CN114621569A - Preparation method of high-strength bamboo fiber/polylactic acid weather-resistant fully-degradable composite material and composite material - Google Patents
Preparation method of high-strength bamboo fiber/polylactic acid weather-resistant fully-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 fully-degradable composite material and the composite material, belonging to the technical field of environment-friendly composite materials. 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 a polylactic acid matrix and obtain the high-filling master batch of the bamboo fiber and the uniformly dispersed composite material with good dispersibility and processability. The method has the advantages of simple production process, easy large-scale production, wide and easily-obtained natural fiber raw materials, low production cost, excellent comprehensive performance of the composite material and wide application prospect.
Description
Technical Field
The invention relates to a high-performance bamboo-plastic composite material of polylactic acid reinforced by natural bamboo fiber, in particular to a preparation method of a weather-resistant fully-degradable bamboo fiber/polylactic acid composite material and the composite material, belonging to the technical field of environment-friendly composite materials.
Background
The traditional petroleum-based plastics are widely applied to various fields of industry and life, but become a great deal of solid waste due to nondegradable property after consumption, use and abandonment, namely, white pollution, and cause huge environmental pollution and ecological damage. In order to solve the global problem, the development of environment-friendly polymer materials is urgently needed, so that the research and development of degradable polymer materials draw extensive attention and attention. In the last two decades, with the emphasis on research and production of degradable materials in academic and industrial circles, dozens of industrial varieties represented by polylactic acid (PLA) have been successfully developed.
In order to further reduce the cost of PLA, improve the mechanical strength, expand the application range of materials and simultaneously not damage the degradability of PLA, researches and developments of natural fiber reinforced PLA composite materials are started in recent years. Natural fibers with high mechanical properties, such as bamboo fibers, are wide in source and low in cost, reflect good environmental friendliness and sustainability, and are considered to be excellent reinforcement phases for developing high-strength polylactic acid composite materials.
For example, 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 feed comprises the following raw materials in parts by weight: 60-80 parts of polylactic acid, 10-30 parts of talcum powder, 3-15 parts of modified bamboo fiber, 2-15 parts of toughening agent, 0.1-0.3 part of coupling agent, 0.1-0.3 part of antioxidant, 0.2-0.6 part of auxiliary antioxidant, 0.2-0.5 part of lubricant, 0.2-1 part of nucleating agent, 0.1-0.3 part of anti-floating fiber agent and 0.5-3 parts of anti-hydrolysis agent. The composite material solves the problems of rough surface, silver wire, local black spots and poor compatibility of polylactic acid and bamboo fiber of a bamboo fiber/polylactic acid composite material product by modifying and thermally treating the bamboo fiber, treating the bamboo fiber and talcum powder by using a coupling agent and mixing the bamboo fiber and the talcum powder according to a certain material mixing sequence and proper extrusion process parameters. However, the interfacial compatibility with the polylactic acid matrix still remains to be improved. This often results in composites that are more hygroscopic, less dimensionally stable, and products that are prone to cracking. In addition, since natural fibers have high strength and high rigidity, processability of the composite material is impaired to some extent, and it is difficult to process and mold a composite material having a high filling content. Therefore, the bamboo fiber needs to be modified in a targeted manner so as to meet the application requirements of the bamboo fiber in the reinforced polylactic acid composite material.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and meet the requirements of the industries of wood plastic, building and packaging on high-strength weather-resistant fully-degradable composite materials. The invention provides a preparation method of a high-strength bamboo fiber/polylactic acid weather-resistant fully-degradable composite material, which uniformly introduces coupling modified bamboo fibers into a polylactic acid matrix through two-step melt blending, thereby synchronously improving the mechanical property and the weather resistance of the fully-degradable polylactic acid 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 fully-degradable composite material comprises the following steps:
s1, preparing coupling modified bamboo fibers: uniformly stirring and dispersing the bamboo fiber and the coupling agent in a water-ethanol mixed solution, putting the mixture into a microwave reaction kettle for reaction, filtering and drying to obtain coupled modified bamboo fiber; the reaction temperature in the microwave reaction kettle is 100-140 ℃, and the reaction time is 5-60 minutes;
s2, preparing the high-filling master batch: putting the coupled modified bamboo fiber, polylactic acid, a compatilizer and an antioxidant into mixing equipment for melt blending to obtain a coupled modified bamboo fiber high-filling polylactic acid master batch;
s3, preparing the bamboo fiber reinforced polylactic acid composite material: and mixing the coupled modified bamboo fiber high-filling polylactic acid master batch with polylactic acid, and putting the mixture into mixing equipment for melt blending to obtain the high-strength weather-resistant fully-degradable composite material.
