High-strength and high-toughness modified PBAT material and preparation method thereof

Abstract

The application belongs to the field of high polymer materials, and relates to a high-strength and high-toughness modified PBAT material and a preparation method thereof. The application provides a modified PBAT material, raw materials of the modified PBAT material including low-molecular PBAT, diisocyanate and a small-molecule chain extender, and the modified PBAT material being prepared from the raw materials through melt copolymerization; wherein the small-molecule chain extender is selected from one of pentanediamine, 5-(2-hydroxyethyl)-6-methyl-2-aminouracil, adipic acid dihydrazide, N,N-bis(2-hydroxyethyl)oxamide or 1,6-bis(hydroxyethoxycarbonylamino)hexane. The modified PBAT material has good mechanical strength, which can reach 18-55 MPa, and enhanced fracture toughness (>350 MJ / m 3 ), and the elongation at break can reach 800-1700%.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials and relates to a bio-based, environmentally friendly, high-strength, and high-toughness biodegradable bio-based PBAT material and its preparation method. Background Technology

[0002] With technological advancements and continuous improvements in social productivity, human consumption of resources has increased dramatically, leading not only to the depletion of non-renewable resources but also to severe ecological damage and environmental pollution. Therefore, finding suitable bio-based sustainable alternatives for currently used non-renewable products has become a crucial focus of materials science research. Plastic pollution is one of the most pressing environmental problems. Global plastic production increased from 2.3 million tons in 1950 to approximately 450 million tons in 2015, and is projected to reach 900 million tons by 2050. Most traditional plastic products are made from petroleum-based polymers, and most petroleum-based polymers are non-biodegradable, resulting in massive amounts of waste plastics that cause "white pollution." Taking the packaging industry, a typical example of white pollution, as an example, plastic bags have been the second largest source of packaging waste after paper and cardboard in the past decade. According to EU statistics, the recycling rate of all packaging plastic waste generated in 2019 was only 40%. Waste plastics can decompose in small amounts under prolonged physical and chemical stimulation, generating secondary microplastics and nanoplastics. The accumulation of these plastic particles in the Earth's environment has a very adverse impact on humans, wildlife, and their habitats.

[0003] Designing and preparing biodegradable polymers from bio-based renewable resources to produce innovative "bioplastics" for industrial development is a crucial strategy for addressing resource scarcity and environmental pollution. Over the past two decades, numerous bio-based and biodegradable polymers have been proposed and researched to replace fossil fuel-based non-degradable polymers. However, to date, the use of bio-based materials in packaging and disposable tableware (such as straws and spoons) has been limited by their poor barrier properties and weak mechanical properties.

[0004] Polybutylene adipate (PBAT) is an important thermoplastic biodegradable plastic. It is synthesized from terephthalic acid, adipic acid, and 1,4-butanediol through esterification or transesterification reactions. It possesses excellent tensile strength, impact resistance, high heat resistance, and rapid degradation by natural enzymes. PBAT materials are not only biodegradable but also compostable, and can be used in fully degradable packaging films, bags, and agricultural films. However, even PBAT materials exhibit relatively poor mechanical strength (<18 MPa), which significantly limits its application in various fields. Therefore, modification and reinforcement strategies for PBAT materials are particularly important. The most typical modification strategy involves compounding PBAT with brittle and hard polylactic acid (PLA). However, PBAT and PLA have poor compatibility, resulting in poor product uniformity during blending, poor product density, and the presence of micropores or microbubbles.

[0005] Researchers mainly focus on the composite modification of PBAT with PLA and other polymers such as starch, but the synthesis and modification of PBAT as the main polymer alone has received less attention. Summary of the Invention

[0006] To address the aforementioned deficiencies, this invention utilizes a method of chain extension with macromolecular PBAT using a bio-based chain extender that provides multiple hydrogen bond interactions. This method increases the molecular weight of PBAT and enhances the inter-chain forces, resulting in a high-strength, high-toughness, biodegradable bio-based modified PBAT material. The modified PBAT material can be obtained by melt copolymerization of hydroxyl- or carboxyl-terminated PBAT prepolymers with a number-average molecular weight of approximately 3000-30,000 g / mol, along with bio-based diisocyanates (such as PDI) and bio-based small-molecule chain extenders. The resulting modified PBAT material exhibits good mechanical strength (18–55 MPa) and enhanced fracture toughness (>350 MJ / m). 3 The elongation at break can reach 800-1700%.

