ADR and ENR synergistically toughened PLA / PBAT blend and PLA / PBAT / ENR / ADR polymer material

Abstract

The invention belongs to the technical field of blending modification of high-molecular polymers, and particularly relates to an ADR and ENR synergistically toughened PLA / PBAT blend and a PLA / PBAT / ENR / ADR polymer material. According to the PLA / PBAT blend synergistically toughened by ADR and ENR provided by the invention, the preparation method of the PLA / PBAT blend synergistically toughened by ADR and ENR comprises the step of carrying out melt blending on PLA, PBAT, ENR and ADR according to a mass ratio of (80 to 85): (15 to 20): (2 to 10): (3 to 9). ADR and ENR are introduced into a PLA / PBAT system, ADR reactive crosslinking compatibilization and ENR physical toughening synergistic modification are achieved, and the synergistic toughening effect of chemical crosslinking-physical form dual mechanisms enables the blend to have excellent strength, meanwhile, the elongation at break is greatly improved, the notch impact strength can reach 50 kJ / m < 2 > or above, and the elongation at break reaches 450% or above.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of polymer blend modification, and particularly relates to a PLA / PBAT blend toughened by ADR and ENR in cooperation and a PLA / PBAT / ENR / ADR polymer material. BACKGROUND

[0002] Under the increasingly severe environmental challenges, developing bio-based and biodegradable materials to replace petroleum-based polymers has become a key research direction. As a kind of biobased and biodegradable polymer, polylactic acid (PLA) has the advantages of biocompatibility, biodegradability, renewability, recyclability, high mechanical strength and easy processability, and shows important application potential in the fields of sustainable packaging, medical devices and textiles. However, its inherent toughness defect limits its development and application, so it is urgent to toughen PLA. Blending PLA with elastomers is the most common and effective method, but due to the difference in molecular chain structure of the two polymers, it usually leads to poor compatibility. Polybutylene adipate terephthalate (PBAT) as a kind of thermoplastic elastomer with high elasticity and excellent biodegradability is a promising toughening material for PLA. At present, PLA / PBAT blends have been widely studied. However, due to the difference in molecular structure, PBAT and PLA are not compatible at all proportions, which significantly limits the performance improvement.

[0003] In view of the compatibility problem of PLA / PBAT blend, the current compatibilization strategies mainly include reactive compatibilization and non-reactive compatibilization. The former can react with the end groups of PLA and PBAT to form a PLA-PBAT crosslinked network, and simultaneously realize the molecular weight improvement and crosslinked network construction, thereby strengthening the interfacial adhesion of two phases from the chemical level. A variety of reactive chemicals, such as anhydride, peroxide, diisocyanate and epoxide, have been reported as efficient reactive compatibilizers for PLA / PBAT blends. Among them, the epoxy groups in the epoxy chain extender (ADR) containing multifunctional epoxy groups can react with the COOH or OH end groups in PLA and PBAT, thereby enhancing the compatibility and physical properties between polymers.

[0004] In the paper "Enhanced toughness of poly(lactic acid) and poly(butylene adipate-co-terephthalate) blends by incorporating an ADR chain-extending agent and a bio-resourced plasticizer" (International Journal of Biological Macromolecules, 2025, 293: 139344) by Liu et al. on December 30, 2024, it is disclosed that the biobased plasticizer epoxidized linseed oil (ELO) is introduced into the PLA / PBAT system in cooperation with ADR, which effectively improves the compatibility and toughness of the blend. The tensile strain at break and notched impact strength of the PLA / PBAT / ELO / ADR blend (63 / 27 / 10 / 1) reach 286% and 52.53 kJ / m 2 The interfacial interaction between components is significantly enhanced, the melt elasticity, viscosity and hydrophobicity are improved, and the thermal stability is optimized, but the crystallization ability of the blend is inhibited to a certain extent. The elongation at break of the PLA / PBAT / ELO / ADR blend is still low. SUMMARY

[0005] The purpose of the present application is to provide an ADR and ENR synergistically toughened PLA / PBAT blend, which solves the problem that the existing PLA / PBAT blend cannot have good elongation at break while maintaining high impact strength.

[0006] The second purpose of the present application is to provide a PLA / PBAT / ENR / ADR polymer material, which solves the problem that the existing PLA / PBAT-based polymer material cannot have good elongation at break while maintaining high impact strength.

[0007] To solve the above technical problems, the technical scheme of the ADR and ENR synergistically toughened PLA / PBAT blend of the present application is as follows:

[0008] An ADR and ENR synergistically toughened PLA / PBAT blend, the preparation method of the ADR and ENR synergistically toughened PLA / PBAT blend comprises the step of melt blending PLA, PBAT, ENR and ADR in a mass ratio of (80-85):(15-20):(2-10):(3-9).

[0009] The application is an improvement on the prior art, and provides an ADR and ENR synergistically toughened PLA / PBAT blend, by introducing ADR and ENR into PLA / PBAT at the same time, esterification reaction of ADR and the end groups of PLA / PBAT, construction of a three-dimensional chemical crosslinking network, significant improvement of interfacial compatibility, conversion of the blend from an island structure to a uniform co-continuous structure. On the one hand, the PLA chain segment is limited, the crystallization is inhibited, and the thermal stability is improved, on the other hand, as the interface stress transfer is enhanced, the ENR aggregate is converted from a dispersed phase impurity to an effective toughening unit in the network; the introduction of ENR reduces the cold crystallization temperature of PLA through heterogeneous nucleation, and promotes the formation of metastable alpha' crystal form. The synergistic modification of ADR reactive crosslinking compatibilization and ENR physical toughening, the synergistic toughening effect of the "chemical crosslinking-physical morphology" dual mechanism, enables the blend to have excellent strength while the elongation at break is greatly improved.

[0010] The notched impact strength of the PLA / PBAT blend of the application can reach 50 kJ / m 2 The above, the tensile strength reaches 40 MPa or more, the elongation at break reaches 450% or more, and excellent strength and toughness are exhibited, and the design of the high-performance PLA-based biodegradable material provides a key theoretical basis.

[0011] In order to further improve the impact strength and toughness, preferably, the mass ratio of the PLA, PBAT, ENR and ADR is (80-85):(15-20):(2-3):(3-9), or (80-85):(15-20):(2-10):(5-6).

[0012] In order to further improve the impact strength, preferably, the mass ratio of the PLA, PBAT, ENR and ADR is (80-85):(15-20):(4-10):(5-6). The notched impact strength of the blend under this ratio can reach 60 kJ / m 2 Above.

[0013] In order to further improve the mechanical properties of the blend, preferably, the epoxy value of the ENR is 70-80%; the number average molecular weight of the PLA is (2-3) x 10 5 g / mol; the number average molecular weight of the PBAT is (2-3) x 10 4 g / mol; the weight average molecular weight of the ADR is 7000-8000 g / mol, and the epoxy equivalent weight of the ADR is 300-400 g / mol.

[0014] In order to further make the reaction crosslinking compatibilization and physical toughening more complete during melt blending, preferably, the temperature during melt blending is 180-200 DEG C, the rotation speed during melt blending is 50-100 rpm, and the time of melt blending is 8-15 min.

