Composite material prepared by ultrasonic-assisted enzyme treatment of agricultural wastes and method

Abstract

The invention relates to the technical field of agricultural waste treatment, and relates to a composite material prepared by ultrasonic-assisted enzyme treatment of agricultural waste and a method. The method comprises the following steps: plant fiber pretreatment: adding grinding balls into a ball mill, and adding plant fiber powder into the ball mill; drying the sieved product for later use; preparing a buffer solution: dissolving citric acid and sodium citrate with deionized water to obtain an acidic buffer solution; performing ultrasonic-assisted enzyme treatment on fibers: putting the ball-milled plant fiber powder into a beaker, and adding deionized water; uniformly stirring the enzyme solution by using a stirring rod, and then carrying out ultrasonic treatment; centrifuging, taking out precipitate, and drying for later use; and preparation of the plant fiber / PBAT composite material: putting the mixed raw materials into a mold cavity by adopting a hot pressing method, and carrying out compression molding. According to the invention, the chestnut shell fibers are subjected to ball-milling composite ultrasonic-assisted enzyme treatment to obtain the micro-nano plant fibers, so that the plant fibers have the properties of micro-nano materials; the preparation process is simple, the cost is low, and the cost of the PBAT material is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of agricultural waste treatment, in particular to a composite material and a method for preparing a composite material by ultrasonic-assisted enzyme treatment of agricultural waste. Background Art

[0002] As the country attaches great importance to environmental protection and sustainable development, recycling natural polymers from agricultural waste has become a new trend in biodegradable composite materials. Cellulose extracted from agricultural plant waste can produce cellulose with special structures such as cellulose nanofibers, microcrystalline cellulose and cellulose nanoparticles after special processing. It has excellent characteristics such as light weight, biodegradability, high mechanical strength, high specific surface area and chemical modification. It can be used as a raw material for the production of a variety of industrial products and has broad application prospects, such as the production of nanocellulose materials, plant fiberboards, biodegradable tableware, lightweight building materials and new insulation materials. These application areas demonstrate the diversity and potential of cellulose extracted from agricultural plant waste and its derivative materials, which not only help to reduce the environmental burden of waste, but also provide sustainable and environmentally friendly solutions for various industries.

[0003] Chestnuts are widely planted in my country. A large amount of chestnut shell resources are produced during chestnut processing. Millions of tons of chestnut shells are burned or discarded every year, causing environmental pollution and a large amount of resource waste. Chestnut shell plant fiber is mainly composed of cellulose, hemicellulose, lignin and polyphenol compounds. As a filler for bio-based composite materials, it can be used in the preparation of synthetic resins to improve material strength and stability. Therefore, the recycling and reuse of chestnut shells not only helps environmental protection, but also promotes the development of a circular economy and achieves sustainable agricultural development.

[0004] PBAT is a biodegradable polyester material with good processability, mechanical properties and thermal stability. It has obvious advantages in the fields of environmental protection and composite materials applications, but there are also challenges in cost and performance, which need to be overcome through modification and technological innovation. Research on extracting plant fibers from agricultural waste to reinforce PBAT composite materials is being carried out from multiple angles, aiming to improve the performance of the material, reduce costs, and expand its scope of application. The application prospects of agricultural waste in the field of composite materials are broad, which can not only realize the resource utilization of waste, but also help promote environmental protection and sustainable development;

[0005] Untreated chestnut shell powder contains a large amount of small molecular components such as cellulose, lignin and hemicellulose, which have weak bonding force and poor compatibility at the interface of the PBAT matrix, resulting in uneven dispersion of these materials in the PBAT matrix, easy agglomeration, and poor mechanical properties of the composite material. In response to the problem of poor compatibility, the current modification methods are mainly chemical grafting modification or volume modification by adding compatibilizers. However, these methods have many limitations, such as complex grafting reactions that may produce impurities; side reactions that may occur at high temperatures; modification reagents that are not clean enough, non-renewable, and non-degradable; and cumbersome modification steps and long processes. PBAT-based composite materials still need further research and improvement in terms of mechanical properties, cost control, compatibility, and degradation mechanisms. Summary of the invention

[0006] The purpose of the present invention is to address the problems existing in the background technology and propose a method for preparing a composite material by ultrasonic-assisted enzyme treatment of agricultural waste; to adopt the combined action of ball milling physical modification and bio-enzyme biological modification to fully increase the output of nanocellulose and improve the interface compatibility with matrix tissue; and to improve the solubility, degradability and structural properties of plant fibers.

