Plant fiber reinforced foam composite material as well as preparation method and application thereof

Abstract

The invention belongs to the field of material processing, and particularly discloses a plant fiber reinforced foam composite material and a preparation method and application thereof. The composite material comprises a porous material and a polymer film attached to the surface of the porous material, the porous material comprises the following raw materials in parts by mass: 50-85 parts of thermoplastic plastics, 10-40 parts of plant fibers and 5-10 parts of a coupling agent, the porous material is a supercritical gas foaming material. The composite material disclosed by the invention combines the advantages of high strength, renewability and environmental friendliness of the plant fibers and the advantages of light weight, heat insulation, sound absorption and the like of the thermoplastic plastics, and can be applied to many fields. In addition, the composite material disclosed by the invention effectively improves the surface quality and performance of the composite material by utilizing the excellent fitness, wear resistance and aging resistance of the polymer film.

Description

Technical Field

[0001] The present invention belongs to the field of material processing, and in particular relates to a plant fiber reinforced foam composite material and a preparation method and application thereof. Background Art

[0002] As a new type of environmentally friendly, lightweight and low-cost material, plant fiber reinforced foam composites have received widespread attention and application in aviation, construction, transportation, packaging and other fields. This type of material mainly utilizes renewable plant fiber resources and is compounded with polypropylene to form a composite material that has both the natural advantages of plant fiber and the lightweight properties of foam materials. However, during the preparation process of plant fiber reinforced foam composites, factors such as the irregular arrangement of fibers and the surface tension of polypropylene often lead to rough and porous surfaces of the materials, which are prone to cracking and peeling. At the same time, due to the limitations of the supercritical gas microporous foaming process, the surface quality of the products produced is often unsatisfactory, and surface defects such as silver streaks, flow marks, and bubble marks often appear. These surface defects not only affect the aesthetics and comfort of the material, but also greatly restrict the application of plant fiber reinforced foam composite products in applications with high requirements for appearance quality, such as automotive interior and exterior trims and electronic device housings. In addition, plant fiber reinforced foam composites are usually exposed to harsh external environments, such as ultraviolet radiation, saline-alkali erosion, and damp-heat aging. In particular, the damp-heat aging environment will have a serious impact on the long-term performance of plant fiber reinforced foam composites. The performance of plant fiber reinforced foam composites prepared by existing processes generally cannot meet the requirements of long-term use in harsh external environments. Summary of the Invention

[0003] In order to overcome at least one technical problem existing in the above-mentioned prior art, one of the objectives of the present invention is to provide a composite material.

[0004] A second object of the present invention is to provide a method for preparing a composite material.

[0005] A third object of the present invention is to provide an application of the composite material in automotive interior parts or electronic product housings.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] The first aspect of the present invention provides a composite material comprising a porous material and a polymer film adhered to the surface of the porous material; the porous material comprises the following raw materials in parts by mass: 50 to 85 parts of thermoplastic plastic, 10 to 40 parts of plant fiber, and 5 to 10 parts of coupling agent; the porous material is a supercritical gas foaming material.

[0008] In some embodiments of the present invention, the plant fiber is a plant fiber material treated with alkali solution.

[0009] In some embodiments of the present invention, the thermoplastic plastic includes at least one of polypropylene compounds, polyethylene compounds, polystyrene compounds, polybutadiene compounds, polycarbonate compounds, and polyether compounds.

[0010] In some embodiments of the present invention, the coupling agent includes maleic anhydride, a silane coupling agent, and polypropylene grafted with an acrylic compound.

[0011] In some embodiments of the present invention, the polymer film comprises at least one of a polypropylene film, a polyethylene film, and a polybutadiene film.

[0012] In some embodiments of the present invention, the thermoplastic comprises polypropylene, and the polypropylene has a melt index of 10 to 30 g / 10 min measured at 230° C. and a load of 2.16 kg.

