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 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 the fields of aviation, construction, transportation, packaging, etc. This type of material mainly uses renewable plant fiber resources and is compounded with polypropylene to form a composite material that has both the natural advantages of plant fibers and the lightweight characteristics 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, and they are prone to cracking and peeling. At the same time, due to the limitations of the supercritical gas microporous foaming process, the apparent 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 application fields 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, especially the damp-heat aging environment will have a serious impact on the long-term performance of plant fiber reinforced foam composites, and 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 application of the composite material in automobile interior decoration 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 attached to the surface of the porous material; the porous material comprises the following raw materials in parts by weight: 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 includes 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 melt index of the polypropylene measured at 230° C. and a load of 2.16 kg is 10 to 30 g / 10 min.

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

[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 flexural strength of the composite material is 50-55 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, extruded and granulated, and then injection molded into a mold with a polymer film adsorbed on the inner surface. During the injection molding process, a supercritical gas foaming method 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 an extruder; the parameters of the extruder are set as follows: the head temperature is 183-187°C, the temperature of zone I is 188-192°C, the temperature of zone II is 193-197°C, the temperature of zone III is 193-197°C, the temperature of zone IV is 193-197°C, the feeder speed is 1-10rpm, and the 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 as follows: the temperature of zone one is 180-185°C, the temperature of zone two is 185-195°C, the temperature of zone three is 185-195°C, the temperature of zone four is 180-185°C, and the injection pressure is 65-75MPa; the 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 the use of the composite material described in the first aspect of the present invention in automobile interior decoration parts or electronic product housings.

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

[0029] In addition, the preparation method of the present invention effectively improves the problem of surface defects of products caused by microporous foaming molding process by pasting polymer film in the mold and then using supercritical gas foaming method for injection molding, ensuring the stability and consistency of product quality, and effectively improves the surface quality and performance of composite materials by using the excellent adhesion, wear resistance and aging resistance of polymer film. At the same time, the method is simple and easy to operate, does not require major changes to the original molding process, and has broad application prospects and market potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the preparation process of the plant fiber reinforced foam composite material in Example 1.

[0031] Figure 2 This is a schematic diagram of the structure 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 contour 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 is 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 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, the present invention provides a composite material, including a porous material and a polymer film attached to the surface of the porous material. The porous material includes the following raw materials in parts by weight: 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.

[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 value 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, 10 parts, or a range formed by any two of them.

[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 method for preparing the plant fiber is: mixing an alkali solution with the plant fiber material and then heating. In some embodiments of the present invention, the method for preparing the plant fiber is: mixing an alkali solution with the cleaned plant fiber material and then heating, then washing with water until the pH is neutral, and drying to obtain the obtained product.

[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 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 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, or 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 compound 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 value 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, 0.2 mm, or a range formed by any two of them.

[0055] In some embodiments of the present invention, the thickness ratio of the polymer membrane to the porous carrier is 1:(30-60); in some embodiments of the present invention, the thickness ratio of the polymer membrane to the porous carrier can be selected from any value among 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 them.

[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 testing standard for the flexural strength of the composite material is GB / T9341-2008, and the rate is 2 mm / min.

[0059] In some embodiments of the present invention, the impact strength of the composite material is 7-8 KJ / m 2 The test standard for the impact strength of composite materials: Izod beam impact test, in accordance with 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 value of the distance between adjacent wave 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 also 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, a supercritical gas foaming method is used for foaming to obtain a composite material.

[0063] The inventor innovatively adsorbed a layer of polymer film in the mold by electrostatic adsorption, and then used the supercritical gas foaming method to prepare the porous material during the injection molding process. When the mold is heated, the adhesion between the polymer film and the porous material substrate can be improved, and the morphology of the composite material surface can be improved to improve the surface defects of the microporous foamed molded products and improve the molding quality. At the same time, the polymer film can effectively delay the aging of the composite material and increase the service life of the composite material by blocking moisture.