[0007] The technical solution of the present invention:

[0008] The first aspect of the present invention provides a method for preparing a composite material by ultrasonic-assisted enzyme treatment of agricultural waste, comprising the following steps:

[0009] 1) Plant fiber pretreatment:

[0010] Alumina ceramic balls were added to the ball mill, and the plant fiber powder was added to the ball mill. After 24 hours of ball milling, the plant fiber was taken out and sieved with a 200-mesh screen to remove impurities and larger particles. The plant fiber was placed in an electric blast drying oven and dried at 80°C for 12 hours before use.

[0011] 2) Ultrasonic-assisted enzyme treatment of fibers:

[0012] Dissolve citric acid and sodium citrate in deionized water to obtain a buffer solution with a pH value of about 5. Put the ball-milled chestnut shell powder into a beaker and add the deionized buffer solution, mix it with water in a ratio of 1:5, add 5% laccase and 5% hemicellulase in a mass ratio, use a stirring rod to stir the enzyme solution evenly, and then place it in an ultrasonic cell disruptor for ultrasonic treatment. The intermittent ratio is 1:1, the power is 80%, the temperature is 50℃, and the treatment time is 6h. After ultrasonic treatment, place the beaker in a constant temperature water bath and treat it with 50℃ buffer water bath for 12 hours. After the enzyme treatment, rinse the plant fiber with clean water to remove the enzyme treatment product while avoiding the retention of other impurities, and then use a desktop high-speed centrifuge to centrifuge at 8000rad / min for 5min. After centrifugation, take out the precipitate, place it in a blast drying oven at 60℃ for drying, and set it aside after 12h.

[0013] 3) Preparation of plant fiber / PBAT composite materials:

[0014] The dried plant fiber, PBAT and coupling agent are weighed according to the ratio, and then put into a three-dimensional motion mixer for 3 minutes to mix the powders thoroughly to improve the contact between the materials. The hot pressing method is adopted, and the equipment used is a flat vulcanizer. The mixed raw materials are placed in the mold cavity, and after the mold is closed, they are placed on the electric heating plate of the flat vulcanizer for molding. The parameters of the flat vulcanizer are set to 160°C, 4Mpa, and 15min of holding time, and finally placed on the cooling plate for 25min of cooling.

[0015] The second aspect of the present invention provides a green plant fiber / PBAT composite material, which is prepared using the above method. The prepared composite material is used in plant fiber boards, lightweight building material boards and packaging materials; and has the characteristics of full biodegradability, good mechanical properties and strong interface compatibility.

[0016] In this scheme, the modification method adopts the combined action of ball milling physical modification and bio-enzyme biological modification to fully increase the output of nanocellulose and improve the interface compatibility with the matrix tissue.

[0017] Ball milling can reduce the particle size of materials, usually to the micro-nano level. At the same time, the impact force and friction force help to break up the agglomerated particles. The mechanical energy input during ball milling can cause structural and chemical changes in the material, making the amorphous material have unique properties such as high strength and high thermal stability. Ultrasonic assisted enzyme treatment of plant fibers is a method of using ultrasonic technology and enzyme treatment technology to improve the performance of plant fibers. Ultrasonic waves have special properties such as thermal effect, mechanical effect and cavitation effect, which affect the enzymatic reaction rate to varying degrees and increase the activity of enzymes. In addition, they can also change the permeability of cell membranes and enhance material transmission and exchange, so they are widely used in the preparation of enzymatic products. The high-energy mechanical waves generated by ultrasound can generate tiny bubbles and eddies in plant fibers, thereby increasing the permeability of solvents and the activity of enzymes, accelerating the action of enzymes and the decomposition of plant fibers. Ultrasonic assisted enzyme treatment can improve the solubility, degradability and structural properties of plant fibers.

