; the density of the prepared PBAT microfoamed composite material was 0.97 g / cm³. 3 The cell size is 40.3 μm and the cell density is 5.8 × 10⁻⁶. 7 pcs / cm 3 The tensile strength of the PBAT microfoamed composite material is 33 MPa, and the elongation at break is 620%.
[0058] Comparative Example 1
[0059] The preparation method of PBAT-grafted modified chitin nanocrystals (CHW-g-PBAT) is the same as in Example 1.
[0060] The dried PBAT (93 parts), CHW-g-PBAT (7 parts), and chain extender (epoxy chain extender) were then added. ADR43702 parts) were melt-blended in a circulating twin-screw internal mixer to obtain PBAT composite material;
[0061] PBAT composite material and azodicarbonamide were added to an injection molding machine at a weight ratio of 100:2, and chemical microfoaming injection molding was used with a mold opening distance of 1.6 mm to obtain PBAT microfoamed composite material.
[0062] Tests showed that the tensile strength of the prepared PBAT composite material was 46 MPa, and the elongation at break was 610%; the density of the prepared PBAT foamed composite material was 1.03 g / cm³. 3 The cell size is 52.8 μm and the cell density is 3.3 × 10⁻⁶. 7 pcs / cm 3 The tensile strength of the composite foam material is 31 MPa, and the elongation at break is 430%.
[0063] Comparative Example 2
[0064] The preparation method of PBAT-grafted modified chitin nanocrystals (CHW-g-PBAT) is the same as in Example 1.
[0065] The dried PBAT (90 parts), CHW-g-PBAT (10 parts) and chain extender (2 parts) were melt-blended in a circulating twin-screw internal mixer to obtain PBAT composite material;
[0066] PBAT composite material and azodicarbonamide were added to an injection molding machine at a weight ratio of 100:2, and chemical microfoaming injection molding was used with a mold opening distance of 1.6 mm to obtain PBAT microfoamed composite material.
[0067] Tests showed that the tensile strength of the prepared PBAT composite material was 48 MPa, and the elongation at break was 340%; the density of the prepared PBAT foam composite material was 1.05 g / cm³. 3 The cell size is 65.3 μm and the cell density is 1.8 × 10⁻⁶. 7 pcs / cm 3 The tensile strength of the composite foam material is 35 MPa, and the elongation at break is 260%.
[0068] Comparative Example 3
[0069] Add dried PBAT (100 parts) and chain extender (epoxy chain extender) ADR 43703 parts) were melt-blended in a circulating twin-screw internal mixer to obtain PBAT composite material;
[0070] PBAT composite material and azodicarbonamide were added to an injection molding machine at a weight ratio of 100:2, and chemical microfoaming injection molding was used with a mold opening distance of 1.6 mm to obtain PBAT microfoamed composite material.
[0071] Tests showed that the tensile strength of the prepared PBAT composite material was 24 MPa, and the elongation at break was 750%; the density of the prepared PBAT foam composite material was 0.93 g / cm³. 3 The cell size is 45.6 μm and the cell density is 4.8 × 10⁻⁶. 7 pcs / cm 3 The tensile strength of the composite foam material is 20 MPa, and the elongation at break is 600%.
[0072] Comparative Example 4
[0073] The dried PBAT (99 parts), CHW (1 part), and chain extender (epoxy chain extender) were then added. ADR 43701 parts) were melt-blended in a circulating twin-screw internal mixer to obtain PBAT composite material;
[0074] PBAT composite material and azodicarbonamide were added to an injection molding machine at a weight ratio of 100:2, and chemical microfoaming injection molding was used with a mold opening distance of 1.6 mm to obtain PBAT microfoamed composite material.
[0075] Tests showed that the tensile strength of the prepared PBAT composite material was 26 MPa, and the elongation at break was 680%; the density of the prepared PBAT foamed composite material was 0.98 g / cm³.3 The cell size is 48.6 μm and the cell density is 2.1 × 10⁻⁶. 7 pcs / cm 3 The tensile strength of the composite foam material is 18 MPa, and the elongation at break is 470%.
[0076] Comparative Example 5
[0077] The dried PBAT (99 parts), glass fiber (1 part), and chain extender (epoxy chain extender) are then added. ADR4370 (1 part) was melt-blended in a circulating twin-screw internal mixer to obtain PBAT composite material;
[0078] PBAT composite material and azodicarbonamide were added to an injection molding machine at a weight ratio of 100:2, and chemical microfoaming injection molding was used with a mold opening distance of 1.6 mm to obtain PBAT microfoamed composite material.
