CN114621569B - Preparation method of high-strength bamboo fiber/polylactic acid weather-resistant type full-degradable composite material and composite material - Google Patents
Preparation method of high-strength bamboo fiber/polylactic acid weather-resistant type full-degradable composite material and composite material Download PDFInfo
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Abstract
The invention relates to a preparation method of a bamboo fiber/polylactic acid weather-resistant full-degradable composite material and the composite material, and belongs to the technical field of environment-friendly composite materials. The invention adopts a two-step melt blending process to prepare the modified bamboo fiber and the high-filling master batch thereof, and then obtains the composite material formed by directly melt blending the master batch and the polylactic acid, which can promote the uniform dispersion of the modified bamboo fiber, the compatilizer and the antioxidant in the polylactic acid matrix, and obtain the bamboo fiber high-filling master batch and the uniformly dispersed composite material with good dispersibility and processability. The method has the advantages of simple and convenient production process, easy mass production, wide and easily obtained natural fiber raw materials, low production cost, excellent composite material comprehensive performance and wide application prospect.
Description
Technical Field
The invention relates to a high-performance bamboo-plastic composite material reinforced by natural bamboo fibers and polylactic acid, in particular to a preparation method of a bamboo fiber/polylactic acid weather-resistant type full-degradable composite material and the composite material, and belongs to the technical field of environment-friendly composite materials.
Background
The traditional petroleum-based plastic is widely applied to various fields of industry and life, but after consumption, use and abandonment, the petroleum-based plastic becomes a large amount of solid waste due to nondegradability, namely 'white pollution', and causes huge environmental pollution and ecological damage. In order to solve the global problem, development of environment-friendly high polymer materials is urgently needed, so that research and development of degradable high polymer materials are focused and paid attention to. In recent twenty years, with the emphasis placed on research and production of degradable materials in academia and industry, several tens of industrialized varieties represented by polylactic acid (PLA) have been successfully developed.
In order to further reduce the PLA cost, improve the mechanical strength, expand the application range of the material, and simultaneously not damage the degradability of the PLA, the research and development of the natural fiber reinforced PLA composite material are promoted in recent years. Natural fibers with high mechanical properties, such as bamboo fibers, are widely available and low in cost, and show good environmental friendliness and sustainability, and are considered as excellent reinforcing phases for developing high-strength polylactic acid composite materials.
The Chinese patent application with the application number of CN201810096014.6 discloses a bamboo fiber/polylactic acid composite material and a preparation method thereof; the material comprises the following raw materials in parts by weight: 60 to 80 parts of polylactic acid, 10 to 30 parts of talcum powder, 3 to 15 parts of modified bamboo fiber, 2 to 15 parts of toughening agent, 0.1 to 0.3 part of coupling agent, 0.1 to 0.3 part of antioxidant, 0.2 to 0.6 part of auxiliary antioxidant, 0.2 to 0.5 part of lubricant, 0.2 to 1 part of nucleating agent, 0.1 to 0.3 part of anti-floating fiber agent and 0.5 to 3 parts of hydrolysis inhibitor. The composite material solves the problems of rough surface, silver wires, local black spots and poor compatibility of polylactic acid and bamboo fibers of the bamboo fiber/polylactic acid composite material product by modifying and heat treating the bamboo fibers, treating the bamboo fibers and talcum powder by using a coupling agent and according to a certain mixing sequence and proper extrusion process parameters. However, the interfacial compatibility with the polylactic acid matrix is still to be improved. This generally results in a composite material that is more hygroscopic, less dimensionally stable, and the product is prone to cracking. In addition, since natural fibers have high strength and high rigidity, the processability of the composite material is impaired to some extent, and it is difficult to process and form a composite material having a high filler content. Therefore, a specific modification of the bamboo fiber is needed to meet the application requirements of the bamboo fiber in reinforced polylactic acid composite materials.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and meet the requirements of wood-plastic, building and packaging industries on the high-strength weather-proof full-degradation composite material. The invention provides a preparation method of a high-strength bamboo fiber/polylactic acid weather-resistant full-degradable composite material.