[0018] Ultrasonic treatment plays an important role in the treatment and transformation of agricultural waste. It not only improves the treatment efficiency and product quality, but also contributes to environmental protection and sustainable utilization of resources. Ultrasonic-assisted enzyme treatment of biomass technology has potential in improving the efficiency of biomass conversion, but it also faces challenges such as technical optimization, cost control and large-scale application. It is necessary to further explore the coupling mechanism of ultrasound and enzymatic hydrolysis reaction, optimize the technical parameters of ultrasonic treatment, improve the reaction efficiency, and consider its feasibility in industrial applications. By comparing the effect of chestnut shell fiber on the performance of PBAT-based composites before and after treatment with chestnut shell powder, the influence of the interfacial bonding properties and mechanical properties of natural plant fibers and PBAT was studied.

[0019] Compared with the prior art, the present invention has the following beneficial technical effects:

[0020] The present invention obtains micro-nano-scale plant fibers by ball milling composite ultrasonic-assisted enzyme treatment of chestnut shell fibers, so that the plant fibers have many properties of micro-nano materials, such as size effect, surface effect, and enhanced crystallinity and strength, and the plant fibers are compositely compression-molded with PBAT to obtain a composite material with excellent performance and improved interface compatibility between biomass materials and PBAT matrix.

[0021] The composite material of the present invention has a simple preparation process and low cost, which reduces the cost of PBAT materials, has completely degradable properties, and is in line with carbon neutrality and sustainable development goals. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Flow chart of the preparation method in an embodiment of the present invention;

[0023] Figure 2This is a graph showing the mechanical properties test results of the chestnut shell plant fiber / PBAT composite material in an embodiment of the present invention;

[0024] Figure 3 This is a graph showing the water absorption performance of the chestnut shell powder composite material in an embodiment of the present invention;

[0025] Figure 4 This is a physical picture of the composite material in the embodiment of the present invention. DETAILED DESCRIPTION

[0026] The present invention describes the technical solution of the present invention in more detail through the following specific embodiments, but the present invention is not limited to the following specific embodiments.

[0027] In the embodiments, polybutylene adipate terephthalate (PBAT), 200 mesh, Xinjiang Lanshan Tunhe Chemical Co., Ltd.; chestnut shell powder, Changyuan Straw Scale Processing Plant, Baitabu Town, Donghai County; hemicellulase, food grade, Shandong Zhongsen Biotechnology Co., Ltd.; laccase, food grade, Ningxia Xiasheng Industrial Group Co., Ltd.; aluminate coupling agent (DL411), Quanzhou Kangjin New Material Technology Co., Ltd.

[0028] Example 1

[0029] The present invention provides a method for preparing a composite material by ultrasonic-assisted enzyme treatment of agricultural waste, comprising:

[0030] 1) Plant fiber pretreatment:

[0031] Alumina ceramic balls were added to the ball mill, and the plant fiber powder was added to the ball mill. After 24 hours of ball milling, the plant fiber was taken out and sieved with a 200-mesh screen to remove impurities and larger particles. The plant fiber was placed in an electric blast drying oven and dried at 80°C for 12 hours before use.

[0032] 2) Ultrasonic-assisted enzyme treatment of fibers:

[0033] Dissolve citric acid and sodium citrate in deionized water to obtain a buffer solution with a pH value of about 5. Put the ball-milled chestnut shell powder into a beaker and add the deionized buffer solution, mix it with water in a ratio of 1:5, add 5% laccase and 5% hemicellulase, use a stirring rod to stir the enzyme solution evenly, and then place it in an ultrasonic cell disruptor for ultrasonic treatment. The intermittent ratio is 1:1, the power is 80%, the temperature is 50℃, and the treatment time is 6h. After ultrasonic treatment, place the beaker in a constant temperature water bath and treat it with 50℃ buffer water bath for 12 hours. After the enzyme treatment, rinse the plant fiber with clean water to remove the enzyme treatment product while avoiding the retention of other impurities, and then use a desktop high-speed centrifuge to centrifuge at 8000rad / min for 5min. After centrifugation, take out the precipitate, place it in a blast drying oven at 60℃ for drying, and set it aside after 12h.

[0034] 3) Preparation of plant fiber / PBAT composite materials:

[0035] Weigh 5% enzyme-treated and dried chestnut shell powder, 95% PBAT and 5% aluminate coupling agent by mass percentage, put them into a three-dimensional motion mixer and mix them for 3 minutes to fully mix the powders to improve the contact between the materials. The hot pressing method is adopted, and the equipment used is a flat vulcanizer. The mixed raw materials are placed in the mold cavity, and after the mold is closed, they are placed on the electric heating plate of the flat vulcanizer for compression molding. The parameters of the flat vulcanizer are set to a temperature of 160°C, a pressure of 4Mpa, a holding time of 15min, and finally placed on a cooling plate for 25min to obtain a composite material plate.

