Bio-based high-strength and high-toughness polylactic acid / polyamide 11 alloy material and preparation method thereof

Abstract

The invention discloses a bio-based high-strength and high-toughness polylactic acid / polyamide 11 alloy material and a preparation method thereof in the field of high polymer materials. The bio-based high-strength and high-toughness polylactic acid / polyamide 11 alloy material comprises the following raw materials in percentage by weight: 60-80% of poly-L-lactic acid, 13-37% of polyamide 11 and 3-7% of a reactive compatilizer. The reactive compatilizer is obtained by reacting amino-terminated polyamide 11 and hydroxyl-terminated poly (dextrolactic acid) with an epoxy chain extender, the size of a polyamide 11 phase can be effectively reduced by adding the reactive compatilizer, polylactic acid is subjected to heterogeneous nucleation on a polyamide 11 crystal, and the spherocrystal size of polylactic acid is remarkably reduced, so that the polylactic acid-poly (dextrolactic acid) composite material is obtained. And the polylactic acid / polyamide 11 alloy material shows excellent ductility and crystallization capability. According to the invention, the spherocrystal size and density of the polylactic acid are regulated and controlled by regulating and controlling the size and phase structure of the polyamide 11, the obtained alloy material overcomes the defect of poor toughness of the polylactic acid, the production process is simple, and the used polylactic acid and polyamide 11 are bio-based materials and meet the requirements of green development.

Description

Technical Field

[0001] The present invention relates to the field of polymer materials, and in particular to a bio-based alloy material and a preparation method thereof. Background Art

[0002] Conventional petroleum-based polymer materials such as polystyrene, polyethylene, and polyethylene terephthalate are derived from non-renewable resources and are difficult to degrade in the natural environment. After being discarded, they cause serious and irreversible environmental problems. Therefore, bio-based materials have received widespread attention and are considered to be the most promising substitutes for petroleum-based polymer materials.

[0003] Polylactic acid (PLA) is a polymer material with both bio-based sources and biodegradable properties. It has excellent biocompatibility, mechanical strength and processing properties, but its poor ductility and crystallization ability limit the use of its products. Therefore, a large number of researchers have focused on toughening and modifying polylactic acid to expand the application range of polylactic acid. Blending with high elastomers is an efficient modification method for polylactic acid, which can greatly improve the ductility and impact resistance of polylactic acid and obtain a polylactic acid / elastomer mixture with excellent toughness and crystallization ability. Among them, polyamide (PA) has the advantages of high compressive strength, excellent toughness, fatigue resistance and high softening temperature, which can complement the advantages of PLA to obtain a polylactic acid / polyamide alloy material with excellent comprehensive performance.

[0004] Using bio-based nylon to replace conventional petroleum-based nylon to modify polylactic acid can obtain a complete bio-based blend, which is more in line with the green renewable concept. Polyamide 11 (PA11) is a high-performance bio-based polymer processed from castor oil (castor oil is extracted from natural castor seeds). Although the performance between polyamide 11 and polylactic acid is complementary, its blend often causes significant phase separation due to poor interfacial effects, and the mechanical properties are not greatly improved, so it is necessary to improve the interfacial compatibility between the polylactic acid matrix and the nylon base particles. It is reported that p-toluenesulfonic acid is used as a catalyst to induce ester-amide exchange reaction in polyamide 11 and polylactic acid blends to reduce interfacial tension. Due to the reduction of interfacial tension, the elongation at break is increased by about 50%. In patent CN102391628A, a third component elastomer is added to polylactic acid and polyamide 11 to improve the compatibility between polymers, thereby obtaining a material with excellent elongation at break and impact strength, but its tensile strength is lower than that of pure polylactic acid. Therefore, it is crucial to develop a modification method for all-biobased polylactic acid / polyamide alloys with high strength and high toughness. Summary of the invention

[0005] The present invention provides a bio-based high-strength and high-toughness polylactic acid / polyamide 11 alloy material and a preparation method thereof, aiming to solve the problem in the prior art that polylactic acid-based alloy materials are difficult to achieve a balance between tensile strength and ductility.