The technical scheme for solving the problems is as follows:
a preparation method of a high-strength bamboo fiber/polylactic acid weather-resistant type full-degradable composite material comprises the following steps:
s1, preparing coupled modified bamboo fibers: uniformly stirring and dispersing the bamboo fiber and the coupling agent in a water-ethanol mixed solution, placing the mixture into a microwave reaction kettle for reaction, filtering and drying to obtain the coupling modified bamboo fiber; the reaction temperature in the microwave reaction kettle is 100-140 ℃ and the reaction time is 5-60 minutes;
s2, preparing high-filling master batches: placing the coupling modified bamboo fiber, polylactic acid, a compatilizer and an antioxidant into mixing equipment for melt blending to obtain coupling modified bamboo fiber high-filling polylactic acid master batch;
s3, preparing a bamboo fiber reinforced polylactic acid composite material: and mixing the coupling modified bamboo fiber high-filling polylactic acid master batch with polylactic acid, and placing the mixture into mixing equipment for melt blending to obtain the high-strength weather-proof full-degradable composite material.
In the technical scheme, the bamboo fibers are extracted from naturally grown bamboos; generally, the diameter of the bamboo fiber is 10-500 mu m, the length of the bamboo fiber is 0.1-5 mm, and the water content of the bamboo fiber is 2-9%.
As the preferable technical scheme, in the step S1, the coupling agent is a silane coupling agent, and the mass ratio of the silane coupling agent to the bamboo fiber is 1 (20-50).
As the preferable choice of the technical scheme, in the step S1, the coupling agent is at least one of octadecylamine coupling agent, isocyanate coupling agent, aluminate coupling agent and titanate coupling agent, and the mass ratio of the coupling agent to the bamboo fiber is 1 (40-100).
In the step S1, the mass ratio of water to ethanol is (1:9) - (9:1), and the mass ratio of bamboo fiber to water-ethanol mixed solution is (2:1) - (1:5).
As the optimization of the technical scheme, in the step S2, the melt blending equipment is one of a high-speed mixer, an open mill, a turnover internal mixer, a continuous internal mixer, a reciprocating screw extruder, a flat double screw extruder, a conical double screw extruder, a single screw extruder, a Z-type kneader, a screw kneader, a vacuum kneader and a horizontal double screw mixer, the melt blending temperature is 120-230 ℃, and the energy consumption per unit mass in the melt blending process is 0.1-2 kWh/kg.
As the preferable technical scheme, in the step S2, the mass fraction of the coupling modified bamboo fiber in the high-filling master batch is 20-90%.
In the step S2, the compatibilizer is preferably at least one of a maleic anhydride grafted polyolefin elastomer, a maleic anhydride grafted ethylene-methyl acrylate copolymer, a maleic anhydride grafted ethylene-ethyl acrylate copolymer, a maleic anhydride grafted ethylene-butyl acrylate copolymer, and glycidyl methacrylate, and the mass fraction of the compatibilizer in the high-filling master batch is 1-20%.
As the optimization of the technical scheme, in the step S2, the compatilizer is at least one of polyethylene glycol, epoxidized soybean oil, stearic acid, stearate, tetrabutyl titanate, reactive polyepoxy compatibilizer and acetyl tri-n-butyl citrate, and the mass fraction of the compatilizer in the high-filling master batch is 0.1-5%.
As the optimization of the technical scheme, in the step S2, the antioxidant is at least one of hindered amine antioxidants, hindered phenol antioxidants and phosphite antioxidants, and the mass fraction of the antioxidant in the high-filling master batch is 0.3-2%.
As the preferable technical scheme, in the step S3, the mass ratio of the high-filling master batch to the polylactic acid is (1:9) - (9:1).
As a preferable mode of the above technical scheme, in step S3, the melt blending apparatus is one of a high-speed mixer, an open mill, a roll-over internal mixer, a continuous internal mixer, a reciprocating screw extruder, a flat twin screw extruder, a conical twin screw extruder, a single screw extruder, a Z-type kneader, a screw kneader, a vacuum kneader and a horizontal twin screw mixer, the melt blending temperature is 120 ‒ ℃ and the energy consumption per unit mass in the melt blending process is 0.05 ‒ kWh/kg.
It is an object of the present invention to provide a composite material prepared by the above method.
The bamboo fiber reinforced polylactic acid composite material obtained by the preparation method has the tensile strength of more than 65 MPa, the bending strength of more than 107 MPa and the aging induction time of more than 45 min.
