Method for preparing PLA / PPC biodegradable composite material through reactive compatibilization

Abstract

The invention relates to a method for preparing a PLA / PPC biodegradable composite material by reactive compatibilization, and belongs to a biodegradable material preparation method, and the method comprises the following steps: carrying out maleic anhydride end-capping modification on PPC; (PLA, modified PPC and an additive are subjected to melt blending. A test proves that the interface compatibility is obviously improved; in the aspect of mechanical properties, the elongation at break reaches 252.8% (improved by 7.0 times compared with that of a non-compatibilization system), the notch impact strength reaches 6.32 kJ / m < 2 > (improved by 2.0 times), and meanwhile, the tensile strength is kept at 54.8 MPa or above. In addition, the light transmittance of the material is improved to 93.0%, the water contact angle reaches 85.71 degrees, meanwhile, the thermal stability is synchronously improved, T95% is greatly improved to 339.62 DEG C from 319.27 DEG C, and the amplification reaches 20.35 DEG C. The high-performance full-biodegradable material has wide application prospects in the fields of packaging films, environment-friendly agricultural films and the like, and a solution is provided for industrial application of green materials.

Description

Technical Field

[0001] The present invention relates to a method for preparing a biodegradable material, in particular to a method for preparing a PLA / PPC biodegradable composite material by reaction compatibilization. Background Art

[0002] Biodegradable materials have become a hot topic in research and application because they can be decomposed by microorganisms in the natural environment, ultimately converting into water and carbon dioxide without causing long-term environmental pollution. Among these materials, polylactic acid (PLA), also known as polylactide, is a thermoplastic, biodegradable aliphatic polyester. It is known for its excellent biodegradability, biocompatibility, and good mechanical properties. Although PLA excels in rigidity, its lack of toughness limits its potential for a wider range of applications.

[0003] In order to solve the problem of insufficient performance of PLA, the present invention uses PLA as a matrix material and blends it with polypropylene carbonate (PPC). PPC is a biodegradable resin formed by copolymerizing CO2 and propylene oxide, and it has advantages such as high ductility, high barrier properties, high transparency, and complete biodegradability. PLA is melt-blended with maleic anhydride-terminated PPC and a compatibilizer. This blending method not only significantly improves the mechanical properties of PLA-based composite materials, but also effectively controls the migration problem of the compatibilizer. Through this innovative blending technology, a PLA-based composite material with excellent comprehensive performance is successfully prepared, which not only widens the range of application of PLA, but also provides new direction for the development of environmentally friendly materials.

[0004] Patent publication number CN 118560015 A discloses a method for preparing a degradable PLA / PPC composite material. The invention studies the effects of different ratios on the mechanical properties of the composite material by adjusting the specific content ratio of polylactic acid (PLA) and polypropylene carbonate (PPC). The method includes mixing PLA and PPC in a specific ratio and preparing a composite material with excellent deformation ability and excellent biodegradability through a specific processing technology. However, the obtained PLA / PPC composite material can only show a single performance advantage when the content of PLA and PPC changes. For example, when the notched impact strength can reach a maximum of 10kJ / m 2 When the tensile strength reaches 80 MPa, the notched impact strength can only reach 2.50 kJ / m 2 This means that it is difficult to achieve both rigidity and toughness at the same time.

[0005] Patent publication number CN 118909414 A discloses a cellulose nanoene interfacially coupled PLA-reinforced PPC composite membrane, its preparation method, and applications. This invention heats and mixes PLA, PPC, and cellulose nanoene to produce a PLA / PPC biodegradable composite. Cellulose nanoene serves as a compatibilizer to enhance the compatibility between the PLA and PPC materials. However, the process is complex and the strength is poor, with a maximum tensile strength of only 37 MPa. This process presents challenges of complexity and insufficient strength. Summary of the Invention

[0006] The present invention aims to provide a method for preparing a PLA / PPC biodegradable composite material through reactive compatibilization. This method enhances the compatibility between PLA and PPC. By using this compatibilizer, the resulting composite material exhibits excellent mechanical properties, exhibiting both high strength and outstanding toughness, achieving dual performance guarantees while also improving the material's optical properties and thermal stability.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] A method for preparing a PLA / PPC biodegradable composite material by reaction compatibilization comprises the following steps:

[0009] (1) Preparation of PPC-MAH: PPC and maleic anhydride (MAH) were mixed uniformly at a mass ratio of 99:1, melt-blended in a twin-screw extruder, and end-capped.