[0013] In some embodiments of the present invention, the plant fiber is alkali-treated bamboo fiber.

[0014] In some embodiments of the present invention, the coupling agent comprises maleic anhydride grafted polypropylene.

[0015] In some embodiments of the present invention, the polymer film has a thickness of 0.1 to 0.2 mm.

[0016] In some embodiments of the present invention, the foaming gas in the supercritical gas foaming method includes at least one of nitrogen, argon, and carbon dioxide.

[0017] In some embodiments of the present invention, the tensile strength of the composite material is 35-38 MPa.

[0018] In some embodiments of the present invention, the composite material has a flexural strength of 50 to 55 MPa.

[0019] In some embodiments of the present invention, the impact strength of the composite material is 7 to 8 kJ / m 2 .

[0020] In some embodiments of the present invention, the surface roughness of the composite material is ≤1 μm.

[0021] The second aspect of the present invention provides a method for preparing the composite material according to the first aspect of the present invention, comprising the following steps:

[0022] The raw materials for preparing the porous material are mixed and extruded into granules, and then injection-molded into a mold with a polymer film adsorbed on the inner surface. During the injection molding process, supercritical gas foaming is used for foaming to obtain the composite material.

[0023] In some embodiments of the present invention, the mold with the polymer film adsorbed on the inner surface is prepared by a preparation method comprising the following steps: first subjecting the polymer film to corona treatment, and then electrostatically adsorbing the polymer film on the inner surface of the mold.

[0024] In some embodiments of the present invention, the extrusion temperature of the extrusion granulation step is 180-200°C; in some embodiments of the present invention, the extrusion temperature of the extrusion granulation step is 183-197°C; in some embodiments of the present invention, the extrusion granulation step is performed by extruding using an extruder; the parameters of the extruder are set as follows: head temperature is 183-187°C, zone I temperature is 188-192°C, zone II temperature is 193-197°C, zone III temperature is 193-197°C, zone IV temperature is 193-197°C, feeder speed is 1-10rpm, and main engine speed is 1-10rpm.

[0025] In some embodiments of the present invention, the temperature of the injection molding step is 180-195°C; in some embodiments of the present invention, the injection molding step is performed using an injection molding machine; the parameters of the injection molding machine are set to: zone 1 temperature is 180-185°C, zone 2 temperature is 185-195°C, zone 3 temperature is 185-195°C, zone 4 temperature is 180-185°C, injection pressure is 65-75MPa; cooling time is 10-50s.

[0026] In some embodiments of the present invention, the temperature of the mold is 80-100°C.

[0027] The third aspect of the present invention provides use of the composite material described in the first aspect of the present invention in automotive interior parts or electronic product housings.

[0028] The beneficial effects of the present invention are: the composite material of the present invention combines the high strength, renewability and environmental friendliness of plant fibers with the lightweight, heat-insulating and sound-absorbing advantages of thermoplastics, and can be applied in many fields, for example: many parts in automobiles, such as dashboards, door panels, seat backs, etc. The composite material has a low density and weight, which can significantly reduce the overall weight of the automobile.

[0029] Furthermore, the preparation method of the present invention effectively improves the surface defects of products caused by microcellular foaming processes by attaching a polymer film to a mold and then using supercritical gas foaming to perform injection molding. This ensures the stability and consistency of product quality. Furthermore, the excellent conformability, wear resistance, and aging resistance of the polymer film are utilized to effectively improve the surface quality and performance of the composite material. Furthermore, the method is simple to operate and does not require significant changes to the existing molding process, thus having broad application prospects and market potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the preparation process of the plant fiber reinforced foam composite material in Example 1.

[0031] Figure 2 This is a schematic structural diagram of a mold used in the preparation of the plant fiber reinforced foam composite material in Example 1.

[0032] Figure 3 Schematic diagram of the interface formation mechanism between the PP film and the substrate in Example 1.

[0033] Figure 4 This is the surface SEM image of the plant fiber reinforced foam composite material in Example 1.

