Environment-friendly high-performance bamboo-plastic composite material as well as preparation method and application thereof

Abstract

The invention provides a green and environment-friendly high-performance bamboo-plastic composite material and a preparation method and application thereof.The green and environment-friendly high-performance bamboo-plastic composite material is prepared from long-chain-chain PBS, modified calcium carbonate, bamboo powder and fluorine-containing auxiliaries, KH-570 is loaded on the surface of ground calcium carbonate, then the bamboo powder and the fluorine-containing auxiliaries are added in sequence, surface modification is conducted on the bamboo powder through impact force and friction force, and the bamboo-plastic composite material is obtained. Mixing the obtained modified bamboo powder / calcium carbonate with long-chain branch PBS in a double-screw extruder; according to the scheme, better interface cohesiveness is provided for the composite material by introducing the long-chain branch PBS, and entanglement among PBS molecular chains is increased by the long-chain branch structure, so that the matrix material has higher melt strength and better fluidity in a molten state; the bamboo powder and the calcium carbonate are subjected to surface modification treatment, more polar groups or functional groups with good compatibility with a PBS matrix are introduced, the modified bamboo powder / calcium carbonate is obtained, and the mechanical property, the thermal property, the interfacial compatibility and the crystallization property of the composite material are overall improved. The tensile strength of the obtained product is 13.61 MPa, and the elongation at break is 53%.

Description

Technical Field

[0001] The present application relates to the technical field of composite materials, and in particular to a green, environmentally friendly, high-performance bamboo-plastic composite material and a preparation method and application thereof. Background Art

[0002] Wood and plastic are commonly used materials in packaging, construction, and other fields. However, wood is susceptible to corrosion and cracking, while pure plastic products are difficult to degrade and pose significant environmental pollution risks. Existing wood-plastic composites (WPCs) are composed of wood fibers combined with polyethylene (PE) and polypropylene (PP), but their mechanical properties (such as flexural strength and impact resistance) are limited by the length of the wood fibers and the interfacial bonding strength. Bamboo fiber, due to its higher aspect ratio and cellulose content, is theoretically more suitable as a reinforcing phase than wood fiber. However, the polar hydroxyl groups (—OH) on the surface of bamboo fiber are poorly compatible with non-polar plastics (such as PP), resulting in weak interfacial bonding. Bamboo powder is a polar material, making it difficult to form chemical bonds when compounded with non-polar materials such as plastics. Improving the interfacial compatibility of bamboo-plastic composites (BPCs) and ensuring the dispersion of bamboo materials in the resin matrix are key technologies for improving the performance of BPCs and are currently the focus and difficulty of interfacial modification research.

[0003] Patent CN119331344 A discloses a method and application for melt-catalyzed modification of bamboo powder / polypropylene composites. The composite material preparation method comprises the following steps: uniformly spraying a hydroalcoholic solution of a composite silane coupling agent onto the surface of the bamboo powder and drying to obtain the modified bamboo powder; then uniformly mixing polypropylene, a silicone masterbatch (containing 50% polydimethylsiloxane), the modified bamboo powder, and a cobalt acetylacetonate / manganese acetylacetonate catalyst in separate temperature zones, and melt-extruding the resulting modified bamboo powder / polydimethylsiloxane / polypropylene composite. The invention utilizes the hydrolysis of the alkoxy groups in the composite silane coupling agent to form silanols, which react with the hydroxyl groups on the bamboo powder surface to form hydrogen bonds and condense into covalent bonds. Simultaneously, the amino and imine groups in the coupling agent also form hydrogen bonds with the hydroxyl groups, thereby hydrophobically modifying the bamboo powder. The polydimethylsiloxane in the silicone masterbatch and the silanol groups on the surface of the modified bamboo powder undergo a melt-catalyzed dehydrogenation reaction, forming a stable chemical bond and an interface layer, enhancing compatibility between the bamboo powder and the polypropylene. However, it uses non-degradable PP material; and adopts KH-550 and KH-792 composite coupling agents. The amine group of KH-550 and the amine / imine group of KH-792 can both react with the hydroxyl groups of bamboo powder, but the reaction rates are different (imine groups are more active than amine groups), which may weaken the "infiltration-surface" synergistic effect or the surface coverage is insufficient, unable to form an effective interfacial transition layer, and the hydrophobicity improvement is limited. The two silane coupling agents have different solubility and diffusion rates (KH-550 is slightly more water-soluble than KH-792). Local concentration unevenness is prone to occur during solution preparation or melt blending, resulting in inconsistent modification effects between bamboo powder particles. The composite system may introduce more side reaction products (such as amino cross-linking byproducts), requiring additional optimization of washing or drying processes, increasing production costs. Moreover, the composite coupling agent acts on bamboo powder mainly through physical adsorption (hydrogen bonds) and weak chemical adsorption (silicon-oxygen bonds). Under high temperature and high humidity environments, hydrogen bonds are easily broken, resulting in problems such as interface compatibility decaying over time.

[0004] Therefore, how to modify bamboo powder and plastic polymer matrix to improve the interfacial adhesion effect has become the primary issue to be faced in the preparation of BPC with good performance. Summary of the Invention

[0005] This application is made in view of the above-mentioned issues, and its purpose is to provide a green, environmentally friendly, high-performance bamboo-plastic composite material, as well as its preparation method and application, which effectively improves the melt strength and mechanical properties of PBS and enhances the mechanical properties, thermal stability and interface compatibility of the composite material.

[0006] The first aspect of the present application provides a green, environmentally friendly, high-performance bamboo-plastic composite material, comprising long-chain branched PBS, modified calcium carbonate, bamboo powder and a fluorine-containing additive; the modified calcium carbonate, bamboo powder and fluorine-containing additive are obtained to obtain modified bamboo powder / calcium carbonate, and the long-chain branched PBS is mixed with the modified bamboo powder / calcium carbonate to obtain a bamboo-plastic composite material.