[0036] Example 2

[0037] The present invention provides a method for preparing a composite material by ultrasonic-assisted enzyme treatment of agricultural waste, comprising:

[0038] 1) Plant fiber pretreatment:

[0039] Alumina ceramic balls were added to the ball mill, and the plant fiber powder was added to the ball mill. After 24 hours of ball milling, the plant fiber was taken out and sieved with a 200-mesh screen to remove impurities and larger particles. The plant fiber was placed in an electric blast drying oven and dried at 80°C for 12 hours before use.

[0040] 2) Ultrasonic-assisted enzyme treatment of fibers:

[0041] Dissolve citric acid and sodium citrate in deionized water to obtain a buffer solution with a pH value of about 5. Put the ball-milled chestnut shell powder into a beaker and add the deionized buffer solution, mix it with water in a ratio of 1:5, add 5% laccase and 5% hemicellulase, use a stirring rod to stir the enzyme solution evenly, and then place it in an ultrasonic cell disruptor for ultrasonic treatment. The intermittent ratio is 1:1, the power is 80%, the temperature is 50℃, and the treatment time is 6h. After ultrasonic treatment, place the beaker in a constant temperature water bath and treat it with 50℃ buffer water bath for 12 hours. After the enzyme treatment, rinse the plant fiber with clean water to remove the enzyme treatment product while avoiding the retention of other impurities, and then use a desktop high-speed centrifuge to centrifuge at 8000rad / min for 5min. After centrifugation, take out the precipitate, place it in a blast drying oven at 60℃ for drying, and set it aside after 12h.

[0042] 3) Preparation of plant fiber / PBAT composite materials:

[0043] Weigh 10% of the chestnut shell powder after enzyme treatment and drying, 90% of PBAT and 5% of the aluminate coupling agent by mass percentage, put them into a three-dimensional motion mixer and mix them for 3 minutes to fully mix the powders to improve the mutual contact between the materials. The hot pressing method is adopted, and the equipment used is a flat vulcanizer. The mixed raw materials are placed in the mold cavity, and after the mold is closed, they are placed on the electric heating plate of the flat vulcanizer for compression molding. The parameters of the flat vulcanizer are set to a temperature of 160°C, a pressure of 4Mpa, a holding time of 15min, and finally placed on a cooling plate for 25min to obtain a composite material plate.

[0044] Example 3

[0045] The present invention provides a method for preparing a composite material by ultrasonic-assisted enzyme treatment of agricultural waste, comprising:

[0046] 1) Plant fiber pretreatment:

[0047] Alumina ceramic balls were added to the ball mill, and the plant fiber powder was added to the ball mill. After 24 hours of ball milling, the plant fiber was taken out and sieved with a 200-mesh screen to remove impurities and larger particles. The plant fiber was placed in an electric blast drying oven and dried at 80°C for 12 hours before use.

[0048] 2) Ultrasonic-assisted enzyme treatment of fibers:

[0049] Dissolve citric acid and sodium citrate in deionized water to obtain a buffer solution with a pH value of about 5. Put the ball-milled chestnut shell powder into a beaker and add the deionized buffer solution, mix it with water in a ratio of 1:5, add 5% laccase and 5% hemicellulase, use a stirring rod to stir the enzyme solution evenly, and then place it in an ultrasonic cell disruptor for ultrasonic treatment. The intermittent ratio is 1:1, the power is 80%, the temperature is 50℃, and the treatment time is 6h. After ultrasonic treatment, place the beaker in a constant temperature water bath and treat it with 50℃ buffer water bath for 12 hours. After the enzyme treatment, rinse the plant fiber with clean water to remove the enzyme treatment product while avoiding the retention of other impurities, and then use a desktop high-speed centrifuge to centrifuge at 8000rad / min for 5min. After centrifugation, take out the precipitate, place it in a blast drying oven at 60℃ for drying, and set it aside after 12h.