[0007] The technical solution of this invention:

[0008] The first technical problem to be solved by the present invention is to provide a modified PBAT material, wherein the raw materials of the modified PBAT material include PBAT, diisocyanate and a small molecule chain extender, and the modified PBAT material is obtained by melt copolymerization of the raw materials; wherein the small molecule chain extender is selected from one of: pentanediamine (PDA), 5-(2-hydroxyethyl)-6-methyl-2-aminouracil (UPy), adipic acid dihydrazide (ADH), N,N-di(2-hydroxyethyl)oxalamide (BHO) or 1,6-bis(hydroxyethoxycarbonylamino)hexane (BHH).

[0009] Furthermore, the mass ratio of each raw material is as follows: 80-96 parts by weight of PBAT, 3.0-8.0 parts by weight of diisocyanate, and 1.6-12.0 parts by weight of small molecule chain extender. The molar ratio of PBAT diol (or diacid), diisocyanate (PDI), and small molecule chain extender is 1:2-2.5:1-1.5.

[0010] Furthermore, the diisocyanate includes: pentamethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and diphenylmethane-4,4'-diisocyanate.

[0011] Preferably, the diisocyanate is a bio-based diisocyanate. More preferably, the diisocyanate is pentamethylene diisocyanate (PDI).

[0012] Furthermore, the PBAT is a hydroxyl or carboxyl-terminated PBAT prepolymer with a number-average molecular weight of 3000 to 20,000 g / mol.

[0013] Furthermore, the PBAT is selected from substances with the following structures:

[0014]

[0015] Furthermore, the modified PBAT material has a mechanical strength of 18–55 MPa and an elongation at break of 800–1700%.

[0016] The second technical problem to be solved by the present invention is to provide a method for preparing the above-mentioned modified PBAT material, wherein the preparation method is selected from one of the following methods:

[0017] Method 1 (two-step method (or prepolymerization method)): First, PBAT and diisocyanate are prepolymerized at 150-180℃ for 0.5-1h under the action of a catalyst; then, a small molecule chain extender is added and the chain extension reaction is carried out at 180-240℃ for 0.5-2h to obtain the modified PBAT material.

[0018] Method 2 (one-step method): PBAT, diisocyanate, small molecule chain extender and catalyst are subjected to chain extension reaction at 180-240℃ for 0.5-3h to obtain the modified PBAT material.

[0019] Furthermore, in the above method, the PBAT needs to be dewatered before use, such as by vacuuming at 100°C for 0.5-2 hours to remove residual water.

[0020] Furthermore, in the above method, the catalyst is selected from: stannous octoate (Sn(Oct)2) or dibutyltin dilaurate (DBTDL), etc.

[0021] Furthermore, in the above method, an organotin catalyst is used to accelerate the polymerization reaction. Taking DBTDL as an example, its dosage is 0.5 to 1 wt% of the monomer PBAT.

[0022] The third technical problem solved by this invention is to provide a method for increasing the molecular weight of PBAT prepolymer. The method involves introducing diisocyanate and a small molecule chain extender into the PBAT prepolymer and obtaining modified PBAT through melt copolymerization. The small molecule chain extender is selected from one of the following: pentanediamine (PDA), 5-(2-hydroxyethyl)-6-methyl-2-aminouracil (UPy), adipic acid dihydrazide (ADH), N,N-bis(2-hydroxyethyl)oxalamide (BHO), or 1,6-bis(hydroxyethoxycarbonylamino)hexane (BHH).

[0023] Furthermore, the mass ratio of PBAT, diisocyanate, and small molecule chain extender is: 80–96 parts by weight of PBAT, 3.0–8.0 parts by weight of diisocyanate, and 1.6–12.0 parts by weight of small molecule chain extender. The molar ratio of PBAT diol (or diacid), PDI, and small molecule chain extender is 1:2–2.5:1–1.5.

[0024] The fourth technical problem to be solved by the present invention is to provide a method for improving the strength and toughness of PBAT through supramolecular interactions. The method is as follows: introducing diisocyanate and a small molecule chain extender into the PBAT prepolymer, and obtaining modified PBAT by melt copolymerization; wherein the small molecule chain extender is selected from one of: pentanediamine (PDA), 5-(2-hydroxyethyl)-6-methyl-2-aminouracil (UPy), adipic acid dihydrazide (ADH), N,N-bis(2-hydroxyethyl)oxalamide (BHO) or 1,6-bis(hydroxyethoxycarbonylamino)hexane (BHH).

