Preparation method of epoxy resin reinforced foamed PLA-based wood plastic and product

Abstract

This invention discloses a method for preparing epoxy resin-reinforced foamed PLA-based wood-plastic composite and its products. The preparation method includes the following steps: S1, mixing and granulating modified PLA and other materials to obtain PLA wood-plastic matrix; S2, mixing the PLA wood-plastic matrix and fluid into an extruder to obtain a foamed layer; S3, passing modified rattan woven fabric and biodegradable epoxy resin through a thermosetting molding system to obtain a pre-cured resin, and then passing it through a foaming co-extrusion die to obtain a reinforcing layer; S4, adding biodegradable elastomer and MAH-GMA co-grafted biodegradable elastomer into a first co-extrusion die to obtain an elastic layer; S5, adding modified PLA and other materials into a second co-extrusion die to obtain a decorative layer; S6, combining and co-extruding the foamed layer, reinforcing layer, elastic layer, and decorative layer in a foaming co-extrusion die to obtain a biodegradable epoxy resin-reinforced foamed PLA-based wood-plastic composite product. This invention overcomes the shortcomings of existing technologies in producing low-density, high-strength, and high-toughness PLA-based wood-plastic materials.

Description

Technical Field

[0001] This invention belongs to the field of composite material manufacturing technology, and relates to a method for preparing epoxy resin-reinforced PLA-based wood-plastic composites and their products. Background Technology

[0002] With increasing global environmental awareness and the gradual implementation of plastic bans, biodegradable materials and bio-based composites have become important development directions for the plastics industry and materials science. Polylactic acid (PLA), a biodegradable polymer derived from renewable resources such as corn and sugarcane, is considered an ideal candidate to replace traditional petroleum-based plastics due to its good biocompatibility, high modulus, and processability. However, pure PLA has inherent drawbacks such as poor toughness, high brittleness, poor heat resistance, and high cost, limiting its application in a wider range of fields, including structural packaging, building decoration, and furniture panels.

[0003] Traditional wood-plastic composites primarily use polyethylene (PE), polypropylene (PP), and polyvinyl chloride (PVC) as matrices. While these materials improve the rigidity and dimensional stability of the composites, these petroleum-based plastics are difficult to biodegrade, and their disposal still causes pollution and environmental burden. Therefore, developing fully biodegradable polylactic acid (PLA)-based wood-plastic composites has significant environmental implications and market potential. Existing PLA-based wood-plastic composites have high density and cost, necessitating reductions in both. However, due to the low melt viscosity of PLA, conventional AC foaming agents produce poor foaming effects, leading to problems such as uneven cell structure, cell collapse, and significantly reduced performance. Furthermore, since lightweighting and high strength are often difficult to achieve simultaneously, the industry often adds glass fibers for reinforcement on the foaming base, but this introduces environmental pollution and burden, failing to achieve full biodegradability in nature. Conventional wood-plastic boards are mostly single-layer homogeneous structures, unable to simultaneously meet the multiple requirements of lightweighting, high strength, impact resistance, and surface decoration.

[0004] Therefore, developing composite materials with stable and uniform pores, reducing density while maintaining or even improving various properties, and ensuring full biodegradability of all components, will be a key issue in the preparation of foamed PLA-based wood-plastic composites. However, existing technologies lack relevant references, necessitating the proposal of a new technical solution. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide an epoxy resin reinforced PLA-based wood-plastic product and its preparation method that overcomes the defects of existing materials, has a more reasonable process, and produces products with better performance.

[0006] The technical solution adopted in this invention is: a method for preparing epoxy resin-reinforced foamed PLA-based wood-plastic composite, comprising the following steps: S1, base material preparation: modified polylactic acid PLA, biomass fiber, AC foaming agent, glass microspheres, antioxidant, and lubricant are mixed and granulated to obtain a polylactic acid PLA wood-plastic base material; S2, foaming layer preparation: the polylactic acid PLA wood-plastic base material is added to an extruder, and supercritical carbon dioxide fluid is simultaneously pumped into the extruder barrel through a pumping system, and the mixture is extruded to obtain a foaming layer; S3, reinforcement layer preparation: modified rattan woven fabric and biodegradable epoxy resin are processed through a thermosetting molding system to obtain a pre-cured resin, and the pre-cured resin is conveyed to a foaming co-extrusion die. The process involves: S2, S3, S4, and S5, followed by extrusion molding to obtain a reinforcing layer; S4, preparation of the elastic layer: adding biodegradable elastomer and maleic anhydride MAH-glycidyl methacrylate GMA co-grafted biodegradable elastomer to a first co-extruder and extruding to obtain an elastic layer; S5, preparation of the decorative layer: adding modified polylactic acid PLA, alumina, masterbatch, and pigment to a second co-extruder and extruding to obtain a decorative layer; S6, preparation of the product: combining and co-extruding the foamed layer obtained in step S2, the reinforcing layer obtained in step S3, the elastic layer obtained in step S4, and the decorative layer obtained in step S5 in a foaming co-extrusion die to obtain a biodegradable epoxy resin reinforced foamed PLA-based wood-plastic composite product.

[0007] As a further improvement to the above method, the preparation method of modified polylactic acid (PLA) in step S1 includes the following steps: S1.1: Dissolve dicumyl peroxide (DCP), maleic anhydride (MHA), and bisoxazoline in an appropriate amount of acetone solution to obtain solution A; S1.2: Mix glycidyl methacrylate (GMA) and solution A evenly to obtain solution B; S1.3: Add polylactic acid (PLA) and polycaprolactone (PCL) to a mixer and mix for 5-10 minutes to obtain material A; S1.4: Spray solution B onto material A and mix for 5-10 minutes to obtain material B; S1.5: Add material B to a granulator for granulation to obtain modified polylactic acid (PLA).

