Environment-friendly degradable modified composite material, preparation method and application

Abstract

The invention belongs to the technical field of biodegradable materials, and particularly relates to an environment-friendly degradable modified composite material, a preparation method and application. Aiming at the problems that an existing biodegradable material is high in brittleness, insufficient in low-temperature toughness, poor in water resistance, difficult to control in degradation rate, easy to separate in copolymerization of PBAT and PTMO and the like, the composite material is prepared from PBAT, PBS, PLA, an inorganic mineral filler, natural plant fibers, a PBAT-PTMO block copolymer and the like according to an optimized proportion through raw material pretreatment, multi-stage mixing and melt plasticizing molding. The PBAT-PTMO block copolymer is prepared through a thiol-acrylate click reaction, the number-average molecular weight of the PBAT-PTMO block copolymer is 20000-30000 g / mol, and the dispersity PDI of the PBAT-PTMO block copolymer is smaller than or equal to 1.96. The material has high strength and high toughness, the degradation rate is controllable, the requirements of multiple fields such as packaging bags, disposable tableware and agricultural plastic mulching films can be met, and the problem that the performance and the degradability of a traditional material are difficult to balance is effectively solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of biodegradable materials, and in particular relates to an environmentally friendly degradable modified composite material, a preparation method and an application thereof. Background Art

[0002] The widespread use of plastic products has become an integral part of modern life, yet the environmental impacts they pose are becoming increasingly severe. Due to their structural characteristics, traditional plastics are difficult to degrade in the natural environment. The long-term accumulation of large amounts of discarded plastics has led to deteriorating soil quality, increased water pollution, and disrupted ecosystems, posing a significant threat to the Earth's ecological environment. According to relevant research reports, hundreds of millions of tons of plastic waste are generated globally each year, and this figure is steadily increasing. Against this backdrop, the development of highly efficient and environmentally friendly biodegradable plastics has become a pressing task for global research and industry to replace traditional plastics, alleviate the increasing pressure of environmental pollution, and achieve sustainable development goals.

[0003] In the research and development of biodegradable plastics, polylactic acid (PLA) and polybutylene adipate / terephthalate (PBAT) have attracted considerable attention and are widely used. PLA, due to its high hardness and strength, provides excellent structural support for biodegradable products. However, its high glass transition temperature significantly increases its brittleness, making it susceptible to fracture and damage when subjected to external impact, significantly limiting its application in applications requiring high toughness. To address this issue, Chinese patent CN105542423A discloses a biodegradable mulch film and its preparation method. By incorporating PBAT as an elastomer, the film improves flexibility and elasticity while reducing brittleness. However, the film degrades rapidly, degrading within 75 days. This cannot meet the long-term coverage requirements for crops with long growth cycles (such as corn and cotton, whose growth periods exceed 90 days). This results in a lack of mulch protection during the critical growth period, impacting yield and quality, and limiting the large-scale promotion and application of biodegradable mulch films.

[0004] Currently, PBAT synthesis processes have developed, including co-esterification, fractionation, and tandem esterification, enabling industrial production through one-step or two-step polymerization. For example, Cao Jie's article "Fully Biodegradable PBAT Synthesis Process" describes the one-step method as a direct polycondensation reaction to produce a high-molecular-weight product, eliminating the need for a chain extension step, simplifying the process and reducing costs. The two-step method, which involves first preparing a low-molecular-weight PBAT and then increasing the molecular weight with a chain extender, offers the advantages of shorter reaction times and higher production capacity. While PBAT exhibits excellent flexibility and processing properties, meeting the requirements of various molding processes, it still faces numerous challenges. First, the rigidity of the aromatic units (butylene terephthalate segments) in the molecular chain results in insufficient low-temperature toughness, making it susceptible to brittleness when used as ground film in cold regions. Second, its water resistance is poor, and long-term exposure to humid environments leads to a degradation of its mechanical properties. Third, the difficulty in balancing melt strength and elastic modulus limits its application in elastic materials.

[0005] To overcome the performance limitations of PBAT, recent research has focused on modifying its molecular structure. Patents CN113956488A and CN113897043A, for example, propose embedding flexible polyether segments into the PBAT molecular structure through a catalytic transesterification reaction, resulting in a block copolymer with stress-induced self-reinforcement. This copolymer generates oriented microfibers in situ when subjected to stress, simultaneously enhancing both toughness and strength. Blending with PLA significantly improves the composite's performance. This technology eliminates traditional fiber pre-preparation processes, resulting in a simple and environmentally friendly process. However, it also suffers from drawbacks such as uncontrollable block structure, susceptibility to high-temperature degradation of the polyether segments, and insufficient selectivity in the catalytic system, which makes it difficult to suppress side reactions.

[0006] As a flexible polyether chain segment, polytetramethylene oxide (PTMO) has been widely used in materials such as polyurethane (TPU) to improve its flexibility and durability. However, the introduction of PTMO chain segments into the PBAT molecular structure to form PBAT-PTMO block copolymers still faces the following technical challenges: (1) PBAT is a semi-aromatic polyester and PTMO is a polyether. The polarity and chemical structure of their molecular chains are quite different. Direct copolymerization easily leads to phase separation and makes it difficult to form a stable block structure, which in turn affects the uniformity of the mechanical properties of the material; (2) The ends of PBAT chain segments are mostly hydroxyl or carboxyl groups, while the ends of PTMO are usually hydroxyl groups. Ester exchange reaction or polycondensation reaction requires an efficient catalytic system, but existing catalysts such as tetrabutyl titanate or Stannous octoate and other agents have insufficient selectivity for ester-ether coupling, which can easily lead to side reactions such as PBAT segment degradation and PTMO cyclization to produce tetrahydrofuran; (3) Existing polymerization methods make it difficult to achieve precise control of block length, and it is also impossible to accurately control the length ratio of PBAT and PTMO segments to balance degradability and mechanical properties; (4) PTMO segments are prone to oxidative degradation at high temperatures, while the condensation and processing temperatures of PBAT are often as high as 210-280°C. The mismatch in thermal stability between the two may lead to the breakage of PTMO segments during polymerization or processing, affecting the structure and performance of the product.

[0007] To address these challenges, researchers have begun exploring new modification methods, such as reinforcing with nanofillers and improving the compatibility of PLA and PBAT through copolymerization. However, these methods only improve certain mechanical properties of the material, and suffer from drawbacks such as a failure to simultaneously increase degradation rates, making biodegradable plastics difficult to meet the needs of complex application scenarios. Therefore, combining the advantages of different polymer types to break through the existing component framework design through modification processes and the introduction of new elastomeric materials has become the key to the next step in developing high-performance biodegradable plastics. This also has the potential to achieve a perfect balance between mechanical properties and degradability to meet diverse application requirements. Summary of the Invention

[0008] In view of the many shortcomings of existing biodegradable plastics, the present invention aims to develop a new environmentally friendly biodegradable modified composite material. By precisely controlling the ratios and properties of multiple raw materials and introducing innovative modification processes, the material's performance is deeply optimized. To address the technical issues of existing PBAT materials, such as insufficient low-temperature toughness, poor water resistance, and difficult-to-control melt properties, as well as phase separation, insufficient catalyst selectivity, difficult block length control, and thermal stability mismatches during the copolymerization of PBAT and PTMO, this solution uses a thiol-acrylate click reaction to prepare block copolymers. By utilizing its high efficiency, high selectivity, and low-temperature reaction properties, this solution overcomes the inherent shortcomings of traditional transesterification or polycondensation reactions, achieving controlled block copolymerization of PBAT and PTMO and further expanding its wide application in a variety of fields, such as packaging bags, disposable tableware, and agricultural mulch films. This approach fully meets the increasingly stringent performance standards and functional requirements of environmentally friendly biodegradable materials in various industries, fills the gaps in existing technologies in the field of high-performance biodegradable plastics, and leads the innovative development and upgrading transformation of the biodegradable materials industry. Based on this, the present invention provides an environmentally friendly biodegradable modified composite material, preparation method, and application.

[0009] To achieve the above object, the present invention adopts the following technical scheme: an environmentally friendly biodegradable modified composite material, which is mainly made of the following raw materials in percentage by weight: polybutylene adipate / terephthalate: 18%-28%; polybutylene succinate: 10%-16%; polylactic acid: 28%-55%; inorganic mineral filler: 5%-18%, the filler is any one or more combinations of talc, calcium sulfate, calcium silicate and calcium carbonate, and its particle size is 800 mesh-3000 mesh; natural plant fiber: 2%-5%; PBAT-PTMO block copolymer: 2%-8 %, the PBAT-PTMO block copolymer is prepared from a polybutylene adipate / terephthalate prepolymer and a polytetrahydrofuran prepolymer in a molar ratio of 1:1.05-1:1.2, the number average molecular weight of the copolymer is 20,000-30,000 g / mol, and the dispersion PDI is ≤1.96; nano-silica: 0%-2%; additives: 2%-10%, the additives are maleic anhydride, 2-imidazolidone and styrene and glycidyl acrylate copolymer, the mass ratio of the three is 0.4:0.4:1; plasticizer: 0%-1%, the plasticizer is preferably tributyl citrate.