[0015] The technical scheme of the PLA / PBAT / ENR / ADR polymer material of the present application is:

[0016] A PLA / PBAT / ENR / ADR polymer material, and a preparation method of the PLA / PBAT / ENR / ADR polymer material, which comprises the step of compression molding the ADR and ENR synergistically toughened PLA / PBAT blend.

[0017] In order to further improve the forming efficiency of the polymer material, preferably, the compression pressure during the compression molding is 10-15 MPa, the hot-pressing time during the compression molding is 5-10 min, and the temperature during the compression molding is 190-200°C.

[0018] In order to further improve the notched impact strength and heat distortion temperature of the polymer material, preferably, annealing treatment is performed after the compression molding. The annealing treatment can greatly improve the notched impact strength of the blend, and the notched impact strength can reach 70 kJ / m 2 above, and improve the heat distortion temperature of the blend.

[0019] More preferably, the PLA, PBAT, ENR and ADR with a mass ratio of (80-85):(15-20):(2-4):(5-7) are melt blended and then compression molded, and annealing treatment is performed after the molding. The notched impact strength of the blend after the annealing treatment under this ratio can reach 80 kJ / m 2 above.

[0020] More preferably, the PLA, PBAT, ENR and ADR with a mass ratio of (80-85):(15-20):(2-3):(5-6) are melt blended and then compression molded, and annealing treatment is performed after the molding. The notched impact strength of the blend after the annealing treatment under this ratio can reach 100 kJ / m 2 above.

[0021] In order to further improve the crystal type transformation, preferably, the temperature of the annealing treatment is 120-160°C, and the time of the annealing treatment is 30-50 min.

[0022] In order to further improve the annealing performance, preferably, cooling is performed in ice water at 0-5°C for 5-10 min after the annealing treatment. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The infrared spectrograms of blends with different formulations;

[0024] Figure 2 The XPS spectrograms of blends with different formulations;

[0025] Figure 3 Mechanical property test results of different formula blends before and after annealing;

[0026] Figure 4 Torque and stress-strain curves of different formula blends;

[0027] Figure 5 Low temperature impact test results of different formula blends;

[0028] Figure 6 XRD patterns of different formula blends after annealing treatment;

[0029] Figure 7 Heat distortion temperature of different formula blends before and after annealing;

[0030] Figure 8 Thermal performance test results of different formula blends;

[0031] Figure 9 DSC curve of different formula blends before annealing;

[0032] Figure 10 Rheological property test results of different formula blends;

[0033] Figure 11 Tan delta curve and Cole-Cole curve of different formula blends;

[0034] Figure 12 Impact fracture SEM morphology of different formula blends;

[0035] Figure 13 Mechanical property test results of blend LB / E-X;

[0036] Figure 14 SEM of DCM etched frozen section of different formula blends;

[0037] Figure 15 Crosslinking degree test results of different formula blends;

[0038] Figure 16 Interface structure schematic diagram of ADR and ENR synergistically toughened PLA / PBAT blend of the application. DETAILED DESCRIPTION

[0039] The technical concept of the ADR and ENR synergistically toughened PLA / PBAT blend provided by the application is as follows:

[0040] The PLA / PBAT blend of the prior art can improve the compatibility and toughness of the blend by introducing ELO and ADR into the PLA / PBAT system, and the tensile strain at break and notched impact strength reach 286% and 52.53 kJ / m 2 , respectively; or introducing ADR and OMMT nanoparticles into the PLA / PBAT system, and the purpose of improving the impact toughness of the blend is achieved with a small amount of ADR, and the impact strength reaches 35.71 kJ / m 2 .

[0041] The PLA / PBAT blend of the present application is modified by introducing ADR and ENR into the PLA / PBAT system, and the synergistic modification of ADR reactive crosslinking and ENR physical toughening improves the elongation at break of the blend while maintaining excellent strength, and the notched impact strength reaches 50 kJ / m 2 . The elongation at break is more than 450%.

[0042] The PLA / PBAT blend of the present application is modified by introducing ADR and ENR into the PLA / PBAT system, and the synergistic modification of ADR reactive crosslinking and ENR physical toughening improves the elongation at break of the blend while maintaining excellent strength, and the notched impact strength reaches 50 kJ / m 5 . Specifically, the degree of epoxidation of the ENR used in the present application is 70-80%; the number average molecular weight of the PLA is (2-3) x 10 4 g / mol; the number average molecular weight of the PBAT is (2-3) x 10 2 g / mol; and the weight average molecular weight of the ADR is 7000-8000 g / mol, and the epoxy equivalent weight of the ADR is 300-400 g / mol.

[0043] Specifically, the raw materials are subjected to melt blending in a torque rheometer, the temperature during melt blending is 180-200 DEG C, the rotation speed during melt blending is 50-100 rpm, and the time for melt blending is 8-15 min.

[0044] More preferably, the mass ratio of the PLA, PBAT, ENR and ADR is (80-85):(15-20):(4-10):(5-6), and the notched impact strength of the blend under this ratio can reach 60 kJ / m 2 .

[0045] The PLA / PBAT / ENR / ADR polymer material provided by the application is prepared by the method comprising melt blending the above-mentioned blend and then performing mold pressing forming, and then performing annealing treatment at 120-160 ℃ for 30-50 min after forming, and then placing the blend in ice water at 0-5 ℃ for 5-10 min after the annealing treatment.

[0046] More preferably, the PLA, PBAT, ENR and ADR are melt blended in a mass ratio of (80-85):(15-20):(2-4):(5-7), and then performing mold pressing forming, and then performing annealing treatment after forming. The notched impact strength of the blend under this ratio can reach 80 kJ / m 2 above.

[0047] More preferably, the PLA, PBAT, ENR and ADR are melt blended in a mass ratio of (80-85):(15-20):(2-3):(5-6), and then performing mold pressing forming, and then performing annealing treatment after forming. The notched impact strength of the blend under this ratio can reach 100 kJ / m 2 above.

[0048] It can be understood that the mold pressing forming comprises a preheating stage, a hot pressing stage and a cooling stage. In the preheating stage, only the material is heated without applying pressure; in the hot pressing stage, the mold pressing pressure is 10-15 MPa and the temperature is 190-200 ℃; and in the cooling stage, cooling is performed under the mold pressing pressure, and the cold pressing time is 5-10 min.

[0049] Specifically, the annealing treatment is performed in a blast drying oven.

[0050] The embodiments of the application are further described below in combination with specific examples. The chemical reagents involved in the following examples are commercially available conventional goods, and no special instructions are given. Among them, polylactic acid (PLA, M n = 2.3 x 10 5 g / mol, M w / M n = 1.5) is purchased from Total Corbion Company (Paris, France); polybutylene adipate terephthalate (PBAT, M n = 2.0 x 10 4 g / mol, M w / M n = 1.1) and an epoxy chain extender ADR (Joncryl ADR-4468, M w= 7250 g / mol, epoxy equivalent weight 310 g / mol) purchased from BASF (Ludwigshafen, Germany); Epoxidized natural rubber ENR (epoxidation degree 70%) purchased from Shuangyao Biotech Co., Ltd. (Yunnan, China); Dichloromethane (DCM) purchased from Wenlong Chemical Reagent Co., Ltd. (Guangdong, China).