In the technical scheme of the invention, the bamboo fiber is extracted from naturally growing 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%.
Preferably, in 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).
Preferably, in the step S1, the coupling agent is at least one of an octadecylamine coupling agent, an isocyanate coupling agent, an aluminate coupling agent and a titanate coupling agent, and the mass ratio of the coupling agent to the bamboo fiber is 1 (40-100).
In the above technical solution, in step S1, the mass ratio of water to ethanol is (1: 9) - (9: 1), and the mass ratio of the bamboo fiber to the water-ethanol mixture is (2: 1) - (1: 5).
Preferably, in step S2, the melt blending device is one of a high-speed mixer, an open mill, a turnover 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 to 230 ℃, and the energy consumption per unit mass in the melt blending process is 0.1 to 2 kWh/kg.
Preferably, in step S2, the mass fraction of the coupled modified bamboo fiber in the highly filled masterbatch is 20 to 90%.
Preferably, in step S2, the compatibilizer is 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 highly filled masterbatch is 1 to 20%.
Preferably, in step S2, the compatibilizer is at least one of polyethylene glycol, epoxidized soybean oil, stearic acid, stearate, tetrabutyl titanate, a reactive polyepoxy compatibilizer, and tributyl acetylcitrate, and the mass fraction of the compatibilizer in the highly filled masterbatch is 0.1 to 5%.
Preferably, in step S2, the antioxidant is at least one of hindered amine antioxidant, hindered phenol antioxidant and phosphite antioxidant, and the mass fraction of the antioxidant in the highly filled masterbatch is 0.3-2%.
Preferably, in step S3, the mass ratio of the highly filled masterbatch to the polylactic acid is (1: 9) - (9: 1).
Preferably, in step S3, the melt blending device is one of a high-speed mixer, an open mill, a roll-over type 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 ‒ 230 ℃, and the energy consumption per unit mass in the melt blending process is 0.05 ‒ 1 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 fully-degradable composite material provided by the invention comprises coupled modified bamboo fiber, polylactic acid, a compatilizer and an antioxidant; the coupling modified bamboo fiber is natural bamboo fiber modified by a coupling agent prepared by microwave-assisted synthesis reaction; the coupling agent is at least one of silane coupling agent, octadecyl amine 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 tributyl 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 conclusion, the invention has the following beneficial effects:
(1) the method is based on the technical route of microwave-assisted synthesis reaction, can efficiently promote hydroxyl substitution reaction of various coupling agents on the surface of the bamboo fiber, realizes coupling modification of the bamboo fiber, has mild reaction conditions, and only uses water and ethanol as environment-friendly solvents;
(2) according to the invention, through the coupling reaction on the surface of the fiber, a coupling agent modification layer is directly formed on the surface of the bamboo fiber, so that the affinity and the interface bonding strength to a polylactic acid matrix are improved, and the agglomeration 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 high-filling master batch of the bamboo fiber 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, and is favorable for 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 a technical route of combining microwave-assisted synthesis reaction with masterbatching processing technology, promotes the modified bamboo fiber and the auxiliary agent to be uniformly dispersed in a polylactic acid matrix and obtains high interface bonding strength, and fully exerts the unique functions of reinforcement, oxidation resistance and aging resistance. The method has the advantages of simple production process, easy large-scale production, wide and easily-obtained natural fiber raw materials, low production cost, excellent comprehensive performance of the composite material and wide application prospect.