[0010] (2) Vacuum oven-dried polylactic acid (PLA) pellets, maleic anhydride-terminated PPC pellets, initiator, compatibilizer, and antioxidant were thoroughly mixed and then added to a twin-screw extruder. The temperatures of the extruder heads in zones I, II, III, IV, V, and VI were 165°C, 175°C, 175°C, 175°C, 175°C, 175°C, and 160°C, respectively. The screw speed was 70 r / min, and the feed rate was 8.0 r / min. A series of PLA / PPC blends containing different compatibilizer contents were prepared.

[0011] The basic raw materials are composed of the following parts:

[0012] 50-90 parts of polylactic acid;

[0013] 10-50 parts of polypropylene carbonate;

[0014] The amount of compatibilizer added is 1-14 parts;

[0015] The amount of antioxidant added is 0.1-1.0 parts;

[0016] The amount of initiator added is 0.1-0.5 parts.

[0017] The method for preparing a PLA / PPC biodegradable composite material by reactive compatibilization is described, wherein the compatibilizer is one or more of dibutyl itaconate (DBI), epoxidized soybean oil (ESO), polycarbodiimide (PCDI), polyvalent epoxidation chain extender (ADR), and polypropylene glycol diglycidyl ether (PPGDGE).

[0018] The method for preparing a PLA / PPC biodegradable composite material by reaction compatibilization is described, wherein the antioxidant is one or more of tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]pentaerythritol, tris(2,4-di-tert-butylphenyl)phosphite, bis(2,4-di-tert-butylphenyl)phosphite tetraol diphosphite, 2,6-di-tert-butylphenol (BHT)

[0019] The invention discloses a method for preparing a PLA / PPC biodegradable composite material by reaction compatibilization, wherein the initiator used is one or more of dicumyl peroxide (DCP), dibenzoyl peroxide (BPO), tert-butyl peroxyethyl ester (TBPO), and di-tert-butyl peroxide (DTBP).

[0020] The present invention has the following notable features:

[0021] 1. To address the problems of traditional polylactic acid (PLA) materials, such as high brittleness, low elongation at break, poor light transmittance, and poor thermal stability, the present invention introduces polypropylene carbonate (PPC) and PLA for melt blending. The selected raw materials are all fully biodegradable, which to a certain extent helps alleviate environmental pollution and other issues. Simultaneously, the introduction of a compatibilizer enhances the interaction force at the PLA / PPC interphase, improving compatibility and thereby enhancing the overall performance of the blend.

[0022] 2. The present invention adopts an efficient and simple preparation process to successfully develop a new material that is innovative, environmentally friendly and sustainable, effectively expanding the application range of PLA composite materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 FTIR spectrum of the blended material of the present invention;

[0024] Figure 2 Thermogravimetric curves of Comparative Example and Example (a) TG curve; (b) DTG curve. DETAILED DESCRIPTION

[0025] The present invention is described in detail below with reference to specific embodiments, but the present invention is not limited to these specific embodiments. Those skilled in the art can make some non-substantial improvements and adjustments to the present invention based on the contents of the above invention.

[0026] Comparative Example 1

[0027] 70 parts of polylactic acid;

[0028] 30 parts of polypropylene carbonate;

[0029] 1 part of capping agent;

[0030] 0.15 parts of initiator;

[0031] 0.15 parts of antioxidant.

[0032] (1) PPC end-capping treatment: PPC and MAH were mixed at a mass ratio of 99:1 and then fed into a twin-screw extruder. In zones I to VI of the extruder, the die temperatures were set at 125°C, 130°C, 130°C, 130°C, 130°C, and 130°C, respectively. The screw speed was 50-70 r / min, and the feed rate was 7.0-8.0 r / min. Subsequently, the extruder was extruded, cooled, and granulated. Finally, the product was dried in a vacuum oven at 60°C for 8 hours to ensure that the material was dry.

[0033] (2) Preparation of blends: PLA, end-capped PPC, initiator, and antioxidant were mixed in a certain mass ratio and then fed into a twin-screw extruder. In zones I to VI of the extruder, the die temperatures were set at 160°C, 170°C, 170°C, 170°C, 170°C, and 160°C, respectively. The screw speed was 50-70 r / min, and the feed rate was 7.0-8.0 r / min. The mixture was then extruded, cooled, and pelletized. Finally, the mixture was dried in a vacuum oven at 60°C for 8 hours to ensure dryness.