[0007] In any embodiment, the composite material is composed of the following parts by weight: 100 parts by weight of long-chain branched PBS, 10-20 parts by weight of modified calcium carbonate, 10-20 parts by weight of bamboo powder, and 0.5-1.5 parts by weight of a fluorine-containing additive.

[0008] In any embodiment, the long-chain branched PBS is obtained by reacting PBS, a composite initiator and a multifunctional monomer through a twin-screw extruder. During the reaction, the weight proportion of the components is as follows: 100 parts by weight of PBS, 0.3-0.5 parts by weight of the composite initiator, and 3-5 parts by weight of the multifunctional monomer.

[0009] In any embodiment, the modified calcium carbonate is obtained by loading the silane coupling agent KH-570 on the surface of heavy calcium carbonate, and the mass of the silane coupling agent KH-570 is 1.5 to 3 wt% of the heavy calcium carbonate.

[0010] In any embodiment, the mass ratio of the modified calcium carbonate to the bamboo powder is 1:1.

[0011] In any embodiment, the bamboo powder has a particle size of 200-300 meshes and a moisture content of less than 0.5%, and the fluorine-containing auxiliary agent is perfluorohexanoic acid.

[0012] A second aspect of the present application further provides a method for preparing a green, environmentally friendly, high-performance bamboo-plastic composite material, comprising the following steps:

[0013] S1. In a high-speed mixer, a certain amount of KH-570 is first loaded on the surface of heavy calcium carbonate to obtain modified calcium carbonate;

[0014] S2, adding bamboo powder and fluorine-containing additives in sequence to obtain a modified bamboo powder / calcium carbonate mixture;

[0015] S3, weighing 9 / 10 of the PBS resin, initiator, and multifunctional monomer according to the mass ratio, drying the PBS resin, and dissolving the composite initiator in an acetone solution, and then blending the dried PBS resin, the dissolved initiator solution, and the multifunctional monomer to obtain a mixture;

[0016] S4, the mixed material is fed into the main feed port of a twin-screw extruder, and the remaining 1 / 10 PBS resin is fed into the side feed port at the third section;

[0017] S5. The modified bamboo powder / calcium carbonate mixture is introduced into the system through the side feeding port at the 6th stage of the twin-screw extruder, and granulated by extrusion through the twin-screw extruder to obtain a long-chain branched PBS / bamboo powder / calcium carbonate composite material.

[0018] In any embodiment, the extrusion process parameters of the twin-screw extruder are: extrusion temperature of 120-160° C., main engine speed of 100-200 rpm, main feed speed of 5-10 rpm, and side feed speed of 5-10 rpm.

[0019] In any embodiment, the twin-screw extruder is provided with 8 sections, and the temperatures of each section from the main feed port to the die are: zone 1: 120-130°C, zone 2: 130-140°C, zone 3: 130-140°C, zone 4: 140-150°C, zone 5: 140-150°C, zone 6: 140-150°C, zone 7: 140-150°C, zone 8: 150-160°C, and die: 145-155°C.

[0020] In any embodiment, the third to sixth sections of the twin-screw extruder are provided with a side feed port and equipped with a two-stage side feeder, the length-to-diameter ratio of the twin-screw extruder is 48:1, and the torque level is T / A 3 =8~15N·m / cm 3 .

[0021] The third aspect of the present application provides an application of a green, environmentally friendly, high-performance bamboo-plastic composite material, including the application of the composite material of the first aspect of the present application or the composite material prepared according to the method of the second aspect of the present application in the fields of packaging, home appliances, and automobiles.

[0022] Beneficial effects of this application:

[0023] (1) The functional group of KH 570 (γ-methacryloxypropyltrimethoxysilane) is a double bond (-CH=CH2). Under the action of a composite initiator (such as benzoyl peroxide / curing agent dipentadiene pentadiene (BPO / DHBP)), the double bond of KH-570 opens and forms a covalent bond (such as a CC bond) with the PBS main chain (-O-CH2-CH2-) through a free radical chain reaction. The grafting rate can reach 0.9-1.2% (FTIR characterization shows 1630 cm -1 The double bond peak intensity at the bottom of the coupling agent is significantly reduced); in addition, the silyl group (-OCH3) of KH-570 is hydrolyzed and condensed with the hydroxyl group of bamboo powder to form Si-OC bonds. At the same time, the polymer side chain is anchored to the PBS main chain through covalent bonds, forming a three-dimensional chemical bond network of "bamboo powder-Si-OC-KH570-PBS", forming an interfacial chemical bond with a binding energy 2-3 orders of magnitude higher than that of the hydrogen bond system (DSC test shows that the interfacial melting peak temperature increases by 12-15°C); this has achieved a breakthrough in the chemical reaction mechanism from "physical adsorption" to "chemical bonding", and by utilizing the free radical polymerization characteristics of double bonds, the "surface modification" of traditional coupling agents is transformed into "polymer-filler interfacial chemical bonding", fundamentally solving the limitation of the composite system's reliance on physical effects.

[0024] (2) This application adopts a single KH-570 system, which avoids the problem of proportion control of the composite system, simplifies the production process through a single reagent, and simultaneously utilizes the specific reaction (double bond polymerization) of KH-570 and PBS to achieve a synergistic effect of compatibility improvement and polymer structure control. This is a technical path that cannot be achieved by the composite coupling agent system in the comparative document; the technical route is more efficient and controllable, the process is simplified, and the performance fluctuation between batches is controlled within ±3%, which saves production costs and improves product stability.

[0025] (3) The modification of bamboo powder is divided into three stages: in the first stage, bamboo powder is first added to the mixed system, and the bamboo powder that is easy to disperse and first contacts the modified heavy calcium carbonate is modified; in the second stage, the bamboo powder that is difficult to disperse is further dispersed under the impact of the modified heavy calcium carbonate, and this part of the bamboo powder is modified; in the third stage, a fluorine-containing auxiliary agent is added to the mixed system. The fluorine-containing auxiliary agent is perfluorohexanoic acid. Under the action of fluorine atoms, the hydrogen bonds between the bamboo powders are destroyed, which is conducive to further dispersion of the bamboo powder. The surface hydroxyl groups of this part of the further dispersed bamboo powder react with the carboxylic acid contained at the end of the fluorine-containing auxiliary agent, showing lipophilicity and being modified. After these three stages of modification, the bamboo powder is fully dispersed and completely modified.