[0051] I. Specific embodiments of the PLA / PBAT blend and PLA / PBAT / ENR / ADR polymer material synergistically toughened by ADR and ENR of the present application

[0052] The PLA / PBAT blend synergistically toughened by ADR and ENR of the present application is prepared by the following preparation method:

[0053] The PLA and PBAT were dried in an oven at 60℃ for 12 h, and then physically premixed according to the formulation in Table 1, and then the premixed material was added into the cavity of a torque rheometer at one time, and then melt blended in the torque rheometer at 190℃ at a rotation speed of 80 rpm for 14 min to obtain a blend.

[0054] The PLA / PBAT / ENR / ADR polymer material of the present application is prepared by the following preparation method:

[0055] The granules formed by crushing the above blend were placed in a specific mold, and a flat vulcanizing machine was used for molding, specifically: preheating and softening at 190℃ for 5 min, then hot pressing, the mold pressing pressure during hot pressing was 10 MPa, the temperature was 190℃, the hot pressing time was 5 min, then cold pressing, the cold pressing time was 5 min. The molded sample was placed in a blast drying oven preheated to 120℃, the annealing time was 30 min, and then the sample was quickly placed in 0℃ ice water for 5 min.

[0056] The raw material formulations of different blends are shown in Table 1. Among them, PLA / PBAT / ENR / ADR (80:20:2:X) is abbreviated as LB / E2 / AX, AX represents different amounts of ADR; PLA / PBAT / ADR / ENR (80:20:5:X) is abbreviated as LB / A5 / EX, EX represents different amounts of ENR. Phr represents the mass fraction of additives in 100 parts of the sample.

[0057] Table 1 Raw material formulations of different blends

[0058]

[0059]

[0060] The blends of different raw material formulations in Table 1 obtained according to the above preparation method are the PLA / PBAT blends synergistically toughened by ADR and ENR provided by the present application. The polymer material obtained according to the above preparation method is the PLA / PBAT / ENR / ADR polymer material provided by the present application.

[0061] II. Experimental Examples

[0062] 1) Test objects

[0063] In this experimental example, the blends of different formulations shown in Table 2 and the PLA / PBAT / ENR / ADR polymer materials made therefrom are tested for performance. Among them, PLA / PBAT (80:20) is abbreviated as LB; PLA / PBAT / ENR (80:20:2) is abbreviated as LB / E2; and PLA / PBAT / ADR (80:20:5) is abbreviated as LB / A5.

[0064] Table 2: Blends of different formulations

[0065]

[0066]

[0067] 2) Test methods

[0068] The contact angle was measured using a JC2000D1 contact angle meter (China, Shanghai Zhongchen Digital Technology Equipment Co., Ltd.) to measure the water contact angle (WCA) and oil contact angle (OCA) of PLA, PBAT and ENR. The measurement was carried out at room temperature, using 5 μL of wetting reagent. The average result of five measurements for each sample was reported.

[0069] Fourier transform infrared (FT-IR) was measured using a NICOLET-is 10 Fourier transform infrared spectrometer (USA, Thermo) with a scanning range of 4000-500 cm -1 , a resolution of 4 cm -1 , and a scanning number of 32.

[0070] X-ray photoelectron spectroscopy (XPS) was measured using a Scientific K-Alpha X-ray photoelectron spectrometer (USA, Thermo) under the conditions of 12 KV and 6 mA, with a wide energy range of 0 to 1350 eV.

[0071] The notched impact test was carried out using a S8225X cantilever beam impact tester (China, Shanghai Sichuan Test Equipment Co., Ltd.) according to the "GB / T1843-2008 standard for impact test of impact samples with 2 mm V-shaped notches, size 80 mm x 10 mm x 4 mm", and the average result of five measurements for each sample was reported.

[0072] Tensile test was performed on UTM2000 (SMTS, Shenzhen, China) with a tensile rate of 15 mm / min according to GB / T 1040.2-2006 on tensile samples with dimensions of 75 mm x 4 mm x 2 mm.

[0073] X-ray diffraction (XRD) was performed on D8 Advance (Bruker, USA) with Cu-Ka as radiation source, scanning range of 5-30°, step of 0.05°, scanning voltage and scanning current of 40 kV and 40 mV, respectively, on a disc with diameter of 20 mm and height of 2 mm.

[0074] Heat deflection temperature (HDT) was performed on HDT / V-12 (Chengde Jinjian Instrument and Equipment Co., Ltd., China) with silicone oil as heat conducting medium, heating rate of 120 °C / h, standard deflection of 0.34 mm, sample size of 80 mm x 10 mm x 4 mm according to GB / T 1633.

[0075] Thermogravimetric analysis (TG) was performed on TG209 (NETZSCH, Germany) under N2 atmosphere with a heating rate of 10 °C / min from room temperature to 600 °C on 5 mg sample.

[0076] Differential scanning calorimetry (DSC) was performed on Q100 (TA, USA) under N2 atmosphere with a heating rate of 10 °C / min from room temperature to 210 °C on 7-10 mg sample for 5 min to remove thermal history. Then the sample was cooled to room temperature with a rate of 10 °C / min for 5 min and cycled twice.

[0077] The crystallinity Xcof PLA in the sample was corrected by the following equation:

[0078]

[0079] ΔH m and ΔH cc represent the melting enthalpy and cold crystallization enthalpy, respectively, W f represents the mass ratio of PLA in the blend, ΔH m represents the standard melting enthalpy of PLA when fully crystallized (93.6 J / g).

[0080] Rheology was performed on HAAKE Mars III (Thermo, USA) with a scanning frequency range of 0.01-100 Hz and an amplitude of 5% at 190 °C on a disc with diameter of 20 mm and height of 2 mm.

[0081] SEM was performed using a Regulus 8100 type (HITACHI, Japan) scanning electron microscope, gold sputtering 210s for impact fracture of the sample and dichloromethane (DCM) etching liquid nitrogen freezing fracture test.

[0082] 3) Test results

[0083] (1) Interfacial interaction

[0084] Evaluating the interfacial interaction of the polymer helps to evaluate the compatibility of the dispersed phase and the continuous phase, the phase morphology distribution and the stress transfer efficiency. These interactions can be evaluated by measuring the interfacial tension using the CA measurement method. The Owens-Wendt method can be used to calculate the surface energy (γ), the polar component (γ p ) and the dispersive component (γ d ).

[0085] γ = γ p + γ d (2)

[0086]

[0087] Where γ, γ p and γ d represent the surface energy, the polar component and the dispersive component, θ represents the contact angle of the liquid with the polymer, s and l represent the solid and liquid respectively. The contact angle is measured using ion-free water (H2O) and diiodomethane (CH2I2) with greater polarity, The contact angle and surface tension of PLA, PBAT and ENR are shown in Table 3.