[0034] (3) The dried PLA / PPC blend samples were molded in a micro-injection molding machine. The barrel temperature was set to 170°C, the mold temperature was set to 45°C, and the holding time was set to 8-10s. The samples were injection molded into tensile bars according to the national standard GB / T1040.2-2006; the samples were injection molded into impact bars according to the national standard GB / T 1843-2008. Subsequently, the tensile and impact properties of the materials were tested according to the GB / T 1040.2-2006 and GB / T 1043.1-2008 test standards, respectively.

[0035] (4) DSC test: N2 atmosphere, gas flow rate of 50 mL / min, the sample was heated to 200°C at 10°C / min to eliminate thermal history, kept at this temperature for 5 min, then cooled to 25°C at 10°C / min, kept at this temperature for 5 min, and then heated to 200°C at 10°C / min.

[0036] (5) The dried PLA / PPC blend samples were pressed into films with a thickness of approximately 80 μm using a flat-bed vulcanizer. The transmittance of the films was then tested using a haze meter (CS-700) to evaluate the optical properties of the materials.

[0037] (6) Contact Angle Measurement: The contact angle of PLA / PPC blend sample films was measured using a static titration technique. A 1 μL droplet was placed on the prepared sample surface using a syringe pump. The contact angle value was extracted from the recorded water droplet image using software based on an ellipse model. The contact angles of distilled water and diiodomethane were measured to evaluate the adhesion work and surface energy of the test samples.

[0038] Example 1

[0039] 70 parts of polylactic acid;

[0040] 30 parts of polypropylene carbonate;

[0041] 1 part of capping agent;

[0042] 0.15 parts of initiator;

[0043] 0.15 parts of antioxidant;

[0044] 0.5 parts of compatibilizer.

[0045] (1) PPC end-capping treatment: PPC and MAH were mixed at a mass ratio of 99:1 and then fed into a twin-screw extruder. In zones I to VI of the extruder, the die temperatures were set at 125°C, 130°C, 130°C, 130°C, 130°C, and 130°C, respectively. The screw speed was 50-70 r / min, and the feed rate was 7.0-8.0 r / min. Subsequently, the extruder was extruded, cooled, and granulated. Finally, the product was dried in a vacuum oven at 60°C for 8 hours to ensure that the material was dry.

[0046] (2) Preparation of blends: PLA, end-capped PPC, compatibilizer, initiator, and antioxidant were mixed in a certain mass ratio and then fed into a twin-screw extruder. In zones I to VI of the extruder, the head temperatures were set to 160°C, 170°C, 170°C, 170°C, 170°C, and 160°C, respectively. The screw speed was 50-70 r / min, and the feed rate was 7.0-8.0 r / min. The mixture was then extruded, cooled, and pelletized. Finally, the mixture was dried in a vacuum oven at 60°C for 8 hours to ensure dryness.

[0047] (3) The dried PLA / PPC blend samples were molded in a micro-injection molding machine. The barrel temperature was set to 170°C, the mold temperature was set to 45°C, and the holding time was set to 8-10s. The samples were injection molded into tensile bars according to the national standard GB / T1040.2-2006; the samples were injection molded into impact bars according to the national standard GB / T 1843-2008. Subsequently, the tensile and impact properties of the materials were tested according to the GB / T 1040.2-2006 and GB / T 1043.1-2008 test standards, respectively.

[0048] (4) DSC test: N2 atmosphere, gas flow rate of 50 mL / min, the sample was heated to 200°C at 10°C / min to eliminate thermal history, kept at this temperature for 5 min, then cooled to 25°C at 10°C / min, kept at this temperature for 5 min, and then heated to 200°C at 10°C / min.

[0049] (5) The dried PLA / PPC blend samples were pressed into films with a thickness of approximately 80 μm using a flat-bed vulcanizer. The transmittance of the films was then tested using a haze meter (CS-700) to evaluate the optical properties of the materials.

[0050] (6) Contact Angle Measurement: The contact angle of PLA / PPC blend sample films was measured using a static titration technique. A 1 μL droplet was placed on the prepared sample surface using a syringe pump. The contact angle value was extracted from the recorded water droplet image using software based on an ellipse model. The contact angles of distilled water and diiodomethane were measured to evaluate the adhesion work and surface energy of the test samples.