[0026] (4) Long-term effectiveness and controllability of performance improvement

[0027] Durable interfacial compatibility: Chemical bonding rather than hydrogen bonding enables the composite material to retain 92% of its tensile strength after immersion in 80°C hot water for 24 hours, significantly reducing the risk of interfacial debonding in hot and humid environments.

[0028] Specific matching of long-chain branched PBS: The double bond polymerization of KH-570 can induce PBS to form a long-chain branched structure (GPC test shows that the branching degree increases from 0.8% to 5.6%). The long chain branch further enhances the mechanical interlocking with bamboo powder through the "entanglement effect", and by triggering the polymerization reaction, it achieves this synergistic enhancement effect with the PBS molecular chain. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of the positions of the various zones of the twin-screw extruder in the embodiment of this application;

[0030] Figure 2 This is a schematic diagram of the reaction principle of KH-570 surface-modified bamboo powder in this application example;

[0031] Figure 3 This is the technical roadmap for the twin-screw extruder preparation method of this application;

[0032] Figure 4 The graphs are test diagrams of tensile properties of composite materials of Examples and Comparative Examples;

[0033] Figure 5The graph is a test graph of the notched impact performance of the composite materials of the embodiment and the comparative example;

[0034] Figure 6 The torque curves of the composite materials of the embodiment and the comparative example are shown;

[0035] Figure 7 The scanning electron microscope images of the composite materials of the examples and comparative examples, long-chain branched PBS, blank bamboo powder and blank calcium carbonate;

[0036] Figure 8 The X-ray diffraction patterns of the composite materials of Examples and Comparative Examples are shown. DETAILED DESCRIPTION

[0037] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the green, environmentally friendly, high-performance bamboo-plastic composite material, its preparation method, and its application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters or repeated descriptions of substantially identical structures may be omitted. This is to avoid unnecessary redundancy and facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to facilitate a thorough understanding of the present application by those skilled in the art and are not intended to limit the subject matter recited in the claims.

[0038] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0039] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0040] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0041] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0042] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0043] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0044] In one embodiment of the present application, the present application proposes a green, environmentally friendly, high-performance bamboo-plastic composite material, comprising long-chain branched PBS, modified calcium carbonate, bamboo powder and a fluorine-containing additive; the modified calcium carbonate, bamboo powder and fluorine-containing additive are obtained to obtain modified bamboo powder / calcium carbonate, and the long-chain branched PBS is mixed with the modified bamboo powder / calcium carbonate to obtain a bamboo-plastic composite material.

[0045] The composite material is composed of the following parts by weight: 100 parts by weight of long-chain branched PBS, 10-20 parts by weight of modified calcium carbonate, 10-20 parts by weight of bamboo powder, and 0.5-1.5 parts by weight of a fluorine-containing additive.

[0046] Regarding optimizing the composite material composition, when the modified calcium carbonate content is low, the modified calcium carbonate cannot effectively impact the bamboo powder, resulting in poor bamboo powder dispersion, which leads to weak composite material resistance to impact at notches. When the bamboo powder content is low, although a small amount of bamboo powder is well dispersed, the modification effect is good, and the compatibility is good, the bamboo powder acts similarly to chopped fiber reinforcement, effectively transferring stress and improving the tensile strength and flexural modulus of the composite material. Therefore, a low bamboo powder content is not only detrimental to the high-value utilization of bamboo powder, but also hinders the optimization of the tensile strength and flexural modulus of the composite material. Excessive amounts of modified calcium carbonate and bamboo powder make it difficult to disperse the calcium carbonate and bamboo powder in the composite material, reducing its tensile strength. This application optimizes the content of bamboo powder and modified calcium carbonate, adding appropriate amounts of bamboo powder and modified calcium carbonate to the composite material to fill the gaps between long-chain branched PBS, absorb impact energy, and improve the composite material's impact resistance.

[0047] Bamboo powder and modified calcium carbonate can limit the movement of PBS molecular chains and enhance the internal stability of the material, thereby improving the thermal stability of the composite material and improving the flame retardant properties of the composite material.

[0048] Through a large number of experimental studies, it was found that the addition of fluorine-containing additives and their dosage are closely related to the elongation at break and tensile strength. The factors affecting the elongation at break are: bamboo powder content > fluorine-containing additive content > modified calcium carbonate content; the factors affecting the tensile strength are: fluorine-containing additive content > bamboo powder content > modified calcium carbonate content. Fluorine-containing additives can generate hydrogen bonds (0-H…F) with the hydroxyl groups in bamboo powder, overcoming the intermolecular forces generated by hydrogen bonding (OH…O) between the bamboo powder itself and reducing the agglomeration of the bamboo powder itself; further, the use of perfluorohexanoic acid, whose terminal carboxylic acid group (-COOH) undergoes a condensation reaction with the hydroxyl groups of bamboo powder, further improving the dispersibility of the bamboo powder. However, the compatibility of fluorine-containing additives with PBS is limited, and excessive addition can easily form microphase separation in the matrix, becoming a stress concentration point. Therefore, the present application adds fluorine-containing additives and optimizes their addition amount to solve the agglomeration problem of bamboo powder, improve the dispersion performance of bamboo powder, achieve a good composite effect with long-chain branched BPS, and improve the mechanical properties, thermal stability, interface compatibility and other properties of the composite material.

[0049] The long-chain branched PBS is obtained by reacting PBS, a composite initiator and a multifunctional monomer through a twin-screw extruder. During the reaction, the weight proportion of the components is as follows: 100 parts by weight of PBS, 0.3-0.5 parts by weight of the composite initiator, and 3-5 parts by weight of the multifunctional monomer.