[0088] Table 3 Contact angle and surface tension of PLA, PBAT and ENR

[0089]

[0090] The interfacial tension and the adhesion work are determined using equations (4), (5), and the thermodynamic stable morphology of the ternary blend can be predicted based on the diffusion coefficient theory. In an incompatible ternary blend composed of three components (a is the matrix), the diffusion coefficient is determined using equation (6).

[0091]

[0092] λ cb = γ ba - γ ca - γ bc (6)

[0093] The interfacial tension and the adhesion work are determined using equations (4), (5), and the thermodynamic stable morphology of the ternary blend can be predicted based on the diffusion coefficient theory. In an incompatible ternary blend composed of three components (a is the matrix), the diffusion coefficient is determined using equation (6). ab and W ab and λ ijdenoted as the diffusion coefficient of polymer i and polymer j, γ ij is the interfacial tension between polymer i and polymer j. Wherein, polymer a is PLA matrix, and polymers b and c represent PBAT and ENR respectively. The interfacial tension, diffusion coefficient and adhesion work are shown in Table 4.

[0094] Table 4 Interfacial tension, diffusion coefficient and adhesion work

[0095]

[0096] If λ cb is positive, it indicates that polymer b can be wrapped by polymer c, and for the diffusion coefficient of three-component blends, one positive value and two negative values indicate that one copolymer tends to be located at the interface of the other two polymers. The data in Table 4 show that in the PLA / PBAT / ENR ternary blend, the interfacial tension of PBAT / ENR is much lower than that of PLA / ENR, indicating that the interaction between ENR and PBAT is stronger than that between PLA. When the ternary blend is blended at the same time, PBAT has a higher affinity for ENR and tends to form an interfacial layer by wrapping ENR in PBAT. The adhesion work also supports this observation, as the adhesion work of PLA / ENR is lower than that of PLA / PBAT and PBAT / ENR.

[0097] Based on the analysis of interfacial interaction, PBAT tends to wrap ENR particles. However, high epoxidation (70%) of ENR makes it difficult to react in situ with PBAT, which leads to the formation of physical hydrogen bonding between its epoxy groups and the terminal hydroxyl groups of PBAT. The hydrogen bonding between PBAT and ENR is formed between the epoxy groups of ENR and the terminal hydroxyl groups of PBAT, as well as the dipole-dipole interaction between the C=O of PBAT and the -OH (produced by ring opening of epoxy groups) of ENR, and the enhancement of these interactions significantly improves the intermolecular forces and interfacial adhesion between PBAT and ENR.

[0098] (2) Infrared spectroscopy

[0099] Figure 1 are the infrared spectra of blends of different formulations. Wherein Figure 1 (a) shows the effect of different ADR contents on the FTIR of LB / E2 blend, the left side is the full spectrum and the right side is the enlarged view of the shaded part of the full spectrum, there is no significant difference in the spectral characteristics of PLA and LB, indicating that they only undergo physical blending without chemical reaction when there is no chain extender. The introduction of ENR leads to a significant enhancement of the absorption peaks at 2943 cm -1 (methylene stretching vibration) and 728 cm -1 (in-plane bending vibration of continuous methylene). The absorption peak at 1744 cm -1carboxyl C=0 stretching vibration of PLA, while 1710 cm -1 stretching vibration of PBAT ester group, PBAT tends to wrap ENR to form agglomerates, and a large number of PBAT agglomerates cause the enhancement of the stretching vibration peak of the ester group, reflecting the weak interaction between the epoxy group of ENR and the end group of PLA, which is consistent with the diffusion coefficient results. With the addition of ADR, the LB / E2 / AX blend 2943 cm -1 and 728 cm -1 The peak intensity gradually weakens and the peak shape narrows, which is due to the fact that ADR promotes the entanglement of PLA, PBAT and ENR molecular chains through chain extension and crosslinking, making the arrangement of -CH2- groups change from disordered physical dispersion to ordered chemical crosslinking, and the vibration environment tends to be consistent, which indirectly proves that the interfacial compatibility is improved.

[0100] Figure 1 (b) presents the spectral influence of different ENR contents on the LB / A5 blend when the fixed ADR is 5 phr. The LB / A5 blend 1710 cm -1 The peak intensity is significantly enhanced, which is due to the ring-opening esterification reaction between the epoxy group of ADR and the end carboxyl group of PLA and PBAT to generate new ester bonds. With the increase of ENR content, the LB / A5 / EX blend 2943 cm -1The methylene stretching vibration peak was significantly broadened and enhanced, indicating that the unreacted ENR existed in the form of physical blending. Because the epoxy groups of ADR preferentially react with the LB end groups, the epoxy groups of the excess ENR cannot participate in the reaction due to steric hindrance and limited reaction sites, and the disordered packing of the methylene groups leads to a variety of vibration environments. It is worth noting that the conclusions of Nghia et al. (Quantitative analysis for reaction between epoxidized natural rubber and poly(L-lactide) through 1H-NMR spectroscopy[J]. Journal of Applied Polymer Science, 2010, 115(6): 3598-3604.) and Tanrattanakul et al. (Rubber toughening of nylon 6 with epoxidized natural rubber[J]. Polymer Testing, 2008, 27(7): 794-800) that "the epoxy groups of ENR directly react with the carboxyl end groups of PLA" have not been observed in this system. On the contrary, the epoxy groups of high-epoxidized ENR70 are densely distributed in the rubber main chain, which is prone to form intramolecular / intermolecular hydrogen bonds and steric hindrance, hindering in-situ chemical reaction with the LB end groups. SEM characterization simultaneously showed that larger ENR agglomerates appeared at the interface when the ENR content was high, further supporting the toughening mechanism of physical blending dominated by ENR rather than chemical crosslinking.

[0101] (3) XPS

[0102] The surface elemental composition of LB / E2 / A9, LB / E2, LB, LB / A5 and LB / A5 / E10 blends was quantitatively characterized by XPS, Figure 2 The XPS spectra of different formulations of blends are shown in Figure 6, where Figure 2 (a) is the XPS total spectrum, Figure 2 (b) is the C1s spectrum, Figure 2 (c) is the O1s spectrum. The C, O element content ratios obtained from the XPS spectra are shown in Table 5.

[0103] Table 5 C, O element content ratios

[0104]

[0105]

[0106] From Figure 2As can be seen from (a) and Table 5, all samples are mainly composed of C and O, and the changes in their content (Table 5) are closely related to the reactivity and interfacial behavior of ADR and ENR. The increase in the amount of ADR added leads to an increase in carbon content, indicating that the epoxy group of ADR and the terminal carboxyl / hydroxyl group of LB undergo a chain extension reaction to form a longer ester bond-connected chain segment. The reaction consumes polar oxygen-containing groups (such as carboxyl-COOH), and through cross-linking reactions, the molecular chain is extended and the free polar groups are reduced, prompting the LB segment to form a network structure through ester exchange reaction, significantly improving the carbon skeleton density, which is consistent with the 1710 cm-1 peak in the infrared spectrum. -1 The appearance of the ester peak and the narrowing of the methylene vibration peak confirm the "disorder-to-order" trend. The introduction of excess ENR leads to an increase in the O content, as the hydroxyl (-OH) or ether (-COC-) bonds generated after ring opening increase the proportion of surface polar oxygen-containing groups. Furthermore, self-crosslinking or intramolecular hydrogen bonding of ENR hinders in-situ reaction with the blend, corroborating the agglomeration observed by SEM.