Specifically, the high-strength bamboo fiber/polylactic acid weather-resistant type full-degradable composite material provided by the invention consists of coupled modified bamboo fibers, polylactic acid, a compatilizer and an antioxidant; the coupling modified bamboo fiber is natural bamboo fiber modified by a coupling agent prepared by a microwave-assisted synthesis reaction; the coupling agent is at least one of silane coupling agent, octadecylamine coupling agent, isocyanate coupling agent, aluminate coupling agent and titanate coupling agent; the compatilizer is at least one of polyethylene glycol, epoxidized soybean oil, stearic acid, stearate, tetrabutyl titanate, reactive polyepoxy compatibilizer, acetyl tri-n-butyl citrate, maleic anhydride grafted polyolefin elastomer, maleic anhydride grafted ethylene-methyl acrylate copolymer, maleic anhydride grafted ethylene-ethyl acrylate copolymer, maleic anhydride grafted ethylene-butyl acrylate copolymer and glycidyl methacrylate; the antioxidant is at least one of hindered amine antioxidant, hindered phenol antioxidant and phosphite antioxidant. The tensile strength of the bamboo fiber reinforced polylactic acid fully-degradable composite material is more than 65 MPa, the bending strength is more than 107 MPa, and the aging induction time is more than 45 min.
In summary, the invention has the following beneficial effects:
(1) The invention is based on the technical route of microwave-assisted synthesis reaction, can efficiently promote the hydroxyl substitution reaction of various coupling agents on the surface of the bamboo fiber, realizes the coupling modification of the bamboo fiber, has mild reaction conditions, and uses only water and ethanol as environment-friendly solvents;
(2) According to the invention, through the coupling reaction of the fiber surface, a coupling agent modification layer is directly formed on the bamboo fiber surface, so that the affinity and interface bonding strength of the polylactic acid matrix are improved, and the aggregation among the bamboo fibers is inhibited;
(3) The invention adopts a two-step melt blending process, firstly prepares the modified bamboo fiber and the high-filling master batch thereof, and then obtains the composite material formed by directly melt blending the master batch and the polylactic acid, which can promote the uniform dispersion of the modified bamboo fiber, the compatilizer and the antioxidant in the polylactic acid matrix, and obtain the bamboo fiber high-filling master batch and the uniformly dispersed composite material with good dispersibility and processability;
(4) The composite material has the characteristics of high tensile strength, high impact strength, excellent weather resistance and the like, and the processing method reflects the characteristics of environmental protection, low cost and the like, thereby being beneficial to expanding the application and development of the natural fiber/polylactic acid composite material in the fields of high-performance structural materials, high-end functional materials and the like;
(5) The invention adopts the technical route of combining the microwave-assisted synthesis reaction and the mother granulating processing technology, promotes the modified bamboo fiber and the auxiliary agent to be uniformly dispersed in the polylactic acid matrix, obtains high interface bonding strength, and fully plays the unique functions of strengthening, resisting oxidation and resisting aging. The method has the advantages of simple and convenient production process, easy mass production, wide and easily obtained natural fiber raw materials, low production cost, excellent composite material comprehensive performance and wide application prospect.
Drawings
FIG. 1 is a flow chart of a preparation method of the weather-resistant full-degradable high-strength bamboo fiber/polylactic acid composite material;
fig. 2 is a digital photograph of natural bamboo fiber and microwave-assisted synthesis of coupled modified bamboo fiber in example 1 of the present invention.
Detailed Description
The invention is described in further detail below with reference to the accompanying drawings.
Example 1
As shown in fig. 1, the preparation method of the weather-resistant full-degradable high-strength bamboo fiber/polylactic acid composite material comprises the following steps:
s11, preparing a coupling modified bamboo fiber: 10g of bamboo fiber (manufactured by Guangdong wood flour processing factory, anhui, diameter 10 ‒ mu m, length 0.1 ‒ & lt 1 & gt mm, water content 2.5%) and 0.2g of silane coupling agent (model KH-550) are uniformly stirred and dispersed in 5g of water-ethanol (mass ratio 1:9) mixed solution, and then the mixed solution is placed into a microwave reaction kettle (Nanjing European instrument and equipment company) to react for 5 minutes at 140 ℃, and then filtered and dried to obtain 10.5g of coupled modified bamboo fiber;
s12, preparing high-filling master batches: sequentially carrying out melt blending on 20 parts of coupled modified bamboo fibers, 79.7 parts of polylactic acid, 0.1 part of compatilizer (epoxidized soybean oil) and 0.3 part of hindered phenol antioxidant (model 1098) by a high-speed mixer and a flat double-screw extruder, wherein the melt blending temperature is 150 ℃, and obtaining the coupled modified bamboo fiber high-filling polylactic acid master batch after the energy consumption per unit mass of the melt blending reaches 0.1 kWh/kg;
s13, preparing a bamboo fiber reinforced polylactic acid composite material: and mixing 90 parts of high-filling master batch and 10 parts of polylactic acid, and sequentially carrying out melt blending by a turnover internal mixer and a single screw extruder, wherein the melt blending temperature is 150 ℃, and after the energy consumption per unit mass of the melt blending reaches 0.05 kWh/kg, obtaining the high-strength weather-resistant full-degradable composite material.