[0034] Figure 5 This is the surface SEM image of the plant fiber reinforced foam composite material in Comparative Example 1.

[0035] Figure 6 This is a 3D outline diagram of the plant fiber reinforced foam composite material in Example 1.

[0036] Figure 7 This is a 3D contour diagram of the plant fiber reinforced foam composite material in Comparative Example 1.

[0037] Figure 8 This is a cross-sectional SEM image of the plant fiber reinforced foam composite material in Example 1. DETAILED DESCRIPTION

[0038] The specific implementation of the present invention will be further described in detail below in conjunction with the accompanying drawings and examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that if there are any processes that are not particularly described in detail below, they can be implemented or understood by those skilled in the art with reference to the prior art. The reagents or instruments used that do not indicate the manufacturer are all conventional products that can be purchased commercially.

[0039] In some embodiments of the present invention, a composite material is provided, comprising a porous material and a polymer film adhered to the surface of the porous material. The porous material comprises the following raw materials in parts by weight: 50-85 parts thermoplastic, 10-40 parts plant fiber, and 5-10 parts coupling agent; the porous material is a supercritical gas foam material.

[0040] In some embodiments of the present invention, the mass parts of the thermoplastic plastic can be any value of 50 parts, 52 parts, 54 parts, 56 parts, 58 parts, 60 parts, 62 parts, 64 parts, 66 parts, 68 parts, 70 parts, 72 parts, 74 parts, 76 parts, 78 parts, 80 parts, 82 parts, 84 parts, 85 parts, or a range formed by any two of them.

[0041] In some embodiments of the present invention, the mass proportion of plant fiber can be any one of 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, 22 parts, 24 parts, 26 parts, 28 parts, 30 parts, 32 parts, 34 parts, 36 parts, 38 parts, 40 parts, or a range formed by any two of them.

[0042] In some embodiments of the present invention, the weight percentage of the coupling agent may be any one of 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, and 10 parts, or a range formed by any two of the above.

[0043] In some embodiments of the present invention, the plant fiber is a plant fiber material treated with alkali solution. In some embodiments of the present invention, the plant fiber is a bamboo fiber treated with alkali solution.

[0044] In some embodiments of the present invention, the alkali solution is selected from at least one of sodium hydroxide and potassium hydroxide.

[0045] In some embodiments of the present invention, the plant fiber is prepared by mixing an alkali solution with a plant fiber material and then heating it. In some embodiments of the present invention, the plant fiber is prepared by mixing an alkali solution with a cleaned plant fiber material and then heating it, then washing it with water until the pH is neutral, and drying it.

[0046] In some embodiments of the present invention, the temperature of the heating step is 55-70°C; in some embodiments of the present invention, the temperature of the heating step can be any value of 55°C, 58°C, 60°C, 62°C, 64°C, 66°C, 68°C, 70°C or a range formed by any two of them.

[0047] In some embodiments of the present invention, the time of the heating step is 1 to 10 hours; in some embodiments of the present invention, the time of the heating step is any value among 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h or a range value formed by any two of them.

[0048] In some embodiments of the present invention, the thermoplastic plastic includes at least one of polypropylene compounds, polyethylene compounds, polybutadiene compounds, and polycarbonate compounds; in some embodiments of the present invention, the thermoplastic plastic includes polypropylene compounds; in some embodiments of the present invention, the thermoplastic plastic includes polypropylene.

[0049] In some embodiments of the present invention, the melt index of polypropylene measured at 230°C and a load of 2.16 kg is 10 to 30 g / 10 min; in some embodiments of the present invention, the melt index of polypropylene measured at 230°C and a load of 2.16 kg is any one of 10 g / 10 min, 12 g / 10 min, 14 g / 10 min, 16 g / 10 min, 18 g / 10 min, 20 g / 10 min, 22 g / 10 min, 24 g / 10 min, 26 g / 10 min, 28 g / 10 min, and 30 g / 10 min, or a range formed by any two of the values.