[0107] C1s spectrum of the blend ( Figure 2 b) shows that the addition of excess ENR causes ENR ring opening and self-crosslinking, resulting in the appearance of a characteristic COC peak at 287.9 ​​eV. The CC bond ratio in LB / E2 / A9 is significantly higher than that in other samples, reflecting the high degree of ordering of the alkyl segments at high ADR content. This is consistent with the narrowing effect of the -CH2- vibration peak in the infrared spectrum, demonstrating that molecular chain entanglement is enhanced by efficient crosslinking.

[0108] O1s spectrum of the blend ( Figure 2 In c), LB and LB / A5 showed a significant C=O advantage, corresponding to the enrichment of PLA / PBAT main chain ester groups and unreacted carboxyl groups. In contrast, the C=O ratio of LB / E2 and LB / A5 / E10 decreased and CO increased. This change indicates that the introduction of E2 and E10 promoted the formation of COC or -OH, thereby changing the chemical environment of the blend, which is complementary to the appearance of the COC peak in the carbon spectrum. Through the coordinated characterization of infrared spectroscopy and XPS, the ADR-dominated LB / E2 / AX system showed clear chemical cross-linking characteristics, while the ENR-dominated LB / A2 / EX system mainly showed a physical blending state. The chemical cross-linking network of ADR and the physical agglomeration of ENR in the two systems led to significant differentiation in mechanical properties.

[0109] (4) Mechanical properties

[0110] The mechanical properties test results of polymer materials made of blends with different formulations before and after annealing are as follows: Figure 3 As shown, Figure 3 (a) is the LB / E2 / AX notched impact strength, Figure 3(b) is the tensile strength and elongation at break of LB / E2 / AX, Figure 3 (c) is the LB / E2 / AX notched impact strength, Figure 3 (d) is the tensile strength and elongation at break of LB / A5 / EX. Figure 4 As shown, Figure 4 (a) is the torque of LB / E2 / AX blend, Figure 4 (b) is the torque of LB / A5 / EX blend, Figure 4 (c) is the stress-strain curve of LB / E2 / AX blend, Figure 4 (d) Stress-strain curve of LB / AS / EX blend.

[0111] Figure 3 In (a), the notched impact strength of LB / E2 without ADR is only 6.3 kJ / m 2 , although purer PLA (2.3kJ / m 2 ) was improved, but the toughening effect was limited, reflecting the weak interfacial interaction between ENR and PLA / PBAT matrix. As the ADR content increased, the notched impact strength of LB / E2 / AX blends showed a nonlinear trend of first rising to a peak and then decreasing, with a maximum value of 59.4 kJ / m at 5 phr ADR. 2 The annealing process further promotes the orderly arrangement of the molecular chains, making the network structure more regular and stable, and the notched impact strength is further improved to 100.6kJ / m 2 , compared with pure PLA, it achieved a breakthrough increase of 2583% and 4374%. When the ADR content exceeds 5phr, the notched impact strength begins to decline. This is mainly attributed to the fact that when the ADR content exceeds the optimal cross-linking ratio (5phr), the end group depletion causes insufficient reaction sites, the steric hindrance caused by molecular chain crowding, and the decrease in interfacial reaction efficiency caused by the deterioration of dispersion, resulting in a decrease in the degree of cross-linking. This is consistent with the Figure 4 (a) The torque values ​​corresponding to the blends.

[0112] The elongation at break of the ADR-dominated blend is as follows: Figure 3 As shown in (b), the LB / E2 system achieves an elongation at break of 299.7% due to the high elasticity of ENR. The system is mainly composed of linear LB molecules and lacks effective cross-linking nodes. The stress-strain curve shows weak strain hardening ( Figure 4 After the addition of ADR, the hardness increased to 512.5% ​​and remained stable. The cross-linked network structure formed by the addition of ADR provided sufficient cross-linking nodes, resulting in obvious strain hardening.

[0113] Figure 3(c) In the LB / A5 / EX system dominated by ENR, the notched impact strength shows a steady upward trend, reaching a maximum of 82.4 kJ / m 2 , only slightly decreased when the ENR content was 10phr. This behavior is consistent with Colyer [ According to the theory of , during the fracture process, cracks propagate along the interface between the PLA matrix and the rubber particles. The rubber phase can absorb and dissipate crack energy, thereby preventing brittle fracture of the blend. As the rubber content increases, the formation of more energy dissipation sites further improves the notched impact strength. After annealing, the notched impact strength shows an asymmetric trend of first increasing and then decreasing. The core cause is the Ostwald ripening behavior of the ENR particles and the critical size pointed out by Wu et al. The annealing process provides energy for molecular chain movement, prompting Ostwald ripening of the ENR particles. Small particles dissolve and reattach to the surface of large particles, exceeding the optimal size of the elastomer particles. When the optimal size is below the critical value, the material exhibits toughness, while above the critical value, it exhibits brittleness. The stress concentration effect is enhanced, but the energy dissipation efficiency is reduced, resulting in a decrease in notched impact strength.

[0114] The tensile strength after annealing showed a significant decrease, such as Figure 3 (d) This may be due to the agglomeration of large ENR particles formed after annealing, which leads to the deterioration of the interfacial interaction.

[0115] The low temperature impact test results after freezing at 0℃ for 48h are as follows Figure 5 As shown, Figure 5 (a) is the low temperature impact test results of LB / E2 at different ADR contents, Figure 5 (b) Low-temperature impact test results of LB / A5 at different ENR contents. The notched impact strength of the LB / A5 / E6 blend exhibits minimal attenuation, significantly lower than that of other systems, demonstrating excellent low-temperature toughness. ENR's Tg of approximately -40°C is well below the test temperature (0°C), allowing it to maintain rubbery chain mobility at low temperatures. The addition of ADR failed to significantly improve the low-temperature toughness of the blend, stemming from the low-temperature rigidity of the cross-linked network it constructs.

[0116] 5) XRD

[0117] The effects of ADR and ENR on the crystallization properties of PLA were studied by XRD. The XRD patterns of the polymer materials made of the blend after annealing were as follows: Figure 6 As shown. Among them, Figure 6 (a) is the XRD pattern of LB / E2 / AX, Figure 6 (b) XRD pattern of LB / A5 / EX.

[0118] Figure 6(a) showed that pure PLA exhibited typical characteristic peaks of the stable alpha crystal form, (110) / (200) peak (2Q = 17.0°), (010) peak (2Q = 15.2°) and (210) peak (2Q = 22.6°), corresponding to a highly ordered orthorhombic crystal structure. The introduction of ENR in LB / E2 blends resulted in a significant attenuation of the (010) peak intensity, while the (110) / (200) peak decreased, indicating a decrease in the perfection of the alpha crystal form to form (a + a') crystal form, which is closely related to the steric hindrance effect of ENR rubber segments. High content of ENR segments hindered the ordered packing of PLA molecular chains, reducing the crystallinity from 54.4% of pure PLA to 40.5% of LB / E2 (Table 7). The (010) and (210) peaks completely disappeared in LB / E2 / AX blends as the ADR content increased, and the (110) / (200) peak shifted to low angles and significantly weakened, revealing the transformation of the alpha crystal form to the metastable alpha' crystal form. This phenomenon is attributed to the restriction of the crosslinked network constructed by ADR on the motion of PLA segments. Compared with the diffraction peaks of the alpha crystal form, the diffraction peaks of the alpha' crystal form are wider and fewer, forming a metastable alpha' crystal form, which exhibits lower heat resistance and higher elongation at break.