Example 2
As shown in fig. 1, the preparation method of the weather-resistant full-degradable high-strength bamboo fiber/polylactic acid composite material comprises the following steps:
s21, preparing coupled modified bamboo fibers: 10g of bamboo fiber (manufactured by Guangdong wood flour processing factory, anhui, with the diameter of 400 ‒ mu m, the length of 2 ‒ mm and the water content of 8.9%) and 0.5g of silane coupling agent (model KH-560) are stirred and dispersed uniformly in 50g of water-ethanol (mass ratio of 9:1) mixed solution, and then the mixed solution is placed into a microwave reaction kettle (manufactured by Nanjing European instrument and equipment company) to react for 60 minutes at 100 ℃, and then filtered and dried to obtain 10.8g of coupled modified bamboo fiber;
s22, preparing high-filling master batches: carrying out melt blending on 90 parts of coupled modified bamboo fibers, 3 parts of polylactic acid, 5 parts of compatilizer (polyethylene glycol), 0.5 part of hindered phenol antioxidant (model 1010), 0.5 part of hindered phenol antioxidant (model 1076) and 1 part of phosphite antioxidant (model Irgamox B) sequentially by a high-speed mixer and a reverse internal mixer, wherein the melt blending temperature is 150 ℃, and obtaining the coupled modified bamboo fiber high-filling polylactic acid master batch after the unit mass energy consumption of the melt blending reaches 2 kWh/kg;
s23, preparing a bamboo fiber reinforced polylactic acid composite material: 10 parts of high-filling master batch and 90 parts of polylactic acid are mixed, melt blending is carried out by a conical double-screw extruder, the melt blending temperature is 150 ℃, and after the energy consumption per unit mass of the melt blending reaches 1 kWh/kg, the high-strength weather-proof full-degradable composite material is obtained.
Example 3
As shown in fig. 1, the preparation method of the weather-resistant full-degradable high-strength bamboo fiber/polylactic acid composite material comprises the following steps:
s31, preparing a coupling modified bamboo fiber: 100g of bamboo fiber (manufactured by Guangdong wood flour processing factory, anhui, with the diameter of 100 ‒ mu m, the length of 1 ‒ mm and the water content of 4.5%) and 1g of titanate coupling agent are stirred and dispersed uniformly in 200g of water-ethanol (mass ratio of 1:4), placed into a microwave reaction kettle (manufactured by Nanjing European instrument and equipment company), reacted for 10 minutes at 120 ℃, filtered and dried to obtain 104.2g of coupling modified bamboo fiber;
s32, preparing high-filling master batches: carrying out melt blending on 40 parts of coupling modified bamboo fiber, 57 parts of polylactic acid, 1 part of compatilizer (maleic anhydride grafted ethylene-methyl acrylate copolymer), 0.5 part of hindered phenol antioxidant (model 1010), 0.5 part of thioester antioxidant (model DLTP) and 1 part of phosphite antioxidant (model 168) sequentially through an open mill and a single screw extruder, wherein the melt blending temperature is 150 ℃, and obtaining coupling modified bamboo fiber high-filling polylactic acid master batch after the unit mass energy consumption of melt blending reaches 0.5 kWh/kg;
s33, preparing a bamboo fiber reinforced polylactic acid composite material: 50 parts of high-filling master batch and 50 parts of polylactic acid are mixed, melt blending is carried out by a flat double-screw extruder, the melt blending temperature is 180 ℃, and after the energy consumption per unit mass of the melt blending reaches 0.2 kWh/kg, the high-strength weather-proof full-degradable composite material is obtained.