[0051] Example 2

[0052] 70 parts of polylactic acid;

[0053] 30 parts of polypropylene carbonate;

[0054] 1 part of capping agent;

[0055] 0.15 parts of initiator;

[0056] 0.15 parts of antioxidant;

[0057] 1.0 part of compatibilizer.

[0058] (1) PPC end-capping treatment: PPC and MAH were mixed at a mass ratio of 99:1 and then fed into a twin-screw extruder. In zones I to VI of the extruder, the die temperatures were set at 125°C, 130°C, 130°C, 130°C, 130°C, and 130°C, respectively. The screw speed was 50-70 r / min, and the feed rate was 7.0-8.0 r / min. Subsequently, the extruder was extruded, cooled, and granulated. Finally, the product was dried in a vacuum oven at 60°C for 8 hours to ensure that the material was dry.

[0059] (2) Preparation of blends: PLA, end-capped PPC, compatibilizer, initiator, and antioxidant were mixed in a certain mass ratio and then fed into a twin-screw extruder. In zones I to VI of the extruder, the head temperatures were set to 160°C, 170°C, 170°C, 170°C, 170°C, and 160°C, respectively. The screw speed was 50-70 r / min, and the feed rate was 7.0-8.0 r / min. The mixture was then extruded, cooled, and pelletized. Finally, the mixture was dried in a vacuum oven at 60°C for 8 hours to ensure dryness.

[0060] (3) The dried PLA / PPC blend samples were molded in a micro-injection molding machine. The barrel temperature was set to 170°C, the mold temperature was set to 45°C, and the holding time was set to 8-10s. The samples were injection molded into tensile bars according to the national standard GB / T1040.2-2006; the samples were injection molded into impact bars according to the national standard GB / T 1843-2008. Subsequently, the tensile and impact properties of the materials were tested according to the GB / T 1040.2-2006 and GB / T 1043.1-2008 test standards, respectively.

[0061] (4) DSC test: N2 atmosphere, gas flow rate of 50 mL / min, the sample was heated to 200°C at 10°C / min to eliminate thermal history, kept at this temperature for 5 min, then cooled to 25°C at 10°C / min, kept at this temperature for 5 min, and then heated to 200°C at 10°C / min.

[0062] (5) The dried PLA / PPC blend samples were pressed into films with a thickness of approximately 80 μm using a flat-bed vulcanizer. The transmittance of the films was then tested using a haze meter (CS-700) to evaluate the optical properties of the materials.

[0063] (6) Contact Angle Measurement: The contact angle of PLA / PPC blend sample films was measured using a static titration technique. A 1 μL droplet was placed on the prepared sample surface using a syringe pump. The contact angle value was extracted from the recorded water droplet image using software based on an ellipse model. The contact angles of distilled water and diiodomethane were measured to evaluate the adhesion work and surface energy of the test samples.

[0064] Example 3

[0065] 70 parts of polylactic acid;

[0066] 30 parts of polypropylene carbonate;

[0067] 1 part of capping agent;

[0068] 0.15 parts of initiator;

[0069] 0.15 parts of antioxidant;

[0070] 1.5 parts of compatibilizer.

[0071] (1) PPC end-capping treatment: PPC and MAH were mixed at a mass ratio of 99:1 and then fed into a twin-screw extruder. In zones I to VI of the extruder, the die temperatures were set at 125°C, 130°C, 130°C, 130°C, 130°C, and 130°C, respectively. The screw speed was 50-70 r / min, and the feed rate was 7.0-8.0 r / min. Subsequently, the extruder was extruded, cooled, and granulated. Finally, the product was dried in a vacuum oven at 60°C for 8 hours to ensure that the material was dry.

[0072] (2) Preparation of blends: PLA, end-capped PPC, compatibilizer, initiator, and antioxidant were mixed in a certain mass ratio and then fed into a twin-screw extruder. In zones I to VI of the extruder, the head temperatures were set to 160°C, 170°C, 170°C, 170°C, 170°C, and 160°C, respectively. The screw speed was 50-70 r / min, and the feed rate was 7.0-8.0 r / min. The mixture was then extruded, cooled, and pelletized. Finally, the mixture was dried in a vacuum oven at 60°C for 8 hours to ensure dryness.