[0025] Furthermore, the mass ratio of PBAT, diisocyanate, and small molecule chain extender is: 80–96 parts by weight of PBAT, 3.0–8.0 parts by weight of diisocyanate, and 1.6–12.0 parts by weight of small molecule chain extender. The molar ratio of PBAT diol (or diacid), PDI, and small molecule chain extender is 1:2–2.5:1–1.5.

[0026] The beneficial effects of this invention are:

[0027] 1. This invention directly uses low molecular weight PBAT with dihydroxyl-terminated (or partially carboxyl-terminated) PBAT as a base, and utilizes fully bio-based polyisocyanates and small molecule chain extenders to carry out chain extension reactions without solvents, thus preparing modified PBAT materials in a relatively short reaction time. Compared to raw PBAT, the obtained modified PBAT material has a significantly increased molecular weight and enhanced mechanical strength and fracture toughness. Compared to commercial high molecular weight PBAT, it also exhibits significantly enhanced mechanical strength and fracture toughness. The tensile strength of the modified PBAT material can reach 52 MPa, the elongation at break can reach 1601%, and the fracture toughness can reach 390 MJ / m. 3 .

[0028] 2. The modified, reinforced, and toughened PBAT material obtained by this invention has high strength, high toughness, and adjustable mechanical properties. By changing the content of comonomers and the ratio of different types of chain extenders, the mechanical properties of the modified PBAT material can be effectively controlled.

[0029] 3. The modified, reinforced, and toughened PBAT material obtained by this invention has good remodeling and processing properties, and can be remodeled multiple times by means of hot pressing, etc., with a high material performance retention rate in the short term.

[0030] 4. The modified, reinforced, and toughened PBAT material obtained by this invention has high biodegradability and bio-based properties, which is in line with the current strategies for dealing with problems such as "white pollution" and "depletion of fossil energy" and has sustainable development.

[0031] 5. The adjustable high strength and high toughness of the modified, reinforced, and toughened PBAT material obtained by this invention make it of significant application value in the fields of disposable packaging, disposable tableware, and controllable degradable structural components / implants.

[0032] 6. The preparation process of this invention is simple, the raw materials are readily available and are all bio-based, the reaction process is solvent-free, there is no need to worry about chemical reagent pollution and recycling issues, it has good controllability and reproducibility, and the modified reaction products do not require complex chemical treatment processes, making it very suitable for large-scale industrial production. Attached Figure Description

[0033] Figure 1 The prepolymerization method (two-step method) chain extension reaction formula used in this invention is named PBAT-Rx-S as the modified PBAT material obtained.

[0034] Figure 2 The one-step chain extension reaction formula used in this invention results in a modified PBAT material named PBAT-Rx-T.

[0035] Figure 3The stress-strain curves of PABT raw materials with a molecular weight of 7,200 g / mol in Examples 1-3 are as follows: Figure 3 As shown, PABT-1 corresponds to Example 1, PABT-2 corresponds to Example 2, and PABT-3 corresponds to Example 3.

[0036] Figure 4 Pull-up curves of the modified PBAT materials obtained in Example 1: (a) PBAT-Upy, (b) PBAT-BHO, and (c) PBAT-ADH.

[0037] Figure 5 The thermal stability results of the PBAT-BHH material prepared in Example 2.

[0038] Figure 6 Photograph of the PBAT-BHH-S1 material casting sample prepared in Example 2.

[0039] Figure 7 PBAT-BHH-S prepared in Example 2 x Stress-strain curves of thin film spline.

[0040] Figure 8 Photographs of the PBAT-BHH-T1 material prepared in Example 3 after being pulled directly out of the reaction flask and cooled (left image), and the PBAT-BHH-T2 material precipitated in methanol (right image).

[0041] Figure 9 Photographs of the thin film and the cut stretch strip of the PBAT-BHH-T1 material prepared in Example 3.