[0119] The heat distortion temperature was used to evaluate the heat resistance of the material, and the heat distortion temperatures of the blends before and after annealing were as shown in Figure 7 Figure 7 (a) is the heat distortion temperature of LB / E2 / AX before and after annealing, Figure 7 (b) is the heat distortion temperature of LB / A5 / EX before and after annealing. It can be seen from Figure 7 that the heat resistance after annealing is greatly reduced with the formation of alpha' crystal form.

[0120] The XRD pattern of the LB / A5 system Figure 6 (b) showed that there was only a very weak (110) / (200) peak without ENR, reflecting the strong inhibition of excessive crosslinking caused by excess ADR on crystallization. After the introduction of ENR, the (110) / (200) peak gradually increased in intensity and shifted to high angles, and the (203) peak appeared and gradually increased. It may be because ENR reduces the density of ADR crosslinking nodes, releasing the motion space of PLA segments, and promoting the formation of alpha' crystal form.

[0121] 6) Thermal properties

[0122] The effect of ENR and ADR on the thermal stability of the blend was studied by TG, and the thermal performance test results of the blend were as shown in Figure 8 Figure 8 (a) is the TG curve, Figure 8 (b) is the DTG curve, Figure 8 (c) is the first heating DSC scan curve after annealing, Figure 8 ​​(d) is the second heating DSC scan after annealing. The characteristic parameters of the TG analysis of the blends are shown in Table 6. 5％ T5% refers to the temperature at which 5% of the sample mass is lost. max Tmax refers to the temperature at which the maximum mass loss rate occurs.

[0123] Table 6. Characteristic parameters of the TG analysis of the blends

[0124]

[0125]

[0126] Figure 8 (a) and Figure 8 (b) and Table 6 reveal the complex evolution of the degradation behavior. The original LB blend presents a typical two-step degradation process, the first step corresponding to the degradation of PLA (T max PLA = 347.3 °C) and the second step attributed to the degradation of PBAT (T max PBAT = 380.7 °C). The two-component degradation peaks are completely separated, proving that LB is a thermodynamically incompatible system. PBAT is more thermally stable than PLA due to the higher thermal resistance of the aromatic ring in the molecular structure of PBAT.

[0127] The introduction of ENR in the LB / E2 blend causes the disappearance of the independent degradation peak of PBAT, replaced by a degradation peak at 405.2 °C T max ENR . This is not much different from the T max ENR = 400 °C of pure ENR, indicating that ENR forms a physical wrapping interface layer with PBAT, forming a core-shell structure, coupling the degradation behavior of the two, but without chemical crosslinking, which is consistent with the results of the diffusion coefficient. The addition of ADR makes the degradation behavior of the blend present new characteristics, the T max PLA of PLA increases significantly from 347.3 °C to 388 °C, the PBAT / ENR-related degradation peaks merge into a single peak at 423 °C, and the maximum thermal degradation steps are close to each other. Reflecting the chemical reaction of ADR with the blend through the epoxy group, a chemical crosslinking network is constructed. Increasing the degree of chain entanglement, which requires higher energy in the decomposition process, and improving the thermal stability of the copolymer. Promote the compatibility of ENR and PBAT, eliminate the phase separation interface, form a synergistic degradation behavior.

[0128] The effect of ENR and ADR on the crystallization and thermal transition of the blend was analyzed by DSC, and the DSC curve of the blend before annealing is shown in Figure 9 Figure 9 ​(a) is the first heating DSC heating scan before annealing, Figure 9 (b) is the second heating DSC heating scan before annealing. The first heating curve of the blends after annealing is shown in Fig. Figure 8 (c). The characteristic parameters of the first heating DSC of the blends are listed in Table 7, T g represents the glass transition temperature, T cc represents the cold crystallization temperature, ΔH cc represents the cold crystallization enthalpy, T m represents the melting temperature, ΔH m represents the melting enthalpy, X C represents the crystallinity. The cold crystallization peak of all blends after annealing disappears, the addition of ENR and ADR makes a small exothermic peak before melting compared with polylactic acid, and T m shifts to low temperature, which corresponds to the solid-state recrystallization process of metastable a' crystal form to stable a crystal form, which is consistent with the results of XRD, indicating that the initial crystals formed during the annealing process are mainly in the form of a' crystal with low order degree. Although the annealing temperature of 120°C is conducive to the growth of stable a crystal form, due to the nucleation effect of ENR on PLA, the cold crystallization temperature shifts to low temperature, and the flexible rubber segment of ENR hinders the ordered packing of PLA molecular chains through steric hindrance effect, finally drives the blend to form a' crystal form.

[0129] Table 7 Characteristic parameters of the first heating DSC of the blends

[0130]

[0131]

[0132] The first heating scan eliminates the thermal history by isothermal treatment at 200°C, and the second heating curve Figure 8 (d) shows that the introduction of ENR and ADR has little effect on T g (59-61°C), indicating that the activity of the chain segments in the amorphous region of the blend has not been significantly changed. After the addition of ENR (LB / E2), T cc decreases to 94.9°C, and an obvious exothermic peak appears before melting, which is consistent with the results obtained by the first heating. The addition of ADR leads to T ccThe crystallinity of the PLA blend increases inversely, and this effect intensifies with increasing ADR content. This is attributed to the reaction of the epoxy groups of the ADR with the LB end groups to form a cross-linked network, which extends the PLA molecular chain and restricts segmental motion, ultimately leading to a decrease in crystallinity. Notably, the LB / E2 / A9 blend exhibits dual melting peaks during the second heating. The low-temperature peak is associated with the simultaneous melting of the original α phase and the α'-to-α transition, reflecting a melt-recrystallization process rather than a solid-state transformation. The high-temperature peak, however, is associated with the melting of crystals formed during the α'-to-α transition. The crystallinity is only 4.1%, demonstrating that the rigidification and spatial confinement of the molecular chains induced by excess chain extender weaken the ordered arrangement of the segments. Although the cross-linking degree does not reach its maximum, its inhibitory effect on crystallization increases with the ADR content. In summary, ENR promotes low-temperature crystallization and induces the formation of the α' phase through heterogeneous nucleation, while ADR inhibits crystallization by restricting segmental motion.

[0133] 7) Rheological properties

[0134] The dynamic shear rheological test was used to analyze the molecular chain entanglement behavior and cross-linking network construction of the blend. The rheological performance test results are as follows: Figure 10 As shown, Figure 10 (a) is the complex viscosity of LB / E2 / AX, Figure 10 (b) is the LB / E2 / AX storage modulus, Figure 10 (c) is the LB / E2 / AX loss modulus, Figure 10 (d) is the complex viscosity of LB / A5 / EX, Figure 10 (e) is the storage modulus of LB / A5 / EX, Figure 10 (f) is the loss modulus of LB / A5 / EX. The low-frequency slopes and power-law exponents of the storage modulus (G′) and storage modulus (G″) are shown in Table 8.