Drawings
FIG. 1 is a flow chart of a preparation method of the high-strength bamboo fiber/polylactic acid weather-resistant fully-degradable composite material;
fig. 2 is a digital photograph of the natural bamboo fiber and the microwave-assisted synthetic coupled modified bamboo fiber in example 1 of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
Example 1
As shown in fig. 1, a preparation method of a high-strength bamboo fiber/polylactic acid weather-resistant full-degradable composite material comprises the following steps:
s11, preparing coupling modified bamboo fibers: mixing 10g of bamboo fiber (diameter 10 ‒ 100 mu m, length 0.1 ‒ 1 mm, water content 2.5%) and 0.2g of silane coupling agent (type KH-550) in 5g of water-ethanol (mass ratio 1: 9) mixed solution, stirring and dispersing uniformly, placing the mixture into a microwave reaction kettle (Nanjing Europe-first apparatus company), reacting for 5 minutes at 140 ℃, filtering and drying to obtain 10.5g of coupled modified bamboo fiber;
s12, preparing the high-filling master batch: sequentially carrying out melt blending on 20 parts of coupled modified bamboo fiber, 79.7 parts of polylactic acid, 0.1 part of compatilizer (epoxidized soybean oil) and 0.3 part of hindered phenol antioxidant (model 1098) through a high-speed mixer and a flat double-screw extruder, wherein the melt blending temperature is 150 ℃, and obtaining a coupled modified bamboo fiber high-filling polylactic acid master batch after the unit mass energy consumption of the melt blending reaches 0.1 kWh/kg;
s13, preparing the bamboo fiber reinforced polylactic acid composite material: and (3) mixing 90 parts of the high-filling master batch and 10 parts of polylactic acid, and then carrying out melt blending by using 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 fully-degradable composite material.
Example 2
As shown in fig. 1, a preparation method of a high-strength bamboo fiber/polylactic acid weather-resistant fully-degradable composite material comprises the following steps:
s21, preparing coupling modified bamboo fibers: mixing 10g of bamboo fiber (diameter 400 ‒ 500 mu m, length 2 ‒ 5mm, water content 8.9%) and 0.5g of silane coupling agent (type KH-560) in 50g of water-ethanol (mass ratio 9: 1) mixed solution, stirring and dispersing uniformly, placing the mixture into a microwave reaction kettle (Nanjing Europe-first apparatus company), reacting at 100 ℃ for 60 minutes, filtering and drying to obtain 10.8g of coupled modified bamboo fiber;
s22, preparing the high-filling master batch: sequentially carrying out melt blending on 90 parts of coupled modified bamboo fiber, 3 parts of polylactic acid, 5 parts of compatilizer (polyethylene glycol), 0.5 part of hindered phenol antioxidant (type 1010), 0.5 part of hindered phenol antioxidant (type 1076) and 1 part of phosphite antioxidant (type Irgamox B) by using a high-speed mixer and an overturning internal mixer, wherein the melt blending temperature is 150 ℃, and obtaining coupled modified bamboo fiber high-filled polylactic acid master batch after the energy consumption per unit mass of the melt blending reaches 2 kWh/kg;
s23, preparing the bamboo fiber reinforced polylactic acid composite material: mixing 10 parts of high-filling master batch and 90 parts of polylactic acid, and carrying out melt blending by a conical double-screw extruder at the temperature of 150 ℃, so as to obtain the high-strength weather-resistant fully-degradable composite material after the energy consumption per unit mass of the melt blending reaches 1 kWh/kg.
Example 3
As shown in fig. 1, a preparation method of a high-strength bamboo fiber/polylactic acid weather-resistant fully-degradable composite material comprises the following steps:
s31, preparing coupling modified bamboo fibers: 100g of bamboo fiber (a processing plant of Anhui Guangdong Xinglong wood flour, the diameter is 100 ‒ 400 mu m, the length is 1 ‒ 3mm, the water content is 4.5%) and 1g of titanate coupling agent are uniformly stirred and dispersed in 200g of water-ethanol (mass ratio is 1: 4) mixed solution, the mixed solution is placed into a microwave reaction kettle (Nanjing Xiou instrument and equipment company) to react for 10 minutes at 120 ℃, and the mixed solution is filtered and dried to obtain 104.2g of coupled modified bamboo fiber;
s32, preparing the high-filling master batch: carrying out melt blending on 40 parts of coupled 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) by an open mill and a single screw extruder in sequence, wherein the melt blending temperature is 150 ℃, and obtaining coupled modified bamboo fiber high-filling polylactic acid master batch after the unit mass energy consumption of the melt blending reaches 0.5 kWh/kg;
s33, preparing the bamboo fiber reinforced polylactic acid composite material: and (3) mixing 50 parts of the high-filling master batch and 50 parts of polylactic acid, and carrying out melt blending by a flat double-screw extruder at the melt blending temperature of 180 ℃, so as to obtain the high-strength weather-resistant fully-degradable composite material after the energy consumption per unit mass of the melt blending reaches 0.2 kWh/kg.