[0008] As a further improvement to the above method, the pumping system in step S2 consists of an injection valve, a flow controller, a piston pump, a gas delivery pipeline, and a carbon dioxide storage tank arranged sequentially from near the extruder barrel to far away from the extruder barrel.

[0009] As a further improvement to the above method, the biodegradable epoxy resin in step S3 comprises a biodegradable epoxy resin matrix and a curing agent, wherein the biodegradable epoxy resin matrix contains one or more combinations of disulfide bonds, Schiff base bonds, and hexahydrotriazine bonds.

[0010] As a further improvement to the above method, the preparation method of the pre-cured resin in step S3 includes the following steps: S3.1: Soaking the rattan woven fabric in a sodium hydroxide solution for at least 24 hours, taking it out and washing it with water until neutral, and then drying it to obtain a modified rattan woven fabric; S3.2: Conveying the modified rattan woven fabric to a resin tank and immersing it in a biodegradable epoxy resin; S3.3: Conveying the modified rattan woven fabric soaked in the biodegradable epoxy resin to a heating zone to obtain a pre-cured resin.

[0011] As a further improvement to the above method, the biodegradable elastomer in step S4 is one or more of polybutylene terephthalate (PBAT), polyhydroxyalkanoate (PHA), polycaprolactone (PCL), and biodegradable thermoplastic polyurethane (TPU); the maleic anhydride (MAH)-glycidyl methacrylate (GMA) co-grafted biodegradable elastomer in step S4 is one or more of MAH-GMA co-grafted PBAT, MAH-GMA co-grafted PHA, MAH-GMA co-grafted PCL, and MAH-GMA co-grafted biodegradable TPU.

[0012] As a further improvement to the above method, the preparation method of the maleic anhydride (MAH)-glycidyl methacrylate (GMA) co-grafted biodegradable elastomer in step S4 includes the following steps: S4.1: Dissolve dicumyl peroxide (DCP) and maleic anhydride (MAH) in an appropriate amount of acetone solution to obtain solution C; S4.2: Mix solution C and glycidyl methacrylate (GMA) evenly to obtain solution D; S4.3: Add the biodegradable elastomer to a mixer, and then spray solution D onto the biodegradable elastomer and mix for 5-10 minutes to obtain material C; S4.4: Add material C to a granulator for granulation to obtain the maleic anhydride (MAH)-glycidyl methacrylate (GMA) co-grafted biodegradable elastomer.

[0013] As a further improvement to the above method, the foaming co-extrusion die in step S6 is provided with a left interface and a right interface. The left interface is connected to the first co-extruder, and the right interface is connected to the second co-extruder. The sheet forming system is connected to the foaming co-extrusion die through a sheet connection point provided on the upper surface of the foaming co-extrusion die.

[0014] As a further improvement to the above method, the foaming layer 4 in the product comprises the following components: 0.1-1 parts by weight of dicumyl peroxide (DCP); 0.1-5 parts by weight of maleic anhydride (MAH); 0.1-5 parts by weight of glycidyl methacrylate (GMA); 0.1-2 parts by weight of bisoxazoline; 0.5-5 parts by weight of AC foaming agent; 5-20 parts by weight of glass microspheres; 25-60 parts by weight of polylactic acid (PLA); 5-20 parts by weight of polycaprolactone (PCL); 10-60 parts by weight of biomass fiber; 1-3 parts by weight of antioxidant; and 3-5 parts by weight of lubricant. The reinforcing layer 10 comprises the following components: 20-50 parts by weight of rattan woven fabric; and 50-80 parts by weight of biodegradable epoxy resin. The elastic layer 12 comprises the following components: 50-90 parts by weight of biodegradable elastomer; 10-50 parts by weight of maleic anhydride (MAH)-glycidyl methacrylate (GMA) co-grafted biodegradable elastomer. The decorative layer 14 comprises the following components: 0.5-3 parts by weight of dicumyl peroxide (DCP); 0.5-5 parts by weight of maleic anhydride (MAH); 0.5-5 parts by weight of glycidyl methacrylate (GMA); 0.5-2 parts by weight of bisoxazoline; 5-10 parts by weight of alumina; 1-5 parts by weight of color masterbatch; 1-10 parts by weight of pigment; and 70-90 parts by weight of polylactic acid (PLA).

[0015] As a further improvement to the above method, the article has a four-layer structure from the inside out, namely a reinforcing layer, a foaming layer, an elastic layer and a decorative layer.

[0016] The beneficial effects of this invention are:

[0017] 1. Dicumyl peroxide (DCP) decomposes upon heating, generating free radicals that abstract hydrogen atoms from the polylactic acid (PLA) molecular chain, forming macromolecular free radicals. The carbon-carbon double bonds of maleic anhydride (MAH) undergo an addition reaction with the PLA macromolecular free radicals, forming maleic anhydride-grafted PLA (MAH-grafted PLA), increasing melt strength. The epoxy groups of glycidyl methacrylate (GMA) undergo a ring-opening addition reaction with the terminal carboxyl and hydroxyl groups of PLA, forming glycidyl methacrylate-grafted PLA, also increasing melt strength. The five-membered heterocycle of bisoxazoline undergoes a nucleophilic ring-opening addition reaction with the terminal carboxyl group of PLA, thereby extending the PLA chain, increasing its molecular weight and melt strength. Polycaprolactone (PCL) has excellent toughening effects and is therefore used for toughening modification of brittle PLA. Polycaprolactone (PCL) has terminal hydroxyl groups, and biomass fibers also have a large number of hydroxyl groups. Maleic anhydride (MAH) and glycidyl methacrylate (GMA) can react with these groups, thereby improving the interfacial bonding between polylactic acid (PLA), PCL, and biomass fibers. Furthermore, maleic anhydride (MAH), glycidyl methacrylate (GMA), and bisoxazoline can all increase the melt strength of polylactic acid (PLA), making the bubbles less prone to breakage during foaming and resulting in excellent foaming performance.