[0135] Table 8 Slopes and power law exponents of G′ and G″ in the low frequency region

[0136]

[0137] Figure 10 (a) It can be seen that PLA, LB, and LB / E2 exhibit rheological characteristics relatively close to Newtonian fluids in the low-frequency region, reflecting the free motion state of linear molecular chains. The introduction of ENR into LB / E2 blends significantly reduces the complex viscosity (η), which is attributed to the lower T of the ENR rubber segment. gThis enhanced the mobility of PLA's amorphous chain segments and reduced melt viscosity. LB / E2 / AX blends containing ADR exhibited significant shear-thinning behavior, indicating that ADR formed a chemically crosslinked network through esterification of epoxy groups with the LB / E2 end groups. The substantial increase in η in the low-frequency region is consistent with the solid-like elastic response of the crosslinked network, while the shear-thinning in the high-frequency region stems from reversible untangling at high shear rates. The η of the LB / E2 / A5 blend was two orders of magnitude higher than that of LB / E2, with this behavior being particularly pronounced at low frequencies and weakening with increasing frequency due to shear-thinning.

[0138] Figure 10 As can be seen from (b) and (c), the storage modulus (G′) and storage modulus (G″) of the LB / E2 blend are lower than those of PLA, reflecting a decrease in matrix stiffness due to physical blending of the elastomers. The introduction of ADR leads to an order of magnitude increase in the modulus. With the addition of ADR, the modulus first increases and then decreases across the entire frequency range, which is related to the formation of molecular entanglement and the construction of a cross-linked network, demonstrating that there is an optimal ratio for ADR addition. The slope of G′ in the low-frequency region can also be used to investigate the effects of the interaction between ENR and ADR and PLA. The slope of the uncompatibilized LB / E2 is close to that of PLA, indicating that the weak interfacial interaction between ENR and PLA does not alter the chain motion mode. The slope of the ADR-modified system first decreases and then increases with increasing ADR content, with the minimum value occurring in the LB / E2 / A5 blend. This phenomenon can be explained by the cross-linked network constructed by ADR and the enhanced interfacial interaction between PLA and ENR. The enhanced cross-linked network increases the elastic response of the blend, exhibiting a higher G′ at low frequencies.

[0139] ENR-dominated blends such as Figure 10 As shown in (d)-(f), η, G′, and G″ all remain stable as ENR increases from 2 to 10 phr, in contrast to the changes in the ADR system. This demonstrates that ENR does not participate in chemical crosslinking and exists primarily as physically dispersed elastomer particles.

[0140] Dynamic mechanical analysis reveals the relaxation behavior and network structure evolution of the blends, and Tanδ and Cole-Cole curves provide characterization of the molecular chain entanglement state and interface interaction. Figure 11 As shown. Figure 11 (a) is the Tanδ curve of LB / E2 / AX, Figure 11 (b) is the Cole-Cole curve of LB / E2 / AX, Figure 11 (c) is the Tanδ curve of LB / A5 / EX, Figure 11 (d) is the Cole-Cole curve of LB / A5 / EX.

[0141] Figure 11 (a) PLA, LB, and LB / E2 blends exhibit steep slopes at the end of the Tanδ curve, reflecting their fluid characteristics dominated by viscous response. This behavior stems from the free movement of linear molecular chains and the lack of elastic constraints of an effective cross-linked network, which leads to irreversible deformation under external force. The introduction of ADR significantly changes this trend. The slope of the low-frequency region of the ADR-containing blend decreases significantly and the full-frequency region shows a stable trend, indicating that the elastic response is enhanced with the formation of the cross-linked network. It is worth noting that the LB / E2 / A1 and LB / E2 / A9 blends show an upward-warping phenomenon at the end. This is because the low degree of cross-linking causes a wide distribution of relaxation times, which makes disentanglement more likely to occur at low frequencies.

[0142] Figure 11 The Cole–Cole curve (b) is often used to illustrate the viscoelastic properties and structural differences of heterogeneous polymer systems with relaxation time distributions at a given temperature. PLA exhibits a standard semicircle, corresponding to the relaxation behavior of a single molecular segment. LB blends exhibit a double semicircle characteristic, demonstrating independent relaxation of the two phases due to poor compatibility. With the introduction of ADR, the double semicircle gradually disappears and evolves into a tailing curve, showing a trend of first increasing and then decreasing, with the LB / E2 / A5 blend having the longest tail. The higher the degree of upward curvature at the end of the blend curve, the more cross-linked networks there are in the blend system, which are difficult to disentangle during shear, demonstrating that the degree of tailing is positively correlated with the perfection of the cross-linked network.

[0143] Figure 11 For the ENR-dominant blends in (c) and (d), increasing ENR from 2 to 10 phr does not significantly alter the Tanδ curves. This demonstrates that the physical dispersion of ENR does not significantly alter the viscosity-elasticity balance of the matrix and does not participate in chemical crosslinking. However, the tailing in the Cole–Cole curves increases somewhat. This is because when ENR is embedded in the crosslinked network as moderately dispersed aggregates, these aggregates act as stress concentration points and obstacles to chain motion, inducing relaxation in a dynamic shear field. The degree of tailing increases with increasing adhesion between the ENR aggregates and the crosslinked network, consistent with the SEM results.

[0144] 8) SEM

[0145] The correlation between the mechanical properties and microstructure of the polymer materials made of the blend was characterized by impact cross-section SEM. The impact cross-section SEM morphology is shown in Figure 2. Figure 12 As shown, Figure 12 (a) is LB, Figure 12 (b) is LB / A5, Figure 12 (c) is LB / E2, Figure 12 (d) is LB / E2 / A1, Figure 12 (e) is LB / E2 / A5, Figure 12(f) is LB / E2 / A9, Figure 12 (g) is LB / A5 / E2, Figure 12 (h) is LB / A5 / E6, Figure 12 (i) is LB / A5 / E10.

[0146] As Figure 12 (a) shows, the original LB blend presents a typical "sea-island structure", PLA as the continuous phase wraps the PBAT dispersed phase, the interface between the two phases is clear and there are a large number of phase separation areas, reflecting the thermodynamic incompatibility of PLA and PBAT due to the difference in polarity. Figure 12 (b) shows that the introduction of ADR in the LB / A5 blend causes a significant change in the phase morphology, the sea-island structure gradually changes to a co-continuous structure. In the LB / E2 system, Figure 4 c), ENR forms agglomerates due to the difference in polarity with PLA. But PBAT selectively wraps ENR due to its higher diffusion coefficient, forming a PBAT-ENR core-shell structure. This structure makes the stress concentration area around the ENR agglomerates, and the regular particle pull-out holes can be seen on the impact fracture surface.