[0006] To this end, the present invention provides a bio-based high-strength and high-toughness polylactic acid / polyamide 11 alloy material, comprising raw materials in weight percentage:

[0007] Poly-L-lactic acid: 60-80%;

[0008] Polyamide 11: 13-37%;

[0009] Reactive compatibilizer: 3-7%;

[0010] The chemical structural formula of the reactive compatibilizer is as follows:

[0011]

[0012] The substance was named: PA11-SG-PDLA;

[0013] Among them, x is 45-55, y is 3-6, z is 0-3, a is 3-6, n is 400-800, and m is 200-350.

[0014] The polyamide 11 selected in the present invention is a bio-based material. Compared with other polymers in the polyamide family, such as PA6, PA66, etc. (melting points are about 220°C and 250°C), the long-chain PA11 (melting point is about 180°C) has a melting point and thermal processing conditions similar to those of polylactic acid, which can avoid thermal decomposition during the modification process of polylactic acid.

[0015] At the same time, the toughness of polylactic acid is also related to its crystal morphology. Pure PLA has poor crystallization ability, and the spherulites formed during the crystallization process are large in diameter and small in number, which leads to the brittleness of PLA. In the present invention, due to the hydrogen bond interaction in PA11, although the melting point is close to that of polylactic acid, PA11 crystallizes preferentially during the processing, and as a heterogeneous nucleation site, polylactic acid crystallizes on the basis of PA11 spherulites. By regulating the size and phase structure of PA11, the spherulite size and density of polylactic acid can be regulated. PLA forms a large number of spherulites with small diameters during the crystallization process, and the toughness is significantly improved.

[0016] The reactive compatibilizer is a graft copolymer (PA11-SG-PDLA) in which poly(d-lactic acid) (PDLA) and amino-terminated polyamide 11 are grafted on the main chain of epoxy chain extender (SG). Due to the stereocomplex crystallization between PDLA and poly(l-lactic acid) (PLLA) through hydrogen bonding and the presence of PA11, the reactive compatibilizer improves the interfacial compatibility and adhesion between PA11 and PLLA, and the size of PA11 phase in PLA is reduced from 20-50μm to 1-5μm; PA11 crystallizes preferentially and acts as a nucleation site to promote the crystallization of PLA on its crystals; PA11 and stereocomplex crystallization simultaneously induce heterogeneous nucleation of PLA and improve the crystallization ability of PLA, so that the spherulites formed by the PLA matrix during the crystallization process are transformed from large diameter and small number to small diameter and large number. Therefore, the graft copolymer as a reactive compatibilizer can give the composite material higher tensile strength and high toughness.

[0017] The present invention finds that the amount of reactive compatibilizer added has a significant effect on the toughness of the material: as the content of the reactive compatibilizer increases, the compatibility between the two phases of the composite material increases, which ultimately leads to a continuous increase in the elongation at break; at the same time, the increase in the reactive compatibilizer can also increase the tensile strength of the material, which may be attributed to the formation of interfacial SC crystals. However, when the content of the reactive compatibilizer exceeds a certain critical point, the mechanical properties of the material gradually decrease, which may be because the excessive SG in the reactive compatibilizer causes a large number of cross-linking reactions to occur in the system, forming cross-linking points, making the material brittle and reducing toughness.

[0018] Furthermore, the preparation steps of the reactive compatibilizer include:

[0019] 1) Mixing amino-terminated polyamide 11, poly (dextral lactic acid) and epoxy chain extender in a weight ratio of 1:(0.5-2):(1.8-2.2), adding a catalyst, heating and reacting to obtain a graft copolymer (PA11-SG-PDLA);

[0020] 2) The graft copolymer obtained in step 1) is pelletized, crushed and dried to obtain a reactive compatibilizer.

[0021] The present invention prepares a PA11-SG-PDLA graft copolymer by simple melt blending. In step 1), the epoxy group in the epoxy chain extender reacts with the terminal hydroxyl group of poly (dextral lactic acid) and the terminal amine group of polyamide 11 to form a graft copolymer. It should be noted that the epoxy chain extender should be excessive so that the graft copolymer contains residual epoxy groups and its reactivity in subsequent capacity expansion is guaranteed.