Example 4
As shown in fig. 1, a preparation method of a high-strength bamboo fiber/polylactic acid weather-resistant fully-degradable composite material comprises the following steps:
s41, preparing coupling modified bamboo fibers: mixing 1000g of bamboo fiber (diameter of 20-300 mu m, length of 0.5-3 mm, water content of 5.5%) and 25g of isocyanate coupling agent (type KH-25) in 1000g of water-ethanol (mass ratio of 3: 1) mixed solution, uniformly stirring and dispersing the mixture in a microwave reaction kettle (Nanjing Europe-first instrument and equipment company), reacting at 130 ℃ for 30 minutes, filtering and drying to obtain 1054.5g of coupled modified bamboo fiber;
s42, preparing the high-filling master batch: carrying out melt blending on 50 parts of coupled modified bamboo fiber, 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) through a high-speed mixer and a flat double-screw extruder in sequence, wherein the melt blending temperature is 150 ‒ 200 ℃, and after the energy consumption per unit mass of the melt blending reaches 0.8 kWh/kg, obtaining coupled modified bamboo fiber high-filling polylactic acid master batch;
s43, preparing the bamboo fiber reinforced polylactic acid composite material: and (3) mixing 70 parts of the high-filling master batch and 30 parts of polylactic acid, and carrying out melt blending by a high-speed mixer and a screw kneading machine in sequence, wherein the melt blending temperature is 150 ℃, and the high-strength weather-resistant fully-degradable composite material is obtained after the energy consumption per unit mass of the melt blending reaches 0.9 kWh/kg.
Example 5
As shown in fig. 1, a preparation method of a high-strength bamboo fiber/polylactic acid weather-resistant fully-degradable composite material comprises the following steps:
s51, preparing coupling modified bamboo fibers: mixing 1000g of bamboo fiber (diameter of 80-500 mu m, length of 1.5-4 mm, water content of 6.5%) and 10g of aluminate coupling agent (model DL-411) in 2000g of water-ethanol (mass ratio of 3: 2) mixed solution, uniformly stirring and dispersing the mixture in a microwave reaction kettle (Nanjing Europe-first instrument and equipment company), reacting for 30 minutes at 130 ℃, filtering and drying to obtain 1062.3g of coupled modified bamboo fiber;
s52, preparing the high-filling master batch: melting and blending 80 parts of coupled modified bamboo fiber, 13.5 parts of polylactic acid, 5 parts of compatilizer (reactive multi-epoxy compatibilizer) and 1.5 parts of thioester antioxidant (model DSTP) by a vacuum kneader and a continuous internal mixer in sequence, wherein the melting and blending temperature is 150 ℃, and after the energy consumption per unit mass of the melting and blending reaches 0.3kWh/kg, the coupled modified bamboo fiber high-filling polylactic acid master batch is obtained;
s53, preparing the bamboo fiber reinforced polylactic acid composite material: and (3) mixing 30 parts of the high-filling master batch and 70 parts of polylactic acid, and then carrying out melt blending by a high-speed mixer and a reciprocating screw extruder at the temperature of 180 ℃ to obtain the high-strength weather-resistant fully-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)
Basically, the method of example 1 is adopted to prepare master batches and composite materials, except that in the example, no modification is carried out on mineral micro powder, 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 after the unit mass energy consumption of the melt blending reaches 0.1 kWh/kg, the coupled modified bamboo fiber high-filling polylactic acid master batches are obtained; and then uniformly stirring 90 parts of the obtained high-filling master batch and 10 parts of polylactic acid, and carrying out melt blending by using a turnover internal mixer and a single-screw extruder in sequence, wherein the melt blending temperature is 150 ℃, and after the energy consumption per unit mass of the melt blending reaches 0.05 kWh/kg, the composite material is obtained.