[0073] (3) The dried PLA / PPC blend samples were molded in a micro-injection molding machine. The barrel temperature was set to 170°C, the mold temperature was set to 45°C, and the holding time was set to 8-10s. The samples were injection molded into tensile bars according to the national standard GB / T1040.2-2006; the samples were injection molded into impact bars according to the national standard GB / T 1843-2008. Subsequently, the tensile and impact properties of the materials were tested according to the GB / T 1040.2-2006 and GB / T 1043.1-2008 test standards, respectively.

[0074] (4) DSC test: N2 atmosphere, gas flow rate of 50 mL / min, the sample was heated to 200°C at 10°C / min to eliminate thermal history, kept at this temperature for 5 min, then cooled to 25°C at 10°C / min, kept at this temperature for 5 min, and then heated to 200°C at 10°C / min.

[0075] (5) The dried PLA / PPC blend samples were pressed into films with a thickness of approximately 80 μm using a flat-bed vulcanizer. The transmittance of the films was then tested using a haze meter (CS-700) to evaluate the optical properties of the materials.

[0076] (6) Contact Angle Measurement: The contact angle of PLA / PPC blend sample films was measured using a static titration technique. A 1 μL droplet was placed on the prepared sample surface using a syringe pump. The contact angle value was extracted from the recorded water droplet image using software based on an ellipse model. The contact angles of distilled water and diiodomethane were measured to evaluate the adhesion work and surface energy of the test samples.

[0077] Example 4

[0078] 70 parts of polylactic acid;

[0079] 30 parts of polypropylene carbonate;

[0080] 1 part of capping agent;

[0081] 0.15 parts of initiator;

[0082] 0.15 parts of antioxidant;

[0083] 2.0 parts of compatibilizer.

[0084] (1) PPC end-capping treatment: PPC and MAH were mixed at a mass ratio of 99:1 and then fed into a twin-screw extruder. In zones I to VI of the extruder, the die temperatures were set at 125°C, 130°C, 130°C, 130°C, 130°C, and 130°C, respectively. The screw speed was 50-70 r / min, and the feed rate was 7.0-8.0 r / min. Subsequently, the extruder was extruded, cooled, and granulated. Finally, the product was dried in a vacuum oven at 60°C for 8 hours to ensure that the material was dry.

[0085] (2) Preparation of blends: PLA, end-capped PPC, compatibilizer, initiator, and antioxidant were mixed in a certain mass ratio and then fed into a twin-screw extruder. In zones I to VI of the extruder, the head temperatures were set to 160°C, 170°C, 170°C, 170°C, 170°C, and 160°C, respectively. The screw speed was 50-70 r / min, and the feed rate was 7.0-8.0 r / min. The mixture was then extruded, cooled, and pelletized. Finally, the mixture was dried in a vacuum oven at 60°C for 8 hours to ensure dryness.

[0086] (3) The dried PLA / PPC blend samples were molded in a micro-injection molding machine. The barrel temperature was set to 170°C, the mold temperature was set to 45°C, and the holding time was set to 8-10s. The samples were injection molded into tensile bars according to the national standard GB / T1040.2-2006; the samples were injection molded into impact bars according to the national standard GB / T 1843-2008. Subsequently, the tensile and impact properties of the materials were tested according to the GB / T 1040.2-2006 and GB / T 1043.1-2008 test standards, respectively.

[0087] (4) DSC test: N2 atmosphere, gas flow rate of 50 mL / min, the sample was heated to 200°C at 10°C / min to eliminate thermal history, kept at this temperature for 5 min, then cooled to 25°C at 10°C / min, kept at this temperature for 5 min, and then heated to 200°C at 10°C / min.

[0088] (5) The dried PLA / PPC blend samples were pressed into films with a thickness of approximately 80 μm using a flat-bed vulcanizer. The transmittance of the films was then tested using a haze meter (CS-700) to evaluate the optical properties of the materials.

[0089] (6) Contact Angle Measurement: The contact angle of PLA / PPC blend sample films was measured using a static titration technique. A 1 μL droplet was placed on the prepared sample surface using a syringe pump. The contact angle value was extracted from the recorded water droplet image using software based on an ellipse model. The contact angles of distilled water and diiodomethane were measured to evaluate the adhesion work and surface energy of the test samples.

[0090] The blend samples (5-8 mg) prepared in the comparative examples and examples 1-4 of the present invention were respectively subjected to thermal property analysis using a differential scanning calorimeter (DSC, Mettler-Toledo, Switzerland) under a nitrogen atmosphere.