[0050] 3) Preparation of plant fiber / PBAT composite materials:

[0051] Weigh 15% of enzyme-treated and dried chestnut shell powder, 85% of PBAT and 5% of aluminate coupling agent by mass percentage, put them into a three-dimensional motion mixer and mix them for 3 minutes to fully mix the powders to improve the contact between the materials. The hot pressing method is adopted, and the equipment used is a flat vulcanizer. The mixed raw materials are placed in the mold cavity, and after the mold is closed, they are placed on the electric heating plate of the flat vulcanizer for compression molding. The parameters of the flat vulcanizer are set to a temperature of 160°C, a pressure of 4Mpa, a holding time of 15min, and finally placed on a cooling plate for 25min to obtain a composite material plate.

[0052] Comparative Example 4

[0053] The present invention provides a method for preparing a composite material by ultrasonic-assisted enzyme treatment of agricultural waste, comprising:

[0054] 1) Plant fiber pretreatment:

[0055] The plant fiber was sieved with a 200-mesh screen to remove impurities and larger particles, and then placed in an electric blast drying oven to dry at 80° C. for 12 hours for use.

[0056] 2) Preparation of plant fiber / PBAT composite materials:

[0057] Weigh 5% dried chestnut shell powder, 95% PBAT and 5% aluminate coupling agent by mass percentage, put them into a three-dimensional motion mixer and mix them for 3 minutes to fully mix the powders to improve the contact between the materials. The hot pressing method is adopted, and the equipment used is a flat vulcanizer. The mixed raw materials are placed in the mold cavity, and after the mold is closed, they are placed on the electric heating plate of the flat vulcanizer for compression molding. The parameters of the flat vulcanizer are set to a temperature of 160°C, a pressure of 4Mpa, a holding time of 15min, and finally placed on a cooling plate for 25min to obtain a composite material plate.

[0058] Comparative Example 5

[0059] The present invention provides a method for preparing a composite material by ultrasonic-assisted enzyme treatment of agricultural waste, comprising:

[0060] 1) Plant fiber pretreatment:

[0061] The plant fiber was sieved with a 200-mesh screen to remove impurities and larger particles, and then placed in an electric blast drying oven to dry at 80° C. for 12 hours for use.

[0062] 2) Preparation of plant fiber / PBAT composite materials:

[0063] Weigh 10% dried chestnut shell powder, 90% PBAT and 5% aluminate coupling agent by mass percentage, put them into a three-dimensional motion mixer and mix them for 3 minutes to fully mix the powders to improve the contact between the materials. The hot pressing method is adopted, and the equipment used is a flat vulcanizer. The mixed raw materials are placed in the mold cavity, and after the mold is closed, they are placed on the electric heating plate of the flat vulcanizer for compression molding. The parameters of the flat vulcanizer are set to a temperature of 160°C, a pressure of 4Mpa, a holding time of 15min, and finally placed on a cooling plate for 25min to obtain a composite material plate.

[0064] Comparative Example 6

[0065] The present invention provides a method for preparing a composite material by ultrasonic-assisted enzyme treatment of agricultural waste, comprising:

[0066] 1) Plant fiber pretreatment:

[0067] The plant fiber was sieved with a 200-mesh screen to remove impurities and larger particles, and then placed in an electric blast drying oven to dry at 80° C. for 12 hours for use.

[0068] 2) Preparation of plant fiber / PBAT composite materials:

[0069] Weigh 15% dried chestnut shell powder, 85% PBAT and 5% aluminate coupling agent by mass percentage, put them into a three-dimensional motion mixer and mix them for 3 minutes to fully mix the powders to improve the contact between the materials. The hot pressing method is adopted, and the equipment used is a flat vulcanizer. The mixed raw materials are placed in the mold cavity, and after the mold is closed, they are placed on the electric heating plate of the flat vulcanizer for compression molding. The parameters of the flat vulcanizer are set to a temperature of 160°C, a pressure of 4Mpa, a holding time of 15min, and finally placed on a cooling plate for 25min to obtain a composite material plate.

[0070] The raw material proportions of the embodiments and comparative examples are shown in the following table:

[0071] Table 1 Plant fiber / PBAT composite material ratio

[0072]

[0073] Mechanical property test of composite materials: tensile properties are tested using the test method for determining tensile properties of plastics specified in GBT1040.4-2006. The bending properties of composite materials are tested using the test method for determining bending properties of plastics specified in GBT9341-2008. The impact properties of composite materials are tested using the test method for simply supported beam impact toughness of fiber reinforced plastics specified in GBT1463-2005.