[0079] Tests showed that the tensile strength of the prepared PBAT composite material was 27 MPa, and the elongation at break was 500%; the density of the prepared PBAT microfoamed composite material was 1.14 g / cm³. 3 The cell size is 72.5 μm and the cell density is 7.3 × 10⁻⁶. 6 pcs / cm 3 The tensile strength of the PBAT microfoamed composite material is 19 MPa, and the elongation at break is 390%.
[0080] Comparative Example 6
[0081] The dried PBAT (99 parts) and CHW-g-PBAT (1 part) were melt-blended in a circulating twin-screw internal mixer to obtain PBAT composite material.
[0082] PBAT composite material and azodicarbonamide were added to an injection molding machine at a weight ratio of 100:2, and chemical microfoaming injection molding was used with a mold opening distance of 1.6 mm to obtain PBAT microfoamed composite material.
[0083] Tests showed that the tensile strength of the prepared PBAT composite material was 30 MPa, and the elongation at break was 820%; the density of the prepared PBAT foamed composite material was 0.96 g / cm³. 3 The cell size is 41.6 μm and the cell density is 5.5 × 10⁻⁶. 7 pcs / cm 3 The tensile strength of the composite foam material is 24 MPa, and the elongation at break is 620%.
[0084] The test results of Examples 1-4 and Comparative Examples 1-6 are shown in Table 1:
[0085] Table 1 Comparison of Test Results
[0086]
[0087] As can be seen from Table 1:
[0088] As shown in Examples 1-4 and Comparative Examples 1-3, adding an appropriate amount of PBAT grafted with chitin whiskers can effectively strengthen and toughen PBAT. The modified PBAT has a lower apparent density after foaming, and exhibits smaller cell diameter and higher cell density, demonstrating excellent foaming performance. However, when the content of CHW-g-PBAT is low, this strengthening and toughening effect is not obvious. Conversely, if the content of CHW-g-PBAT is too high, it is prone to agglomeration in the matrix, which leads to a reduction in the free volume of PBAT molecular chains and restricts their movement. This situation will significantly reduce the elongation at break of the PBAT composite material; at the same time, an excessively high CHW-g-PBAT content will lead to an increase in the density of the foamed PBAT microfoamed composite material, an increase in cell diameter, and a decrease in cell density. This not only reduces its mechanical properties but also affects the foaming quality.
[0089] As shown in Examples 1 and Comparative Examples 4-5, compared to glass fiber and chitin whiskers, PBAT-grafted chitin whiskers significantly improve the tensile strength and elongation at break of PBAT. Therefore, CHW-g-PBAT more efficiently toughens and strengthens PBAT. Simultaneously, the PBAT / CHW-g-PBAT microfoamed composite material has lower density, smaller cell diameter, and higher cell density, indicating that PBAT-grafted chitin whiskers are more conducive to improving the foaming properties of PBAT.
[0090] As can be seen from Example 1 and Comparative Example 6, the synergistic effect of grafted modified chitin whiskers and chain extenders can make PBAT microfoamed materials have better foaming quality and better mechanical properties, indicating that the simultaneous addition of grafted modified chitin whiskers and chain extenders is more beneficial to improving the foaming performance of PBAT.
[0091] This invention utilizes surface modification technology to graft PBAT onto the surface of chitin whiskers (CHW) to improve the compatibility of CHW and PBAT. During the grafting modification process, if the quality of the CHW is too low, the yield of the grafted product will be too low, making it impossible to effectively purify and filter the grafted product. Conversely, if the quality of the CHW is too high, since the grafting reaction and the synthesis reaction of PBAT occur simultaneously, the available functional groups for the grafting reaction are limited, which cannot effectively improve the grafting rate and will instead lead to a waste of raw materials. The ratio of acid to alcohol also affects the effective grafting of PBAT onto CHW to some extent; when the proportion of alcohol is too high, it will have a certain inhibitory effect on the grafting of CHW.
[0092] This invention selects biodegradable and high-modulus chitin whiskers as a reinforcing agent. Chitin whiskers, with their high modulus and biodegradability, are a highly efficient and environmentally friendly nanofiber-like reinforcing agent, enabling complete biodegradation of PBAT-based reinforced composites. Through surface modification technology, PBAT segments with the same composition as the PBAT matrix are introduced onto the surface of the chitin whiskers. This design ensures good compatibility between the chitin whiskers and the matrix, resulting in thorough dispersion within the matrix. The PBAT segments grafted onto the surface of the chitin whiskers can bond and entangle with the PBAT matrix, helping to solve key problems such as the difficulty in uniformly dispersing reinforcing fillers and the weak interfacial bonding between fillers and the matrix in composite materials. Chitin whiskers uniformly distributed in the PBAT matrix can more effectively transfer shear stress through various mechanisms such as load transfer, pull-out effect, crack deflection, and crack bridging. This design achieves a dual effect of reinforcement and toughening, allowing grafted chitin whiskers to more effectively improve the mechanical properties of PBAT-based composites compared to traditional reinforcing agents. The tensile strength of the modified chitin whisker-reinforced and toughened PBAT composite material is 25–50 MPa, and the elongation at break is 650%–1000%.