[0010] As a further supplement to the above technical solution, the preparation method of the PBAT-PTMO block copolymer comprises the following steps: Step a, preparation of a thiol-terminated PBAT prepolymer: terephthalic acid, adipic acid, 1,4-butanediol, and 2-mercaptoethanol are mixed in a molar ratio of 1:1:5.5-6.5:0.8-1.2, and 0.05% to 0.1% of the first catalyst, 0.03% to 0.05% of a composite antioxidant, and 0.01% to 0.03% of a thiol protective agent are added based on the total weight of the monomers; under nitrogen protection, the temperature is first raised to 160-170° C. for esterification reaction for 1.5-2 hours, and then the temperature is raised to 180-190° C. and polycondensed under reduced pressure for 6-8 hours to obtain a thiol-terminated PBAT prepolymer with a number average molecular weight of 4000-5000 g / mol; Step b, preparation of a single-end acrylate-based PTMO prepolymer: adding 0.5% to 1% by weight of boron trifluoride ether complex to tetrahydrofuran, stirring and ring-opening polymerization at 0 to 10° C. under nitrogen protection for 4 to 6 hours to obtain a hydroxyl-terminated PTMO intermediate; adding acrylic acid to the hydroxyl-terminated PTMO intermediate, with a molar ratio of acrylic acid to terminal hydroxyl group of 1.1:1, adding 0.1% of a second catalyst based on the total mass of the reaction system, reacting at 80° C. for 3 hours, removing unreacted monomers by vacuum distillation, washing three times with 5% NaHCO3 solution, and then vacuum dehydrating to obtain a single-end acrylate-based PTMO prepolymer with a number average molecular weight of 1800 to 2200 g / mol; Step c, block copolymerization: the thiol-terminated PBAT prepolymer of step a and the single-terminated acrylate-terminated PTMO prepolymer of step b are mixed in a molar ratio of 1:1.05-1.2, and 0.1%-0.15% of the total mass of the prepolymer is added with a composite initiator; under nitrogen protection, the mixture is stirred and irradiated with ultraviolet light at 40-50° C. for 2-2.5 hours to form a block copolymer with a number average molecular weight of 20,000-30,000 g / mol and a PDI of ≤1.96; Step d, purification treatment: pour the block copolymer of step c into ethanol for precipitation, filter, wash with deionized water 2 to 3 times, and vacuum dry to obtain a PBAT-PTMO block copolymer.

[0011] The PBAT-PTMO block copolymer has the chemical structure of the following formula I:

[0012] Wherein: the degree of polymerization m of the PBAT segment is an integer of 17 to 22; the degree of polymerization n of the PTMO segment is an integer of 23 to 28.

[0013] As a further supplementary explanation of the above technical solution, in step 1, the first catalyst is tetrabutyl titanate, the composite antioxidant is a mixture of triphenyl phosphite and hindered phenol antioxidant 1010, and the mass ratio of the two is 1:1; the thiol protective agent is 2,6-lutidine; the second catalyst in step 2 is p-toluenesulfonic acid; and the composite initiator in step 3 is benzophenone and triethylamine, and the mass ratio of the two is 1:1.2~1.5.

[0014] As a further supplement to the above technical solution, the molar ratio of terephthalic acid, adipic acid, 1,4-butanediol, and 2-mercaptoethanol in step 1 is 1:1:6:1; the molar ratio of PBAT prepolymer to PTMO prepolymer in step 3 is 1:1.08.

[0015] As a further supplement to the above technical solution, the vacuum degree of the reduced pressure polymerization reaction in step 1 is 0.08~0.1MPa, the temperature of the vacuum dehydration in step 2 is 50~60℃, the vacuum degree is 0.09~0.1MPa, and the dehydration time is 2~3h; the wavelength of the ultraviolet light in step 3 is 365nm, and the light intensity is 150~200mW / cm 2 , stirring rate 350~400r / min; drying temperature in step 4 60~70℃, drying time 8~10h.

[0016] As a further supplement to the above technical solution, the natural plant fiber is any one of cotton fiber, hemp fiber, bamboo fiber, coconut shell fiber, and corn straw fiber; the natural plant fiber is first steam-exploded into fine fibers with a fiber length of 0.5-2 mm, then alkalized for 1-2 hours, and then rinsed with deionized water to neutrality and dried.

[0017] As a further supplement to the above technical solution, the dosage of the silane coupling agent KH550 is 8%-12% of the mass of the nano-silica, the working ultrasonic power of the ultrasonic cleaning machine is 300-500W, and the processing time is 15-25 minutes. The ultrasonic cavitation effect synergizes with the coupling agent to make the coupling agent more evenly coat the particle surface, forming a stable chemical bonding layer, enhancing compatibility with the matrix and interfacial adhesion, improving the tensile strength, elongation at break and thermal stability of the composite material, inhibiting the generation of material defects caused by nanoparticle agglomeration, and ensuring the uniformity of the material's microstructure and consistency of macroscopic performance.

[0018] A method for preparing an environmentally friendly degradable modified composite material comprises the following steps: S1 Raw material pretreatment: Polylactic acid is vacuum dried at 45-50°C for 4-5 hours; inorganic mineral fillers and nano-silica are preheated at 100-110°C for 30-35 minutes; natural plant fibers are pretreated by steam explosion to obtain 0.5-2 mm fine fibers, which are then alkalized with 5% NaOH solution for 1-2 hours, rinsed to neutrality, and then dried; S2 Premixing: Weigh PBAT, dried PLA, PBS, preheated inorganic mineral filler, modified natural plant fiber, modified nano-silica, PBAT-PTMO block copolymer, tributyl citrate and 70% additives in proportion and put them into a high-speed mixer, mixing at 500-900 rpm for 7-8 minutes; S3 secondary premixing: Add the remaining 30% additives and premix for 5-6 minutes at a medium speed of 240-260 rpm to optimize the uniformity of raw material distribution, ensure that the additives fully interact with the raw materials, and improve the compatibility of the system; S4 Melting, plasticizing and molding: The mixed material is fed into a co-rotating twin-screw extruder with the screw temperature set at 60-180°C, the screw speed at 150-250rpm, and the screw aspect ratio at 48:1-56:1. Under these conditions, the raw materials are fully melted, plasticized, mixed evenly, and extruded stably. The extruded strips are air-cooled and drawn, cut into pellets with a spacing of 4.6-4.8mm, vibrated and screened, and transported to the finished product silo.

[0019] An environmentally friendly, biodegradable modified composite material is being used in the manufacture of packaging bags, disposable tableware, and agricultural mulch films. By precisely controlling its degradation rate, this composite material can meet the needs of various scenarios while minimizing environmental impact. Furthermore, its excellent mechanical properties and stability ensure the safety and durability of the product during use, providing strong support for the widespread adoption of green and environmentally friendly materials.

[0020] Compared with the prior art, the present invention has the following advantages: The present invention introduces PBAT-PTMO block copolymers and adds modified natural plant fibers and nano-silica, and combines inorganic mineral fillers to redesign the ratio of bio-based degradable materials such as PBAT, PBS, and PLA. Among them, PLA provides a high-strength skeleton for the material, PBAT and PBAT-PTMO block copolymers synergistically optimize the material's excellent flexibility and impact resistance, nano-silica and natural plant fibers enhance interfacial bonding, and inorganic mineral fillers optimize mechanical properties, thereby improving the overall comprehensive performance of the material. The tensile strength of the composite material can reach 30-35MPa, and the elongation at break is increased to 500%-800%, solving the problem of the difficulty of balancing the strength and toughness of traditional degradable materials. At the same time, PBS and natural plant fibers form a gradient degradation mechanism, which, combined with the degradation characteristics of PBAT and PLA, achieves a dynamic balance of stable use of the material in the natural environment and efficient degradation after disposal, meeting the protection needs of long-cycle crop mulch.

[0021] The present invention's modification process for natural plant fibers and nano-silica significantly improves the interfacial compatibility of composite materials. For example, natural plant fibers are steam-exploded to form microfibers, which are then alkalized to enhance interfacial bonding strength, ensuring that the density deviation of the modified pellets is only 1.8%, and the melt mass flow rate deviation is 1.7%, with no significant fiber-matrix interface delamination. After treatment with the silane coupling agent KH550 and ultrasound, a stable chemical bonding layer forms on the surface of the nano-silica, improving dispersion uniformity and reducing the agglomeration rate to below 5%. This significantly optimizes the thermal stability and tensile strength of the composite material, avoiding material defects caused by particle agglomeration.

[0022] The composite material preparation method of the present invention ensures the uniformity and performance stability of the material through step-by-step pretreatment and multi-stage mixing processes. PLA is vacuum dried to remove moisture to avoid hydrolysis and degradation during processing; inorganic minerals and nano-silica are preheated to reduce interface bubbles; and natural plant fibers are soaked in ethanol to improve wettability. High-speed mixing breaks up the agglomeration of raw materials through strong shear force, and medium-speed secondary premixing ensures uniform dispersion of the additives, reducing the dispersion coefficient of each component of the composite material to below 1.2, improving the uniformity of the microstructure, and avoiding performance fluctuations caused by local component differences. The twin-screw extrusion parameters match the melting characteristics of the raw materials, making it suitable for large-scale production, and the yield rate is increased to more than 95%. The present invention forms a block copolymer with controllable structure by copolymerizing a terminal thiol-based PBAT prepolymer and a single-ended acrylate-based PTMO prepolymer in a specific molar ratio under ultraviolet light initiation, with a number average molecular weight of 20,000-30,000 g / mol and a dispersion PDI ≤ 1.96. The low-temperature reaction conditions of 40-50°C in the preparation process avoid high-temperature oxidative degradation of the PTMO segment, and the composite initiator improves the reaction selectivity, so that the side reaction inhibition rate reaches more than 90%. The introduction of this block copolymer increases the low-temperature impact strength of the degradable composite material to 8-10 kJ / m 2 , which solves the low-temperature brittleness problem of traditional PBAT, while enhancing the compatibility with the matrix resin, effectively improving the comprehensive mechanical properties of the material and expanding its application areas.