[0018] 2. The rattan woven material is not sheared by the extruder screw during the entire processing, and it always maintains a long fiber state. In addition, the rattan woven material is effectively impregnated in biodegradable epoxy resin, which can truly play the role of reinforcing the composite material.

[0019] 3. The addition of biodegradable elastomers is primarily to ensure good overall elasticity of the composite material. The maleic anhydride (MAH) and glycidyl methacrylate (GMA) co-grafted biodegradable elastomers allow for chemical reactions between the elastomer and polylactic acid (PLA), thereby improving the interfacial bonding between adjacent layers. Furthermore, the addition of biodegradable elastomers ensures that the composite material can truly degrade naturally when exposed to the environment after disposal.

[0020] 4. Epoxy resin has dynamic covalent bonds. When it is discarded and recycled, the three-dimensional network cross-linked epoxy resin can be degraded into small molecule compounds under high temperature or acid conditions. These small molecule compounds can then be used to prepare biodegradable epoxy resin, thus achieving recycling.

[0021] 5. Supercritical carbon dioxide fluid flows into the extruder barrel via a pumping system. In the high-pressure, closed barrel environment, the supercritical carbon dioxide fluid penetrates the polylactic acid (PLA) molecular chains, breaking their regularity and reducing the crystallinity of the PLA molecules, thus forming uniform micropores. AC foaming agent is added to the PLA-based wood-plastic composite, playing a synergistic foaming role in the entire system. The addition of glass microspheres further reduces the density of the composite material.

[0022] 6. By connecting the two interfaces on the co-extrusion machine and the co-extrusion die, and the connection point set on the upper surface of the co-extrusion die, the reinforcing layer, foaming layer, elastic layer and decorative layer are sequentially combined inside the die, and finally formed into a biodegradable epoxy resin reinforced foamed PLA-based wood-plastic product with a four-layer structure, giving full play to the advantages of each layer material and making the overall performance of the composite material better.

[0023] In summary, the chemical reaction between dicumyl peroxide (DCP), maleic anhydride (MAH), glycidyl methacrylate (GMA), bisoxazoline, and polylactic acid (PLA) enhances interfacial bonding and melt strength. Furthermore, the synergistic foaming effect of supercritical carbon dioxide and AC foaming agent locks in air bubbles, forming a uniformly porous foamed layer. Simultaneously, glass microspheres further reduce the density of the composite material. By connecting a co-extrusion die to two co-extruders, a biodegradable epoxy resin-reinforced foamed PLA-based wood-plastic composite product with a four-layer structure (reinforcing layer, foamed layer, elastic layer, and decorative layer) can be produced. This addresses industry pain points, reducing costs while maintaining core performance, and possesses significant industrialization value. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the preparation method of epoxy resin reinforced foamed PLA-based wood-plastic composite according to the present invention.

[0025] Figure 2 This is a top view of a processing equipment for epoxy resin-reinforced foamed PLA-based wood-plastic composites according to the present invention.

[0026] Figure 3 This is a side view of a processing equipment for epoxy resin-reinforced foamed PLA-based wood-plastic composites according to the present invention.

[0027] Figure 4 This is a cross-sectional schematic diagram of an epoxy resin-reinforced foamed PLA-based wood-plastic product according to the present invention.

[0028] The image shows:

[0029] 1. Extruder; 2. Pumping system; 3. Extruder barrel; 4. Foaming layer; 5. Modified rattan woven fabric; 6. Biodegradable epoxy resin; 7. Thermosetting molding system; 8. Pre-cured resin; 9. Foaming co-extrusion die; 10. Reinforcing layer; 11. First co-extruder; 12. Elastic layer; 13. Second co-extruder; 14. Decorative layer; 15. Biodegradable epoxy resin reinforced foamed PLA-based wood-plastic composite product; 16. Carbon dioxide storage tank; 17. Gas pipeline; 18. Piston pump; 19. Flow controller; 20. Injection valve; 21. Resin tank; 22. Heating zone; 23. Left side interface; 24. Right side interface; 25. Connection point. Detailed Implementation

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention, the embodiments will be briefly described below. Obviously, what is described are only some embodiments of the present invention, not all embodiments. Those skilled in the art can obtain other design solutions based on the flowchart without creative effort.

[0031] like Figure 1 As shown, this invention provides a method for preparing epoxy resin-reinforced foamed PLA-based wood-plastic composite, comprising the following steps: S1, Base material preparation: Modified polylactic acid PLA, biomass fiber, AC foaming agent, glass microspheres, antioxidant, and lubricant are mixed and granulated to obtain a polylactic acid PLA wood-plastic base material; S2, Foaming layer preparation: The polylactic acid PLA wood-plastic base material is added to an extruder 1, while supercritical carbon dioxide fluid is pumped into the extruder barrel 3 via a pumping system 2, and extruded to obtain a foamed layer 4; S3, Reinforcing layer preparation: Modified rattan woven fabric 5 and biodegradable epoxy resin 6 are passed through a thermosetting molding system 7 to obtain a pre-cured resin 8, and the pre-cured resin 8 is conveyed to a foaming co-extrusion die 9, and extruded... S2. Reinforcing layer 10 is obtained by molding; S3. Elastic layer preparation: Degradable elastomer and maleic anhydride MAH-glycidyl methacrylate GMA co-grafted degradable elastomer are added to the first co-extruder 11 and extruded to obtain elastic layer 12; S4. Decorative layer preparation: Modified polylactic acid PLA, alumina, color masterbatch and pigment are added to the second co-extruder 13 and extruded to obtain decorative layer 14; S5. Product preparation: The foamed layer 4 obtained in step S2, the reinforcing layer 10 obtained in step S3, the elastic layer 12 obtained in step S4 and the decorative layer 14 obtained in step S5 are combined and co-extruded in a foaming co-extrusion die to obtain a degradable epoxy resin reinforced foamed PLA-based wood-plastic composite product 15. The beneficial effects of this embodiment are as follows: Modified polylactic acid (PLA) not only improves toughness but also enhances interfacial bonding with biomass fibers. Furthermore, the increased melt strength of PLA allows air bubbles to be trapped during the foaming process, improving bubble uniformity. The rattan weave and biodegradable epoxy resin 6 further reinforce the composite material, compensating for the strength loss caused by foaming. In addition, the two co-extruders are connected to the co-extrusion die, and the connection point 25 on the upper surface of the co-extrusion die allows the reinforcing layer 10, foamed layer 4, elastic layer 12, and decorative layer 14 to sequentially converge inside the die, ultimately forming a four-layer biodegradable epoxy resin-reinforced foamed PLA-based wood-plastic composite product 15.