[0050] In some embodiments of the present invention, the coupling agent includes acrylic acid grafted polypropylene.

[0051] In some embodiments of the present invention, the polymer film comprises at least one of a polypropylene film, a polyethylene film, and a polybutadiene film. In some embodiments of the present invention, the polymer film is a polypropylene film.

[0052] In some embodiments of the present invention, the polymer film includes at least two of polypropylene film, polyethylene film, and polybutadiene film; the polymer film is a composite film formed by laminating at least two films selected from polypropylene film, polyethylene film, and polybutadiene film.

[0053] In some embodiments of the present invention, the coupling agent includes maleic anhydride grafted polypropylene.

[0054] In some embodiments of the present invention, the thickness of the polymer film is 0.1-0.2 mm. In some embodiments of the present invention, the thickness of the polymer film is any one of 0.1 mm, 0.11 mm, 0.12 mm, 0.13 mm, 0.14 mm, 0.15 mm, 0.16 mm, 0.17 mm, 0.18 mm, 0.19 mm, and 0.2 mm, or a range formed by any two of the values.

[0055] In some embodiments of the present invention, the thickness ratio of the polymer membrane to the porous support is 1:(30-60); in some embodiments of the present invention, the thickness ratio of the polymer membrane to the porous support can be selected from any value of 1:30, 1:32, 1:34, 1:36, 1:38, 1:40, 1:42, 1:44, 1:46, 1:48, 1:50, 1:52, 1:54, 1:56, 1:58, 1:60, or a range formed by any two of the values.

[0056] In some embodiments of the present invention, the foaming gas in the supercritical gas foaming method includes at least one of nitrogen, argon, and carbon dioxide.

[0057] In some embodiments of the present invention, the tensile strength of the composite material is 35-38 MPa. The test standard for the tensile strength of the composite material is GB / T1040.1-2018, and the test rate is 50 mm / min.

[0058] In some embodiments of the present invention, the flexural strength of the composite material is 50-55 MPa. The flexural strength of the composite material is tested in accordance with GB / T9341-2008 at a rate of 2 mm / min.

[0059] In some embodiments of the present invention, the impact strength of the composite material is 7 to 8 kJ / m 2 The test standard for the impact strength of composite materials is the cantilever beam impact test, which is based on the GB / T1843-2008 test standard V-notch impact specimen.

[0060] In some embodiments of the present invention, the surface roughness of the composite material is ≤1 μm. The surface roughness test uses an optical profilometer to measure the average distance between adjacent peaks on the entire surface, that is, the Ra value. The Ra value of the composite material in the present invention is ≤1 μm.

[0061] In some embodiments of the present invention, the present invention further provides a method for preparing the above composite material, comprising the following steps:

[0062] The raw materials for preparing the porous material are mixed and extruded into granules, and then injection molded into a mold with a polymer film adsorbed on the inner surface. During the injection molding process, supercritical gas foaming method is used for foaming to obtain a composite material.

[0063] The inventors innovatively create a porous material by electrostatically adsorbing a polymer film within the mold. This is then foamed using supercritical gas during the injection molding process. Heating the mold enhances the adhesion between the polymer film and the porous substrate, improving the composite's surface morphology and, consequently, surface defects in microporous foamed products, enhancing molding quality. Furthermore, the polymer film's moisture barrier effectively slows aging and extends the composite's service life.

[0064] In some embodiments of the present invention, the mixing step lasts for 1 to 30 minutes; in some embodiments of the present invention, the mixing step lasts for 3 to 10 minutes; in some embodiments of the present invention, the mixing step lasts for 3 to 5 minutes.