[0022] In addition, the present invention finds that the ratio of amino-terminated polyamide 11, poly (d-lactic acid) and epoxy chain extender in the reactive compatibilizer has a significant influence on the performance of the composite material: only at an appropriate ratio can an appropriate amount of stereocomplex crystals be formed, thereby effectively improving the toughness of the composite material. If the stereocomplex content is too high, the brittleness of the material increases due to hydrogen bonding.

[0023] More preferably, the epoxy chain extender is polystyrene-glycidyl methacrylate, and the epoxy equivalent is 0.3-0.4 mol / 100g.

[0024] More preferably, the catalyst is N,N-dimethyloctadecylamine.

[0025] More preferably, the amount of the catalyst used is 0.1-0.5% of the total mass of the reactive compatibilizer raw material, and more preferably 0.1-0.2%.

[0026] Further preferably, the heating reaction temperature is 180-200° C., the stirring rate is 20-100 rpm, and the time is 2-10 min.

[0027] The above-mentioned method for preparing a bio-based high-strength and high-toughness polylactic acid / polyamide 11 alloy material comprises the following steps:

[0028] A) weighing poly (L-lactic acid), polyamide 11 and a reactive compatibilizer by weight percentage;

[0029] B) Poly(L-lactic acid), polyamide 11 and a reactive compatibilizer are uniformly mixed, melt-blended, extruded into granules and dried to obtain a poly(lactic acid) / polyamide 11 alloy material.

[0030] The melt blending can be achieved by a twin-screw extruder. In the twin-screw extruder, 7 zones are arranged in sequence from the feeding port to the discharging port, and the temperatures of each zone from zone 1 are: 175-185°C, 185-195°C, 195-205°C, 205-215°C, 210-220°C, 215-225°C, 220-230°C, the head temperature is 215-225°C, and the screw speed is controlled to 80-100rpm.

[0031] Compared with the prior art, the beneficial effects of the present invention are:

[0032] (1) The present invention uses polylactic acid and bio-based nylon to blend, and the majority of the prepared alloy material is of bio-based origin, which can reduce the use of non-renewable resources, is green, sustainable, and environmentally friendly.

[0033] (2) The present invention prepares a PA11-SG-PDLA graft copolymer by simple melt blending, and adds it as a reactive compatibilizer to the PA11 and PLLA mixed system. Due to the stereocomplex crystallization between PDLA and PLLA in the graft copolymer and the presence of PA11, the compatibilizer improves the interfacial compatibility and adhesion between PA11 and PLLA, and the size of the PA11 phase in PLA is reduced from 20-50μm to 1-5μm; PA11 crystallizes preferentially and acts as a nucleation site to promote the crystallization of PLA on its crystals.

[0034] (3) PA11 and stereocomplex crystallization simultaneously induced heterogeneous nucleation of PLA and improved the crystallization ability of PLA, so that the spherulites formed in the PLA matrix during the crystallization process changed from large diameter and small number to small diameter and large number.

[0035] (4) The addition of the compatibilizer not only improves the toughness of the composite material, but also improves the crystallization ability of the composite material, realizing the complementary advantages of the two materials, obtaining a polylactic acid / bio-based nylon alloy material with superior comprehensive performance, and expanding the application scope of polylactic acid.

[0036] (5) The materials used in the present invention are all industrial raw materials, and the equipment used is mainly melt blending equipment. The process equipment is simple, the production cost is low, and it is suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 POM diagrams of Example 2, Comparative Example 1 and pure PLLA.

[0038] Figure 2 POM diagrams of Example 2, Comparative Example 1 and pure PLLA.

[0039] Figure 3 The stress-strain curves of different embodiments and different comparative examples are shown in FIG. DETAILED DESCRIPTION

[0040] The present invention is further described below in conjunction with the examples. Main raw material information: PLLA (4032D), Natureworks LLC, USA, weight average molecular weight 1.7×10 5 g / mol; PA11, BECV0 P40 TL, Arkema, France, melt index 3.72 g / 10 min (235 ° C, 2.16 kg); PDLA (D070), TOTAL Corbion, Thailand, weight average molecular weight 6.0 × 10 4 g / mol. SG (ADR4370s), BASF, Germany, weight average molecular weight 6.4×10 3The specific composition ratios of the embodiments and comparative examples are shown in Table 1.