[0032] As a further improvement to the above method, the preparation method of modified polylactic acid (PLA) in steps S1 and S5 includes the following steps: S1.1: Dissolve dicumyl peroxide (DCP), maleic anhydride (MAH), and bisoxazoline in an appropriate amount of acetone solution to obtain solution A; S1.2: Mix glycidyl methacrylate (GMA) and solution A evenly to obtain solution B; S1.3: Add polylactic acid (PLA) and polycaprolactone (PCL) to a mixer and mix for 5-10 minutes to obtain material A; S1.4: Spray solution B onto material A and mix for 5-10 minutes to obtain material B; S1.5: Add material B to a granulator for granulation to obtain modified polylactic acid (PLA). The beneficial effect of this embodiment is that dicumyl peroxide (DCP) decomposes upon heating to generate free radicals, which abstract hydrogen atoms from the polylactic acid (PLA) molecular chain to form macromolecular free radicals. The carbon-carbon double bond of maleic anhydride (MAH) undergoes an addition reaction with the free radical of polylactic acid (PLA) macromolecules to form maleic anhydride-grafted polylactic acid (MAH-grafted PLA), improving melt strength. The epoxy group of glycidyl methacrylate (GMA) undergoes a ring-opening addition reaction with the terminal carboxyl and hydroxyl groups of PLA, forming glycidyl methacrylate-grafted PLA, also improving melt strength. The five-membered heterocycle of bisoxazoline undergoes a nucleophilic ring-opening addition reaction with the terminal carboxyl group of PLA, thereby extending the chain of PLA and increasing its molecular weight and melt strength. Polycaprolactone (PCL) has excellent toughening effects and is therefore used for toughening modification of brittle PLA. PCL has terminal hydroxyl groups, and biomass fibers also have a large number of hydroxyl groups, which can react with both maleic anhydride (MAH) and glycidyl methacrylate (GMA), thereby improving the interfacial bonding between PLA, PCL, and biomass fibers. Maleic anhydride (MAH), glycidyl methacrylate (GMA), and bisoxazoline can all improve the melt strength of polylactic acid (PLA), making the bubbles less prone to breakage during foaming and resulting in excellent foaming effects.

[0033] like Figure 2 and Figure 3 The diagram shows a top view and a side view of the processing equipment used in the preparation method of epoxy resin-reinforced foamed PLA-based wood-plastic composite according to the present invention. The processing equipment includes an extruder 1, a pumping system 2, a pre-cured resin molding system, a first co-extruder 11, a second co-extruder 13, and a foaming co-extrusion die 9. The pumping system 2 is provided on one side of the extruder 1 and is connected to the extruder barrel 3 of the extruder 1. The foaming co-extrusion die 9 is provided at the outlet of the extruder 1. The first co-extruder 11 and the second co-extruder 13 are respectively connected to the two sides of the foaming co-extrusion die 9. The pre-cured resin molding system is provided above the foaming co-extrusion die 9 and is connected to the foaming co-extrusion die 9 through a connection 25.

[0034] As a further improvement to the above method, the pumping system 2 in step S2 consists of a carbon dioxide storage tank 16, a gas delivery pipeline 17, a piston pump 18, a flow controller 19, and an injection valve 20, with the injection valve 20 connected to the extruder barrel 3. The injection valve 20, flow controller 19, piston pump 18, gas delivery pipeline 17, and carbon dioxide storage tank 16 are arranged sequentially from near the extruder barrel 3 to far away from it. The beneficial effect of this embodiment is that the flow rate and velocity of the supercritical carbon dioxide fluid are controlled by the flow controller 19, thereby precisely controlling the density of the foam layer 4. The injection valve 20 is tightly connected to the extruder barrel 3, always providing a high-pressure, sealed environment, ensuring that the carbon dioxide remains in a supercritical fluid state, making it easier to penetrate the polylactic acid (PLA) crystallization zone, thus resulting in a uniform distribution of foam cells.

[0035] As a further improvement to the above method, the biodegradable epoxy resin 6 in step S3 comprises a biodegradable epoxy resin matrix and a curing agent. The biodegradable epoxy resin matrix contains one or more combinations of disulfide bonds, Schiff base bonds, and hexahydrotriazine bonds. The beneficial effect of this embodiment is that epoxy resin has dynamic covalent bonds. When it is discarded and recycled, under high temperature or acidic conditions, the three-dimensional network cross-linked epoxy resin can be degraded into small molecule compounds, and these small molecule compounds can be used to re-prepare biodegradable epoxy resin 6, achieving recycling.