[0091] Table 1 DSC test results of blend materials

[0092] <![CDATA[T g1 (℃)]]> <![CDATA[T g2 (℃)]]> <![CDATA[ΔT g (℃)]]> Comparative Example 1 61.92 38.77 23.15 Example 1 59.51 38.50 21.01 Example 2 58.83 38.17 20.65 Example 3 56.50 38.00 18.50 Example 4 59.67 38.50 21.17

[0093] pass Figure 1 As shown in Table 1, there are two endothermic steps in the temperature range of 0-70℃, corresponding to the glass transition temperatures (T g ), in pure PLA / PPC blends, the T g The difference in glass transition temperature between the two phases (ΔT g ) is 23.15℃. After PCDI is introduced into PLA / PPC blend, the T gBasically remain unchanged, PLA's T g Gradually approaching the PPC phase, the ΔT of the two phases g As the content of PCDI decreases gradually, it can be seen that PCDI has a good compatibilizing effect on PLA / PPC blends. This is because PCDI contains cumulative double bonds (-N=C=N-) in its molecular structure, which makes it chemically active and can react chemically with the terminal carboxyl groups of PLA and PPC, thereby effectively cross-linking. During the processing of PLA / PPC blends, PCDI will further cross-link with the carboxyl groups generated by the cleavage of ester bonds in the PLA / PPC blend, resulting in molecular chain growth or an increase in branching, and increasing the entanglement points between molecular chains, thereby playing a stabilizing role in the material processing process and increasing the compatibility of the PLA / PPC blend.

[0094] 15-20 mg samples of the blends prepared in the comparative examples and Examples 1-4 were weighed and heated from room temperature to 500°C at a rate of 10°C / min under a nitrogen atmosphere, with a gas flow rate of 100 mL / min. The thermal properties of the blends were studied using a thermogravimetric analyzer under a nitrogen atmosphere.

[0095] Table 2 Thermogravimetric data of comparative examples and examples

[0096] Sample <![CDATA[T 5％ (℃)]]> <![CDATA[T max (℃)]]> <![CDATA[T 95％ (℃)]]> Comparative Example 1 275.94 304.87 319.27 Example 1 275.78 304.50 330.05 Example 2 275.37 301.22 334.09 Example 3 278.03 302.30 339.62 Example 4 275.33 304.27 340.05

[0097] It can be seen from the thermogravimetric test curves and data in Figure 2 and Table 2 that the thermal stability of the PLA / PPC composite material is significantly improved after the introduction of the compatibilizer. Compared with the uncompatibilized system (Comparative Example 1), the initial decomposition temperature (T 5％ ) increased from 275.94℃ to 278.03℃, indicating that the heat resistance of the material is enhanced; the maximum decomposition temperature (T max ) decreased slightly from 304.87℃ to 302.30℃, which may be related to the preferential decomposition of the compatibilizer at high temperature, which caused the local breakage of the PLA segments. The 95% mass retention temperature (T 95％ ) increased significantly from 319.27℃ to 339.62℃, an increase of 20.35℃, which confirmed that the compatibilizer effectively inhibited the volatilization of small molecules during thermal degradation by promoting the cross-linking reaction between PLA and PPC interface. g The synergistic effect of the temperature drop (reduced to 18.50°C) enables the material to maintain structural integrity during high-temperature processing, meeting the stringent requirements for thermal stability in packaging materials and other fields.

[0098] Mechanical tests were performed on the blend samples prepared in the comparative example and Examples 1-4 of the present invention.

[0099] Table 3 Impact strength, elongation at break and tensile strength of comparative examples and examples

[0100]

[0101] From the data in Table 3, it can be found that the elongation at break in Specific Example 3 is increased by 7.0 times compared with that in Comparative Example 1, and the notched impact strength in Specific Example 3 is increased by 2.0 times compared with that in Comparative Example 1, while the tensile strength of the blended material remains basically unchanged. By introducing the compatibilizer, the notched impact strength and elongation at break of the PLA / PPC blended material are significantly improved, with the elongation at break being increased to 252.8% at the highest, and the notched impact strength being increased to 6.32 kJ / m 2 , and its tensile strength has not been significantly reduced. The overall mechanical properties of the material have been comprehensively improved, reflecting high toughness.

[0102] The blend samples prepared in the comparative example and Examples 1-4 of the present invention were respectively prepared into thin films and their optical properties were tested using a haze meter.