Example 4
As shown in fig. 1, the preparation method of the weather-resistant full-degradable high-strength bamboo fiber/polylactic acid composite material comprises the following steps:
s41, preparing coupled modified bamboo fibers: mixing 1000g of bamboo fiber (manufactured by Guangdong wood flour processing plant with the diameter of 20-300 mu m, the length of 0.5-3 mm and the water content of 5.5%) and 25g of isocyanate coupling agent (model KH-25) in 1000g of water-ethanol (mass ratio of 3:1), uniformly stirring and dispersing, placing into a microwave reaction kettle (manufactured by Nanjing European instrument and equipment company), reacting for 30 minutes at 130 ℃, filtering and drying to obtain 1054.5g of coupled modified bamboo fiber;
s42, preparing high-filling master batches: sequentially carrying out melt blending on 50 parts of coupling modified bamboo fibers, 29 parts of polylactic acid, 20 parts of compatilizer (glycidyl methacrylate), 0.5 part of hindered phenol antioxidant (model 1024) and 0.5 part of thioester antioxidant (model DSTP) by a high-speed mixer and a flat double-screw extruder, wherein the melt blending temperature is 150 ‒ ℃ and after the energy consumption per unit mass of the melt blending reaches 0.8 kWh/kg, obtaining coupling modified bamboo fiber high-filling polylactic acid master batches;
s43, preparing a bamboo fiber reinforced polylactic acid composite material: and (3) mixing 70 parts of high-filling master batch and 30 parts of polylactic acid, sequentially carrying out melt blending by a high-speed mixer and a screw kneader, wherein the melt blending temperature is 150 ℃, and obtaining the high-strength weather-resistant full-degradable composite material after the energy consumption per unit mass of the melt blending reaches 0.9 kWh/kg.
Example 5
As shown in fig. 1, the preparation method of the weather-resistant full-degradable high-strength bamboo fiber/polylactic acid composite material comprises the following steps:
s51, preparing the coupled modified bamboo fiber: 1000g of bamboo fiber (manufactured by Guangdong wood flour processing factory, anhui, with the diameter of 80-500 mu m, the length of 1.5-4 mm and the water content of 6.5%) and 10g of aluminate coupling agent (model DL-411) are stirred and dispersed uniformly in 2000g of water-ethanol (mass ratio of 3:2), then the mixture is placed into a microwave reaction kettle (manufactured by Nanjing European instrument equipment company) to react for 30 minutes at 130 ℃, and then the mixture is filtered and dried to obtain 1062.3g of coupled modified bamboo fiber;
s52, preparing high-filling master batches: carrying out melt blending on 80 parts of coupling modified bamboo fibers, 13.5 parts of polylactic acid, 5 parts of compatilizer (reactive polyepoxy compatibilizer) and 1.5 parts of thioester antioxidant (model DSTP) sequentially through a vacuum kneader and a continuous internal mixer, wherein the melt blending temperature is 150 ℃, and obtaining coupling modified bamboo fiber high-filling polylactic acid master batch after the energy consumption per unit mass of melt blending reaches 0.3 kWh/kg;
s53, preparing a bamboo fiber reinforced polylactic acid composite material: mixing 30 parts of high-filling master batch and 70 parts of polylactic acid, sequentially carrying out melt blending by a high-speed mixer and a reciprocating screw extruder, wherein the melt blending temperature is 180 ℃, and obtaining the high-strength weather-proof full-degradable composite material after the energy consumption per unit mass of the melt blending reaches 0.4 kWh/kg.
Comparative example 1 (direct addition without modification of bamboo fiber)
The masterbatch and the composite material are basically prepared by adopting the method of the embodiment 1, except that the mineral micro powder is not modified in the embodiment, but 20 parts of bamboo fiber (with the diameter of 10-100 mu m, the length of 0.1-1 mm and the water content of 2.5%), 79.7 parts of polylactic acid, 0.1 part of compatilizer (epoxidized soybean oil) and 0.3 part of hindered phenol antioxidant (model 1098) are subjected to melt blending by a high-speed mixer and a flat double-screw extruder in sequence, the melt blending temperature is 150 ℃, and the coupled modified bamboo fiber high-filling polylactic acid masterbatch is obtained after the unit mass energy consumption of melt blending reaches 0.1 kWh/kg; and then uniformly stirring 90 parts of the obtained high-filling master batch and 10 parts of polylactic acid, sequentially carrying out melt blending by a turnover internal mixer and a single screw extruder, wherein the melt blending temperature is 150 ℃, and obtaining the composite material after the energy consumption per unit mass of the melt blending reaches 0.05 kWh/kg.