[0023] The composite material of the present invention can be widely used in many fields such as agricultural mulch, packaging bags, disposable tableware, etc. due to its balanced mechanical properties, controllable degradation rate, and wide processing adaptability. According to the test report, the tensile strength of the biodegradable express bag reaches 21.2MPa in the longitudinal direction and 30.7MPa in the transverse direction, and the nominal strain at break reaches 713.5% in the longitudinal direction and 525.5% in the transverse direction. It can be seen that the material performs well in terms of strength and toughness, solving the problem that traditional degradable materials have difficulty in balancing strength and toughness. At the same time, the biodegradable shopping bag has a biodegradation rate of 89.4% at 140d, and a relative biodegradation rate of 90.5%. The biodegradable polyester has a biodegradation rate of 87.7% at 180d, indicating that the material has achieved a dynamic balance of stability during use and efficient degradation after disposal, which can meet the growth cycle requirements of the agricultural mulch field under special environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 FTIR spectrum comparison diagram of PBAT-PTMO block copolymer and prepolymer in the present invention.

[0025] Figure 2 1 is a comparison diagram of the hydrogen nuclear magnetic resonance spectra of the PBAT-PTMO block copolymer and the prepolymer in the present invention.

[0026] Figure 3 It is the GPC spectrum of the PBAT-PTMO block copolymer in the present invention.

[0027] Figure 4 This is the XPS spectrum of the S element region of the PBAT-PTMO block copolymer in the present invention.

[0028] Figure 5 It is the DSC curve diagram of the PBAT-PTMO block copolymer in the present invention.

[0029] Figure 6 This is a conversion curve of the PBAT-PTMO block copolymer synthesis reaction in the present invention.

[0030] Figure 7 This is the exothermic curve of the synthesis reaction of the PBAT-PTMO block copolymer in the present invention.

[0031] Figure 8 It is a comparison chart of the tensile strength of different samples in the present invention.

[0032] Figure 9 The figure is a comparison of the elongation at break and the impact strength of different samples in the present invention.

[0033] Figure 10 The graph is a curve showing the biodegradation rate of different samples in the present invention changing with time.

[0034] Figure 11 This is a SEM comparison of the interface bonding of the natural plant fiber before and after modification in the present invention.

[0035] Figure 12 This is a TEM comparison of the dispersion of nano-silica before and after surface modification in the present invention.

[0036] Figure 13 This is a physical picture of the granular material produced using the raw material formulation and preparation process of the present invention.

[0037] Figure 14 The chemical structure, FTIR spectrum and H NMR spectrum of the mid-terminal thiol-based PBAT prepolymer of the present invention are shown.

[0038] Figure 15 The chemical structure, FTIR spectrum and H-NMR spectrum of the single-ended acrylate-based PTMO prepolymer of the present invention are shown.

[0039] Figure 16 The chemical structure, FTIR spectrum and H NMR spectrum of the PBAT-PTMO block copolymer of the present invention are shown. DETAILED DESCRIPTION

[0040] In order to further illustrate the technical solution of the present invention, as shown in the attached Figures 1 to 13 As shown below, in combination with the entire project development process, in order to enable those skilled in the art to better understand and implement it, the raw materials, reagents and catalysts used are all commercially available products, except for common reagents such as ethanol, 5% NaHCO3 solution, deionized water and additives, other specific specifications and manufacturers are shown in Table 1 and Table 2.

[0041]

[0042]

[0043] While polytetramethylenetetramethylene oxide (PTMO) improves toughness and durability through ether bonds, direct copolymerization with PBAT is prone to phase separation due to significant differences in molecular chain polarity and chemical structure. Furthermore, the high condensation and processing temperatures of PBAT prepolymers make PTMO segments susceptible to oxidative degradation at high temperatures, resulting in a thermal stability mismatch. Existing catalysts lack selectivity for ester-ether coupling, which can easily trigger side reactions. Block length is uncontrollable, making it difficult to balance mechanical properties with degradation rate. To address these issues, the present invention prepares PBAT-PTMO block copolymers through block copolymerization of thiol-terminated PBAT prepolymers and single-terminated acrylate-terminated PTMO prepolymers. These copolymers have a number-average molecular weight of 20,000-30,000 g / mol and a polydispersity (PDI) of ≤1.96.

[0044] The following details the synthesis process, chemical structure characterization, and related experimental procedures for the PBAT-PTMO block copolymer, combined with molecular structure design. Furthermore, experimentally verifying the effects of prepolymer molar ratio, reaction temperature, and initiator dosage on copolymer dispersibility, as well as the impact of PBAT and PTMO segment lengths on performance, also compares the performance of this method with that of different processes.

[0045] To enable those skilled in the art to repeat the process, the conventional design parameters that can be obtained through orthogonal experiments in the present invention are not described in detail. In this regard, the present invention further studies and analyzes the key parameters and processes by adjusting them. Therefore, the preparation process of the PBAT-PTMO block copolymer is as follows: Step a: Preparation of thiol-terminated PBAT prepolymer Terephthalic acid, adipic acid, 1,4-butanediol, 2-mercaptoethanol and other raw materials are evenly mixed in a molar ratio of 1:1:6:1. The additives include 0.08% of tetrabutyl titanate, 0.04% of a composite antioxidant, and 0.02% of 2,6-lutidine based on the total weight of the monomers. The composite antioxidant is compounded with triphenyl phosphite and antioxidant 1010 in a mass ratio of 1:1. The reaction is carried out under nitrogen protection, esterification is carried out at 165°C for 2 hours, and vacuum polycondensation is carried out at 185°C and 0.09 MPa for 7 hours to obtain a terminal thiol-based PBAT prepolymer with a number average molecular weight of 4500 g / mol.

[0046] Step b: Preparation of single-ended acrylate-based PTMO prepolymer 0.8% boron trifluoride ether complex was added to the tetrahydrofuran raw material, and the mixture was stirred at 5°C under nitrogen protection for 5 hours to undergo ring-opening polymerization to obtain a terminal hydroxyl PTMO intermediate with an average molecular weight of 2000 g / mol; 0.1% p-toluenesulfonic acid was added to the terminal hydroxyl PTMO intermediate at a molar ratio of acrylic acid to terminal hydroxyl of 1.1:1, and the mixture was reacted at 80°C for 3 hours. The unreacted monomers were removed by vacuum distillation; the mixture was washed three times with 5% NaHCO3, and vacuum dehydrated at 55°C and 0.095 MPa for 2.5 hours to obtain a single-end acrylate-based PTMO prepolymer with a number average molecular weight of 2055 g / mol.

[0047] Step c: Block copolymerization A thiol-terminated PBAT prepolymer and a single-terminated acrylate-terminated PTMO prepolymer were mixed in a molar ratio of 1:1.08, and a composite initiator (0.12% by mass of the total prepolymer) was added, wherein the composite initiator was a mixture of benzophenone and triethylamine in a mass ratio of 1:1.2. Under nitrogen protection, the mixture was irradiated with 365nm UV light (180mW / cm²) and stirred at 45°C and 380r / min for 2.2h to obtain a copolymer with a number average molecular weight of 25,000g / mol.

[0048] Step d: Purification The block copolymer prepared in step c above was poured into ethanol for precipitation, washed with deionized water three times, and dried under vacuum at 65° C. for 9 h to obtain a PBAT-PTMO block copolymer with a dispersity of 1.86. Figure 3 The molecular weight distribution characteristics of the PBAT-PTMO block copolymer are shown: the number average molecular weight is 25,000 g / mol, the weight average molecular weight is 46,500 g / mol, and the dispersion index PDI=1.86, which meets the designed indicators of 20,000~30,000 g / mol and PDI≤1.96. It is confirmed that the thiol-acrylate click reaction can achieve precise control of the molecular weight of the block copolymer, solving the problems of wide molecular weight distribution and uneven structure in traditional copolymerization.

[0049] The thiol-terminated PBAT prepolymer prepared in step a has the chemical structure of Formula II:

[0050] like Figure 14 As shown in the chemical structure of Formula II, the terminal thiol group PBAT prepolymer comprises butylene terephthalate units and butylene adipate units, with a terminal -SH group. Figure 1 Display, FTIR detection 2550cm -1 (-SH); Figure 2 show, 1 In HNMR, δ = 8.1 ppm (terephthalic acid benzene ring hydrogen), δ = 2.3 ppm (adipate methylene hydrogen), and δ = 2.4 ppm (-SH hydrogen) confirmed the structure.

[0051] The single-ended acrylate-based PTMO prepolymer prepared in step b has the chemical structure of Formula III:

[0052] like Figure 15 The chemical structure of Formula III shown is mainly composed of a polytetrahydrofuran segment and an acrylate group at one end. Figure 1 Display, FTIR detection 1630cm -1 (C=C), 1730cm -1 (ester group); Figure 2 show, 1 In HNMR, δ = 3.4 ppm (PTMO methylene hydrogen) and δ = 5.8-6.4 ppm (double bond hydrogen) confirmed the structure.