[0041] Example 1

[0042] A bio-based high-strength and high-toughness polylactic acid / polyamide 11 alloy material is prepared according to the following steps:

[0043] (1) PA11, PDLA and SG were mixed in a weight ratio of 1:1:2 and added to an internal mixer, and 0.2 wt% N,N-dimethyloctadecylamine was added as a catalyst. The mixture was blended at 180°C and 60 rpm for 6 min to obtain a graft copolymer (PA11-SG-PDLA), which was then pelletized and crushed into powder in a pelletizer and dried in a vacuum oven at 60°C for 24 h to obtain a reactive compatibilizer.

[0044] The chemical structure of the reactive compatibilizer is shown below:

[0045]

[0046] Among them, x is 45-55, y is 3-6, z is 0-3, a is 3-6, n is 400-800, and m is 200-350.

[0047] (2) Add 60wt% PLLA, 37wt% PA11 and 3wt% of the reactive compatibilizer synthesized above into a twin-screw extruder, control the heating temperature of the twin-screw extruder from the feed port to the discharge port to be 180°C, 190°C, 200°C, 210°C, 215°C, 220°C, 225°C in sequence, the head temperature is 220°C, the screw speed is controlled at 80rpm, extrude granulate and dry to obtain a mixed masterbatch.

[0048] (3) The masterbatch obtained in step (2) is added into an injection molding machine, and injection molding is performed at 220° C. and 60 MPa injection pressure, and the pressure is maintained for 3 minutes to obtain a standard specimen for performance testing.

[0049] Example 2

[0050] A bio-based high-strength and high-toughness polylactic acid / polyamide 11 alloy material is prepared according to the following steps:

[0051] (1) PA11, PDLA and SG were mixed in a weight ratio of 1:1:2 and added to an internal mixer, and 0.2 wt% N,N-dimethyloctadecylamine was added as a catalyst. The mixture was blended at 200°C and 60 rpm for 6 min to obtain a graft copolymer (PA11-SG-PDLA), which was then pelletized and crushed into powder in a pelletizer and dried in a vacuum oven at 60°C for 24 h to obtain a reactive compatibilizer.

[0052] (2) Add 70wt% PLLA, 25wt% PA11 and 5wt% of the reactive compatibilizer synthesized above into a twin-screw extruder, control the heating temperature of the twin-screw extruder from the feed port to the discharge port to be 180°C, 190°C, 200°C, 210°C, 215°C, 220°C, 225°C in sequence, the head temperature is 220°C, the screw speed is controlled at 100rpm, extrude granulate and dry to obtain a mixed masterbatch.

[0053] (3) This step is the same as in Example 1.

[0054] Example 3

[0055] A bio-based high-strength and high-toughness polylactic acid / polyamide 11 alloy material is prepared according to the following steps:

[0056] (1) PA11, PDLA and SG were mixed in a weight ratio of 1:1:2 and added to an internal mixer, and 0.2 wt% N,N-dimethyloctadecylamine was added as a catalyst. The mixture was blended at 190°C and 60 rpm for 6 min to obtain a graft copolymer (PA11-SG-PDLA), which was then pelletized and crushed into powder in a pelletizer and dried in a vacuum oven at 60°C for 24 h to obtain a reactive compatibilizer.

[0057] (2) Add 70wt% PLLA, 23wt% PA11 and 7wt% of the reactive compatibilizer synthesized above into a twin-screw extruder, control the heating temperature of the twin-screw extruder from the feed port to the discharge port to be 180°C, 190°C, 200°C, 210°C, 215°C, 220°C, 225°C in sequence, the head temperature is 220°C, the screw speed is controlled at 70rpm, extrude granulation and dry to obtain a mixed masterbatch.

[0058] (3) This step is the same as in Example 1.

[0059] Example 4

[0060] A bio-based high-strength and high-toughness polylactic acid / polyamide 11 alloy material is prepared according to the following steps:

[0061] (1) PA11, PDLA and SG were mixed in a weight ratio of 1:2:2 and added to an internal mixer, and 0.2 wt% N,N-dimethyloctadecylamine was added as a catalyst. The mixture was blended at 200°C and 60 rpm for 6 min to obtain a graft copolymer (PA11-SG-PDLA), which was then pelletized and crushed into powder in a pelletizer and dried in a vacuum oven at 60°C for 24 h to obtain a reactive compatibilizer.