[0065] In some embodiments of the present invention, the present invention provides a method for preparing the above composite material, comprising the following steps:

[0066] S1: mixing raw materials including plant fiber, thermoplastic plastic, and coupling agent, then extruding and granulating, and drying to obtain mixture A;

[0067] S2: Injecting the mixed material A into a mold with a polymer film adsorbed on the inner surface thereof and foaming the mixed material A by using a supercritical gas foaming method during the injection molding to obtain a composite material.

[0068] In some embodiments of the present invention, the mold with the polymer film adsorbed on the inner surface is prepared by a preparation method comprising the following steps: first subjecting the polymer film to corona treatment, and then electrostatically adsorbing the polymer film on the inner surface of the mold.

[0069] In some embodiments of the present invention, the extrusion temperature of the extrusion granulation step is 180-200° C.; in some embodiments of the present invention, the extrusion temperature of the extrusion granulation step is 183-197° C. In some embodiments of the present invention, the extrusion granulation step is performed using an extruder; the parameters of the extruder are set as follows: head temperature of 183-187° C., temperature of zone I of 188-192° C., temperature of zone II of 193-197° C., temperature of zone III of 193-197° C., temperature of zone IV of 193-197° C., feeder speed of 1-10 rpm, and main machine speed of 1-10 rpm.

[0070] In some embodiments of the present invention, the temperature of the injection molding step is 180-195° C. In some embodiments of the present invention, the injection molding step is performed using an injection molding machine; the parameters of the injection molding machine are set as follows: zone 1 temperature is 180-185° C., zone 2 temperature is 185-195° C., zone 3 temperature is 185-195° C., zone 4 temperature is 180-185° C., injection pressure is 65-75 MPa; and cooling time is 10-50 seconds.

[0071] In some embodiments of the present invention, the mold temperature is 80-100°C. In some embodiments of the present invention, the mold is provided with a heating device that heats the mold to a temperature of 80-100°C. In some embodiments of the present invention, the heating device is a heating tube. Preheating the mold prevents the temperature of the injection molding material from dropping too quickly during injection molding, which could affect the mechanical properties of the injection molding material. Preheating the mold also allows the polymer film to better adhere to the porous material.

[0072] The following is a further detailed description of the specific implementation of the present invention in conjunction with specific embodiments:

[0073] Example 1

[0074] Reference Figure 1 The preparation process flow chart in this example provides a method for preparing a plant fiber reinforced foam composite material, comprising the following steps:

[0075] (1) Repeatedly wash 4000g of bamboo fiber with distilled water to remove surface dust and other impurities. Subsequently, immerse the washed fibers in a 1.32mol / L NaOH solution and heat in a 60℃ water bath for 4 hours to dissolve impurities such as hemicellulose, gum, and wax in the fibers. Continue washing the fibers with distilled water until the pH value of the washing solution is neutral to obtain purified bamboo fibers. Dry the fibers and set aside.

[0076] (2) 3000 g of dried plant fiber was crushed into 2 mm long particles using a fiber crusher to prepare the plant fiber material. 70 parts of polypropylene, 20 parts of plant fiber material, and 10 parts of maleic anhydride grafted polypropylene were weighed by mass and placed in a high-speed mixer, stirred and mixed thoroughly, and cooled to prepare a premix.

[0077] (3) The premix was added to a twin-screw extruder for extrusion granulation. After extrusion granulation, the particles were dried to obtain premix masterbatch. The drying temperature was 120°C and the drying time was 8 hours. The parameters of the twin-screw extruder were set as follows: head temperature 185°C, zone I temperature 190°C, zone II temperature 195°C, zone III temperature 195°C, zone IV temperature 195°C, feeder speed 5 rpm, and main engine speed 5.5 rpm.

[0078] (4) The polypropylene film (i.e., PP film) is precisely cut according to the shape of the mold, and the cut PP film is corona treated. Then, the corona treated PP film is tightly attached to the inner surface of the upper and lower molds by electrostatic adsorption. Figure 2 As shown in the figure, the voltage is 10 kV, the processing time is 0.5 s, the frequency is 25 kHz, the processing speed is 1 m / min, and the thickness of the PP film is 0.1 mm.