[0053] like Figure 16 As shown, the PBAT-PTMO block copolymer has the chemical structure of the following formula I:

[0054] Wherein: the degree of polymerization m of the PBAT segment is an integer of 17 to 22; the degree of polymerization n of the PTMO segment is an integer of 23 to 28.

[0055] Figure 1 It shows that formula II at 2550cm -1 The characteristic peak of -SH appears at 1630 cm -1 The C=C characteristic peak appears at 1725cm, confirming the presence of terminal functional groups in the prepolymer; the above characteristic peaks in Formula I disappear, leaving only 1725cm -1 (ester bond, PBAT segment) and 1110cm -1 (ether bond, PTMO segment), directly verifying that the thiol-acrylate click reaction was complete and the block copolymer structure was formed.

[0056] Figure 2 The results show that the -SH hydrogen nucleus signal appears at δ = 2.4ppm in formula II, and the double bond hydrogen nucleus signal appears at δ = 5.8~6.4ppm in formula III, which is consistent with the chemical structure of the prepolymer; the above signals disappear in formula I, and δ = 8.1ppm (PBAT segment benzene ring hydrogen) and δ = 3.4ppm (PTMO segment methylene hydrogen) appear at the same time, further confirming that PBAT and PTMO are connected by sulfide bonds to form a block structure, which is completely consistent with the chemical structure of formula I.

[0057] Figure 4 As shown in the figure, through the XPS analysis of the S element, characteristic peaks of the thioether bond appeared at 163.8 eV and 165.0 eV, corresponding to the spin-orbit splitting of the 2p orbital, which directly confirmed that the PBAT and PTMO segments formed a stable chemical connection through the thiol-acrylate click reaction, providing element-level evidence for the block structure shown in Formula I and explaining the molecular mechanism of phase separation size reduction.

[0058] The purified PBAT-PTMO block copolymer particles were added to a twin-screw extruder, melted and plasticized at 160-180°C, extruded into strips and then pelletized; the pellets were injection molded by an injection molding machine and made into tensile specimens (150 mm long and 10 mm wide) and notched impact specimens (80 mm long and 10 mm wide) according to GB / T1040.3-2006 and GB / T1843-2008 standards for mechanical properties testing; another portion of the pellets was pressed into a film with a thickness of 0.5 mm, which was cut into 50 mm × 50 mm specimens for water resistance and thermal stability testing to ensure that the sample size accuracy was consistent with the test standards.

[0059] The test methods are as follows: Tensile strength and elongation at break were tested according to GB / T1040.3-2006 at a rate of 50 mm / min. Low-temperature impact strength at -20°C was tested according to GB / T1843-2008 using the Charpy notched beam method. By-products were qualitatively analyzed by gas chromatography-mass spectrometry, and the content was calculated as the percentage of the total mass of the by-products to the total mass of the raw materials. Cross-sectional morphology was observed using scanning electron microscopy, and phase separation size was calculated. After thermal oxidative aging at 200°C for one hour, molecular weight retention was determined by gel permeation chromatography (GPC), which is the percentage of the number average molecular weight after aging to the initial number average molecular weight.

[0060] To verify the effects of prepolymer molar ratio, reaction temperature, and initiator dosage on the dispersion of copolymers, we set the prepolymer molar ratio, reaction temperature, and initiator dosage as variables, repeated 3 times per group, and fixed the UV intensity at 180 mW / cm 2 , stirring rate 380r / min, reaction time 2.2 hours, and other conditions were consistent with the preparation process.

[0061]

[0062] The orthogonal test results are shown in Table 3. When the prepolymer molar ratio was 1:1.05-1:1.20, the reaction temperature was 40-50°C, and the initiator dosage was 0.10%-0.15%, the dispersion was ≤1.96, and the copolymer structure was uniform. The combination of 1:1.08, 45°C, and 0.12% initiator achieved the lowest dispersion (1.86), representing the optimal parameters. Dispersion significantly increased below and above this range, demonstrating that the core parameter range was well-designed. Exceeding this range can lead to incomplete reaction or exacerbated side reactions. Figure 5The block copolymer exhibits the following thermal properties: dual glass transition temperatures (PTMO segment Tg = -70°C, PBAT segment Tg = 40°C) and a melting peak for the PBAT segment (Tm = 160°C), indicating a microphase separation between the flexible PTMO and rigid PBAT segments. This structure is key to the material's combined high toughness (elongation at break 500%-800%) and high strength (30-35 MPa), overcoming the low-temperature embrittlement of conventional PBAT.

[0063] To investigate the effects of PBAT and PTMO segment length on performance, as shown in Table 4, we employed the following procedures: The PBAT segment degree of polymerization (m) was fixed at 20, and the segment degree of polymerization (n) was adjusted by varying synthesis parameters such as the ring-opening polymerization time of the PTMO prepolymer; and the PTMO segment degree of polymerization (n) was fixed at 25, and the segment degree of polymerization (m) was adjusted by varying the polycondensation time of the PBAT prepolymer. PBAT-PTMO block copolymers with varying segment parameters were prepared using a prepolymer molar ratio of 1:1.08, a reaction temperature of 45°C, and an initiator dosage of 0.12%. Three replicates were used for each group. Mechanical properties such as tensile strength and elongation at break were tested, as well as water resistance after 30 days of immersion in water, to analyze the relationship between segment length and performance.

[0064]

[0065] The results of the gradient experiment are shown in Table 4. When the PTMO segment n=23-28, the elongation at break and the low-temperature impact strength reach the optimal value, and the improvement slows down after n>28; when the PBAT segment m=17-22, the tensile strength and water resistance are balanced, and the toughness decreases after m>22. Figure 6 Under UV initiation at 40-50°C, the reaction reached a conversion rate of 95% within 2 hours, and the reaction was complete with a conversion rate of 98% within 2.2 hours, demonstrating the high efficiency of the thiol-acrylate click reaction. This is consistent with the designed efficient reaction time of 2-2.5 hours, avoiding the problem of chain segment degradation caused by the prolonged high-temperature transesterification reaction. Therefore, m = 17-22 and n = 23-28 are the optimal chain segment ranges for industrial production.

[0066] To compare the performance of the present invention with different preparation processes, we conducted four comparative experiments. Control 1 used a traditional transesterification process (referring to the preparation process in CN113897043A, using Zhuhai TH-801T as the PBAT raw material, Mitsubishi Chemical's PTMG2000 for PTMO, and tetrabutyl titanate as the catalyst, with a reaction time of 4 hours at 230°C); Control 2 used a thiol protective agent-deficient group (excluding 2,6-lutidine, with the remaining preparation process identical to the above); Control 3 used a composite antioxidant-deficient group (adding only antioxidant 1010, with the remaining preparation process identical to the above); and Control 4 used a high-temperature click reaction group (adjusting the reaction temperature from 45°C to 80°C in step c, with the remaining preparation process identical to the above). Each group was tested for byproduct content, dispersion, mechanical properties, and other indicators using the aforementioned testing methods.

[0067]

[0068] The experimental results are shown in Table 5. Compared with the traditional transesterification process, the present invention reduces byproducts by 76%, reduces dispersion by 21%, and improves low-temperature impact strength by 53%, solving the degradation and phase separation problems caused by high temperature. In addition, the mercaptan protective agent can reduce the mercaptan oxidation side reaction by 42%, the composite antioxidant improves thermal stability by 10%, and the low-temperature reaction reduces PTMO degradation by 40%, proving the necessity of each process link. Figure 7 As shown, the exothermic process of the present invention shows remarkable stability. In the reaction temperature range of 40~50℃, the exothermic rate is always stable at 0.4~0.65mW / g, and no sharp exothermic peak occurs. This characteristic is due to the low-temperature reaction characteristics of the thiol-acrylate click reaction, which effectively avoids the oxidative degradation of the PTMO segment due to high temperature and ensures the integrity of the block copolymer molecular structure. On the other hand, the control group 1 adopts the traditional transesterification process and shows a sharp exothermic peak of 2.1mW / g under the high temperature conditions of 230℃. The intense exothermic phenomenon directly leads to the breakage of the PTMO segment, seriously affecting the structure and performance of the product. Due to the lack of thiol protective agent, the exothermic rate of control group 2 is higher than that of the present invention as a whole and fluctuates greatly, indicating that the thiol protective agent plays an important role in inhibiting the thiol oxidation side reaction and stabilizing the reaction exothermicity. Since the control group 3 does not add a composite antioxidant, the exothermicity of the reaction continues to rise in the later stage, further verifying the key significance of the composite antioxidant in maintaining the thermal stability of the reaction. Control group 4 uses a high-temperature click reaction process. The reaction temperature of 80°C results in a significantly higher heat release rate than the present invention, indicating that even with the same click reaction, high temperatures still increase the risk of thermal degradation of the PTMO segment. This shows that the low-temperature click reaction process used in the present invention effectively protects the PTMO segment while ensuring efficient reaction by precisely controlling the reaction exotherm, providing a reliable process guarantee for the preparation of high-performance PBAT-PTMO block copolymers.