[0050] The modified calcium carbonate is obtained by loading a silane coupling agent KH-570 on the surface of heavy calcium carbonate, and the mass of the silane coupling agent KH-570 is 1.5-3 wt% of the heavy calcium carbonate.

[0051] When heavy calcium carbonate is modified with an appropriate amount of silane coupling agent, a layer of silane coupling agent film is wrapped around the surface of the calcium carbonate, with the hydrophobic groups of the silane coupling agent film facing outward. When calcium carbonate is modified with an excessive amount of silane coupling agent, two layers of silane coupling agent film are wrapped around the surface of the calcium carbonate, with the hydrophobic matrix of the first layer of silane coupling agent film still facing outward. Based on similar compatibility, the hydrophobic matrix of the second layer of silane coupling agent film will face the hydrophobic matrix of the first layer of silane coupling agent film, while the hydrophilic matrix of the second layer of silane coupling agent film naturally faces outward. In the present application, the amount of silane coupling agent used in the modified calcium carbonate technology needs to be controlled. Excessive or insufficient silane coupling agent will not achieve good hydrophobic modification of calcium carbonate. The present invention uses excess silane coupling agent to transfer the second layer of silane coupling agent film on the surface of heavy calcium carbonate to the surface of bamboo powder to achieve the modification effect. In this way, a small amount of silane coupling agent is passed through heavy calcium carbonate to increase the surface contact area, and the hard heavy calcium carbonate collides with the bamboo powder to achieve dispersion; at the same time, by first loading the coupling agent on the hard heavy calcium carbonate, the contact probability between the coupling agent and the bamboo powder is increased compared to directly using the coupling agent to modify the bamboo powder; when the surface area is magnified many times, it can have good contact with the bamboo powder, achieving the modification effect.

[0052] The purpose of using KH-570 in the present invention is that the R group of KH-570 contains a double bond, which is grafted onto the PBS main chain through a free radical polymerization reaction under the action of a composite initiator in the long-chain branched PBS, thereby improving the interfacial adhesion performance between the long-chain branched PBS and bamboo powder and improving compatibility.

[0053] To facilitate the dispersion of bamboo powder, the fluorinated additive perfluorohexanoic acid was first added. The order of hydrogen bond strength is: 0-H…F > OH…O > OH…N > NH…N. Because fluorine atoms are more electronegative than oxygen atoms, hydrogen bonds (0-H…F) are more easily formed between the fluorinated additive and the hydroxyl groups in the bamboo powder. This overcomes the intermolecular forces generated by hydrogen bonding (OH…O) within the bamboo powder itself and reduces aggregation. Furthermore, the terminal carboxylic acid group (-COOH) of perfluorohexanoic acid undergoes a condensation reaction with the hydroxyl groups in the bamboo powder, further improving its dispersibility.

[0054] The filling amount of bamboo powder affects the viscosity and fluidity of the interface, which may ultimately affect the surface quality and appearance of the product. It will also cause wear and burden on processing equipment, which will become a factor restricting the large-scale production of the product. Fluorine-containing additives can effectively improve the processing fluidity of composite materials.

[0055] To further enhance the dispersibility of bamboo powder, heavy calcium carbonate is used to impact the bamboo powder, thereby improving its dispersibility. This invention utilizes a technical improvement to modify the heavy calcium carbonate with a precisely measured excess of silane coupling agent. A portion of the excess silane coupling agent is first loaded onto the surface of the heavy calcium carbonate. Then, through a chemical reaction, silanol molecules condense with the surface hydroxyl groups of the bamboo powder to form -Si-bamboo powder covalent bonds. The -Si-bamboo powder covalent bonds are stronger than the hydrogen bonds (O-H...F) formed between the fluorine-containing additive and the hydroxyl groups in the bamboo powder, naturally causing this condensation reaction.

[0056] In some embodiments, the mass ratio of the modified calcium carbonate to the bamboo powder is 1:1.

[0057] In some embodiments, the bamboo powder has a particle size of 200-300 meshes and a moisture content of less than 0.5%, and the fluorine-containing auxiliary agent is perfluorohexanoic acid.

[0058] There is a fluorine atom connected to each carbon atom in the perfluorohexanoic acid chain, and the terminal carboxylic acid group (-COOH) can react with some hydroxyl groups in bamboo powder to improve the fluidity of bamboo powder.

[0059] A second aspect of the present application further provides a method for preparing a green, environmentally friendly, high-performance bamboo-plastic composite material, comprising the following steps:

[0060] S1. In a high-speed mixer, a certain amount of KH-570 is first loaded on the surface of heavy calcium carbonate to obtain modified calcium carbonate;

[0061] S2, adding bamboo powder and fluorine-containing additives in sequence to obtain a modified bamboo powder / calcium carbonate mixture;

[0062] S3, weighing 9 / 10 of the PBS resin, initiator, and multifunctional monomer according to the mass ratio, drying the PBS resin, and dissolving the composite initiator in an acetone solution, and then blending the dried PBS resin, the dissolved initiator solution, and the multifunctional monomer to obtain a mixture;

[0063] S4, the mixed material is fed into the main feed port of a twin-screw extruder, and the remaining 1 / 10 PBS resin is fed into the side feed port at the third section;

[0064] S5. The modified bamboo powder / calcium carbonate mixture is introduced into the system through the side feeding port at the 6th stage of the twin-screw extruder, and granulated by extrusion through the twin-screw extruder to obtain a long-chain branched PBS / bamboo powder / calcium carbonate composite material.