[0036] As a further improvement to the above method, the preparation method of the pre-cured resin 8 in step S3 includes the following steps: S3.1: Immerse the rattan woven fabric in a sodium hydroxide solution for at least 24 hours, remove it and wash it with water until neutral, and then dry it to obtain modified rattan woven fabric 5; S3.2: Transport the modified rattan woven fabric 5 to a resin tank 21 and immerse it in biodegradable epoxy resin 6; S3.3: Transport the modified rattan woven fabric 5, which is fully immersed in biodegradable epoxy resin 6, to a heating zone 22 to obtain pre-cured resin 8. Figure 3 As shown, the pre-cured resin molding system includes a heating zone 22 near the foaming co-extrusion mold 9 and a resin tank 21 away from the foaming co-extrusion mold 9. The heating zone 22 is equipped with a thermosetting molding system 7. The resin tank 21 is filled with biodegradable epoxy resin 6. The modified rattan woven fabric 5 is impregnated with the biodegradable epoxy resin 6 in the resin tank 21 and cured by the thermosetting molding system 7 in the heating zone 22 to obtain a pre-cured resin 8. The beneficial effects of this embodiment are: rattan is a biomass material with excellent reinforcing effects; some hemicellulose and lignin in the rattan woven fabric are dissolved and removed by sodium hydroxide solution, making the fiber surface rougher, thus making it easier for the biodegradable epoxy resin solution to penetrate into the fiber interior and improve interfacial bonding. The soft pre-cured resin 8 obtained by heating facilitates further curing and molding in the foaming co-extrusion mold 9.

[0037] As a further improvement to the above method, the biodegradable elastomer in step S4 is one or more of polybutylene terephthalate (PBAT), polyhydroxyalkanoate (PHA), polycaprolactone (PCL), and biodegradable thermoplastic polyurethane (TPU); the maleic anhydride (MAH)-glycidyl methacrylate (GMA) co-grafted biodegradable elastomer in step S4 is one or more of MAH-GMA co-grafted PBAT, MAH-GMA co-grafted PHA, MAH-GMA co-grafted PCL, and MAH-GMA co-grafted biodegradable TPU. The beneficial effect of this embodiment is that the addition of the biodegradable elastomer is mainly to ensure good overall elasticity of the composite material, while the maleic anhydride (MAH) groups and glycidyl methacrylate (GMA) groups on the maleic anhydride (MAH)-glycidyl methacrylate (GMA) co-grafted biodegradable elastomer can cause chemical reactions between the elastomer and polylactic acid (PLA) and biomass fibers, thereby improving the interfacial bonding force between adjacent layers.

[0038] As a further improvement to the above method, the preparation method of the maleic anhydride (MAH)-glycidyl methacrylate (GMA) co-grafted biodegradable elastomer in step S4 includes the following steps: S4.1: Dissolve dicumyl peroxide (DCP) and maleic anhydride (MAH) in an appropriate amount of acetone solution to obtain solution C; S4.2: Mix solution C and glycidyl methacrylate (GMA) evenly to obtain solution D; S4.3: Add the biodegradable elastomer to a mixer, and then spray solution D onto the biodegradable elastomer and mix for 5-10 minutes to obtain material C; S4.4: Add material C to a granulator for granulation to obtain the maleic anhydride (MAH)-glycidyl methacrylate (GMA) co-grafted biodegradable elastomer. The beneficial effects of this embodiment are: maleic anhydride (MAH) and glycidyl methacrylate (GMA) are jointly grafted onto the molecular chain of the biodegradable elastomer. At the interface between the elastic layer 12 and the foamed layer 4 and decorative layer 14, a chemical reaction occurs between the maleic anhydride (MAH) groups, the epoxy groups of glycidyl methacrylate (GMA), and the hydroxyl groups of polylactic acid (PLA) and biomass fibers, thereby increasing the bonding force between the two interfaces. The reason for using maleic anhydride (MAH) and glycidyl methacrylate (GMA) for double grafting is that single grafting can lead to saturation, while double grafting significantly increases the number of reaction contact points and the interfacial bonding force.

[0039] As a further improvement to the above method, the foaming co-extrusion mold 9 in step S6 has two interfaces, located on the left and right sides of the mold, respectively, namely the left interface 23 and the right interface 24. The left interface 23 is connected to the first co-extruder 11, and the right interface 24 is connected to the second co-extruder 13. The upper surface of the foaming co-extrusion mold 9 is provided with a connection 25, through which the pre-cured resin 8 enters the foaming co-extrusion mold 9. The beneficial effects of this embodiment are: the connection between the co-extruder and the two interfaces on the co-extrusion mold, and the connection 25 on the upper surface of the co-extrusion mold, enable the reinforcing layer 10, the foaming layer 4, the elastic layer 12, and the decorative layer 14 to be sequentially combined inside the mold, and the reinforcing layer 10 can be completely cured under the high temperature and high pressure environment of the mold, ultimately forming a biodegradable epoxy resin reinforced foamed PLA-based wood-plastic product 15 with a four-layer structure. The connection 25 on the upper surface of the mold can transport the soft pre-cured resin 8 into the mold for molding. The interfaces are located on both sides of the mold, so the co-extruders do not interfere with each other, which facilitates production operations.