Comparative example 2 (conventional hydrothermal preparation without microwave-assisted Synthesis reaction)
Basically, the method of example 2 is adopted to prepare the high-filling master batch and the composite material, except that the microwave-assisted synthesis reaction is not adopted in the example, and the coupling modified bamboo fiber is directly prepared by adopting a conventional hydrothermal method, namely, 10g of bamboo fiber (a processing plant of Guangdong Xinglong wood flour of Anhui province, the diameter is 400-500 mu m, the length is 2-5 mm, the water content is 8.9%) and 0.5g of silane coupling agent (type KH-560) are uniformly stirred and dispersed in 50g of water-ethanol (mass ratio is 9: 1) mixed solution, the mixture is placed into a hydrothermal reaction kettle, the mixture is reacted for 60 minutes at 100 ℃, and the mixture is filtered and dried to obtain 10.2g of modified bamboo fiber; sequentially carrying out melt blending on 90 parts of modified bamboo fiber, 3 parts of polylactic acid, 5 parts of compatilizer (polyethylene glycol), 0.5 part of hindered phenol antioxidant (type 1010), 0.5 part of hindered phenol antioxidant (type 1076) and 1 part of phosphite antioxidant (type Irgamox B) by a high-speed mixer and a turnover internal mixer at the temperature of 150 ℃, and obtaining modified bamboo fiber high-filling polylactic acid master batch after the energy consumption per unit mass of the melt blending reaches 2 kWh/kg; mixing 10 parts of high-filling master batch and 90 parts of polylactic acid, and carrying out melt blending by a conical double-screw extruder at the temperature of 180 ℃, so as to obtain the composite material after the energy consumption per unit mass of the melt blending reaches 1 kWh/kg.
Comparative example 3 (direct one-step processing without two-step melt blending technique)
Basically, the method of example 3 is adopted to prepare the coupled modified bamboo fiber and the composite material, except that the example does not adopt a two-step melt blending technology, but directly adopts a one-step method to blend and form, namely, 20 parts of the coupled 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 thioester 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 coupled 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: obtaining tensile and impact sample bars by injection molding of the obtained composite material (the molding temperature is 160-220 ℃), and testing the tensile property of the composite material by using a universal drawing machine (model 5900) of Instron corporation in America according to the tensile property test standard of plastics in ASTM D638-2003 of American society for testing materials; the Flexural Properties of the composites were tested using a universal tester (model 5848) from Instron, USA, according to the Flexural Properties Test Standard ASTM D790-10, Standard Test Methods for Flexible Properties of Unreinforced and Reinforced Plastics and electric Insulating Materials, the American society for testing Materials. At least 3 parallel test specimens were guaranteed per group and the results were averaged.
Oxidative Induction Time (OIT): the Oxidation Induction Time (OIT) refers to the initial time of thermo-oxidative aging of a polymer material in a melting process, and the higher the value of the OIT, the higher the oxidation resistance of the material is. According to performance test standards in LY/T2881 and 2017 determination method for oxidation induction time and oxidation induction temperature of wood-plastic composite material of national forestry administration, the OIT of the composite material is determined by using a differential scanning calorimeter (DSC, model number New Discovery X3) of the American TA company so as to evaluate the thermo-oxidative stability of the composite material. At least 5 replicates of each group were tested and the results averaged.
Evaluation of Natural aging Properties: the flexural and tensile properties of the composites were tested before and after aging under natural conditions according to ASTM D1435-13 Standard Practice for exterior weather of Plastics, American society for testing and materials. The aging place is the roof of the Anhui Sentai wood-plastic group research and development center, and the time is 9 months (1 month in 2021 to 9 months in 2021). At least 5 replicates of each group were tested and the results averaged.
TABLE 1 mechanical Properties and OIT test results of the composites
TABLE 2 mechanical property test results of the composites after natural aging
The experimental results are as follows: table 1 compares the mechanical property test results of the bamboo fiber reinforced polylactic acid composite material, and examples 1 ‒ 5 all have high 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), represent excellent comprehensive mechanical properties, and have 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% reduction compared to example 1), the bending strength of comparative example 2 is only 101.3 MPa (6% reduction compared to example 2), and the elongation at break of comparative example 3 is only 4.7% (19% reduction compared to example 3), so that the use of the composite material as a structural material may be limited.
Also significant is that the examples 1-5 all show excellent antioxidant performance, and the OIT values are all above 45 min. In particular, OIT of example 5 reached 55min, approaching the test limit (60 min), representing excellent antioxidant performance. However, OITs of comparative example 1 in which unmodified bamboo fibers were directly added and comparative example 2 in which hydrothermal modified bamboo fibers were added were only 13min and 15min, respectively, indicating that the coupled modified bamboo fibers synthesized by microwave-assisted synthesis had better structural stability. The OIT of the comparative example 3 which does not adopt the two-step melt blending 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 obviously improving the oxidation resistance of the composite material.