[0065] In the preparation method of the present application, bamboo powder is modified in three stages: the first stage is preliminary modification, in which bamboo powder is added first and reacts before modified heavy calcium carbonate; the second stage is that the bamboo powder that is difficult to disperse is further dispersed under the impact of modified heavy calcium carbonate and is modified by the modified calcium carbonate; the third stage is that a fluorine-containing auxiliary agent is added, and the fluorine-containing auxiliary agent is perfluorohexanoic acid. Under the action of fluorine, the mutual force between the bamboo powders is weakened. At the same time, the carboxylic acid contained at the end of the fluorine-containing auxiliary agent reacts with the hydroxyl group of the bamboo powder. After these three stages of modification, the bamboo powder is fully dispersed and completely modified, thereby improving the interfacial adhesion effect and enhancing the mechanical properties, thermal stability and interfacial compatibility of the composite material.

[0066] The modified bamboo powder / calcium carbonate is introduced in the sixth section of the twin-screw extruder to react with the long-chain PBS and graft onto the PBS backbone, thereby improving the interfacial adhesion between the long-chain PBS and the bamboo powder and enhancing compatibility. If added too early, the double-bond functional groups of KH-570 will easily compete with the multifunctional monomers for positions on the PBS backbone, hindering the formation of long-chain PBS and affecting the melt strength of the composite. Adding it too late will result in uneven mixing and poor dispersion of the modified bamboo powder / calcium carbonate in the composite.

[0067] KH-570 is prepared into a coupling agent solution through a corresponding solvent and loaded on the surface of heavy calcium carbonate through a high-speed mixer to obtain modified calcium carbonate.

[0068] In some embodiments, the melt index of the PBS resin is 20 to 25 g / 10 min; the initiator includes benzoyl peroxide and a dipentadienyl vulcanizer, and the mass ratio of the benzoyl peroxide to the dipentadienyl vulcanizer is 5 to 9:1 to 5; and the multifunctional monomer is 1,6-hexanediol diacrylate.

[0069] In some embodiments, the extrusion process parameters of the twin-screw extruder are: extrusion temperature of 120-160° C., main engine speed of 100-200 rpm, main feed speed of 5-10 rpm, and side feed speed of 5-10 rpm.

[0070] In some embodiments, the twin-screw extruder is provided with 8 sections, and the temperatures from the main feeding port to the die are: zone 1: 120-130°C, zone 2: 130-140°C, zone 3: 130-140°C, zone 4: 140-150°C, zone 5: 140-150°C, zone 6: 140-150°C, zone 7: 140-150°C, zone 8: 150-160°C, and die head: 145-155°C.

[0071] In some embodiments, the third to sixth sections of the twin-screw extruder are provided with a side feed port and equipped with a two-stage side feeder, the length-to-diameter ratio of the twin-screw extruder is 48:1, and the torque level is T / A 3 =8~15N·m / cm3 .

[0072] In this application, the mechanical properties, thermal stability and interface compatibility of the composite material are achieved through the following key technologies.

[0073] First, the introduction of long-chain PBS provides better interfacial adhesion for the composite material. The long-chain structure increases the entanglement between PBS molecular chains, making the matrix material have higher viscosity and better fluidity in the molten state, which is conducive to the uniform dispersion and good bonding of bamboo powder and calcium carbonate in the matrix.

[0074] Secondly, the surface properties of bamboo powder and calcium carbonate also have a significant impact on interfacial compatibility. As a natural fiber, bamboo powder contains a certain number of polar groups, such as hydroxyl groups, on its surface. These groups can form hydrogen bonds and other interactions with polar groups on the PBS molecular chain, thereby enhancing interfacial bonding. Although calcium carbonate is an inorganic filler, its surface can also be treated or modified to introduce some polar groups, improving compatibility with the PBS matrix.

[0075] Furthermore, optimizing the processing technology further enhances interfacial compatibility. During the melt blending process, appropriate processing temperature and rotation speed can better disperse bamboo powder and calcium carbonate in the PBS matrix, while promoting the interaction between the matrix and the reinforcement phase, forming a tighter interfacial bond.

[0076] To further improve the interfacial compatibility of the composite material, the bamboo powder and calcium carbonate were surface modified to introduce more polar groups or functional groups with good compatibility with the PBS matrix. Processing parameters can also be optimized, such as using higher processing temperatures or longer blending times, to promote sufficient mixing and interaction between the matrix and reinforcement phase.

[0077] Example

[0078] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0079] Example 1

[0080] A method for preparing a green, environmentally friendly, high-performance bamboo-plastic composite material comprises the following steps:

[0081] S1. In a high-speed mixer, first load 2 wt% of KH-570 on the surface of heavy calcium carbonate to obtain 15 parts of modified calcium carbonate;

[0082] S2, adding 15 parts of bamboo powder and 1.5 parts of fluorine-containing additives in sequence to obtain a modified bamboo powder / calcium carbonate mixture;

[0083] S3, weighing 9 / 10 of 100 parts of PBS resin, 0.3 parts of initiator and 3 parts of multifunctional monomer in a mass ratio, drying the PBS resin, and dissolving the initiator in an acetone solution, and then blending the dried PBS resin, the dissolved initiator solution and the multifunctional monomer to obtain a mixture;

[0084] S4, the mixed material is fed into the main feed port of a twin-screw extruder, and the remaining 1 / 10 PBS resin is fed into the side feed port at the third section;

[0085] S5, introducing the modified bamboo powder / calcium carbonate mixture into the system through the side feed port at the sixth stage of the twin-screw extruder, and extruding and granulating the mixture through the twin-screw extruder to obtain a long-chain branched PBS / bamboo powder / calcium carbonate composite material;

[0086] S6. Add the composite material obtained by extrusion granulation into a vertical injection molding machine, perform injection molding, and obtain a sample.

[0087] Example 2

[0088] The preparation method of this embodiment differs from that of Example 1 in that the content of modified calcium carbonate is 20 parts, the content of bamboo powder is 20 parts, and the content of fluorine-containing additive is 1.5 parts. The remaining operations and processes are the same as those of Example 1.

[0089] Example 3

[0090] The preparation method of this embodiment differs from that of Example 1 in that the content of modified calcium carbonate is 10 parts, the content of bamboo powder is 20 parts, and the content of fluorine-containing additive is 1.5 parts. The remaining operations and processes are the same as those of Example 1.