Comparative example 2 (preparation by conventional hydrothermal method without microwave assisted Synthesis reaction)
The method of the example 2 is basically adopted to prepare high-filling master batches and composite materials, except that the microwave-assisted synthesis reaction is not adopted in the example, but the conventional hydrothermal method is directly adopted to prepare the coupled modified bamboo fibers, namely 10g of bamboo fibers (manufactured by an Anhui Guangdong wood flour processing factory, the diameter of which is 400-500 mu m, the length of which is 2-5 mm, and the water content of which is 8.9%) and 0.5g of silane coupling agent (model KH-560) are stirred and dispersed uniformly in 50g of water-ethanol (mass ratio of 9:1) mixed liquid, and the mixed liquid is placed into a hydrothermal reaction kettle to react for 60 minutes at 100 ℃, and then filtered and dried to obtain 10.2g of modified bamboo fibers; sequentially carrying out melt blending on 90 parts of modified bamboo fibers, 3 parts of polylactic acid, 5 parts of compatilizer (polyethylene glycol), 0.5 part of hindered phenol antioxidant (model 1010), 0.5 part of hindered phenol antioxidant (model 1076) and 1 part of phosphite antioxidant (model Irgamox B) by a high-speed mixer and a roll-over internal mixer, wherein the melt blending temperature is 150 ℃, and obtaining modified bamboo fiber high-filling polylactic acid master batch after the energy consumption per unit mass of melt blending reaches 2 kWh/kg; 10 parts of high-filling master batch and 90 parts of polylactic acid are mixed, melt blending is carried out by a conical double-screw extruder, the melt blending temperature is 180 ℃, and after the energy consumption per unit mass of the melt blending reaches 1 kWh/kg, the composite material is obtained.
Comparative example 3 (direct one-step processing without two-step melt blending technique)
The method of example 3 is basically adopted to prepare the coupling modified bamboo fiber and the composite material, except that the two-step melt blending technology is not adopted in the example, but the direct one-step blending molding is adopted, namely, 20 parts of coupling modified bamboo fiber, 28.5 parts of polylactic acid, 0.5 part of compatilizer (maleic anhydride grafted ethylene-methyl acrylate copolymer), 0.25 part of hindered phenol antioxidant (model 1010), 0.25 part of thio ester antioxidant (model DLTP) and 0.5 part of phosphite antioxidant (model 168) are sequentially subjected to melt blending through an open mill and a single screw extruder, the melt blending temperature is 150 ℃, and the coupling modified bamboo fiber/polylactic acid composite material is obtained after the unit mass energy consumption of the melt blending reaches 0.5 kWh/kg.
Structural characterization and performance testing
Mechanical property test: the obtained composite material is subjected to injection molding (the molding temperature is 160-220 ℃) to obtain a tensile and impact spline, and the tensile property of the composite material is tested by using a universal stretcher (model 5900) of Instron company in the United states according to the tensile property test standard of plastics in ASTM D638-2003 of the American society for testing materials; according to ASTM D790-10, standard Test Methods for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating of the American society for testing and materialsFlexural performance testing criteria in Materials, the flexural performance of the composite Materials was tested using a universal tester (model 5848) from Instron, usa. At least 3 parallel test samples were secured for each group and the results averaged.
Oxidation Induction Time (OIT): the Oxidation Induction Time (OIT) refers to the initial time of thermal oxidative aging of the polymer material in the melting process, and the larger the value is, the higher the oxidation resistance of the material is. According to the performance test standard of LY/T2881-2017 of the national forestry agency (determination method of oxidation induction time and oxidation induction temperature of Wood-Plastic composite), the OIT of the composite is determined by using a differential scanning calorimeter (DSC, model New Discovery X3) of the American TA company to evaluate the thermo-oxidative stability of the composite. At least 5 replicates per group were tested and the results averaged.