[0062] (2) Add 70wt% PLLA, 25wt% PA11 and 5wt% of the reactive compatibilizer synthesized above into a twin-screw extruder, control the heating temperature of the twin-screw extruder from the feed port to the discharge port to be 180°C, 190°C, 200°C, 210°C, 215°C, 220°C, 225°C in sequence, the head temperature is 220°C, the screw speed is controlled at 60rpm, extrude granulate and dry to obtain a mixed masterbatch.

[0063] (3) This step is the same as in Example 1.

[0064] Example 5

[0065] A bio-based high-strength and high-toughness polylactic acid / polyamide 11 alloy material is prepared according to the following steps:

[0066] (1) PA11, PDLA and SG were mixed in a weight ratio of 1:0.5:2 and added to an internal mixer, and 0.2 wt% N,N-dimethyloctadecylamine was added as a catalyst. The mixture was blended at 200°C and 60 rpm for 6 min to obtain a graft copolymer (PA11-SG-PDLA), which was then pelletized and crushed into powder in a pelletizer and dried in a vacuum oven at 60°C for 24 h to obtain a reactive compatibilizer.

[0067] (2) Add 70wt% PLLA, 25wt% PA11 and 5wt% of the reactive compatibilizer synthesized above into a twin-screw extruder, control the heating temperature of the twin-screw extruder from the feed port to the discharge port to be 180°C, 190°C, 200°C, 210°C, 215°C, 220°C, 225°C in sequence, the head temperature is 220°C, the screw speed is controlled at 60rpm, extrude granulate and dry to obtain a mixed masterbatch.

[0068] (3) This step is the same as in Example 1.

[0069] Example 6

[0070] A bio-based high-strength and high-toughness polylactic acid / polyamide 11 alloy material is prepared according to the following steps:

[0071] (1) PA11, PDLA and SG were mixed in a weight ratio of 1:0.5:1.8 and added to an internal mixer, and 0.1 wt% N,N-dimethyloctadecylamine was added as a catalyst. The mixture was blended at 200°C and 60 rpm for 6 min to obtain a graft copolymer (PA11-SG-PDLA), which was then pelletized and crushed into powder in a pelletizer and dried in a vacuum oven at 60°C for 24 h to obtain a reactive compatibilizer.

[0072] (2) Add 70wt% PLLA, 25wt% PA11 and 5wt% of the reactive compatibilizer synthesized above into a twin-screw extruder, control the heating temperature of the twin-screw extruder from the feed port to the discharge port to be 180°C, 190°C, 200°C, 210°C, 215°C, 220°C, 225°C in sequence, the head temperature is 220°C, the screw speed is controlled at 60rpm, extrude granulate and dry to obtain a mixed masterbatch.

[0073] (3) This step is the same as in Example 1.

[0074] Example 7

[0075] A bio-based high-strength and high-toughness polylactic acid / polyamide 11 alloy material is prepared according to the following steps:

[0076] (1) PA11, PDLA and SG were mixed in a weight ratio of 1:0.5:2.2 and added to an internal mixer, and 0.5 wt% N,N-dimethyloctadecylamine was added as a catalyst. The mixture was blended at 200°C and 60 rpm for 6 min to obtain a graft copolymer (PA11-SG-PDLA), which was then pelletized and crushed into powder in a pelletizer and dried in a vacuum oven at 60°C for 24 h to obtain a reactive compatibilizer.

[0077] (2) Add 80wt% PLLA, 13wt% PA11 and 7wt% of the reactive compatibilizer synthesized above into a twin-screw extruder, control the heating temperature of the twin-screw extruder from the feed port to the discharge port to be 180°C, 190°C, 200°C, 210°C, 215°C, 220°C, 225°C in sequence, the head temperature is 220°C, the screw speed is controlled at 60rpm, extrude granulate and dry to obtain a mixed masterbatch.

[0078] (3) This step is the same as in Example 1.