[0069] In summary, this invention, through precise molecular structure design and optimized process parameters, employs a thiol-acrylate click reaction to effectively address the challenges of phase separation, thermal stability mismatch, and frequent side reactions associated with direct copolymerization of PBAT and PTMO. Orthogonal, gradient, and comparative experiments have demonstrated that the prepared copolymer exhibits a dispersity of ≤1.96 and a uniform structure under conditions such as a prepolymer molar ratio of 1:1.05-1:1.20, a reaction temperature of 40-50°C, and an initiator dosage of 0.10%-0.15%. When the degree of polymerization (m) of the PBAT segment is 17-22 and the degree of polymerization (n) of the PTMO segment is 23-28, optimal overall performance is achieved, with tensile strength of 30-34 MPa, elongation at break of 650%-800%, and low-temperature impact strength of 8.2-9.8 kJ / m². Water resistance and thermal stability are significantly improved, and byproducts are minimal. This process is reproducible and easily industrializable, providing reliable technical support for the widespread application of biodegradable materials.

[0070] This invention uses PBAT, PBS, and PLA as primary raw materials, with inorganic mineral fillers and additives as auxiliary ingredients. By introducing and adjusting the ratio of PBAT-PTMO block copolymers, modified natural plant fibers, nanosilica, and plasticizers, the optimized design of the biodegradable materials, including PBAT, PBS, and PLA, results in a composite material with balanced mechanical properties, controllable degradation rates, and wide processing adaptability. It is widely applicable in a variety of fields, including agricultural mulch, packaging bags, and disposable tableware. This is further illustrated by designing 15 examples and 7 comparative examples, using biodegradable bags, disposable tableware, and granular materials as target products.

[0071] 1. Material composition selection and ratio design The environmentally friendly biodegradable modified composite material developed by the present invention has been determined through preliminary research to have the following raw material ratios: polybutylene adipate / terephthalate: 18%-28%; polybutylene succinate: 10%-16%; polylactic acid: 28%-55%; inorganic mineral filler: 5%-18%; natural plant fiber: 2%-5%; PBAT-PTMO block copolymer: 2%-8%, wherein the PBAT-PTMO block copolymer is composed of a molar ratio of 1:1.05-1:1.2. Polybutylene adipate / terephthalate prepolymer and polytetrahydrofuran prepolymer are prepared through block copolymerization. The copolymer has a number average molecular weight of 20,000-30,000 g / mol and a PDI of ≤1.96. Nanosilica is added at 0%-2%. Additives are added at 2%-10%, consisting of maleic anhydride, 2-imidazolidone, and a copolymer of styrene and glycidyl acrylate in a mass ratio of 0.4:0.4:1. A plasticizer is added at 0%-1%, preferably tributyl citrate. The inorganic mineral filler can be any of talc, calcium sulfate, calcium silicate, and calcium carbonate. The appropriate inorganic mineral filler can be selected based on the intended use.

[0072] 2. Preparation process of composite materials To facilitate repeatable implementation by those skilled in the art, the following basic information about common raw materials is provided: nanosilica was purchased from Taiyuan Kepner Nano Engineering Co., Ltd., bamboo fiber was sourced from Hebei Jigao Chemical Fiber, hemp fiber was sourced from Wuhan Hanma Biotechnology, corn fiber was sourced from Shandong Xinrui New Materials, and talc powder (800 mesh) and calcium carbonate (3000 mesh) were sourced from Shanxi Yishunda Kaolin Co., Ltd. Referring to Tables 1 and 2, the following optimal preparation process is listed as a basic example for subsequent research. The specific preparation process is as follows: 1. Raw material pretreatment: PLA was placed in a vacuum drying oven and vacuum dried at 45°C for 4.5 hours. The purchased fibers were subjected to steam explosion (pressure 2.0 MPa, hold for 12 seconds) to obtain 0.5-2 mm fine fibers. The fibers were then alkalized with 5% NaOH solution in a stirred tank for 1.5 hours, rinsed with deionized water until neutral, and dried in a forced air drying oven at 80°C. Talc and calcium carbonate were placed in an oven and preheated at 105°C for 30 minutes. 10% by weight of silane coupling agent KH550 was added to the nano-silica, ultrasonically treated in an ultrasonic cleaner (400W) for 20 minutes, and then dried in a vacuum drying oven for later use.

[0073] 2. Premixing: Weigh PBAT, PLA, PBS, pretreated plant fiber, inorganic filler, PBAT-PTMO block copolymer and 70% additives according to the formula, add to the high-speed mixer, and stir at 700 rpm for 7.5 minutes.

[0074] 3. Secondary mixing: transfer the premixed materials into the same high-speed mixer, add the remaining 30% additives, adjust the speed to 250 rpm and stir for 5 minutes.

[0075] 4. Melt plasticization and molding: (1) The mixed material is added to a twin-screw extruder (TE-35, aspect ratio 48:1), with the screw temperature of zone 1 at 60°C, zone 2 at 120°C, zone 3 at 160°C, zone 4 at 180°C, and the die head at 170°C, with a speed of 200 rpm. The extruded strips are air-cooled and drawn, then cut into pellets with a spacing of 4.7 mm, and then formed into film products by a film blowing machine (matching film thickness 0.03-0.05 mm). (2) The mixed material is extruded into pellets by a twin-screw extruder (aspect ratio 56:1) (temperature 160-190°C, speed 180 rpm), and then formed into pellets by an injection molding machine (mold temperature 60°C, injection pressure 80 MPa) to produce tableware. (3) The mixed material is extruded into granules through a co-rotating twin-screw extruder (TE-35, Nanjing Keya Chemical Equipment Co., Ltd., aspect ratio 56:1); the granules are screened by a vibrating screener to control the particle size to 1-3 mm and used to produce granules (such as Figure 13 As shown, see Examples 8 and 9 below).

[0076] 5. Post-processing: After the molded product cools and sets, remove the burrs, and pack and store after sampling and testing. Figure 5 As shown, in the finished product silo, the pellets are packaged by a semi-automatic pellet packaging machine. After sealing, these packaged materials can be sold to customers in the market or directly used in the downstream product production process.

[0077] Currently, our workshop is equipped with vertical mixers, express bag film blowing machines, mulch film blowing machines, single-layer film blowing machines, ABA film blowing machines, various bag making machines, slitting machines, and low-temperature granulators. The production process involves a step-by-step pretreatment and multi-stage mixing process. After stirring, the film is blown using a biodegradable film blowing machine, printed with environmentally friendly water-based ink (most air column cushioning bags do not require printing), and finally hot-cut and formed using a bag making machine to produce biodegradable film bags. The mulch film material is stirred, blown using an ABC three-layer co-extrusion film blowing machine, and then slit to produce the biodegradable mulch film.

[0078] In addition, the existing film bag production workshop uses the biodegradable modified composite masterbatch developed by this invention as raw material for production according to production plans or customer order specifications. Through film blowing, printing, winding, bag making and other processes, it produces qualified fully biodegradable customized products and packages them. The main production is PE and fully biodegradable plastic products, including courier bags, ground film, pet bags, garbage bags, seedling bags, and shopping bags.

[0079] 3. Design of the embodiment The environmentally friendly, biodegradable, modified composite materials developed by the present invention were designed based on preliminary research and combined with different application scenarios (films, tableware, and granular materials). The following examples are designed. All examples contain seven raw materials: PBAT, PBS, PLA, PBAT-PTMO, an inorganic mineral filler, natural plant fiber, and an additive. Nanosilica and plasticizers are added according to the performance requirements of the application field, and the total mass percentage of each component is 100%.

[0080] Example 1 (MD): The formulation is 20% PBAT, 10% PBS, 40% PLA, 15% calcium carbonate, 3% bamboo fiber, 7% additives, 3% PBAT-PTMO, 1.5% nano-silica, and 0.5% plasticizer. Film was blown according to the process described in the basic example, with a thickness of 0.03 mm. Performance characteristics showed that infrared analysis showed PBAT as the primary component; longitudinal tensile strength of 21.2 MPa and transverse tensile strength of 30.7 MPa; longitudinal elongation at break of 713.5% and 525.5%; and a 140-day biodegradability of 89.4%.

[0081] Example 2 (ST): Compared to Example 1, the composition was adjusted to 23% PBAT, 12% PBS, and 41% PLA. Calcium carbonate was replaced with talc at 10%, hemp fiber accounted for 4%, additives were 4.5%, PBAT-PTMO was adjusted to 5%, plasticizer was 0.5%, and nano-silica was omitted. The process was the same as in Example 1, with a thickness of 0.04 mm. Infrared analysis showed that the primary component was PBAT; longitudinal tensile strength was 20.8 MPa, transverse tensile strength was 29.5 MPa; longitudinal elongation at break was 680.2%, transverse elongation was 510.3%; and 140-day biodegradability was 88.7%.

[0082] Example 3 (CJ01 Blade): Compared to Example 1, the composition was adjusted to 18% PBAT, 10% PBS, and 53% PLA. Calcium carbonate was replaced with talc at 5%, 3% hemp fiber, 5% additives, 5% PBAT-PTMO, 5% PBAT-PTMO, and 1% nanosilica. The plasticizer was omitted. Injection molding was used, and the length was set at 160 mm. Infrared analysis showed PLA as the primary component; tensile strength was 45 MPa; elongation at break was 35%; and heat deflection temperature was 65°C.

[0083] Example 4 (CJ02 fork): Compared to Example 3, the composition was adjusted to 19% PBAT, 11% PBS, and 52% PLA. Talc accounted for 6%, bamboo fiber replaced hemp fiber at 3%, additives were 4%, PBAT-PTMO was adjusted to 4%, and nano-silica remained at 1%. The process was the same as in Example 3, maintaining a length of 160 mm. Infrared analysis showed PLA as the primary component; tensile strength was 44 MPa; elongation at break was 38%; and heat deflection temperature was 64°C.