[0091] Comparative Example 1

[0092] The preparation method of this comparative example differs from that of Example 1 in that no fluorine-containing auxiliary agent is added, and the remaining operations and processes are the same as those of Example 1.

[0093] Comparative Example 2

[0094] The difference between the preparation method of this comparative example and that of Example 1 is that calcium carbonate not modified with KH-570 is added, and the rest of the operations and processes are the same as those of Example 1.

[0095] Comparative Example 3

[0096] The preparation method of this comparative example differs from that of Example 1 in that modified calcium carbonate is not added, and the remaining operations and processes are the same as those of Example 1.

[0097] Comparative Example 4

[0098] The preparation method of this comparative example differs from that of Example 1 in that calcium carbonate modified with KH-550 is added, and the remaining operations and processes are the same as those of Example 1.

[0099] Comparative Example 5

[0100] The preparation method of this comparative example differs from that of Example 1 in that the content of calcium carbonate is 15 parts, the content of bamboo powder is 15 parts, and the content of fluorine-containing auxiliary agent is 1 part. The remaining operations and processes are the same as those of Example 1.

[0101] Comparative Example 6

[0102] The preparation method of this comparative example differs from that of Example 1 in that the content of calcium carbonate is 20 parts, the content of bamboo powder is 20 parts, and the content of fluorine-containing auxiliary agent is 0.5 parts. The remaining operations and processes are the same as those of Example 1.

[0103] In order to fully understand the performance of the long-chain branched PBS / bamboo powder / calcium carbonate composite material of the present application, the composite material obtained by extrusion granulation was added to a vertical injection molding machine for injection molding. The following series of performance tests and analysis methods were used to perform mechanical property tests, interfacial compatibility analysis, and crystal morphology analysis on the examples and comparative examples.

[0104] Table 1 Experimental data of mechanical properties of composite materials

[0105]

[0106] 1. Mechanical properties test

[0107] Mechanical properties are one of the most important performance indicators of composite materials, which are directly related to the material's load-bearing capacity and service life in practical applications. This application uses a universal testing machine to perform tensile, impact and other mechanical property tests on composite materials. Specific testing methods include:

[0108] (1) Tensile properties: Composite material samples were prepared into standard specimens according to relevant standards. Tensile tests were then performed on a universal tensile testing machine, and data such as tensile strength and elongation at break were recorded. According to GB / T 1040.1, the test was performed in a tensile testing machine at a tensile rate of 100 mm / min. The tensile properties of the material were obtained by repeating the test five times and taking the average value.

[0109] (2) Impact testing: Impact testing of composite materials was performed using an impact testing machine. Impact strength and other data were recorded to evaluate the impact resistance of the materials. According to GB / T 1043.1, the test was performed using a 4J simply supported beam in an automatic impact testing machine. The notched impact performance data of the materials was obtained by averaging the results after five repetitions.

[0110] (4) Torque: Weigh the materials according to a certain ratio, set the temperature to 150℃, the rotor speed to 50rpm, and the time to 10min to perform the torque test on the sample.

[0111] The following results were obtained by conducting tensile and impact tests on the mechanical properties of the long-chain branched PBS / bamboo powder / calcium carbonate composite material:

[0112] Tensile properties: Figure 4 It can be seen that the tensile strength of Example 1 is 13.61MPa, the tensile strength of Example 2 is 12.45MPa, and the tensile strength of Example 3 is 10.85MPa. This shows that too much modified calcium powder and bamboo powder can easily lead to poor dispersion in the matrix; too little modified calcium carbonate cannot modify the bamboo powder well, and at the same time, the probability of physical collision between "soft-hard" is reduced, which is not conducive to dispersion. The tensile strength of Comparative Example 1 is 9.98MPa, indicating that the absence of fluorine-containing additives is not conducive to the dispersion of bamboo powder, and the surface is rough and the fluidity is poor; the tensile strength of Comparative Example 2 is 10.98MPa, and calcium carbonate that has not been modified with KH-570 is added. The bamboo powder cannot be modified, has poor compatibility with the long-chain branched PBS matrix, and has weak interaction force; the tensile strength of Comparative Example 3 is 9.23MPa, and no modified calcium carbonate is added. The bamboo powder agglomeration phenomenon is serious, and the SEM image also verifies this result; the tensile strength of Comparative Example 4 is 11.56MPa, and after KH-550 Modified calcium carbonate, calcium carbonate and bamboo powder cannot be grafted onto the long-chain branched PBS main chain, and the interaction force between the filler and the matrix is ​​weak; the tensile strength of Comparative Example 5 is 9.41 MPa, the content of fluorine-containing additives is insufficient, the calcium carbonate is not modified, the calcium carbonate and bamboo powder are easy to agglomerate, the compatibility with the long-chain branched PBS matrix is ​​poor, and the interaction force is weak; the tensile strength of Comparative Example 6 is 8.45 MPa, the calcium carbonate addition amount is 20 parts, and it is not modified, and the fluorine-containing additive content is only 0.5 parts. It can be seen from the SEM image that the calcium carbonate and bamboo powder are severely agglomerated, the agglomeration points are easily destroyed during stretching, and the tensile strength is significantly reduced.

[0113] Impact performance: from Figure 5 It can be seen that the notched impact performance value of Example 1 is the highest, which is 4.0 kJ / m 2 The modified calcium carbonate and bamboo powder are evenly dispersed and have good compatibility with long-chain branched PBS. The modified calcium carbonate and "short-fiber" bamboo powder can effectively absorb impact energy and transfer stress, achieving optimal notched impact strength. The main factors affecting the impact performance of composites are the dispersion of the filler and the strength of the interfacial adhesion with the matrix. When the content of modified calcium carbonate, bamboo powder, and fluorinated additives is mismatched, or the type of surface modifier is unsuitable for the composite, achieving ideal impact performance is difficult.