Evaluation of Natural aging Properties: the composite was tested for flexural and tensile properties before and after aging under natural conditions according to ASTM D1435-13, standard Practice for Outdoor Weathering of Plastics of the American society for testing and materials. The aging place is the roof of an Anhui forest Taimu plastic group research and development center, and the aging time is 9 months (2021, 1 to 2021, 9 months). At least 5 replicates per group were tested and the results averaged.
TABLE 1 mechanical Properties of composite and OIT test results
TABLE 2 mechanical test results of composite materials after natural aging
Experimental results: table 1 compares the mechanical property test results of the bamboo fiber reinforced polylactic acid composite material, and the embodiment 1 ‒ has higher yield strength (68.4-97.2 MPa), elastic modulus (3328-4561 MPa), bending strength (101.3-128.7 MPa) and oxidation induction time (OIT, 45-55 min), and shows excellent comprehensive mechanical properties and outstanding oxidation resistance. However, the mechanical properties of comparative examples 1 to 3 are significantly reduced, for example, the yield strength of comparative example 1 is only 63.2 MPa (16% lower than that of example 1), the flexural strength of comparative example 2 is only 101.3 MPa (6% lower than that of example 2), and the elongation at break of comparative example 3 is only 4.7% (19% lower than that of example 3), so that the use as a structural material may be limited.
Also significant is that examples 1-5 all exhibited excellent oxidation resistance, with OIT values above 45 min. In particular, the OIT of example 5 reached 55min, approaching the test limit (60 min), and exhibited excellent oxidation resistance. However, the OITs of comparative example 1 directly added with unmodified bamboo fibers and comparative example 2 added with hydrothermally modified bamboo fibers were only 13min and 15min, respectively, demonstrating that the coupled modified bamboo fibers synthesized with microwave assistance have better structural stability. The OIT of comparative example 3 which is not melt blended by the two-step method is only 22min, which shows that the two-step melt blending technical route improves the bonding strength of the bamboo fiber-polylactic acid interface, thereby remarkably improving the oxidation resistance of the composite material.
Table 2 compares the mechanical property test results of the composite material after natural aging with the performance degradation rate before and after aging, examples 1 to 5 show excellent weather resistance, after the composite material is subjected to natural aging for 9 months, the yield strength and the bending strength are maintained at higher levels, the strength degradation rate is not more than 25%, and most of the degradation rate is concentrated in a 10-15% interval. In sharp contrast, the strength reduction ratio of comparative examples 1 to 3 was substantially 50% or more, wherein the yield strength of comparative example 1 was reduced even by 62%, and the performance basis for use as a structural material was substantially lost.
Therefore, the technical scheme provided by the patent enables the affinity of the natural bamboo fiber to the polylactic acid matrix, and the mechanical property, the oxidation resistance and the weather resistance of the composite material to be obviously improved, and the natural bamboo fiber is likely to benefit from: (1) Under the condition of microwave-assisted synthesis reaction, the coupling agent effectively coats the bamboo fiber, so that the affinity of the surface of the filler is improved, the interaction between the filler and a matrix is effectively improved, the dispersibility and the interface bonding strength of the coupling modified bamboo fiber in a high polymer matrix are improved, and the mechanical property of the composite material is greatly improved; (2) The dense coupling agent layer can effectively resist permeation and erosion of oxygen and free radicals, so that the oxidation or aging process of the composite material is effectively delayed; (3) The two-step melt blending technical route promotes the uniform dispersion of the bamboo fibers and the auxiliary agent in the polylactic acid matrix to form a perfect reinforcing network, and endows the composite material with good reinforcing effect and structural uniformity.
The foregoing is merely a preferred embodiment of the invention, and it should be noted that modifications could be made by those skilled in the art without departing from the principles of the invention, which modifications would also be considered to be within the scope of the invention.
Claims (10)
1. A preparation method of a high-strength bamboo fiber/polylactic acid weather-resistant type full-degradable composite material comprises the following steps:
s1, preparing coupled modified bamboo fibers: uniformly stirring and dispersing the bamboo fiber and the coupling agent in a water-ethanol mixed solution, placing the mixture into a microwave reaction kettle for reaction, filtering and drying to obtain the coupling modified bamboo fiber; the reaction temperature in the microwave reaction kettle is 100-140 ℃ and the reaction time is 5-60 minutes;
s2, preparing high-filling master batches: placing the coupling modified bamboo fiber, polylactic acid, a compatilizer and an antioxidant into mixing equipment for melt blending to obtain coupling modified bamboo fiber high-filling polylactic acid master batch;
s3, preparing a bamboo fiber reinforced polylactic acid composite material: and mixing the coupling modified bamboo fiber high-filling polylactic acid master batch with polylactic acid, and placing the mixture into mixing equipment for melt blending to obtain the high-strength weather-proof full-degradable composite material.