[0042] Figure 10 PBAT-BHH-T prepared in Example 3 x Stress-strain curves of thin film spline of material. Detailed Implementation

[0043] This invention utilizes one or more small molecules containing dihydroxy or diamino groups as chain extenders to improve the mechanical properties of PBAT through a chain extension reaction. These small molecule chain extenders can increase the molecular weight of PBAT polymers while introducing multiple hydrogen-bonded supramolecular interactions. The selected small molecule chain extenders can introduce hydrogen bonds of varying strengths and densities, thereby regulating the interaction forces between PBAT macromolecular chains. The intermolecular / internal hydrogen bonds, PBAT crystalline regions, and the microphase separation structure of soft and hard segments bring about strengthening and toughening effects to the modified PBAT material, greatly improving its mechanical properties and thus achieving the enhancement and toughening of PBAT materials.

[0044] This invention prepares modified PBAT materials through melt copolymerization, achieving enhanced and toughened PBAT materials. The main raw materials used in the polymerization reaction are three components: A, B, and C. Component A is PBAT with dihydroxy or dicarboxylic acid groups at the end; component B is diisocyanate (pentamethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane-4,4'-diisocyanate), preferably bio-based pentamethylene diisocyanate (PDI); component C is bio-based small molecules... Chain extenders that can be selected include: pentanediamine (PDA), 5-(2-hydroxyethyl)-6-methyl-2-aminouracil (UPy), adipic acid dihydrazide (ADH), N,N-di(2-hydroxyethyl)oxalamide (BHO), and 1,6-bis(hydroxyethoxycarbonylamino)hexane (BHH). These five bio-based small molecule chain extenders can introduce freely bonded double hydrogen bonds, strongly dimerizing tetrad hydrogen bonds, freely bonded hexad hydrogen bonds, freely bonded dense tetrad hydrogen bonds, and freely bonded loose tetrad hydrogen bonds, respectively. Except for the strong dimerizing tetrad hydrogen bonds introduced by UPy, the number of the other four types of multiple hydrogen bonds is based on the maximum number of hydrogen bonds that a single chain extender unit can form. The main difference between the three lies in the number of methylene intervals (0–6 methylene groups) between the units forming the hydrogen bonds (amide bonds and / or carbamate bonds and / or urea bonds). The differences in the various hydrogen bond supramolecular interactions described above mainly result in different hydrogen bond densities and strengths in PBAT-modified polymers, which in turn lead to different inter-chain interactions and thus different mechanical properties. The structure of the chain extender that can be used in this invention is shown below.

[0045]

[0046] Furthermore, this invention can also prepare a series of PBAT-modified materials with tunable mechanical properties by changing the type of bio-based small molecule chain extender and altering the hydrogen bond density, which can greatly expand the application fields of PBAT. Simultaneously, this invention uses fully bio-based raw materials as chain extenders to enhance and toughen PBAT materials, improving mechanical properties while ensuring their bio-based origin and biodegradability, and holds promise for preparing high-performance, biodegradable, fully bio-based PBAT materials.

[0047] The two-step (or prepolymerization) chain extension reaction formula used in this invention is as follows: Figure 1 As shown. The general formula for the one-step chain extension reaction used is as follows: Figure 2 As shown.

[0048] The specific embodiments of the present invention will be further described below with reference to examples, but the present invention is not limited to the scope of the examples described.

[0049] In this embodiment of the invention, PBAT was purchased from Tongcheng New Materials or Kingfa Science & Technology Co., Ltd.; ADH was purchased from Adamas; PDI was purchased from Mitsui Stabio; and the small molecule chain extenders Upy, BHO, and BHH were synthesized by ourselves.

[0050] In the embodiments of this invention, the small molecule chain extender is prepared by the following method:

[0051] The UPy is synthesized using the following method:

[0052]

[0053] The raw materials for synthesis are as follows: α-acetyl-γ-butyrolactone, guanidine carbonate, triethylamine, and ethanol; ethanol is used as the reaction solvent, and the molar ratio of the other three raw materials is α-acetyl-γ-butyrolactone: guanidine carbonate: triethylamine = 2:1:2.1.

[0054] The specific preparation method is as follows: Weigh the predetermined amounts of raw materials (12.83 g of α-acetyl-γ-butyrolactone, 9.01 g of guanidine carbonate, and 10.63 g of triethylamine) and add them sequentially to a 250 ml three-necked flask. Add 100 ml of ethanol and stir to dissolve. The reaction is carried out under reflux using a spherical condenser at 80 °C for 12 h. As the reaction proceeds, the solution gradually turns yellow and a white turbidity appears.

[0055] Post-processing: The filter cake was directly filtered, then washed three times with ethanol and water alternately; the pH was adjusted to about 6.5 in water, stirred for 10 min, and finally recrystallized in ethanol, filtered again, and dried under vacuum at 45℃ for 24 h to obtain the pure product UPy.