[0084] Example 5 (CJ03 spoon): Compared to Example 3, the composition is adjusted to 20% PBAT, 12% PBS, and 48% PLA. Talc accounts for 6%, bamboo fiber replaces hemp fiber at 3%, additives are 5%, PBAT-PTMO remains at 5%, and nano-silica remains at 1%. The process is the same as in Example 3, and the length is maintained at 160 mm. Infrared analysis shows PLA as the primary component; tensile strength is 42 MPa; elongation at break is 40%; and heat deflection temperature is 63°C.

[0085] Example 6 (CH01 lunch box): Compared to Example 1, the composition is adjusted to 25% PBAT, 15% PBS, and 35% PLA. Calcium carbonate is replaced with talc at 12%, hemp fiber accounts for 3%, additives are 5.5%, PBAT-PTMO is adjusted to 3%, nano-silica is adjusted to 1.5%, and the plasticizer is omitted. Injection molding is used, with dimensions set at 190 × 135 × 56 mm. Infrared analysis shows the main components are a mixture of PBAT, PLA, PBS, talc, and calcium carbonate; tensile strength is 38 MPa; elongation at break is 60%; and 180-day biodegradability is 87.7%.

[0086] Example 7 (CH02 dining lid): Compared to Example 6, the composition remains unchanged at 25% for PBAT, 16% for PBS, and 35% for PLA. Calcium carbonate replaces talc at 14%, and bamboo fiber replaces hemp fiber at 3%. The additive content is 4%, the PBAT-PTMO content is adjusted to 2%, and the nano-silica content is adjusted to 1%. The process is the same as in Example 6, but the dimensions are adjusted to 190 × 135 × 7 mm. Infrared analysis shows that the main components are a mixture of PBAT, PLA, PBS, talc, and calcium carbonate; the tensile strength is 36 MPa; the elongation at break is 70%; and the 180-day biodegradability is 87.2%.

[0087] Example 8 (HYSCST01): Compared to Example 1, the composition was adjusted to 22% PBAT, 14% PBS, and 36% PLA. Calcium carbonate accounted for 12%, and corn straw fiber replaced bamboo fiber at 4%. Additives were added at 5%, PBAT-PTMO was adjusted to 5%, nanosilica remained at 1%, and plasticizer was adjusted to 1%. Extrusion granulation was used. Infrared analysis revealed PBAT as the primary component, starch content was 44%, density deviation was 1.8%, and MFR deviation was 1.7%.

[0088] Example 9 (HYSCMD01): Compared to Example 8, the composition was adjusted to 24% PBAT, 13% PBS, and 36% PLA. Calcium carbonate was replaced with talc at 10% of the total. Corn straw fiber was adjusted to 3%, while the additive content remained at 5%. The PBAT-PTMO content was adjusted to 6%, nano-silica was adjusted to 2%, and the plasticizer content remained at 1%. The process was the same as in Example 8. Infrared analysis revealed the main components to be PBAT, PLA, PBS, and calcium carbonate; the starch content was 42%; the density deviation was 2.0%; and the MFR deviation was 1.9%.

[0089] Example 10 (Film): Compared to Example 1, the composition remains unchanged at 20% for PBAT, 10% for PBS, and 36% for PLA. The calcium carbonate content remains at 18%, bamboo fiber at 3%, additives at 4%, PBAT-PTMO at 8%, plasticizer at 1%, and nano-silica is omitted. A three-layer co-extrusion blown film is used, with a thickness of 0.01mm. Performance characteristics include a longitudinal tensile strength of 22.1 MPa, a transverse tensile strength of 31.2 MPa, and a longitudinal elongation at break of 650.4%.

[0090] Example 11 (Film): Compared to Example 1, the composition was adjusted to 28% PBAT, 16% PBS, and 29% PLA. The calcium carbonate content was 10%, bamboo fiber was 5%, additives were 4%, PBAT-PTMO was 8%, and nano-silica and plasticizer were omitted. The process was the same as in Example 1, with the blown film thickness adjusted to 0.05 mm. Properties were: longitudinal tensile strength of 19.5 MPa, transverse tensile strength of 28.3 MPa, and longitudinal elongation at break of 750.6%.

[0091] Example 12 (Tableware): Compared to Example 3, the composition was adjusted to 22% PBAT, 13% PBS, 48% PLA, 8% talc, 3% hemp fiber, 4% additives, 2% PBAT-PTMO, and the nano-silica was omitted. The process was the same as in Example 3, with a set length of 160 mm. Performance characteristics were: tensile strength 40 MPa, elongation at break 50%, and heat deflection temperature 62°C.

[0092] Example 13 (Tableware): Compared to Example 3, the composition was adjusted to 24% PBAT, 14% PBS, and 42% PLA. Talc accounted for 10%, hemp fiber remained at 3%, additives remained at 4%, PBAT-PTMO was adjusted to 3%, and nano-silica was omitted. Performance characteristics were: tensile strength 39 MPa; elongation at break 55%; and heat deflection temperature 61°C.

[0093] Example 14 (Pellets): Compared to Example 8, the composition was adjusted to 23% PBAT, 12% PBS, and 38% PLA. The calcium carbonate content remained at 12%, the corn straw fiber content remained at 4%, the additive content was 4%, the PBAT-PTMO content was adjusted to 6%, the plasticizer content remained at 1%, and the nano-silica was omitted. The process was the same as in Example 8. The performance was as follows: starch content 41%, density deviation 2.1%, and MFR deviation 2.0%.

[0094] Example 15 (Pellets): Compared to Example 8, the composition was adjusted to 26% PBAT, 13% PBS, 35% PLA, 11% calcium carbonate, 3% corn straw fiber, 4% additives, 7% PBAT-PTMO, and 1% plasticizer. Nanosilica was omitted. Performance characteristics were: starch content 43%, density deviation 1.9%, and MFR deviation 1.8%.

[0095] 4. Comparative design Comparative Example 1 (corresponding to Example 1): The formulation was the same as Example 1, except that the plant fiber was not subjected to steam explosion and alkalization treatment. Properties were: longitudinal tensile strength of 18.5 MPa; transverse tensile strength of 26.3 MPa; longitudinal elongation at break of 550%; and interfacial debonding rate of 15%.

[0096] Comparative Example 2 (corresponding to Example 1): The formulation was the same as Example 1, except that PBAT-PTMO was removed and the PBAT content was adjusted to 23%. Properties were: longitudinal tensile strength of 19.2 MPa; transverse tensile strength of 27.5 MPa; longitudinal elongation at break of 450%; and -20°C impact strength of 4.5 kJ / m².

[0097] Comparative Example 3 (corresponding to Example 3): The formulation is PLA 70%, PBAT 15%, PBS 8%, talc 800 mesh 5%, and additives 2%. Compared with Example 3, the PLA ratio is too high. Performance is: tensile strength 52 MPa; elongation at break 12%; impact strength 3.0 kJ / m².

[0098] Comparative Example 4 (corresponding to Example 6): The formulation is 35% PBAT, 30% PLA, 10% PBS, 15% talc (800 mesh), and 10% additives. Compared with Example 6, the PBAT ratio is too high. Performance is: tensile strength of 22 MPa; 180-day biodegradability of 95%.

[0099] Comparative Example 5 (corresponding to Example 8): The formulation was the same as Example 8, except that the nano-silica was not treated with KH550. The performance was as follows: starch content 38%, density deviation 4.5%, MFR deviation 5.2%, and agglomeration rate 22%.

[0100] Comparative Example 6 (corresponding to Example 1): The formulation was the same as Example 1, omitting the secondary mixing step. The properties were longitudinal tensile strength of 19.2 MPa, transverse tensile strength of 28.1 MPa, and component dispersion coefficient of 1.8.

[0101] Comparative Example 7 (corresponding to Example 1): The formula is 95% PBAT and 5% additives. Compared with Example 1, it is pure PBAT material. The performance is longitudinal tensile strength of 16.8 MPa, transverse tensile strength of 25.1 MPa, and 180-day biodegradability of 85%.

[0102] V. Sampling and testing samples and testing methods The following sampling test sample information is as follows: Biodegradable bags (MD brand) are based on "2021C0816 Biodegradable bags (brand: MD)". The sampling quantity is 50g. The sample is a white translucent bag with a blue pattern on one side of the outer surface. The specification model is 550×(350+90×2)×0.03mm.

[0103] Biodegradable bags (ST brand) are based on "2021C0817 Biodegradable bags (brand: ST)". The sampling quantity is 50g. The sample is a beige translucent bag with a blue pattern on one side of the outer surface. The specification model is 400×(250+55×2)×0.03mm.

[0104] Biodegradable materials (HYSCST01 brand) are based on "2021C0850 Biodegradable materials (brand: HYSCST01)", the sampling quantity is 50g, and the sample is light brown particles.

[0105] Biodegradable disposable knife (CJ01 brand) is based on "2021C0851 Biodegradable disposable knife (brand: CJ01)", the sampling volume is 50g, the sample is a white knife, and the specification model is 160mm.

[0106] Biodegradable disposable tableware cover (brand CH02) is based on "2021C0852 Biodegradable disposable tableware cover (brand: CH02)", the sampling quantity is 50g, the sample is a white cover, and the specification model is 190×135×7mm.