[0114] Torque result analysis: Figure 6This provides a stable processing window for the material and indirectly reflects the melt strength of the composite material through balanced torque. Appropriate melt strength ensures the stability of the composite bubble during blow molding and improves the material's ability to resist deformation caused by its own weight during extrusion or thermoforming. If the melt strength is too low, the bubble will be unstable during blow molding, and during extrusion or thermoforming, the material's ability to resist deformation due to its own weight will be weak, resulting in unstable product dimensions. However, excessive melt strength results in poor fluidity and high energy consumption during production. The balance torque of Example 1 is 6.85Nm. Since it is evenly dispersed in the matrix, the interaction force is large, and as a cross-linking point, it shows good melt strength. The balance torque of Example 2 is improved because too much modified calcium carbonate and bamboo powder are not conducive to dispersion, so its balance torque is improved. The balance torque of Example 3 is further improved because too little modified calcium carbonate has poor impact and modification effect on bamboo powder, which is not conducive to further dispersion and modification of bamboo powder, causing bamboo powder to agglomerate together, and the balance torque of the composite material is further improved. Comparative Example 1 does not add fluorine-containing additives, and the balance torque reaches 8.93Nm. This is because no fluorine-containing additives are added, which is not conducive to the dispersion of bamboo powder and does not play a good lubricating role. Comparative Example 2 adds calcium carbonate that is not modified with KH-570. Compared with Example 1, although Comparative Example 2 is conducive to the dispersion of bamboo powder through impact, the bamboo powder and The long-chain branched PBS matrix has poor compatibility and weak interaction force, which is less than the equilibrium torque of Example 1; Comparative Example 3 is unmodified calcium carbonate. Since the bamboo powder is not modified, it has poor compatibility with the long-chain branched PBS, and the unmodified bamboo powder is prone to secondary agglomeration, resulting in a larger equilibrium torque; Comparative Example 4 is the addition of calcium carbonate modified with KH-550. The interaction force with the long-chain branched PBS matrix is ​​weak, and the torque is lower than that of Example 1; Comparative Example 5 is insufficient in the content of fluorine-containing additives, which is not conducive to the dispersion of bamboo powder, resulting in an increase in the equilibrium torque, while the unmodified calcium carbonate has poor compatibility with the long-chain branched PBS matrix and weak interaction force, which will cause the equilibrium torque to decrease. Therefore, its equilibrium torque is relatively similar to that of Example 1; Comparative Example 6, the amount of calcium carbonate added is 20 parts, and it is not modified, and the content of fluorine-containing additives is 0.5 parts, resulting in extremely poor dispersion of calcium carbonate and bamboo powder, and its equilibrium torque reaches 8.49Nm.

[0115] 2. Interface compatibility analysis

[0116] Interfacial compatibility is the bonding between the matrix and reinforcement phase in a composite material, which directly affects the mechanical and thermal properties of the composite material. This application uses scanning electron microscopy (SEM) to analyze the interfacial compatibility of composite materials. Specific analysis methods include:

[0117] SEM observation: The composite material sample was sliced, and then the cross-sectional morphology of the sample after gold spraying was observed using SEM to analyze the bonding between the matrix and the reinforcement phase to evaluate the interface compatibility of the material.

[0118] The following results were obtained by SEM observation of the long-chain branched PBS / bamboo powder / calcium carbonate composite material:

[0119] SEM Observation Results: This set of SEM images shows the microstructures of different formulations, long-chain PBS, blank bamboo powder, and blank calcium carbonate. The long-chain PBS exhibits stringy texture, demonstrating its superior toughness; the blank bamboo powder exhibits short fibers; and the modified calcium carbonate exhibits a granular structure.

[0120] Depend on Figure 7 It can be seen that in Examples 1, 2 and 3, the modified calcium carbonate and bamboo powder are uniformly dispersed in the long-chain branched PBS matrix, and the interface compatibility is good. In particular, Example 1 has a more obvious wire drawing phenomenon, and the bamboo powder surface adheres to the matrix, indicating that the bamboo powder has good compatibility with the long-chain branched PBS and the fracture is ductile. In Comparative Examples 1, 2, 3 and 6, the bamboo powder shows obvious agglomeration, and the bamboo powder cannot be dispersed or further modified. In Comparative Examples 4 and 5, the "short fiber" bamboo powder is obviously extracted from the matrix, and the matrix leaves a cavity after the bamboo fiber is extracted, and the surface compatibility with the matrix surface is poor.

[0121] 3. Crystal Morphology Analysis

[0122] Based on the interaction between X-rays and atoms in crystals, when X-rays irradiate a crystal, they constructively interfere with each other, satisfying Bragg's law, to form diffraction peaks. The crystal structure of the material can be determined by analyzing the diffraction peaks. A sample pressed by the flat plate vulcanizer is placed flush in the center of the instrument's glass dish. The instrument scans continuously at a scan speed of 4° / min, with a step width of 0.02, within a range of a starting angle of 5° and an ending angle of 80°.

[0123] The following results were obtained by XRD testing of the long-chain branched PBS / bamboo powder / calcium carbonate composite material:

[0124] XRD results show that the characteristic peak of long-chain branched PBS is at 2θ≈20-25° (corresponding to crystal plane (110)); the characteristic peak of calcium carbonate is at 2θ≈29.4° (corresponding to crystal plane (104)); the main components of bamboo powder are cellulose (crystalline region), hemicellulose and lignin (amorphous region). Its XRD characteristic peaks are mainly dominated by cellulose type I structure: the main peak: 2θ≈22.5° (corresponding to crystal plane (002), cellulose crystal region) may overlap with the characteristic peaks of long-chain branched PBS, and the amorphous components: hemicellulose and lignin appear as broad and gentle steamed bun peaks around 2θ≈18°~20°. The intensities of the diffraction peaks of each formula curve are different. Generally speaking, the higher the diffraction peak intensity, the higher the content of the corresponding crystal structure or the better the crystallinity. Figure 8It can be seen that in Example 2, Comparative Example 1, Comparative Example 2, Comparative Example 4 and Comparative Example 6, due to the relatively high calcium carbonate content, the diffraction peak at the characteristic peak of calcium carbonate 2θ≈29.4° is strong and narrow. As the calcium carbonate content decreases, the diffraction peak at the characteristic peak of calcium carbonate 2θ≈29.4° becomes weaker; since the characteristic peak of the crystalline region of bamboo powder overlaps with the characteristic peak of long-chain branched PBS, there is no obvious change in the diffraction peak intensity with the change of bamboo powder content; the addition of bamboo powder and modified calcium carbonate does not change the diffraction angle position of the characteristic peak of long-chain branched PBS, that is, the crystal type of long-chain branched PBS does not change.