[0056] The BHO is synthesized using the following method:

[0057]

[0058] The raw materials for synthesis are as follows: diethyl oxalate, ethanolamine, and ethanol; where ethanol is the reaction solvent, and the molar ratio of the other two raw materials is diethyl oxalate: ethanolamine = 1:3.

[0059] The specific operation is as follows: Weigh 14.51 g of diethyl oxalate and dissolve it in 100 ml of anhydrous ethanol (GR, 99.8%) in a three-necked flask; slowly add 18.32 g of ethanolamine to the flask while stirring. The solution gradually turns white. React at room temperature for 24 hours. After filtration, wash the solid product with anhydrous ethanol and dry it under vacuum at 60 °C for 24 hours to obtain a white solid powder BHO.

[0060] The BHH is synthesized using the following method:

[0061]

[0062] The raw materials for synthesis are as follows: ethylene carbonate and 1,6-hexanediamine. No reaction solvent is required, and the molar ratio of the two raw materials is ethylene carbonate:1,6-hexanediamine = 2 to 2.1:1.

[0063] The specific operation is as follows: Weigh the raw materials (18.49g of ethylene carbonate and 11.62g of 1,6-hexanediamine) according to the predetermined amount and add them to a round-bottom flask. Heat directly to 60°C and stir for 1 hour until no bubbles are generated. Raise the temperature to 95°C and continue the reaction for 3 hours. Vacuum the mixture until no bubbles are generated. Add DMF to dissolve the mixture and precipitate it with ice-cold dichloromethane / ice-cold n-hexane. After filtration, dry the mixture under vacuum at 60°C for 24 hours to obtain the pure product BHH.

[0064] In this embodiment of the invention, mechanical properties were tested using an INSTRON 119 universal testing machine; thermogravimetric analysis was performed using a Netzsch 217 thermogravimetric analyzer.

[0065] Example 1

[0066] Modified PBAT materials are prepared by a two-step method (or prepolymerization method) using dihydroxyl-terminated PBAT, PDI, and one of the small molecule chain extenders Upy, BHO, and ADH, comprising the following steps:

[0067] (1) Weigh a certain amount of PBAT diol with a molecular weight of 7,200 g / mol and hydroxyl-terminated into a round-bottom flask with a side arm, and evacuate it at 100°C for 1 h to remove residual water.

[0068] (2) Weigh out a predetermined amount of PDI (10% excess based on stoichiometry) and DBTDL and add them to a flask. Prepolymerize at 180°C for 0.5 h to obtain the prepolymer.

[0069] (3) Weigh a predetermined amount of small molecule chain extender Upy (or BHO, ADH), add it to a flask, and continue the reaction at 180℃ for 0.5h to obtain modified PBAT materials, which are named PBAT-Upy, PBAT-BHO, and PBAT-ADH respectively.

[0070] The raw material formula for Example 1 is shown in Table 1.

[0071] Table 1. Chain extension reaction formulation for Example 1

[0072]

[0073] In Example 1, the molar ratio of chain extender C to PBAT raw material A was 1:1, and the molar ratio of component B to the total molar ratio of components A+C was 1:1. By controlling the reaction time, PABT material with a molecular weight of 18-23 kg / mol was prepared. Compared to PBAT raw material, the molecular weight of the copolymer increased by 2-3 times.

[0074] The mechanical properties of the raw material PBAT and the lower-content PBAT material prepared in Example 1 were characterized. The stress-strain curves of the PABT raw material are shown below. Figure 3 As shown, tensile tests demonstrate that the tensile strength of PABT raw material is only 8 MPa, and the elongation at break is approximately 160%. The tensile curves for PBAT-Upy, PBAT-BHO, and PBAT-ADH materials are shown below. Figure 4 As shown in Table 2, the mechanical strength of the copolymer continuously increases with the transformation from double hydrogen bonds in Upy and BHO to six hydrogen bonds in ADH. The tensile strength of PBAT-ADH with a molecular weight of 2.5 g / mol reaches 13.5 MPa, and the elongation at break reaches 550%. Compared with the raw material, both mechanical strength and toughness are significantly improved.