[0079] Comparative Example 1

[0080] An organic alloy material is prepared according to the following steps:

[0081] (1) Add 70 wt% PLLA and 30 wt% PA11 into a twin-screw extruder, control the heating temperature of the twin-screw extruder from the feed port to the discharge port to be 180°C, 190°C, 200°C, 210°C, 215°C, 220°C, 225°C in sequence, the head temperature is 220°C, the screw speed is controlled at 100 rpm, extrude granules and dry to obtain a mixed masterbatch.

[0082] (2) The masterbatch obtained in step (1) is added into an injection molding machine, and injection molding is performed at 220° C. and 60 MPa injection pressure, and the pressure is maintained for 3 minutes to obtain a standard specimen for performance testing.

[0083] Comparative Example 2

[0084] An organic alloy material is prepared according to the following steps:

[0085] (1) Add 70wt% PLLA, 25wt% PA11 and 5wt% SG into a twin-screw extruder, control the heating temperature of the twin-screw extruder from the feed port to the discharge port to be 180°C, 190°C, 200°C, 210°C, 215°C, 220°C, 225°C in sequence, the head temperature is 220°C, the screw speed is controlled at 100rpm, extrude granulate and dry to obtain a mixed masterbatch.

[0086] (2) The masterbatch obtained in step (1) is added into an injection molding machine, and injection molding is performed at 220° C. and 60 MPa injection pressure, and the pressure is maintained for 3 minutes to obtain a standard specimen for performance testing.

[0087] Comparative Example 3

[0088] An organic alloy material is prepared according to the following steps:

[0089] (1) PA11, PDLA and SG were mixed in a weight ratio of 1:1:2, added to an internal mixer, and 0.2 wt% N,N-dimethyloctadecylamine was added as a catalyst. The mixture was blended at 200°C and 60 rpm for 6 min to obtain a graft copolymer (PA11-SG-PDLA), which was then pelletized and crushed into powder in a pelletizer and dried in a vacuum oven at 60°C for 24 h to obtain a reactive compatibilizer.

[0090] (2) Add 80wt% PLLA, 19wt% PA11 and 1wt% of the reactive compatibilizer synthesized above into a twin-screw extruder, control the heating temperature of the twin-screw extruder from the feed port to the discharge port to be 180°C, 190°C, 200°C, 210°C, 215°C, 220°C, 225°C in sequence, the head temperature is 220°C, the screw speed is controlled at 60rpm, extrude granulation and dry to obtain a mixed masterbatch.

[0091] (3) This step is the same as in Example 1.

[0092] Comparative Example 4

[0093] An organic alloy material is prepared according to the following steps:

[0094] (1) PA11, PDLA and SG were mixed in a weight ratio of 1:2.5:2 and added to an internal mixer, and 0.2 wt% N,N-dimethyloctadecylamine was added as a catalyst. The mixture was blended at 200°C and 60 rpm for 6 min to obtain a graft copolymer (PA11-SG-PDLA), which was then pelletized and crushed into powder in a pelletizer and dried in a vacuum oven at 60°C for 24 h to obtain a reactive compatibilizer.

[0095] (2) Add 70wt% PLLA, 25wt% PA11 and 5wt% of the reactive compatibilizer synthesized above into a twin-screw extruder, control the heating temperature of the twin-screw extruder from the feed port to the discharge port to be 180°C, 190°C, 200°C, 210°C, 215°C, 220°C, 225°C in sequence, the head temperature is 220°C, the screw speed is controlled at 60rpm, extrude granulate and dry to obtain a mixed masterbatch.

[0096] (3) This step is the same as in Example 1.

[0097] Comparative Example 5

[0098] An organic alloy material is prepared according to the following steps:

[0099] (1) PA11, PDLA and SG were mixed in a weight ratio of 1:1:2 and added to an internal mixer, and 0.2 wt% N,N-dimethyloctadecylamine was added as a catalyst. The mixture was blended at 190°C and 60 rpm for 6 min to obtain a graft copolymer (PA11-SG-PDLA), which was then pelletized and crushed into powder in a pelletizer and dried in a vacuum oven at 60°C for 24 h to obtain a reactive compatibilizer.