[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, and then extruding and granulating, and drying to obtain a mixture A;

[0067] S2: Injecting the mixed material A into a mold with a polymer film adsorbed on the inner surface and foaming it using a supercritical gas foaming method during 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: firstly 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 by extruding an extruder; the parameters of the extruder are set as follows: the head temperature is 183-187°C, the temperature of zone I is 188-192°C, the temperature of zone II is 193-197°C, the temperature of zone III is 193-197°C, the temperature of zone IV is 193-197°C, the speed of the feeder is 1-10rpm, and the speed of the main machine is 1-10rpm.

[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: the temperature of zone 1 is 180-185° C., the temperature of zone 2 is 185-195° C., the temperature of zone 3 is 185-195° C., the temperature of zone 4 is 180-185° C., the injection pressure is 65-75 MPa; and the cooling time is 10-50 s.

[0071] In some embodiments of the present invention, the temperature of the mold is 80-100°C. In some embodiments of the present invention, a heating device is provided in the mold, and the heating device can heat the mold to make the temperature of the mold reach 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 fast during injection molding, which affects the mechanical properties of the injection molding material, and preheating the mold can make the polymer film and the porous material fit together better.

[0072] The specific implementation of the present invention is further described in detail below 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) Wash 4000g of bamboo fiber repeatedly with distilled water to remove dust and other impurities on the surface. Then, immerse all the washed fibers in a 1.32mol / L NaOH solution and heat them in a 60℃ water bath for 4 hours to dissolve impurities such as hemicellulose, gum, and wax in the fibers. Continue to wash the fibers with distilled water until the pH value of the washing water solution is neutral to obtain purified bamboo fibers. After drying, set aside.

[0076] (2) 3000 g of the dried plant fiber was crushed into granules with a length of 2 mm by a fiber crusher, i.e., the plant fiber material. 70 parts of polypropylene, 20 parts of the plant fiber material, and 10 parts of maleic anhydride grafted polypropylene were weighed by weight, and put into a high-speed mixer, stirred and mixed thoroughly, and cooled and discharged to prepare a premix.

[0077] (3) The premix is ​​added to a twin-screw extruder for extrusion granulation, and the particles are dried after extrusion granulation to obtain a premix masterbatch. The drying temperature is 120°C and the drying time is 8 hours. The parameters of the twin-screw extruder are 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 5rpm, and main engine speed 5.5rpm.

[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 closely attached to the inner surfaces of the upper and lower molds by electrostatic adsorption. Figure 2 As shown in the figure, the voltage is 10kv, the processing time is 0.5s, the frequency is 25kHz, the processing speed is 1m / min, and the thickness of the PP film is 0.1mm.

[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 films; 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 detail. Figure 2 shown.

[0080] (5) Place the premix masterbatch into the barrel of a twin-screw injection molding machine and perform supercritical fluid (N 2 ) foaming injection molding, after pressure relief and cooling, the plant fiber reinforced foam composite material in this example is obtained. The process parameters of the injection molding machine include: the temperature of zone 1 is 185°C, the temperature of zone 2 is 190°C, the temperature of zone 3 is 190°C, the temperature of zone 4 is 185°C; the injection pressure is 70MPa, the mold temperature is 90°C, and the cooling time is 30s.

[0081] like Figure 3 As shown in FIG. 1 , 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 shaping process, the polymer chains of the PP film and the matrix (i.e., Figure 3 The lines in the figure are entangled with each other and co-crystallized in the interface region to form polymer crystals (i.e. Figure 3 The purple block in the figure) makes the PP film and the substrate fit closely together. In addition, the injection molding process also produces excellent interface compatibility between the plant fiber and the polypropylene substrate; in addition, the PP film in the present invention can improve the surface properties of the substrate, making the substrate surface smooth and flat, without defects such as bubbles and wrinkles, significantly improving the aesthetics and comfort of the product; on the other hand, it can improve 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) Wash 4000g of bamboo fiber repeatedly with distilled water to remove dust and other impurities on the surface. Then, immerse all the washed fibers in a 1.32mol / L NaOH solution and heat them in a 60℃ water bath for 4 hours to dissolve impurities such as hemicellulose, gum, and wax in the fibers. Continue to wash the fibers with distilled water until the pH value of the washing water solution is neutral to obtain purified bamboo fibers. After drying, set aside.