[0079] The mold used in this example includes an upper mold 1, a lower mold 2, a cooling channel 4, and a heating tube 5; the inner surfaces of the upper mold 1 and the lower mold 2 are both covered with PP film; the upper mold 1 and the lower mold 2 are both provided with a cooling channel 4 and a heating tube 5, as shown in FIG. Figure 2 shown.

[0080] (5) The premix masterbatch was placed into the barrel of a twin-screw injection molding machine and subjected to supercritical fluid (N2) foaming injection molding. After pressure relief and cooling, the plant fiber reinforced foam composite material in this example was obtained. The process parameters of the injection molding machine included: zone 1 temperature of 185°C, zone 2 temperature of 190°C, zone 3 temperature of 190°C, and zone 4 temperature of 185°C; injection pressure of 70 MPa, mold temperature of 90°C, and cooling time of 30 seconds.

[0081] like Figure 3 As shown, after a layer of PP film is attached to the surface of the matrix (i.e., the porous material obtained by injection molding of the premix masterbatch) in the present invention, the PP film melts under the high temperature of the melt and the high pressure of the cavity during injection molding to form a bonding interface between the PP film and the matrix. During the cooling and setting process, the polymer chains of the PP film and the matrix (i.e., Figure 3 lines in the figure) are entangled with each other and co-crystallize to form polymer crystals in the interface region (i.e. Figure 3 The PP film is then tightly bonded to the substrate (see the purple block in the figure). Furthermore, the injection molding process creates excellent interfacial compatibility between the plant fiber and the polypropylene substrate. Furthermore, the PP film of the present invention improves the surface properties of the substrate, making it smooth and flat, free of defects such as bubbles and wrinkles, significantly enhancing the aesthetics and user comfort of the product. Furthermore, it improves the mechanical properties and heat aging resistance of the substrate.

[0082] Comparative Example 1

[0083] This example provides a method for preparing a plant fiber reinforced foam composite material, comprising the following steps:

[0084] (1) Repeatedly wash 4000g of bamboo fiber with distilled water to remove surface dust and other impurities. Subsequently, immerse the washed fibers in a 1.32mol / L NaOH solution and heat in a 60℃ water bath for 4 hours to dissolve impurities such as hemicellulose, gum, and wax. Continue washing the fibers with distilled water until the pH of the washing solution is neutral to obtain purified bamboo fibers. Dry the fibers and set aside.

[0085] (2) 3000 g of dried plant fiber was crushed into 2 mm long particles using a fiber crusher to obtain a plant fiber material. 70 parts of polypropylene, 20 parts of plant fiber material, and 10 parts of maleic anhydride-grafted polypropylene were weighed by mass and placed in a high-speed mixer, stirred and mixed thoroughly, and cooled and discharged to prepare a premix.

[0086] (3) The premix was added to a twin-screw extruder for extrusion granulation. After extrusion granulation, the particles were dried to obtain premix masterbatch, wherein the drying temperature was 120°C, the drying time was 8 hours, and the parameters of the twin-screw extruder were set as follows: head temperature 185°C, zone I temperature 190°C, zone II temperature 195°C, zone III temperature 195°C, zone IV temperature 195°C, feeder speed 5 rpm, and main engine speed 5.5 rpm.

[0087] (4) The premix masterbatch was placed into the barrel of a twin-screw injection molding machine and subjected to supercritical fluid (N2) foaming injection molding. After pressure relief and cooling, the plant fiber reinforced foam composite material in this example was obtained. The process parameters of the injection molding machine included: zone 1 temperature of 185°C, zone 2 temperature of 190°C, zone 3 temperature of 190°C, and zone 4 temperature of 185°C; injection pressure of 70 MPa, mold temperature of 90°C, and cooling time of 30 seconds.