[0100] (2) Add 70wt% PLLA, 21wt% PA11 and 9wt% of the reactive compatibilizer synthesized above into a twin-screw extruder, control the heating temperature of the twin-screw extruder from the feed port to the discharge port to be 180°C, 190°C, 200°C, 210°C, 215°C, 220°C, 225°C in sequence, the head temperature is 220°C, the screw speed is controlled at 70rpm, extrude granulate and dry to obtain a mixed masterbatch.

[0101] (3) This step is the same as in Example 1.

[0102] Performance Testing

[0103] The mechanical properties of the bio-based polylactic acid / polyamide 11 alloy material of the present invention are verified by injection molding the bio-based polylactic acid / polyamide 11 alloy material prepared above into standard tensile specimens of 30.0×5.0×2.0 mm (length, width, thickness) at 220°C in an injection molding machine, and systematically analyzing its mechanical properties. The test results are shown in Table 2, where the tensile strength and elongation at break are tested in accordance with GB / T1040.3-2018.

[0104] The hot stage polarizing microscope test method is: raise the temperature of the sample to 250°C, keep it warm for 3 minutes, then quickly cool it to 130°C and keep it isothermal, and photograph the spherulite growth process.

[0105] Examples 1, 2, 3 and Comparative Examples 1, 3, 5 studied the effects of the addition of compatibilizer and its content on the properties of the composite material; Examples 2, 4, 5 and Comparative Example 4 studied the effects of the component ratio of the compatibilizer on the properties of the composite material.

[0106] Table 1: Composition ratio table of each embodiment and comparative example

[0107]

[0108]

[0109] Table 2: Mechanical properties data of various embodiments and comparative examples

[0110] Sample Yield strength (MPa) Young's modulus (MPa) Elongation at break (%) <![CDATA[Fracture energy (J / m 2 )]]> Example 1 56±4 1743±127 162±32 5223±1057 Example 2 69±2 1825±233 222±15 8805±929 Example 3 59±3 1563±270 136±9 3772±311 Example 4 56±3 1687±170 67±8 1884±162 Example 5 54±4 1708±139 150±13 4592±506 Example 6 50±4 1501±196 59±10 1620±363 Example 7 58±3 1628±265 119±11 3429±218 Comparative Example 1 63±3 1712±153 13±9 290±144 Comparative Example 2 59±4 1857±141 21±5 514±40 Comparative Example 3 55±1 1774±90 76±9 1992±503 Comparative Example 4 53±3 1526±193 41±6 1263±194 Comparative Example 5 56±2 1548±231 52±4 1453±315

[0111] Figure 1 It is the POM diagram of each sample when the temperature is reduced to 130°C. Pure polylactic acid is a homogeneous phase structure, but after adding PA11, due to the incompatibility of PLLA and PA11, many PA11 dispersed domains appeared in Comparative Example 1 (no reactive compatibilizer was added), and the size was relatively large, approximately 20-50μm. After adding the reactive compatibilizer in Example 2, the PA11 dispersed domain was dispersed from larger droplets to a large number of small droplets, with a size of about 1-5μm. This shows that the addition of the reactive compatibilizer induces the morphological evolution of PA11, changes its dispersion state, and thus improves the interfacial interaction between PLLA and PA11.

[0112] Depend on Figure 2 It can be seen that pure PLLA forms spherulites with large diameter and few in number during the crystallization process. When subjected to external force, PLA tends to break at the edge or inside of the large spherulites. After adding the reactive compatibilizer (Example 2), due to the heterogeneous nucleation effect of the reactive compatibilizer, the crystallization ability of PLA is enhanced, so that the spherulites of PLA are not only small in diameter, but also large in number and spread over the entire interface, thus giving the composite material excellent toughness.

[0113] pass Figure 3 It can be concluded that the addition of reactive compatibilizer can effectively improve the mechanical properties of polylactic acid composite materials. At the same time, the composition and amount of compatibilizer also have a great influence on the toughness of the material. The influence of stereocomplex crystallization is studied by Example 2 and Comparative Example 2, and the influence of the proportion of PA11, PDLA and SG components in the compatibilizer is studied by Example 2, 4, 5 and Comparative Example 4, which shows that the presence of stereocomplex crystallization can affect the toughness of the composite material. Only an appropriate amount of stereocomplex crystallization can effectively improve the toughness of the composite material. If the stereocomplex content is too high, the brittleness of the material increases due to hydrogen bonding.