2. The method of manufacturing according to claim 1, characterized in that: in the step S1, the coupling agent is a silane coupling agent, and the mass ratio of the silane coupling agent to the bamboo fiber is 1 (20-50).
3. The method of manufacturing according to claim 1, characterized in that: in the step S1, the coupling agent is at least one of octadecylamine coupling agent, isocyanate coupling agent, aluminate coupling agent and titanate coupling agent, and the mass ratio of the coupling agent to the bamboo fiber is 1 (40-100).
4. The method of manufacturing according to claim 1, characterized in that: in the step S1, the mass ratio of water to ethanol is (1:9) - (9:1), and the mass ratio of bamboo fiber to water-ethanol mixed solution is (2:1) - (1:5).
5. The method of manufacturing according to claim 1, characterized in that: in the step S2, the mass fraction of the coupling modified bamboo fiber in the high-filling master batch is 20-90%.
6. The method of manufacturing according to claim 1, characterized in that: in the step S2, the compatilizer is at least one of maleic anhydride grafted polyolefin elastomer, maleic anhydride grafted ethylene-methyl acrylate copolymer, maleic anhydride grafted ethylene-ethyl acrylate copolymer, maleic anhydride grafted ethylene-butyl acrylate copolymer and glycidyl methacrylate, and the mass fraction of the compatilizer in the high-filling master batch is 1-20%.
7. The method of manufacturing according to claim 1, characterized in that: in the step S2, the compatilizer is at least one of polyethylene glycol, epoxidized soybean oil, stearic acid, stearate, tetrabutyl titanate, reactive polyepoxy compatibilizer and acetyl tri-n-butyl citrate, and the mass fraction of the compatilizer in the high-filling master batch is 0.1-5%.
8. The method of manufacturing according to claim 1, characterized in that: in the step S2, the antioxidant is at least one of hindered amine antioxidants, hindered phenol antioxidants and phosphite antioxidants, and the mass fraction of the antioxidant in the high-filling master batch is 0.3-2%.
9. The method of manufacturing according to claim 1, characterized in that: in the step S3, the mass ratio of the high-filling master batch to the polylactic acid is (1:9) - (9:1).
10. The bamboo fiber reinforced polylactic acid composite material obtained by the preparation method according to any one of claims 1 to 9, which is characterized in that: the tensile strength of the composite material is more than 65 MPa, the bending strength is more than 107 MPa, and the aging induction time is more than 45 min.
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| CN103044839A (en) * | 2012-12-24 | 2013-04-17 | 安徽科聚新材料有限公司 | Polylactic acid composite material and preparation method thereof |
| CN108948395A (en) * | 2018-06-07 | 2018-12-07 | 安徽宏润工艺品有限公司 | A kind of preparation method with the nano-titanium dioxide modified bamboo base-polycaprolactone composite sheet of nano silica- |
| CN112226057A (en) * | 2020-11-04 | 2021-01-15 | 中国矿业大学 | Natural mineral modified degradable high-molecular flame-retardant composite material and preparation method thereof |
| CN112266592A (en) * | 2020-11-04 | 2021-01-26 | 中国矿业大学 | High-conductivity nano-mineral modified fully-degradable polymer composite material and preparation method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103044839A (en) * | 2012-12-24 | 2013-04-17 | 安徽科聚新材料有限公司 | Polylactic acid composite material and preparation method thereof |
| CN108948395A (en) * | 2018-06-07 | 2018-12-07 | 安徽宏润工艺品有限公司 | A kind of preparation method with the nano-titanium dioxide modified bamboo base-polycaprolactone composite sheet of nano silica- |
| CN112226057A (en) * | 2020-11-04 | 2021-01-15 | 中国矿业大学 | Natural mineral modified degradable high-molecular flame-retardant composite material and preparation method thereof |
| CN112266592A (en) * | 2020-11-04 | 2021-01-26 | 中国矿业大学 | High-conductivity nano-mineral modified fully-degradable polymer composite material and preparation method thereof |
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