[0074] Mechanical properties test results of chestnut shell plant fiber / PBAT composites Figure 2shown.

[0075] Figure 2 a is the tensile performance diagram of chestnut shell fiber / PBAT composite material; Figure 1 It can be seen from a that the tensile strength of chestnut shell fiber / PBAT decreases with the increase of chestnut shells, and the tensile strength after enzyme treatment is improved. The tensile strength of 5wt% and 15wt% enzyme-treated chestnut powder / PBAT composite materials is 11.66MPa and 9.33MPa, and the tensile strength of 5wt% and 15wt% unenzyme-treated chestnut shell fiber / PBAT composite materials is 11MPa and 9.3MPa. After enzyme treatment, the tensile strength of 5wt% and 15wt% chestnut powder / PBAT composite materials increased by 6% and 0.32%, respectively.

[0076] Figure 2 b is the bending performance diagram of chestnut shell fiber / PBAT composite material; Figure 1 It can be seen from b that the flexural strengths of 5wt%, 10wt% and 15wt% chestnut shell fiber / PBAT composites without enzyme treatment are 5.65MPa, 7.3MPa and 10.36MPa, respectively. It can be seen that the flexural strength of chestnut shell fiber / PBAT composites increases with the increase of chestnut powder content. The flexural strengths of enzyme-treated chestnut powder / PBAT composites are 9.14MPa, 7.42MPa and 10.42MPa, respectively, which are 61.76%, 1.6% and 0.5% higher than those of composites without enzyme treatment, respectively.

[0077] Figure 2 c is the impact performance diagram of chestnut shell fiber / PBAT composite material; Figure 1 c shows that after enzyme treatment, the impact strength of the 5wt% chestnut shell fiber / PBAT composite material increased from 37.592KJ / m 2 Increased to 52.029KJ / m 2 The impact strength of 15wt% chestnut shell fiber / PBAT composite material increased from 32.645KJ / m 2 Increased to 47.564KJ / m 2 , an increase of 45.7%. Laccase and hemicellulase can catalyze the degradation of hemicellulose and lignin, loosening the bond between cellulose molecules, making cellulose easier to combine with the PBAT matrix and improving the interfacial compatibility between the two.

[0078] The test method for the water absorption performance of composite materials is as follows: cut each group of experimental specimens into a length of 51mm, and then put them into a blast drying oven at 60℃ for 36 hours. After drying, measure the initial mass of each specimen. Then put the specimens into a beaker filled with distilled water, and then put them into a digital constant temperature water bath. After soaking at room temperature for 24 hours, take out the specimens from the water bath, wipe the residual water on the surface of the specimens with a paper towel, and quickly record the mass of the specimens at this time.

[0079] The water absorption rate is calculated as follows:

[0080]

[0081] Where:

[0082] W-water absorption, expressed as a percentage (%);

[0083] m1-the mass of the sample before immersion in water, in grams (g);

[0084] m2-the mass of the sample after immersion in water, in grams (g);

[0085] from Figure 3 It can be seen that the water absorption rate of the enzyme-treated chestnut shell fiber / PBAT composite material at 5wt% and 15wt% is lower than that of the unenzyme-treated chestnut powder / PBAT composite material. The water absorption rate of the 5wt% chestnut powder decreased from 0.95% to 0.58%, a decrease of 63.79%, and the water absorption rate of the 15wt% chestnut powder decreased from 1.66% to 1.35%, a decrease of 22.96%. The water absorption rate of the composite material is closely related to its interfacial compatibility. The change in water absorption will directly affect the mechanical properties, water resistance, stability and other aspects of the composite material. The reduction in water absorption rate indicates that the interfacial compatibility of the composite material has been improved.

[0086] The present invention is modified by ball milling treatment and ultrasonic composite enzyme treatment, and the technical parameters and material ratio are optimized. The modified chestnut shell fiber has better interface compatibility with the PBAT polymer matrix after modification, and the modified chestnut shell fiber can be completely coated in the polymer matrix, and the interface between the two is more tightly bonded, which can give full play to the performance enhancement effect of the fiber. The composite material obtained by the present invention has better performance than the untreated one, has the advantages of environmental friendliness and cost reduction, and has a high promotion value.