[0107] The biodegradable disposable spoon (brand CJ03) is based on "2021C0854 Biodegradable Disposable Spoon (brand: CJ03)", the sampling volume is 50g, the sample is a white spoon, and the specification model is 160mm.

[0108] Biodegradable disposable fork (CJ02 brand) is based on "2021C0855 Biodegradable disposable fork (brand: CJ02)", the sampling volume is 50g, the sample is a white fork, and the specification model is 160mm.

[0109] Biodegradable disposable lunch box (CH01 brand) is based on "2021C0871 Biodegradable Disposable Lunch Box (Brand: CH01)", the sampling quantity is 50g, the sample is a white box, and the specification model is 190×135×56mm.

[0110] Biodegradable materials (HYSCMD01 brand) are based on "2021C0962 Biodegradable materials (brand: HYSCMD01)", the sampling volume is 50g, and the sample is white particles.

[0111] Biodegradable polyester is based on the "2022C0410 Biodegradation Rate Test Report (Biodegradable Polyester)", the sampling volume is 500g, the sample is white granules, and the client indicates that the material is a single component PBAT (see Table 1 Jinfa).

[0112] Starch-based injection molding compound (corresponding to the granular material example) is based on the "Inspection Report Starch-based Injection Molding Compound", the sampling quantity is 300g + 20 specimens, and the sample is light yellow granules.

[0113] According to the "Inspection Report - Express Bags", the sampling quantity of express bags (corresponding to film examples) is 50 pieces. The samples are printed film bags with specifications of thickness 0.05 × length (including sealing tongue) (560+50) × width 540mm.

[0114] Biodegradable shopping bags (physical properties, corresponding film examples) are sampled in accordance with the "Inspection Report - Physical Properties of Biodegradable Shopping Bags". The sampling quantity is 30. The samples are printed shopping bags with handles, with specifications of length 540 × width (400+200) × thickness 0.04mm.

[0115] Biodegradable shopping bags (biodegradable performance, corresponding film examples) are based on the "Biodegradable Shopping Bag Inspection Report on Biodegradable Performance". The sampling quantity is 50. The samples are printed shopping bags with handles, with specifications of length 540×width (400+200)×thickness 0.04mm.

[0116] The above performance tests are carried out in accordance with the following standards: material analysis is carried out using the infrared method of GB / T6040-2019; the biodegradability rate is determined by the CO2 release method in accordance with GB / T19277.1-2011, with three replicate composting containers in each group under composting conditions of 58±2°C and 55±5% humidity; the tensile strength and elongation at break are tested in accordance with GB / T1040.3-2006 (rate 50mm / min), with five parallel samples prepared for each group, and the results are averaged with a relative standard deviation (RSD) of ≤3.2%; the low-temperature impact strength is determined by the simply supported beam notch method at -20°C using six parallel samples according to GB / T1843-2008. The average value is taken after excluding outliers with deviations greater than 10%, with an RSD of ≤4.5%. Referring to GB / T 43196-2023, the cross-sectional morphology of natural plant fiber composites before and after modification was observed using scanning electron microscopy at a magnification of 200x and scales of 50 μm and 5 μm, respectively. After gold-spraying treatment, the dispersion of the fibers and their interfacial bonding with the matrix were observed before and after modification. Transmission electron microscopy was used to analyze the dispersion of nanosilica before and after modification. Ultrathin sections of the samples were prepared with a thickness of 50-100 nm to observe the size, distribution, and agglomeration of the nanoparticles after ultrasonic modification.

[0117] 6. Analysis of experimental results The present invention achieves precise matching of materials and application scenarios by differentially designing the proportions of main components such as PBAT, PLA, and PBS. Film products such as express bags and agricultural mulch films use PBAT 20%-28%, PLA 29%-41%, and are combined with 5%-8% PBAT-PTMO block copolymers. For example, in Example 1, PBAT 20% and PLA 40% have a longitudinal elongation of 713.5% and a transverse elongation of 525.5%, and a 140-day biodegradability of 89.4%. In Example 11, PBAT 28%, PLA 29%, and PBAT-PTMO 8% have a longitudinal elongation of 750.6%, meeting the requirements of high toughness and controlled degradation. Tableware such as knives and forks, and lunch boxes use PLA 35%-53% and PBAT 18%-25%, such as PLA 53% in Example 3. , PBAT18% tensile strength 45MPa, heat deformation temperature 65℃, Example 6 PLA35%, PBAT25% tensile strength 38MPa, elongation at break 60%, adapting to high strength and heat resistance requirements; the granular material is used for subsequent processing with PLA35%-38%, PBAT22%-26%, PBS12%-14%, such as Example 8, the density deviation is 1.8%, and the melt mass flow rate deviation is 1.7%, ensuring the stability of the components; comparative experiments show that the elongation at break of PLA70% in Comparative Example 3 is only 12%, and the tensile strength of PBAT35% in Comparative Example 4 is only 22MPa. Deviating from the adapted ratio will lead to performance degradation.

[0118] Figure 8 In Example 8, after vacuum drying PLA, preheating the inorganic filler, and performing secondary mixing, the MFR fluctuated by ≤0.1 g / 10 min within 15 minutes, with a stable curve, demonstrating uniform component dispersion. In contrast, the PLA group without vacuum drying experienced hydrolytic degradation, resulting in a continuous increase in MFR over time. The inorganic filler group without preheating experienced significant fluctuations due to moisture incorporation, and the group without secondary premixing experienced fluctuations of up to ±0.5 g / 10 min due to uneven dispersion of additives. These results demonstrate that the step-by-step pretreatment and multi-stage mixing process significantly improves melt stability, providing a uniform material base for subsequent molding processes such as blown film and injection molding. This is consistent with the melt mass flow rate deviation of only 1.7% in the example. Furthermore, vacuum drying PLA avoids preheating of hydrolyzed inorganic minerals and reduces bubbles. High-speed premixing combined with medium-speed secondary mixing resulted in a component dispersion coefficient of ≤1.2. Comparative Example 6, which omitted secondary mixing, saw the coefficient increase to 1.8, resulting in a 10% decrease in strength. The film thickness deviation in Example 1 was significantly less than 0.002 mm, as demonstrated by the film blown film process. In the injection molding process for tableware, the heat deformation temperature of Example 3 reaches 65°C. The coordinated design of process and materials avoids the performance fluctuation caused by traditional single process.

[0119] like Figure 9 As shown, the tensile stress-strain curves intuitively demonstrate the optimization of mechanical properties through the synergistic effect of the components. Example 1, due to the inclusion of the PBAT-PTMO block copolymer, exhibits a distinct elastic-plastic transition phase, with an elongation at break reaching 713.5% while maintaining a tensile strength of 21.2 MPa, achieving a balance between strength and toughness. Comparative Example 2, lacking PBAT-PTMO, exhibits a shortened plastic phase, with the elongation at break dropping to 450%, demonstrating the key role of the block copolymer in improving toughness. Comparative Example 3, due to the excessively high proportion of PLA, exhibits a steep curve with no plastic phase and an elongation at break of only 12%, demonstrating high brittleness. The low peak stress of pure PBAT in Comparative Example 7 fails to meet high-strength requirements. This comparison validates the scientific rationale behind the synergistic design of the component ratios and the PBAT-PTMO block copolymer of the present invention, resolving the challenge of achieving a balanced balance of strength and toughness in conventional biodegradable materials. Furthermore, orthogonal experiments demonstrate that a prepolymer molar ratio of 1:1.08 and a copolymer dispersion of 1.86 and a phase separation size of 0.3-0.5 μm at 45°C significantly outperform conventional transesterification processes. In terms of mechanical properties, Example 1 added 2% of the copolymer at -20°C and had a low-temperature impact strength of 9.5 kJ / m². In Comparative Example 2, the impact strength dropped to 4.5 kJ / m² and the elongation at break dropped from 713.5% to 450% without the copolymer.

[0120] Figure 10The results show that the agricultural mulch film of Example 10 achieved a degradation rate of 86.8% in 180 days, with only 35% degradation in the first 90 days, making it suitable for covering long-cycle crops such as corn. The biodegradable bag of Example 1 achieved a degradation rate of 89.4% in 140 days, with an accelerated degradation rate in the medium term, meeting the requirement for rapid degradation after short-term use. The disposable lunch box of Example 6 achieved a degradation rate of 87.7% in 180 days, with a steadily rising curve, meeting the stability requirements of the tableware's lifecycle. In contrast, the comparative example 4, due to its excessively high PBAT ratio, had a degradation rate of 95% in 180 days, resulting in functional failure due to rapid degradation. These results demonstrate that precise matching of degradation rates can be achieved by regulating the component ratios, solving the problem of adapting conventional mulch films to scenarios where they degrade too quickly or incompletely, and further verifying the material's adaptability to different application scenarios.

[0121] Figure 11 Scanning electron microscopy observations of the samples from Example 1 and Comparative Example 1 show that the untreated fibers used in Comparative Example 1 exhibit their original entangled state, with interlocking fiber bundles and a loose structure. This leads to the formation of gaps due to irregular morphology when in contact with the matrix. In Example 1, the modified fibers exhibited uniform dispersion, a roughened surface, and an ordered microstructure. These fibers bonded to the PBAT / PLA matrix, providing a more stable interface. This structural change directly resulted in the significantly higher longitudinal tensile strength of Example 1 than in Comparative Example 1, with no interfacial delamination. This steam explosion-assisted alkalization process demonstrates the ability to optimize fiber morphology and interfacial compatibility.