[0075] Table 2 Tensile properties of PBAT raw material and modified material prepared in Example 1

[0076]

[0077] Example 2

[0078] Taking the preparation of modified PBAT materials via a two-step method (or prepolymerization method) using dihydroxyl-terminated PBAT with PDI and BHH chain extenders as an example, the specific steps are as follows:

[0079] (1) Weigh a certain amount of PBAT diol with a molecular weight of 7,200 g / mol and hydroxyl-terminated into a round-bottom flask with a side arm, and evacuate it at 100°C for 1 h to remove residual water.

[0080] (2) Weigh out a predetermined amount of PDI (10% excess based on stoichiometry) and DBTDL and add them to a flask. Prepolymerize at 180°C for 0.5 h to obtain the prepolymer.

[0081] (3) Weigh a predetermined amount of the small molecule chain extender BHH, add it to a flask, and continue the reaction at 180–220 °C for 1–1.5 h to obtain BHH-modified PBAT material, named PBAT-BHH-S. x .

[0082] The raw material formula for Example 2 is shown in Table 3.

[0083] Table 3 Typical formulation for chain extension reaction in Example 2

[0084]

[0085] The PBAT-BHH material prepared in Example 2 has a number-average molecular weight of 28-35 kg / mol and a white appearance; it exhibits good thermal stability, with a 5% thermal decomposition temperature above 320°C. Figure 5It has good solubility and can be used for hot pressing and solution casting.

[0086] PBAT-BHH-S prepared in Example 2 x The material was prepared into a thin film with a thickness of approximately 0.7 mm by solution casting. Figure 6 (As shown). A film of the same shape was also made from PBAT raw material with a molecular weight of 7.2 kg / mol. Tensile tests were conducted on the film under the same conditions: temperature 25℃; load 50 N; stretching speed 50 mm / min. The stress-strain curve of the PABT raw material is shown below. Figure 3 As shown, tensile tests demonstrate that the tensile strength of PABT raw material is only 8 MPa, and the elongation at break is only about 160%. PBAT-BHH-S x The stress-strain curves of the thin film spline are as follows: Figure 7 As shown in Table 4, the tensile strength is approximately 19 MPa, and the elongation at break is 1300%. Compared to the original PBAT material, the modified PBAT-BHH-S... x The tensile strength of the sample increased by 2.5 times, and the elongation at break increased by 8 times. Currently, the tensile strength of commercially available PBAT materials with a molecular weight of over 100,000 is approximately 15 MPa, and the elongation at break is approximately 800%. Therefore, the mechanical properties of the PBAT-modified material prepared in this invention surpass those of existing high-molecular-weight PBAT materials.

[0087] Table 4. PBAT raw materials and PBAT-BHH-S prepared in Example 2 x Tensile properties of materials

[0088]

[0089] Example 3 One-step method

[0090] (1) Weigh PBAT diol with a molecular weight of 7,200 g / mol and BHH chain extender with hydroxyl end caps into a round-bottom flask with a side support according to the stoichiometric ratio, and evacuate at 100°C for 1 h to remove residual water.

[0091] (2) Weigh out the predetermined amount of PDI (10% excess based on the stoichiometric ratio) and DBTDL and add them to a shangshu flask. Stir well and react at 180-220℃ for 1-1.5 h to obtain BHH-modified PBAT-BHH-T x Material.

[0092] Table 5 Typical formulations for chain extension reaction in Example 3

[0093]

[0094] The PBAT-BHH-T1 material prepared in Example 3 was directly pulled out of the reaction flask and cooled, as shown in the following image. Figure 8 As shown on the left, the precipitate of PBAT-BHH-T2 material in methanol is as follows: Figure 8 As shown on the right. The prepared PBAT-BHH-T x The material has a number-average molecular weight of 40-50 kg / mol and a milky white appearance. It has good thermal stability, with a 5% thermal decomposition temperature above 320℃. It can be dissolved in solvents such as tetrahydrofuran and chloroform, and can be hot-pressed into films or solution-cast into films.

[0095] PBAT-BHH--T prepared in Example 3 x The material was prepared into a thin film with a thickness of approximately 0.7 mm using solution casting. Photographs of the film and the cut stretching strips are shown below. Figure 9 As shown, the cast film sample has a dense appearance, a smooth surface, and is semi-transparent.

[0096] PBAT-BHH-T prepared in Example 3 x Tensile tests on the material film strips showed that its tensile strength was approximately 50 MPa and its elongation at break was approximately 1500%. Figure 10 (As shown in Table 6). Compared to the mechanical properties of PBAT raw materials, PBAT-BHH-T x The material's mechanical strength has increased fivefold, and its elongation at break has increased tenfold. Compared to currently available pure high-molecular-weight PBAT materials, its tensile strength has increased nearly threefold, and its elongation at break has increased nearly twofold.