Table 2 compares the mechanical property test result of the composite material after natural aging and the property reduction rate before and after aging, examples 1 to 5 all show excellent weather resistance, after the composite material undergoes natural aging for 9 months, the yield strength and the bending strength are maintained at higher levels, the strength reduction rate is not more than 25%, and most of the strength reduction rates are concentrated in the range of 10 to 15%. In sharp contrast, the strength reduction rate of comparative examples 1 to 3 is substantially more than 50%, wherein the yield strength of comparative example 1 is even reduced by 62%, and the performance basis for use as a structural material is 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 can possibly benefit from the following characteristics: (1) under the condition of microwave-assisted synthesis reaction, the affinity of the surface of the filler is improved after the bamboo fiber is effectively coated by the coupling agent, the interaction between the filler and the matrix is effectively improved, the dispersibility and the interface bonding strength of the coupled modified bamboo fiber in a polymer matrix are effectively improved, and the mechanical property of the composite material is greatly improved; (2) the compact coupling agent layer can effectively resist the penetration and the erosion of oxygen and free radicals, thereby effectively delaying the oxidation or the aging process of the composite material; (3) the two-step melt blending technical route promotes the bamboo fibers and the auxiliary agent to be uniformly dispersed in the polylactic acid matrix to form a relatively perfect reinforcing network, and endows the composite material with good reinforcing effect and structural uniformity.
The foregoing is only a preferred embodiment of this invention and it should be noted that modifications can be made by those skilled in the art without departing from the principle of the invention and these modifications should also be considered as the protection scope of the invention.
Claims (10)
1. A preparation method of a high-strength bamboo fiber/polylactic acid weather-resistant fully-degradable composite material comprises the following steps:
s1, preparing coupling modified bamboo fibers: uniformly stirring and dispersing the bamboo fiber and the coupling agent in a water-ethanol mixed solution, putting the mixture into a microwave reaction kettle for reaction, filtering and drying to obtain coupled modified bamboo fiber; the reaction temperature in the microwave reaction kettle is 100-140 ℃, and the reaction time is 5-60 minutes;
s2, preparing the high-filling master batch: putting the coupled modified bamboo fiber, polylactic acid, a compatilizer and an antioxidant into mixing equipment for melt blending to obtain a coupled modified bamboo fiber high-filling polylactic acid master batch;
s3, preparing the bamboo fiber reinforced polylactic acid composite material: and mixing the coupled modified bamboo fiber high-filling polylactic acid master batch with polylactic acid, and putting the mixture into mixing equipment for melt blending to obtain the high-strength weather-resistant fully-degradable composite material.
2. The method of claim 1, wherein: in 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 claim 1, wherein: in 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 claim 1, wherein: in step S1, the mass ratio of water to ethanol is (1: 9) - (9: 1), and the mass ratio of the bamboo fiber to the water-ethanol mixture is (2: 1) - (1: 5).
5. The method of claim 1, wherein: in the step S2, the mass fraction of the coupled modified bamboo fiber in the high-filling master batch is 20-90%.
6. The method of claim 1, wherein: in step S2, the compatibilizer is 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 highly filled masterbatch is 1-20%.
7. The method of claim 1, wherein: in step S2, the compatibilizer is at least one of polyethylene glycol, epoxidized soybean oil, stearic acid, stearate, tetrabutyl titanate, a reactive polyepoxy compatibilizer, and acetyl tri-n-butyl citrate, and the mass fraction of the compatibilizer in the highly filled masterbatch is 0.1 to 5%.
8. The method of claim 1, wherein: in the step S2, the antioxidant is at least one of hindered amine antioxidant, hindered phenol antioxidant and phosphite antioxidant, and the mass fraction of the antioxidant in the high-filling master batch is 0.3-2%.
9. The method of claim 1, wherein: in step S3, the mass ratio of the highly filled masterbatch 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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| US20080277055A1 (en) * | 2005-09-26 | 2008-11-13 | Sichuan Shengda Forestry Industry (Group) Co., L., | Manufacturing Process of a Composite Bamboo Board |
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| 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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| US20080277055A1 (en) * | 2005-09-26 | 2008-11-13 | Sichuan Shengda Forestry Industry (Group) Co., L., | Manufacturing Process of a Composite Bamboo Board |
| 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 |
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