[0122] like Figure 12 As shown, the microstructure of the materials prepared in Comparative Example 5 and Example 8 was observed using a transmission electron microscope. In Comparative Example 5, the nano-silica that was not treated with KH550 lacked interface modification, resulting in strong inter-particle agglomeration, forming a large number of agglomerates exceeding 500 nm in size. Some agglomerates were interconnected, with the largest size reaching 1 μm. The nanoparticles were extremely unevenly distributed, and there were almost no effectively dispersed single particles between the agglomerates. In Example 8, after modification with KH550 and synergistic ultrasonic dispersion, the coupling agent grafted onto the surface of the nanoparticles effectively reduced the agglomeration energy barrier. Combined with the mechanical dispersion effect of ultrasound, the particles were evenly dispersed in the matrix, with a single particle size of <50 nm and approximately spherical, a stable inter-particle spacing of 50-100 nm, a consistent distribution density within the field of view, and an agglomeration rate of ≤5%. It can be seen that the synergistic effect of KH550 and ultrasonic treatment can fundamentally improve the dispersion stability of nano-silica.

[0123] In summary, the present invention demonstrates its innovativeness in five key areas: component ratio, modification process, copolymer design, process matching, and application adaptability, through systematic experiments across 15 examples and 7 comparative examples. Experimental data demonstrates that the composite material exhibits superior tensile strength of 30-45 MPa, elongation at break of 500%-800%, and biodegradability of 87%-89%, surpassing traditional solutions in key performance indicators. Furthermore, its performance can be precisely adapted for applications such as films, tableware, and granular materials, fully demonstrating the solution's creativity and practicality.

[0124] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. An environmentally friendly degradable modified composite material, characterized in that: The mass percentage of each raw material is as follows: Polybutylene adipate / terephthalate: 18%-28%; Polybutylene succinate: 10%-16%; Polylactic acid: 28%-55%; Natural plant fiber: 2%-5%; PBAT-PTMO block copolymer: 2%-8%; Inorganic mineral filler: 5%-18%, the filler is any one or more combinations of talc, calcium sulfate, calcium silicate and calcium carbonate, and its particle size is 800-3000 mesh; Additives: 2%-10%, the additives are maleic anhydride, 2-imidazolidinone and styrene-glycidyl acrylate copolymer, the mass ratio of the three is 0.4:0.4:1; Among them, the PBAT-PTMO block copolymer is prepared from a poly(butylene adipate) / terephthalate prepolymer and a poly(tetrahydrofuran) prepolymer in a molar ratio of 1:1.05-1:1.

2. The number average molecular weight of the copolymer is 20,000-30,000 g / mol, and the dispersion PDI is ≤1.

96.

2. The environmentally friendly degradable modified composite material according to claim 1, characterized in that: It also includes 0%-2% of nano silicon dioxide and 0%-1% of a plasticizer, and the plasticizer is preferably tributyl citrate.

3. The environmentally friendly degradable modified composite material according to claim 1, characterized in that: The preparation method of the PBAT-PTMO block copolymer comprises the following steps: Step a, preparation of a thiol-terminated PBAT prepolymer: terephthalic acid, adipic acid, 1,4-butanediol, and 2-mercaptoethanol are mixed in a molar ratio of 1:1:5.5-6.5:0.8-1.2, and 0.05% to 0.1% of the first catalyst, 0.03% to 0.05% of a composite antioxidant, and 0.01% to 0.03% of a thiol protective agent are added based on the total weight of the monomers; under nitrogen protection, the temperature is first raised to 160-170° C. for esterification reaction for 1.5-2 hours, and then the temperature is raised to 180-190° C. and polycondensed under reduced pressure for 6-8 hours to obtain a thiol-terminated PBAT prepolymer with a number average molecular weight of 4000-5000 g / mol; Step b, preparation of a single-end acrylate-based PTMO prepolymer: adding 0.5% to 1% by weight of boron trifluoride ether complex to tetrahydrofuran, stirring and ring-opening polymerization at 0 to 10° C. under nitrogen protection for 4 to 6 hours to obtain a hydroxyl-terminated PTMO intermediate; adding acrylic acid to the hydroxyl-terminated PTMO intermediate, with a molar ratio of acrylic acid to terminal hydroxyl group of 1.1:1, adding 0.1% of a second catalyst based on the total mass of the reaction system, reacting at 80° C. for 3 hours, removing unreacted monomers by vacuum distillation, washing three times with 5% NaHCO3 solution, and then vacuum dehydrating to obtain a single-end acrylate-based PTMO prepolymer with a number average molecular weight of 1800 to 2200 g / mol; Step c, block copolymerization: the thiol-terminated PBAT prepolymer of step a and the single-terminated acrylate-terminated PTMO prepolymer of step b are mixed in a molar ratio of 1:1.05-1.2, and 0.1%-0.15% of the total mass of the prepolymer is added with a composite initiator; under nitrogen protection, the mixture is stirred and irradiated with ultraviolet light at 40-50° C. for 2-2.5 hours to form a block copolymer with a number average molecular weight of 20,000-30,000 g / mol; Step d, purification treatment: pour the block copolymer of step c into ethanol for precipitation, filter, wash with deionized water 2 to 3 times, and vacuum dry to obtain a PBAT-PTMO block copolymer with a dispersion index PDI ≤ 1.

96. The PBAT-PTMO block copolymer has the following chemical structure: ， Wherein: the degree of polymerization m of the PBAT segment is an integer of 17 to 22; the degree of polymerization n of the PTMO segment is an integer of 23 to 28.

4. The environmentally friendly degradable modified composite material according to claim 3, characterized in that: In step 1, the first catalyst is tetrabutyl titanate, the composite antioxidant is a mixture of triphenyl phosphite and hindered phenol antioxidant 1010, and the mass ratio of the two is 1:1; the thiol protective agent is 2,6-lutidine; the second catalyst in step 2 is p-toluenesulfonic acid; and the composite initiator in step 3 is benzophenone and triethylamine, and the mass ratio of the two is 1:1.2~1.

5.

5. The environmentally friendly degradable modified composite material according to claim 3, characterized in that: The molar ratio of terephthalic acid, adipic acid, 1,4-butanediol, and 2-mercaptoethanol in step 1 is 1:1:6:1; the molar ratio of PBAT prepolymer to PTMO prepolymer in step 3 is 1:1.

08.

6. The environmentally friendly degradable modified composite material according to claim 3, characterized in that: The vacuum degree of the reduced pressure polymerization reaction in step 1 is 0.08-0.1 MPa, the temperature of the vacuum dehydration in step 2 is 50-60°C, the vacuum degree is 0.09-0.1 MPa, and the dehydration time is 2-3 hours; the wavelength of the ultraviolet light in step 3 is 365 nm, and the light intensity is 150-200 mW / cm 2 , stirring rate 350~400r / min; drying temperature in step 4 60~70℃, drying time 8~10h.

7. The environmentally friendly degradable modified composite material according to claim 2, characterized in that: The natural plant fiber is any one of cotton fiber, hemp fiber, bamboo fiber, coconut shell fiber, and corn straw fiber; the natural plant fiber is first subjected to steam explosion treatment to form fine fibers with a fiber length of 0.5-2 mm, then subjected to alkalization treatment for 1-2 hours, and then rinsed with deionized water to neutrality and dried.

8. The environmentally friendly degradable modified composite material according to claim 2, characterized in that: The nano-silica is prepared by adding 8% to 12% of the mass of the silane coupling agent KH550, and ultrasonically treating the nano-silica for 15 to 25 minutes. The acoustic cavitation effect is used to cooperate with the coupling agent so that the coupling agent can more evenly coat the particle surface to form a stable chemical bonding layer.

9. A method for preparing the environmentally friendly degradable modified composite material according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1 Raw material pretreatment: Polylactic acid is vacuum dried at 45-50°C for 4-5 hours; inorganic mineral fillers and nano-silica are preheated at 100-110°C for 30-35 minutes; natural plant fibers are pretreated by steam explosion to obtain 0.5-2 mm fine fibers, which are then alkalized with 5% NaOH solution for 1-2 hours, rinsed to neutrality, and then dried; S2 Premixing: Weigh PBAT, dried PLA, PBS, preheated inorganic mineral filler, modified natural plant fiber, modified nano-silica, PBAT-PTMO block copolymer, tributyl citrate and 70% additives in proportion and put them into a high-speed mixer, mixing at 500-900 rpm for 7-8 minutes; S3 secondary premixing: Add the remaining 30% additives and premix for 5-6 minutes at a medium speed of 240-260 rpm to optimize the uniformity of raw material distribution, ensure that the additives fully interact with the raw materials, and improve the compatibility of the system; S4 Melting, plasticizing and molding: The mixed material is fed into a co-rotating twin-screw extruder with the screw temperature set at 60-180°C, the screw speed at 150-250rpm, and the screw aspect ratio at 48:1-56:

1. Under these conditions, the raw materials are fully melted, plasticized, mixed evenly, and extruded stably. The extruded strips are air-cooled and drawn, cut into pellets with a spacing of 4.6-4.8mm, vibrated and screened, and transported to the finished product silo.

10. Use of the environmentally friendly degradable modified composite material according to any one of claims 1 to 8 in the preparation of packaging bags, disposable tableware, and agricultural mulch films.

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