[0147] The addition of ADR in the LB / E2 / AX blend triggers the evolution of the phase morphology again Figure 12 (d)-(f)), the crosslinking network constructed by ADR increases the torque from 2.4 N·m to 6 N·m Figure 13 ) in the shear field, causing the ENR agglomerates to break up and the particle size to decrease, existing in the PLA matrix in a co-continuous structure. When the ADR content exceeds 5 phr, the ENR particle size does not decrease but increases, due to the decrease in the strength of the sol caused by the decrease in the crosslinking network.

[0148] In the LB / A5 / EX system, the sea-island structure is gradually strengthened Figure 13 (g)-(i)) with the increase of ENR content, but the impact strength continues to rise. This is due to the chain extension effect of ADR, which makes the wrapping of PBAT on ENR form a "flexible agglomerate reinforced continuous phase". The PBAT wrapped ENR acts as an intermediate phase, which is crosslinked with the PLA matrix under the action of ADR, and the ENR elastomer is transformed from "isolated islands in the PLA matrix" to "effective toughening units in the PBAT continuous phase". This structure makes large-size ENR particles still dissipate energy through the synergistic mechanism of multiple crazing initiation-interface debonding-shear band expansion, and its elastic deformation capacity is efficiently transmitted through the crosslinking network between PBAT and PLA interface, which is consistent with the poor notched impact strength of LB / EX blend without ADR in Figure 13 (a) is the notched impact strength of LB / EX, Figure 14 (a) is the notched impact strength of LB / EX, Figure 14(b) is the notched impact strength of LB / E8, which is only 8.3 kJ / m 2 However, for each blend, there is an optimal particle size in the dispersed phase that can produce the best mechanical properties. When the particle size exceeds the critical value, the internal defects of the particle size (such as cavities, interface debonding) increase, and the crack is easy to quickly expand along the particle boundary, which in turn causes the toughness to decrease.

[0149] The crosslinked network of the blend was visualized by DCM etching technology. The frozen section of the sample was immersed in DCM at room temperature to remove the uncrosslinked PLA phase. The SEM images of the DCM-etched frozen section of the blend are shown in Figure 14 , wherein,

[0150] Figure 14 (a) is LB / E2 / A5, Figure 14 (b) is LB / E2 / A9, Figure 15 (c) is LB / A5 / E6, Figure 15 (d) is LB / A5 / E10.

[0151] Figure 15 The crosslinking degree test results of the blend are shown in Figure 14 (a) is LB / B2 / AX, Figure 15 (b) is LB / A5 / EX.

[0152] As shown in Figure 14 (a), the LB / E2 / A5 blend shows strong etching resistance due to the higher crosslinking degree (52.9%, as shown in Figure 13 ), and only irregular micron-sized cavities are formed on the surface after etching, without clear network structure. This is because the ADR chain extension forms a uniform and dense crosslinked network, and the ENR elastomer is uniformly anchored in the matrix. After the uncrosslinked linear PLA phase is selectively removed, the remaining crosslinked phase still maintains complete continuity, hindering further DCM erosion.

[0153] In contrast, Figure 14 (b) LB / E2 / A9 blend after etching presents a clear network framework structure, with ENR agglomerates exposed at the network nodes. This is consistent with Figure 16 results, and the ENR agglomerates are firmly imprisoned in the effective toughening units in the continuous phase formed by the crosslinked network.

[0154] In the LB / A5 / E6 and LB / A5 / E10 blends, the surface morphology after etching presents differentiated characteristics, as shown in ​(c) and (d) are shown. In LB / A5 / E6, ENR is uniformly dispersed on the surface of the crosslinked network with small agglomerates, which reflects that the ENR particles are effectively wrapped by the moderately crosslinked network, and the surface epoxy groups form hydrogen bonding with PBAT to become flexible nodes in the network. In LB / A5 / E10, ENR agglomerates are unable to be trapped and stress cannot be fully dispersed, resulting in a decrease in mechanical properties, because ENR agglomerates are locally crowded and aggregated in the holes of the crosslinked network. In summary, the improvement of the mechanical properties of the blend is essentially due to the synergistic effect of the rigid skeleton of the crosslinked network and the flexible nodes of ENR elastomer. The crosslinked network converts ENR from a dispersed impurity to a network functional unit through chemical anchoring and physical constraint, so that ENR can dissipate energy through its own deformation when stressed, and also serve as a stress transfer hub to strengthen the matrix and synergistically deform. The possible interface structure is shown in ​ .

[0155] Finally, it should be noted that: the above only for the preferred embodiments of the present application, and not for limiting the present application, although the foregoing embodiments of the present application are described in detail, for those skilled in the art, it still can be modified, or part of the technical features of the equivalent replacement, within the spirit and principles of the present application, any modification, equivalent replacement, improvement, etc., should be included within the scope of the present application.

Claims

1. A PLA / PBAT blend synergistically toughened by ADR and ENR, characterized in that: The preparation method of the ADR and ENR synergistically toughened PLA / PBAT blend comprises the steps of melt-blending PLA, PBAT, ENR and ADR in a mass ratio of (80-85): (15-20): (2-10): (3-9).

2. The PLA / PBAT blend synergistically toughened by ADR and ENR according to claim 1, characterized in that The mass ratio of PLA, PBAT, ENR and ADR is (80-85): (15-20): (2-3): (3-9), or (80-85): (15-20): (2-10): (5-6).

3. The PLA / PBAT blend synergistically toughened by ADR and ENR according to claim 1, characterized in that The mass ratio of PLA, PBAT, ENR and ADR is (80-85): (15-20): (4-10): (5-6).

4. The PLA / PBAT blend synergistically toughened by ADR and ENR according to any one of claims 1 to 3, characterized in that: The epoxidation degree of the ENR is 70-80%; the number average molecular weight of the PLA is (2-3)×10 5 g / mol; the number average molecular weight of the PBAT is (2~3)×10 4 The weight average molecular weight of the ADR is 7000-8000 g / mol, and the epoxy equivalent weight of the ADR is 300-400 g / mol.

5. The PLA / PBAT blend synergistically toughened by ADR and ENR according to claim 1, characterized in that The temperature during the melt blending is 180-200° C., the rotation speed during the melt blending is 50-100 rpm, and the melt blending time is 8-15 minutes.

6. A PLA / PBAT / ENR / ADR polymer material, characterized in that: The method for preparing the PLA / PBAT / ENR / ADR polymer material comprises the step of compression molding the PLA / PBAT blend synergistically toughened by ADR and ENR as described in any one of claims 1 to 5.

7. The PLA / PBAT / ENR / ADR polymer material according to claim 6, wherein: The compression molding process comprises a compression pressure of 10-15 MPa, a hot pressing time of 5-10 min, and a temperature of 190-200° C.

8. The PLA / PBAT / ENR / ADR polymer material according to claim 6 or 7, wherein: Annealing treatment is performed after compression molding.

9. The PLA / PBAT / ENR / ADR polymer material according to claim 8, wherein The annealing temperature is 120-160° C., and the annealing time is 30-50 minutes.

10. The PLA / PBAT / ENR / ADR polymer material according to claim 8, wherein After annealing, cool in ice water at 0-5°C for 5-10 minutes.

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