[0114] Examples 1, 2, 3 and Comparative Examples 1, 3, 5 studied the effect of the addition of compatibilizer and its content on the toughness of the material: as the content of the compatibilizer increases, the compatibility between the two phases of the composite material increases, which ultimately leads to a continuous increase in the elongation at break; at the same time, the increase in the compatibilizer can also increase the tensile strength of the material, which may be attributed to the formation of interfacial SC crystals. In the above embodiments, the mechanical properties of Example 2 are the best. On the premise of having a higher yield strength, it also has an elongation at break of up to 222%, achieving a balance between rigidity and toughness. When the content of the compatibilizer is higher than 5%, the mechanical properties of the material decrease, which may be because the excessive SG in the compatibilizer causes a large number of cross-linking reactions to occur in the system, forming cross-linking points, making the material brittle and reducing toughness.

[0115] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent transformation made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A bio-based high-strength and high-toughness polylactic acid / polyamide 11 alloy material, Features: Including weight percentage of raw materials: Poly-L-lactic acid: 60-80%; Polyamide 11: 13-37%; Reactive compatibilizer: 3-7%; The chemical structural formula of the reactive compatibilizer is as follows: Among them, x is 45-55, y is 3-6, z is 0-3, a is 3-6, n is 400-800, and m is 200-350.

2. A bio-based high-strength and high-toughness polylactic acid / polyamide 11 alloy material according to claim 1, It is characterized in that The reactive compatibilizer is a product of a grafting reaction between poly (dextral lactic acid) and amino-terminated polyamide 11 on the main chain of an epoxy chain extender, and the preparation steps thereof include: 1) mixing amino-terminated polyamide 11, poly (dextral lactic acid) and epoxy chain extender in a weight ratio of 1:(0.5-2):(1.8-2.2), adding a catalyst, heating and reacting to obtain a graft copolymer; 2) The graft copolymer obtained in step 1) is pelletized, crushed and dried to obtain a reactive compatibilizer.

3. A bio-based high-strength and high-toughness polylactic acid / polyamide 11 alloy material according to claim 2, It is characterized in that The epoxy chain extender is polystyrene-glycidyl methacrylate, and the epoxy equivalent is 0.3-0.4 mol / 100g.

4. A bio-based high-strength and high-toughness polylactic acid / polyamide 11 alloy material according to claim 2, It is characterized in that The catalyst is N,N-dimethyloctadecylamine.

5. A bio-based high-strength and high-toughness polylactic acid / polyamide 11 alloy material according to claim 4, It is characterized in that The amount of the catalyst used is 0.1-0.5% of the total mass of the raw materials for preparing the reactive compatibilizer.

6. The bio-based high-strength and high-toughness polylactic acid / polyamide 11 alloy material according to claim 2, It is characterized in that In the step 1), the heating reaction temperature is 180-200° C., the stirring rate is 20-100 rpm, and the time is 2-10 min.

7. A method for preparing the bio-based high-strength and high-toughness polylactic acid / polyamide 11 alloy material according to any one of claims 1 to 6, It is characterized in that The steps include: A) weighing poly (L-lactic acid), polyamide 11 and a reactive compatibilizer by weight percentage; B) Poly-L-lactic acid, polyamide 11 and a reactive compatibilizer are uniformly mixed, melt-blended, extruded into granules and dried to obtain a bio-based high-strength and high-toughness poly-lactic acid / polyamide 11 alloy material.

8. The method for preparing the bio-based high-strength and high-toughness polylactic acid / polyamide 11 alloy material according to claim 7, It is characterized in that In step B), the melt blending is achieved by a twin-screw extruder, in which 7 zones are sequentially arranged from the feed port to the discharge port, and the temperatures of the zones starting from zone 1 are: 175-185°C, 185-195°C, 195-205°C, 205-215°C, 210-220°C, 215-225°C, 220-230°C, the die temperature is 215-225°C, and the screw speed is controlled to 80-100rpm.

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