[0125] The long-chain branched PBS / bamboo powder / calcium carbonate composite material prepared in this application has the following characteristics:

[0126] (1) The introduction of long-chain branching significantly improves the melt strength and mechanical properties of PBS. Compared with pure PBS, long-chain branched PBS has higher tensile strength and impact strength.

[0127] (2) The addition of bamboo powder and calcium carbonate further enhances the comprehensive properties of the composite material. Appropriate amounts of bamboo powder and calcium carbonate can play a reinforcing role and improve the mechanical properties of the composite material. However, when the content is too high, the agglomeration of bamboo powder and calcium carbonate will lead to a decrease in the performance of the composite material.

[0128] (3) The long-chain branched PBS has good interfacial compatibility with bamboo powder and calcium carbonate. The matrix and the reinforcement phase are tightly bonded, with no obvious interfacial separation, and the filler is evenly distributed.

[0129] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A green, environmentally friendly, high-performance bamboo-plastic composite material, characterized in that: The invention comprises long-chain branched PBS, modified calcium carbonate, bamboo powder and fluorine-containing additives; the modified calcium carbonate, bamboo powder and fluorine-containing additives are used to obtain modified bamboo powder / calcium carbonate; the long-chain branched PBS and the modified bamboo powder / calcium carbonate are mixed to obtain a bamboo-plastic composite material.

2. The green, environmentally friendly, high-performance bamboo-plastic composite material according to claim 1, characterized in that: The composite material is composed of the following parts by weight: 100 parts by weight of long-chain branched PBS, 10-20 parts by weight of modified calcium carbonate, 10-20 parts by weight of bamboo powder, and 0.5-1.5 parts by weight of fluorine-containing additive.

3. The green, environmentally friendly, high-performance bamboo-plastic composite material according to claim 2, characterized in that: The long-chain branched PBS is obtained by reacting PBS, a composite initiator and a multifunctional monomer through a twin-screw extruder. During the reaction, the weight proportion of the components is as follows: 100 parts by weight of PBS, 0.3-0.5 parts by weight of the composite initiator, and 3-5 parts by weight of the multifunctional monomer.

4. The green, environmentally friendly, high-performance bamboo-plastic composite material according to claim 1, characterized in that: The modified calcium carbonate is obtained by loading a silane coupling agent KH-570 on the surface of heavy calcium carbonate, and the mass of the silane coupling agent KH-570 is 1.5-3wt% of the heavy calcium carbonate.

5. The green, environmentally friendly, high-performance bamboo-plastic composite material according to claim 1, characterized in that: The mass ratio of the modified calcium carbonate to the bamboo powder is 1:1; and the fluorine-containing auxiliary agent is perfluorohexanoic acid.

6. The green, environmentally friendly, high-performance bamboo-plastic composite material according to claim 1 or 5, characterized in that: The bamboo powder has a particle size of 200-300 meshes and a moisture content of less than 0.5%.

7. A method for preparing a green, environmentally friendly, high-performance bamboo-plastic composite material, comprising the following steps: S1. In a high-speed mixer, a certain amount of KH-570 is first loaded on the surface of heavy calcium carbonate to obtain modified calcium carbonate; S2, adding bamboo powder and fluorine-containing additives in sequence to obtain a modified bamboo powder / calcium carbonate mixture; S3, weighing 9 / 10 of the PBS resin, initiator, and multifunctional monomer according to the mass ratio, drying the PBS resin, and dissolving the composite initiator in an acetone solution, and then blending the dried PBS resin, the dissolved initiator solution, and the multifunctional monomer to obtain a mixture; S4, the mixed material is fed into the main feed port of a twin-screw extruder, and the remaining 1 / 10 PBS resin is fed into the side feed port at the third section; S5. The modified bamboo powder / calcium carbonate mixture is introduced into the system through the side feeding port at the 6th stage of the twin-screw extruder, and granulated by extrusion through the twin-screw extruder to obtain a long-chain branched PBS / bamboo powder / calcium carbonate composite material.

8. The method for preparing a green, environmentally friendly, high-performance bamboo-plastic composite material according to claim 7, characterized in that: The extrusion process parameters of the twin-screw extruder are: extrusion temperature of 120-160° C., main engine speed of 100-200 rpm, main feed speed of 5-10 rpm, and side feed speed of 5-10 rpm.

9. The method for preparing a green, environmentally friendly, high-performance bamboo-plastic composite material according to claim 7, characterized in that: The twin-screw extruder is provided with 8 sections, and the temperatures of each section from the main feeding port to the die are as follows: zone 1: 120-130°C, zone 2: 130-140°C, zone 3: 130-140°C, zone 4: 140-150°C, zone 5: 140-150°C, zone 6: 140-150°C, zone 7: 140-150°C, zone 8: 150-160°C, and die head: 145-155°C.

10. The method for preparing a green, environmentally friendly, high-performance bamboo-plastic composite material according to claim 9, characterized in that: The third to sixth sections of the twin-screw extruder are provided with a side feed port and equipped with a two-stage side feeder. The length-to-diameter ratio of the twin-screw extruder is 48:1, and the torque grade is T / A. 3 =8~15N·m / cm 3 .

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