[0097] Table 6. PBAT-BHH-T prepared in Example 3 x Tensile properties of materials

[0098]

[0099] In summary, this invention effectively increases the molecular weight of PBAT prepolymer and significantly improves the mechanical strength and toughness of PBAT materials by modifying PBAT with a bio-based chain extender that can introduce hydrogen-bonded supramolecular interactions. Furthermore, the mechanical properties can be effectively and controllably regulated by changing the content of the chain extender and the copolymerization method.

Claims

1. A modified PBAT material, characterized in that, The modified PBAT material comprises PBAT, diisocyanate, and a small molecule chain extender as raw materials, and is obtained by melt copolymerization of the raw materials. The mass ratio of the raw materials is: 80-96 parts by weight of PBAT, 3.0-8.0 parts by weight of diisocyanate, and 1.6-12.0 parts by weight of small molecule chain extender. The small molecule chain extender is selected from one of 5-(2-hydroxyethyl)-6-methyl-2-aminouracil, adipic acid dihydrazide, N,N'-di(2-hydroxyethyl)oxalamide, or 1,6-bis(hydroxyethoxycarbonylamino)hexane. The modified PBAT material has multiple hydrogen bond supramolecular interactions introduced by the small molecule chain extender.

2. The modified PBAT material according to claim 1, characterized in that, The diisocyanate includes: pentamethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, or diphenylmethane-4,4'-diisocyanate.

3. A modified PBAT material according to claim 1 or 2, characterized in that, The diisocyanate is pentamethylene diisocyanate.

4. A modified PBAT material according to claim 1 or 2, characterized in that, The PBAT is a hydroxyl or carboxyl-terminated PBAT with a number average molecular weight of 3000 to 20,000 g / mol.

5. The modified PBAT material according to claim 4, characterized in that, The PBAT is selected from substances with the following structures: , or 。 6. A method for preparing the modified PBAT material according to any one of claims 1 to 5, characterized in that, The preparation method is selected from one of the following methods: Method 1: First, prepolymerize PBAT and diisocyanate at 150–180°C for 0.5–1 h under the action of a catalyst; then add a small molecule chain extender and react at 180–240°C. o The modified PBAT material was obtained by performing a chain extension reaction at C for 0.5–2 h. Method 2: The modified PBAT material is prepared by reacting PBAT, diisocyanate, small molecule chain extender and catalyst at 180~240℃ for 0.5~3h.

7. The method for preparing the modified PBAT material according to claim 6, characterized in that, The catalyst is selected from stannous octoate or dibutyltin dilaurate; the amount of the catalyst is 0.5 to 1 wt% of the mass of PBAT.

8. A method for increasing the molecular weight of PBAT prepolymer, characterized in that, The method is as follows: diisocyanate and a small molecule chain extender are introduced into PBAT prepolymer, and modified PBAT is obtained by melt copolymerization; wherein, the small molecule chain extender is selected from one of 5-(2-hydroxyethyl)-6-methyl-2-aminouracil, adipic acid dihydrazide, N,N'-bis(2-hydroxyethyl)oxalamide or 1,6-bis(hydroxyethoxycarbonylamino)hexane; the mass ratio of PBAT, diisocyanate and small molecule chain extender is: 80~96 parts by weight of PBAT, 3.0~8.0 parts by weight of diisocyanate and 1.6~12.0 parts by weight of small molecule chain extender.

9. A method for improving the mechanical strength and toughness of PBAT through supramolecular interactions, characterized in that, The method is as follows: diisocyanate and a small molecule chain extender are introduced into PBAT prepolymer, and modified PBAT is obtained by melt copolymerization; wherein, the small molecule chain extender is selected from one of 5-(2-hydroxyethyl)-6-methyl-2-aminouracil, adipic acid dihydrazide, N,N'-bis(2-hydroxyethyl)oxalamide or 1,6-bis(hydroxyethoxycarbonylamino)hexane; the mass ratio of PBAT, diisocyanate and small molecule chain extender is: 80~96 parts by weight of PBAT, 3.0~8.0 parts by weight of diisocyanate and 1.6~12.0 parts by weight of small molecule chain extender.

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