[0087] The above examples show that the green plant fiber / PBAT composite material prepared by the present invention has the characteristics of good mechanical properties, no pollution, easy processing and biodegradability. The addition of modified chestnut shell fiber improves the performance of the composite material, reduces the cost, realizes the resource utilization of waste, and helps promote environmental protection and sustainable development.

[0088] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited thereto, and various changes can be made within the knowledge scope of technicians in the relevant technical field without departing from the purpose of the present invention.

Claims

1. A method for preparing a composite material by ultrasonic-assisted enzyme treatment of agricultural waste, characterized in that: The specific steps include: S1. Plant fiber pretreatment: Add grinding balls to a ball mill, add plant fiber powder to the ball mill, take out the plant fiber after ball milling for 24 hours, sieve to remove impurities and larger particles; put the sieved product into an electric hot air drying oven and dry it at 80°C for 12 hours for use; S2, ultrasonic-assisted enzyme treatment of fiber: dissolve citric acid and sodium citrate in deionized water to obtain an acidic buffer solution; put the ball-milled plant fiber powder into a beaker and add the deionized buffer solution at a solid-liquid ratio of 1:5, mix well and then add enzyme powder; use a stirring rod to stir the enzyme solution evenly and then perform ultrasonic treatment; after ultrasonic treatment, treat in a water bath for 12 hours; after the enzyme treatment, rinse with clean water, take out the precipitate after centrifugation, place it in a forced air drying oven at 60°C for drying, and set it aside after 12 hours; S3. Preparation of plant fiber / PBAT composite materials: The dried plant fiber, PBAT and coupling agent are weighed according to the ratio, and then mixed to make the powders fully mixed; the mixed raw materials are placed in the mold cavity by hot pressing, and the mold is closed and molded.

2. The method for preparing composite materials by ultrasonic-assisted enzyme treatment of agricultural waste according to claim 1, characterized in that: In step S1, the pH value of the acidic buffer solution is 5.

3. The method for preparing composite materials by ultrasonic-assisted enzyme treatment of agricultural waste according to claim 1, characterized in that: In step S2, the grinding balls are alumina ceramic balls; the plant fiber is chestnut shell powder; and the sieving is performed using a 200-mesh sieve.

4. The method for preparing composite materials by ultrasonic-assisted enzyme treatment of agricultural waste according to claim 1, characterized in that: The enzyme powder in step S3 has a mass proportion of 5% laccase and 5% hemicellulase.

5. The method for preparing composite materials by ultrasonic-assisted enzyme treatment of agricultural waste according to claim 1, characterized in that: In step S3, an ultrasonic cell disruptor is used for ultrasonic treatment, with an intermittent ratio of 1:1, a power of 80%, a temperature of 50° C., and a treatment time of 6 hours.

6. The method for preparing composite materials by ultrasonic-assisted enzyme treatment of agricultural waste according to claim 1, characterized in that: After the ultrasonic treatment in step S3, the beaker was placed in a constant temperature water bath with a 50° C. buffer solution for enzyme treatment for 12 hours.

7. The method for preparing composite materials by ultrasonic-assisted enzyme treatment of agricultural waste according to claim 1, characterized in that: In step S3, a desktop high-speed centrifuge is used for centrifugation at 8000 rad / min for 5 minutes; after centrifugation, the precipitate is taken out.

8. The method for preparing composite materials by ultrasonic-assisted enzyme treatment of agricultural waste according to claim 1, characterized in that: In step S4, the weighed raw materials are placed in a three-dimensional motion mixer and mixed for 3 minutes to fully mix the powders to increase the contact between the materials.

9. The method for preparing composite materials by ultrasonic-assisted enzyme treatment of agricultural waste according to claim 1, characterized in that: In step S4, a flat plate vulcanizer is used for hot pressing, and the parameters of the flat plate vulcanizer are set to a temperature of 160° C., a pressure of 4 MPa, a holding time of 15 min, and finally the product is placed on a cooling plate for a cooling time of 25 min.

10. A green plant fiber / PBAT composite material, prepared by the method according to any one of claims 1 to 9, characterized in that: The prepared composite material is used in plant fiber boards, light building material boards and packaging materials; and has the properties of full biodegradability, mechanical properties and interface compatibility.

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