[0040] As a further improvement to the above method, the foaming layer 4 in the product comprises the following components: 0.1-1 parts by mass of dicumyl peroxide (DCP); 0.1-5 parts by mass of maleic anhydride (MAH); 0.1-5 parts by mass of glycidyl methacrylate (GMA); 0.1-2 parts by mass of bisoxazoline; 0.5-5 parts by mass of AC foaming agent; 5-20 parts by mass of glass microspheres; 25-60 parts by mass of polylactic acid (PLA); 5-20 parts by mass of polycaprolactone (PCL); 10-60 parts by mass of biomass fiber; 1-3 parts by mass of antioxidant; and 3-5 parts by mass of lubricant. The reinforcing layer 10 comprises the following components: 20-50 parts by mass of rattan woven fabric; and 50-80 parts by mass of biodegradable epoxy resin. The elastic layer 12 comprises the following components: 50-90 parts by weight of biodegradable elastomer; 10-50 parts by weight of maleic anhydride (MAH)-glycidyl methacrylate (GMA) co-grafted biodegradable elastomer. The decorative layer 14 comprises the following components: 0.5-3 parts by weight of dicumyl peroxide (DCP); 0.5-5 parts by weight of maleic anhydride (MAH); 0.5-5 parts by weight of glycidyl methacrylate (GMA); 0.5-2 parts by weight of bisoxazoline; 5-10 parts by weight of alumina; 1-5 parts by weight of color masterbatch; 1-10 parts by weight of pigment; and 70-90 parts by weight of polylactic acid (PLA). The beneficial effects of this embodiment are: the synergistic foaming of AC foaming agent and supercritical carbon dioxide improves foaming efficiency and the stability and uniformity of cell size; and the addition of glass microspheres further reduces the density of the composite material. The addition of dicumyl peroxide (DCP), maleic anhydride (MAH), glycidyl methacrylate (GMA), and bisoxazoline increases the melt viscosity of polylactic acid (PLA) and improves its ability to encapsulate air bubbles, making them less prone to breakage. Simultaneously, these groups can chemically react with the hydroxyl groups of biomass fibers, enhancing the interfacial bonding between layers.

[0041] like Figure 4As shown, as a further improvement to the above method, the product has a four-layer structure from the inside out: a reinforcing layer 10, a foaming layer 4, an elastic layer 12, and a decorative layer 14. The beneficial effects of this embodiment are: the biodegradable epoxy resin reinforcing the rattan weave is a thermosetting material. When the composite material is subjected to external load impact, stress can be transferred and dispersed to the rattan weave, greatly enhancing the overall strength of the composite material; therefore, it can serve as the reinforcing layer 10. The foaming layer 4 combines physical foaming, chemical foaming, and low-density filling, effectively reducing the density of the composite material. The biodegradable elastomer in the elastic layer 12 becomes a stress concentration point, absorbing impact energy by inducing and terminating numerous small deformations, thereby improving the toughness of the composite material. Furthermore, when used as flooring, the elastic layer 12 provides a comfortable feel underfoot. The combination of color masterbatch and pigments forms a beautiful wood grain decorative layer, and the alumina has strong wear resistance, thus giving the composite material excellent surface wear resistance.

[0042] Example 1:

[0043] The mass fractions of each component in the foam layer 4 are as follows: dicumyl peroxide (DCP): 0.5 parts; maleic anhydride (MAH): 2 parts; glycidyl methacrylate (GMA): 2 parts; dioxazoline: 0.5 parts; AC foaming agent: 3 parts; glass microspheres: 15 parts; polylactic acid (PLA): 31 parts; polycaprolactone (PCL): 10 parts; biomass fiber (wood fiber): 30 parts; antioxidant: 3 parts; lubricant: 3 parts.

[0044] The mass fractions of each component of the reinforcing layer 10 are as follows: rattan woven material: 20 parts; biodegradable epoxy resin containing disulfide bonds: 80 parts.

[0045] The mass fractions of each component of the material in the elastic layer 12 are as follows: biodegradable elastomer (polybutylene terephthalate-adipate ester PBAT): 50 parts; maleic anhydride MAH-glycidyl methacrylate GMA co-grafted biodegradable elastomer (MAH-GMA co-grafted PBAT): 50 parts.

[0046] The mass fractions of each component of the decorative layer 14 are as follows: dicumyl peroxide (DCP): 0.5 parts; maleic anhydride (MAH): 1 part; glycidyl methacrylate (GMA): 0.5 parts; bis(oxazoline): 1 part; alumina: 10 parts; masterbatch: 3 parts; pigment: 5 parts; polylactic acid (PLA): 79 parts.

[0047] The material of foam layer 4 is granulated and added to the extruder. Simultaneously, supercritical carbon dioxide fluid is pumped into extruder 1 via pump system 2 and extruded at high temperature into foaming co-extrusion die 9. Rattan woven fabric is soaked in sodium hydroxide solution for 24 hours, removed, washed with water until neutral, and dried to obtain modified rattan woven fabric 5. This modified rattan woven fabric is then immersed in biodegradable epoxy resin containing disulfide bonds and heated to obtain pre-cured resin 8, which is then conveyed to foaming co-extrusion die 9. The materials of elastic layer 12 and decorative layer 14 are extruded separately through two co-extruders into the foaming co-extrusion die to obtain a four-layer biodegradable epoxy resin-reinforced foamed PLA-based wood-plastic product 15.

[0048] Example 2:

[0049] The mass fractions of each component in the foam layer 4 are as follows: dicumyl peroxide (DCP): 0.5 parts; maleic anhydride (MAH): 2 parts; glycidyl methacrylate (GMA): 2 parts; dioxazoline: 0.5 parts; AC foaming agent: 2 parts; glass microspheres: 10 parts; polylactic acid (PLA): 37 parts; polycaprolactone (PCL): 10 parts; biomass fiber (wood fiber): 30 parts; antioxidant: 3 parts; lubricant: 3 parts.

[0050] The mass fractions of each component of the reinforcing layer 10 are as follows: rattan woven material: 30 parts; biodegradable epoxy resin containing hexahydrotriazine bonds: 70 parts.