[0093] Grafted chitin whiskers can entangle with the molecular chains of the PBAT matrix, increasing intermolecular forces and reducing chain mobility. This helps to appropriately increase the melt viscosity of PBAT and prevent cell cracking and coalescence during foaming. Furthermore, chitin whiskers can work in conjunction with chain extenders to increase the branching degree of the PBAT molecular chains, transforming them from a linear structure to a three-dimensional structure, thereby improving the melt strength and foaming properties of PBAT.
[0094] In summary, grafted chitin whiskers can act as a reinforcing agent to strengthen and toughen PBAT resin, and can also synergistically work with chain extenders to increase the melt viscosity and melt strength of the PBAT matrix, thereby improving its foaming properties. The density of the obtained modified chitin whisker-reinforced and toughened PBAT composite foam material is 0.85–1.05 g / cm³. 3 The tensile strength is 20–35 MPa, and the elongation at break is 500%–900%.
[0095] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.
Claims
1. A method for preparing a modified chitosan whisker-reinforced and toughened PBAT microcellular composite material, characterized in that, include: Chitosan whiskers (CHW) were mixed with 1,4-butanediol (BDO) and dispersed uniformly. Then, 1,6-adipic acid (AA) and terephthalic acid (TPA) were added to obtain the reaction system. The content of the chitosan whiskers (CHW) was 1-3 wt% of the total mass of the acid and alcohol (BDO+AA+TPA), the molar ratio of 1,6-adipic acid (AA) to terephthalic acid (TPA) was 40:60-60:40, and the molar ratio of alcohol to acid (BDO:AA+TPA) was 1:1-1.6:
1. The reaction system is heated to 180~200℃, a catalyst is added, and esterification is carried out under a nitrogen atmosphere for 6~8h; wherein, the catalyst is one or more of tetrabutyl titanate, tetraethyl titanate or tetraisopropyl titanate, and the molar ratio of the catalyst to acid AA+TPA is 1~5:1000. Then the temperature is raised to 230~240℃ and polycondensed at 80~120Pa for 3~4 hours until the viscosity of the reactants no longer increases, thus obtaining the PBAT / CHW complex. The PBAT / CHW composite was purified, and the precipitate was washed, centrifuged, and dried to obtain PBAT-grafted modified chitin nanofibers CHW-g-PBAT; wherein the purification solvent was chloroform and the washing solvent was chloroform. The dried PBAT, CHW-g-PBAT, and chain extender are melt-blended to obtain the modified chitin whisker-reinforced and toughened PBAT composite material. The chain extender is any one or more combinations of epoxy compounds, dianhydrides, diisocyanates, phosphites, or dioxazolines. The melt-blending is performed using a circulating twin-screw internal mixer at a temperature of 160-190°C for 5-20 minutes. The weight proportions of PBAT, CHW-g-PBAT, and the chain extender are: PBAT 95-99.9 parts, CHW-g-PBAT 0.1-5 parts, and chain extender 1-5 parts. Chitosan whisker-reinforced and toughened PBAT composite material and a foaming agent are added to an injection molding machine and chemically micro-foamed injection molding is used to obtain modified chitosan whisker-reinforced and toughened PBAT micro-foamed composite material. The foaming agent is one of azodicarbonamide (AC), sodium bicarbonate, and 4,4'-oxobis(benzenesulfonyl)hydrazine (OBSH). The weight ratio of chitosan whisker-reinforced and toughened PBAT composite material particles to foaming agent is 100:1 to 100:
5. The chemically micro-foamed injection molding is performed with the following parameters: injection temperature 160-190℃, injection speed 120-200 mm / s, injection pressure 100-200 MPa, and mold retraction distance 0.6-2 mm.
2. The preparation method according to claim 1, characterized in that: The chitin whiskers are high-rigidity organic whisker reinforcements prepared by sulfuric acid hydrolysis using natural shrimp and crab shell powder as raw material. The whisker diameter is 20~100nm and the aspect ratio is 20:1~50:1.