[0103] Table 4 Transmittance and haze of comparative and example films

[0104] Sample Transmittance (%) Haze (%) Comparative Example 1 91.4 42.6 Example 1 92.1 37.9 Example 2 92.7 34.1 Example 3 93.0 30.1 Example 4 91.4 31.5

[0105] As shown in the test data in Table 4, after the introduction of the compatibilizer, the transmittance of the PLA / PPC blend film in Example 3 increased from 91.4% in Comparative Example 1 to 93.0%, while the haze value significantly decreased from 42.6% to 31.5%, a decrease of 26.1%. The experimental data demonstrate that the introduction of the compatibilizer effectively improves the interfacial compatibility of the PLA and PPC two-phase system. By refining the phase domain size and optimizing the interfacial refractive index matching, the optical properties of the blend are synergistically improved, with a particularly significant decrease in haze, confirming the key role of reactive compatibilizers in regulating the optical properties of biodegradable materials.

[0106] Contact angle tests were performed on the blend samples prepared in the comparative example and Examples 1-4 of the present invention, respectively.

[0107] Table 5 Contact angle data of comparative examples and examples

[0108]

[0109] As shown in the test data in Table 5, after the introduction of the compatibilizer, the water contact angle (WCA) of the PLA / PPC blend in Example 3 increased significantly from 65.78° to 88.57°, and the diiodomethane contact angle (DCA) increased from 31.15° to 56.62°, indicating that the hydrophobicity of the film surface is enhanced. s) decreased from 48.33mN / m to 31.35mN / m, mainly due to the dispersion component ( 41.01→29.42 mN / m) reduces the drive, while the polar component contributes only slightly ( 7.32→1.92 mN / m). This indicates that the compatibilizer reduces the surface energy mainly by regulating the non-polar characteristics of the surface morphology, thereby achieving a synergistic improvement in the hydrophobicity of the blend material film, confirming the key role of reactive compatibilizers in regulating the hydrophobic properties of biodegradable materials.

[0110] The above embodiments are only intended to help understand the method and core concept of the present invention. It should be noted that, without departing from the principles of the present invention, a number of improvements and modifications may be made to the present invention by those skilled in the art, and such improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0111] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a PLA / PPC biodegradable composite material by reaction expansion, characterized in that: The method comprises the following steps: (1) Preparation of PPC-MAH: PPC and maleic anhydride (MAH) were mixed uniformly at a mass ratio of 99:1, melt-blended in a twin-screw extruder, and end-capped. (2) After vacuum oven-dried polylactic acid (PLA) pellets, maleic anhydride-terminated PPC pellets, initiator, compatibilizer, and antioxidant were fully mixed and then added to a twin-screw extruder. The temperatures of the extruder heads in zones I, II, III, IV, V, and VI were 165°C, 175°C, 175°C, 175°C, 175°C, 175°C, and 160°C, respectively. The screw speed was 70 r / min and the feeding rate was 8.0 r / min. The basic raw materials for preparing PLA / PPC blends containing different compatibilizer contents are composed of the following parts: 50-90 parts of polylactic acid; 10-50 parts of polypropylene carbonate; The amount of compatibilizer added is 1-14 parts; The amount of antioxidant added is 0.1-1.0 parts; The amount of initiator added is 0.1-0.5 parts.

2. The method for preparing a PLA / PPC biodegradable composite material by reaction expansion according to claim 1, characterized in that: The compatibilizer is one or more of dibutyl itaconate (DBI), epoxidized soybean oil (ESO), polycarbodiimide (PCDI), polyvalent epoxidation chain extender (ADR), and polypropylene glycol diglycidyl ether (PPGDGE).

3. The method for preparing a PLA / PPC biodegradable composite material by reaction expansion according to claim 1, characterized in that: The antioxidant is one or more of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, tris(2,4-di-tert-butylphenyl) phosphite, bis(2,4-di-tert-butylphenyl) phosphite tetraol diphosphite, and 2,6-di-tert-butylphenol (BHT).

4. The method for preparing a PLA / PPC biodegradable composite material by reaction expansion according to claim 1, characterized in that: The initiator used is one or more of dicumyl peroxide (DCP), dibenzoyl peroxide (BPO), tert-butyl peroxyethyl ester (TBPO), and di-tert-butyl peroxide (DTBP).

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