[0085] (2) 3000 g of the dried plant fiber was crushed into 2 mm long particles by a fiber crusher to obtain a plant fiber material. 70 parts of polypropylene, 20 parts of the plant fiber material, and 10 parts of maleic anhydride grafted polypropylene were weighed by mass, put into 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 a 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 was 185°C, zone I temperature was 190°C, zone II temperature was 195°C, zone III temperature was 195°C, zone IV temperature was 195°C, feeder speed was 5 rpm, and main engine speed was 5.5 rpm.

[0087] (4) Place the premix masterbatch into the barrel of a twin-screw injection molding machine and perform supercritical fluid (N 2 ) foaming injection molding, after pressure relief and cooling, the plant fiber reinforced foam composite material in this example is obtained. The process parameters of the injection molding machine include: the temperature of zone 1 is 185°C, the temperature of zone 2 is 190°C, the temperature of zone 3 is 190°C, the temperature of zone 4 is 185°C; the injection pressure is 70MPa, the mold temperature is 90°C, and the cooling time is 30s.

[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, an optical profilometer was then used to characterize the surface of the plant fiber reinforced foam composite material in Example 1 and Comparative Example 1, respectively. Figure 6 and Figure 7 As shown. Figures 4 to 7 It can be seen that the present invention can significantly improve the surface morphology and quality of the plant fiber reinforced foam composite material by introducing the PP film and utilizing the excellent adhesion, wear resistance and anti-aging properties of the PP film, 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 induces the appearance of a large number of foaming micronuclei under the action of plant fibers, so that the pore size is reduced, the pore density is increased, and the mechanical properties can be improved.

[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 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 wave peaks on the overall surface, that is, the Ra value;

[0096] The test standard for the surface friction coefficient is GB / T 10006. The specific test method is as follows: under dry sliding conditions, the test is carried out using a room temperature friction and wear tester (HT-1000, Lanzhou Zhongke Kaihua Technology Co., Ltd. (Lanzhou, China)). The test load is 15N, the sliding radius is 5mm, the rotation speed is 700r / min, and the test time is 10min.

[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 can be seen from Table 1, the plant fiber reinforced foam composite material in 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, and 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 box. 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 can significantly improve the aging resistance of the composite material by compounding a layer of PP film on the surface of the material, and the tensile strength retention rate, bending strength retention rate, and impact strength retention rate in the aging resistance test are significantly higher than those of the composite material without the PP film in Comparative Example 1. In addition, the color difference change of the composite material of the present invention in the aging resistance test is smaller 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 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 to improve 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 composite material products. The PP film has good non-polarity, and it can be attached to the surface of the composite material to 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, which can maintain the environmental protection characteristics of the material in combination with the plant fiber reinforced foam composite material, and meets 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 surface of the mold, which reduces the production difficulty and cost, can achieve a fast and efficient laminating process, and improve production efficiency.

[0106] The above is a detailed description of the embodiments of the present invention, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. A composite material, characterized in that: It 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 weight: 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 melt index of the polypropylene measured at 230° C. and a load of 2.16 kg is 10 to 30 g / 10 min.

4. The composite material according to claim 1, characterized in that: The polymer film comprises 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 is 35-38 MPa; (b) flexural strength of 50 to 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, extruded and granulated, and then injection molded into a mold with a polymer film adsorbed on the inner surface. During the injection molding process, a supercritical gas foaming method is used for foaming to obtain the composite material.

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

9. The method for preparing a composite material according to claim 6, characterized in that: 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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