[0088] Performance testing:

[0089] The SEM images of the plant fiber reinforced foam composite materials in Example 1 and Comparative Example 1 were respectively measured using a scanning electron microscope. Figure 4 and Figure 5 As shown, the surfaces of the plant fiber reinforced foam composite materials in Example 1 and Comparative Example 1 were characterized using an optical profilometer, as shown in FIG. Figure 6 and Figure 7 As shown. Figures 4 to 7 It can be seen that the present invention, by introducing PP film and utilizing the excellent conformability, wear resistance and anti-aging properties of PP film, can significantly improve the surface morphology and quality of plant fiber reinforced foam composite materials, making the surface of the composite material smooth and flat, without defects such as bubbles and wrinkles.

[0090] The surface morphology of the cross section of the plant fiber reinforced foam composite material in Example 1 was tested using a scanning electron microscope. The specific test results are as follows: Figure 8 As shown. Figure 8 It can be seen that the present invention effectively reduces the density of the composite material through the supercritical gas microporous foaming molding process, and under the action of plant fibers, induces the emergence of a large number of foaming micronuclei, reduces the pore size, increases the pore density, and improves the mechanical properties.

[0091] The tensile strength, flexural strength, impact strength, surface roughness and surface friction coefficient of the plant fiber reinforced foam composite materials in Example 1 and Comparative Example 1 were tested respectively. The specific testing methods are as follows:

[0092] The test standard for tensile strength is GB / T1040.1-2018, and the test rate is 50 mm / min.

[0093] Bending strength test standard: GB / T9341-2008, rate is 2mm / min;

[0094] Impact strength test standard: Izod beam impact test, in accordance with GB / T1843-2008 test standard V-notch impact specimen;

[0095] The surface roughness test uses an optical profilometer to measure the average distance between adjacent peaks on the entire surface, which is the Ra value;

[0096] The surface friction coefficient was tested according to GB / T 10006. The specific test method was as follows: dry sliding conditions were performed using a room-temperature friction and wear tester (HT-1000, Lanzhou Zhongke Kaihua Technology Co., Ltd. (Lanzhou, China)). The test load was 15 N, the sliding radius was 5 mm, the rotation speed was 700 rpm, and the test time was 10 min.

[0097] The specific test results measured according to the above test method are shown in Table 1 below:

[0098] Table 1 Mechanical properties and surface roughness performance data

[0099] Tensile strength / MPa Bending strength / MPa <![CDATA[Impact strength / KJ / m 2 > Surface roughness / μm Surface friction coefficient Example 1 36.8 51.9 7.6 0.644 0.339 Comparative Example 1 32.4 43.1 6.8 5.868 0.384

[0100] As shown in Table 1, the plant fiber reinforced foam composite material of the present invention significantly improves the mechanical properties of the composite material by compounding a layer of PP film on the surface of the material, significantly improves the surface roughness of the composite material, and increases its surface friction coefficient.

[0101] With reference to the SAE J2527 standard, the aging performance data of the plant fiber reinforced foam composite materials in Example 1 and Comparative Example 1 were tested after continuous aging for 1200 hours in a weathering aging chamber. The specific test results are shown in Table 2 below.

[0102] Table 2 Aging performance data

[0103] Tensile strength retention rate / % Bending strength retention rate / % Impact strength retention rate / % Chromatic Aberration Example 1 89.5 90.1 90.9 19.45 Comparative Example 1 76.5 75.4 74.6 33.52

[0104] As shown in Table 2, the plant fiber-reinforced foam composite material of the present invention, by adding a PP film to the surface, significantly improves its aging resistance. During the aging test, the tensile strength retention rate, flexural strength retention rate, and impact strength retention rate were significantly higher than those of the composite material without the PP film in Comparative Example 1. Furthermore, the color difference of the composite material of the present invention during the aging test was less than that of the composite material in Comparative Example 1.