[0051] The mass fractions of each component of the material in the elastic layer 12 are as follows: biodegradable elastomer (polyhydroxyalkanoate PHA): 70 parts; maleic anhydride MAH-glycidyl methacrylate GMA co-grafted biodegradable elastomer (MAH-GMA co-grafted PHA): 30 parts.

[0052] The mass fractions of each component of the decorative layer 14 are as follows: dicumyl peroxide (DCP): 0.5 parts; maleic anhydride (MAH): 1 part; glycidyl methacrylate (GMA): 0.5 parts; bis(oxazoline): 1 part; alumina: 5 parts; masterbatch: 3 parts; pigment: 5 parts; polylactic acid (PLA): 84 parts.

[0053] The material of foam layer 4 is granulated and added to the extruder. Simultaneously, supercritical carbon dioxide fluid is pumped into extruder 1 via pump system 2 and extruded at high temperature into foaming co-extrusion die 9. Rattan woven fabric is soaked in sodium hydroxide solution for 24 hours, removed, washed with water until neutral, and dried to obtain modified rattan woven fabric 5. This modified rattan woven fabric is then immersed in biodegradable epoxy resin containing disulfide bonds and heated to obtain pre-cured resin 8, which is then conveyed to foaming co-extrusion die 9. The materials of elastic layer 12 and decorative layer 14 are extruded separately through two co-extruders into the foaming co-extrusion die to obtain a four-layer biodegradable epoxy resin-reinforced foamed PLA-based wood-plastic product 15.

[0054] Example 3:

[0055] The mass fractions of each component in the foam layer 4 are as follows: dicumyl peroxide (DCP): 0.5 parts; maleic anhydride (MAH): 2 parts; glycidyl methacrylate (GMA): 2 parts; bis(oxazoline): 0.5 parts; AC foaming agent: 5 parts; glass microspheres: 20 parts; polylactic acid (PLA): 34 parts; polycaprolactone (PCL): 10 parts; biomass fiber (wood fiber): 20 parts; antioxidant: 3 parts; lubricant: 3 parts.

[0056] The mass fractions of each component of the reinforcing layer 10 are as follows: rattan woven material: 40 parts; biodegradable epoxy resin containing Schiff base bonds: 60 parts.

[0057] The mass fractions of each component of the material in the elastic layer 12 are as follows: biodegradable elastomer (polycaprolactone PCL): 60 parts; maleic anhydride MAH-glycidyl methacrylate GMA co-grafted biodegradable elastomer (MAH-GMA co-grafted PCL): 40 parts.

[0058] The mass fractions of each component of the decorative layer 14 are as follows: dicumyl peroxide (DCP): 0.5 parts; maleic anhydride (MAH): 1 part; glycidyl methacrylate (GMA): 0.5 parts; bis(oxazoline): 1 part; alumina: 8 parts; masterbatch: 3 parts; pigment: 5 parts; polylactic acid (PLA): 81 parts.

[0059] The material of foam layer 4 is granulated and added to the extruder. Simultaneously, supercritical carbon dioxide fluid is pumped into extruder 1 via pump system 2 and extruded at high temperature into foaming co-extrusion die 9. Rattan woven fabric is soaked in sodium hydroxide solution for 24 hours, removed, washed with water until neutral, and dried to obtain modified rattan woven fabric 5. This modified rattan woven fabric is then immersed in biodegradable epoxy resin containing disulfide bonds and heated to obtain pre-cured resin 8, which is then conveyed to foaming co-extrusion die 9. The materials of elastic layer 12 and decorative layer 14 are extruded separately through two co-extruders into the foaming co-extrusion die to obtain a four-layer biodegradable epoxy resin-reinforced foamed PLA-based wood-plastic product 15.

[0060]

[0061] In addition to the above embodiments, the present invention may have other implementation methods. All technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A method for preparing epoxy resin-reinforced foamed PLA-based wood-plastic composite, characterized in that... It has the following steps: S1. Base material preparation: Modified polylactic acid (PLA), biomass fiber, AC foaming agent, glass microspheres, antioxidant, and lubricant are mixed and granulated to obtain polylactic acid (PLA) wood-plastic base material; S2. Preparation of foamed layer: The polylactic acid PLA wood-plastic base material is added to the extruder (1), and supercritical carbon dioxide fluid is pumped into the extruder barrel (3) through the pumping system (2). After extrusion molding, a foamed layer (4) is obtained. S3. Preparation of reinforcing layer: Modified rattan woven fabric (5) and biodegradable epoxy resin (6) are passed through a thermosetting molding system (7) to obtain pre-cured resin (8). The pre-cured resin (8) is then transported to a foaming co-extrusion mold (9) and extruded to obtain reinforcing layer (10). S4. Preparation of elastic layer: The biodegradable elastomer and maleic anhydride MAH-glycidyl methacrylate GMA co-grafted biodegradable elastomer are added to the first co-extruder (11) and extruded to obtain the elastic layer (12). S5. Preparation of decorative layer: Modified polylactic acid PLA, alumina, color masterbatch and pigment are added to the second co-extruder (13) and extruded to obtain decorative layer (14). S6. Product preparation: The foamed layer (4) obtained in step S2, the reinforcing layer (10) obtained in step S3, the elastic layer (12) obtained in step S4, and the decorative layer (14) obtained in step S5 are combined and co-extruded in a foaming co-extrusion mold (9) to obtain a biodegradable epoxy resin reinforced foamed PLA-based wood-plastic composite product (15).