[0105] In summary: the plant fiber reinforced foam composite material prepared by the preparation method of the present invention has low density, good surface quality, high mechanical properties, low cost, and is green and environmentally friendly. The present invention uses alkali solution to perform surface treatment on the plant fiber, so that the surface of the plant fiber is uneven, which can produce excellent interface compatibility between the plant fiber and the polypropylene matrix, and solve the problems of difficult compatibility between the plant fiber and the polymer matrix and poor interface bonding force. In addition, the present invention introduces PP film during injection molding, which improves the surface quality of the composite material, and its surface becomes smoother and flatter, without defects such as bubbles and wrinkles, which significantly improves the aesthetics and comfort of the composite material product. The PP film has good non-polarity. When it is attached to the surface of the composite material, it can significantly block moisture from entering the material, avoid hydrolysis of the plant fiber under the action of water molecules, thereby extending the service life of the composite material product and improving the mechanical properties of the composite material product. The PP film used in the present invention is an environmentally friendly material. When combined with the plant fiber reinforced foam composite material, it can maintain the environmental protection characteristics of the material and meet the requirements of sustainable development. In addition, the preparation method of the present invention is simple and easy to operate, and only requires laminating the PP film on the mold surface, which reduces the production difficulty and cost, can achieve a fast and efficient laminating process, and improve production efficiency.

[0106] While the embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described above. Various modifications may be made within the scope of knowledge possessed by a person skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof may be combined with one another unless there is a conflict.

Claims

1. A composite material, characterized in that: The invention comprises a porous material and a polymer film attached to the surface of the porous material; the porous material comprises the following raw materials in parts by mass: 50 to 85 parts of thermoplastic plastic, 10 to 40 parts of plant fiber, and 5 to 10 parts of coupling agent; the porous material is a supercritical gas foaming material.

2. The composite material according to claim 1, characterized in that: The plant fiber is a plant fiber material treated with alkali solution; And / or, the thermoplastic plastic includes at least one of polypropylene compounds, polyethylene compounds, polystyrene compounds, polybutadiene compounds, polycarbonate compounds, and polyether compounds; And / or, the coupling agent includes maleic anhydride, silane coupling agent, and acrylic acid compound grafted polypropylene; And / or, the foaming gas in the supercritical gas foaming method includes at least one of nitrogen, argon, and carbon dioxide.

3. The composite material according to claim 1, characterized in that: The thermoplastic plastic includes polypropylene, and the polypropylene has a melt index of 10 to 30 g / 10 min measured at 230° C. and a load of 2.16 kg.

4. The composite material according to claim 1, characterized in that: The polymer film includes at least one of a polypropylene film, a polyethylene film, and a polybutadiene film; And / or, the polymer film has a thickness of 0.1 to 0.2 mm.

5. The composite material according to any one of claims 1 to 4, characterized in that: The composite material has at least one of the following characteristics: (a) Tensile strength of 35-38 MPa; (b) flexural strength of 50-55 MPa; (c) Impact strength is 7-8KJ / m 2 ; (d) Surface roughness ≤ 1 μm.

6. The method for preparing the composite material according to any one of claims 1 to 5, characterized in that: The following steps are involved: The raw materials for preparing the porous material are mixed and extruded into granules, and then injection-molded into a mold with a polymer film adsorbed on the inner surface. During the injection molding process, supercritical gas foaming is used for foaming to obtain the composite material.

7. The method for preparing a composite material according to claim 6, wherein: The mold with the polymer film adsorbed on the inner surface is prepared by a preparation method comprising the following steps: firstly subjecting the polymer film to corona treatment, and then allowing the polymer film to be electrostatically adsorbed on the inner surface of the mold.

8. The method for preparing a composite material according to claim 6, wherein: The extrusion temperature of the extrusion granulation step is 180-200°C.

9. The method for preparing a composite material according to claim 6, wherein: The temperature of the injection molding step is 180-195°C.

10. Use of the composite material according to any one of claims 1 to 5 in automobile interior decoration parts or electronic product housings.

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