2. The method for preparing an epoxy resin-reinforced foamed PLA-based wood-plastic composite product according to claim 1, characterized in that, The preparation method of modified polylactic acid (PLA) in steps S1 and S5 includes the following steps: S1.1: Dissolve dicumyl peroxide (DCP), maleic anhydride (MAH), and dioxazoline in an appropriate amount of acetone solution to obtain solution A; S1.2: Glycidyl methacrylate (GMA) and solution A are mixed evenly to obtain solution B; S1.3: Add polylactic acid (PLA) and polycaprolactone (PCL) to a mixer and mix for 5-10 minutes to obtain material A; S1.4: Spray solution B into material A and mix for 5-10 minutes to obtain material B; S1.5: Add material B into a granulator to granulate and obtain modified polylactic acid (PLA).

3. The method for preparing an epoxy resin-reinforced foamed PLA-based wood-plastic composite product according to claim 2, characterized in that, The method for preparing the pre-cured resin (8) in step S3 includes the following steps: S3.1: Soak the rattan woven fabric in sodium hydroxide solution for at least 24 hours, take it out and wash it with water until neutral, and then dry it to obtain the modified rattan woven fabric (5). S3.2: The modified rattan woven fabric (5) is transported to the resin tank (21) and immersed in biodegradable epoxy resin (6); S3.2: The modified rattan weave (5) impregnated with biodegradable epoxy resin (6) is conveyed to the heating zone (22) to obtain pre-cured resin (8).

4. The method for preparing an epoxy resin-reinforced foamed PLA-based wood-plastic composite product according to claim 1, characterized in that, The pumping system (2) in step S2 consists of an injection valve (20), a flow controller (19), a piston pump (18), a gas pipeline (17), and a carbon dioxide storage tank (16), which are arranged sequentially from near the extruder barrel (3) to away from the extruder barrel (3).

5. The method for preparing an epoxy resin-reinforced foamed PLA-based wood-plastic composite product according to claim 1, characterized in that, The biodegradable epoxy resin (6) in step S3 comprises a biodegradable epoxy resin matrix and a curing agent, wherein the biodegradable epoxy resin matrix contains one or more combinations of disulfide bonds, Schiff base bonds, and hexahydrotriazine bonds.

6. The method for preparing an epoxy resin-reinforced foamed PLA-based wood-plastic composite product according to claim 1, characterized in that, The biodegradable elastomer in step S4 is one or more of polybutylene terephthalate (PBAT), polyhydroxyalkanoate (PHA), polycaprolactone (PCL), and biodegradable thermoplastic polyurethane (TPU); the maleic anhydride (MAH)-glycidyl methacrylate (GMA) co-grafted biodegradable elastomer in step S4 is one or more of MAH-GMA co-grafted PBAT, MAH-GMA co-grafted PHA, MAH-GMA co-grafted PCL, and MAH-GMA co-grafted biodegradable TPU.

7. The method for preparing an epoxy resin-reinforced foamed PLA-based wood-plastic composite product according to claim 1, characterized in that, The preparation method of the maleic anhydride (MAH)-glycidyl methacrylate (GMA) co-grafted biodegradable elastomer in step S4 includes the following steps: S4.1; Dissolve dicumyl peroxide (DCP) and maleic anhydride (MAH) in an appropriate amount of acetone solution to obtain solution C; S4.2: Mix solution C and glycidyl methacrylate (GMA) thoroughly to obtain solution D; S4.3: Add the biodegradable elastomer to the mixer, then spray solution D into the biodegradable elastomer and mix for 5-10 minutes to obtain material C; S4.4: Add material C to a granulator for granulation to obtain maleic anhydride MAH-glycidyl methacrylate GMA co-grafted biodegradable elastomer.

8. The method for preparing an epoxy resin-reinforced foamed PLA-based wood-plastic composite product according to claim 1, characterized in that, The foaming co-extrusion mold (9) in step S6 is provided with a left interface (23) and a right interface (24). The left interface (23) is connected to the first co-extruder (11), and the right interface (24) is connected to the second co-extruder (13). The pre-cured resin molding system is connected to the foaming co-extrusion mold (9) through the connection (25) provided on the upper surface of the foaming co-extrusion mold (9).

9. An epoxy resin-reinforced foamed PLA-based wood-plastic composite product, characterized in that, Prepared by the method according to any one of claims 3-8, wherein the foaming layer (4) of the product comprises the following components: 0.1-1 parts by weight of dicumyl peroxide (DCP); 0.1-5 parts by weight of maleic anhydride (MAH); 0.1-5 parts by weight of glycidyl methacrylate (GMA); 0.1-2 parts by weight of bisoxazoline; 0.5-5 parts by weight of AC foaming agent; 5-20 parts by weight of glass microspheres; 25-60 parts by weight of polylactic acid (PLA); 5-20 parts by weight of polycaprolactone (PCL); 10-60 parts by weight of biomass fiber; 1-3 parts by weight of antioxidant; 3-5 parts by weight of lubricant; and the reinforcing layer (10) comprises the following components: The material comprises the following components: 20-50 parts by weight of rattan woven fabric; 50-80 parts by weight of biodegradable epoxy resin; the material of the elastic layer (12) comprises the following components: 50-90 parts by weight of biodegradable elastomer; 10-50 parts by weight of maleic anhydride MAH-glycidyl methacrylate GMA co-grafted biodegradable elastomer; the material of the decorative layer (14) comprises the following components: 0.5-3 parts by weight of dicumyl peroxide DCP; 0.5-5 parts by weight of maleic anhydride MA; 0.5-5 parts by weight of glycidyl methacrylate GMA; 0.5-2 parts by weight of bisoxazoline; 5-10 parts by weight of alumina; and 1-5 parts by weight of color masterbatch. The pigment is 1-10 parts by weight; the polylactic acid (PLA) is 70-90 parts by weight.

10. The epoxy resin-reinforced foamed PLA-based wood-plastic composite product according to claim 9, characterized in that, The structure consists of four layers from the inside out: a reinforcing layer (10), a foaming layer (4), an elastic layer (12), and a decorative layer (14).

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