CN116041926A - Polylactic acid thermoplastic composite material with high mechanical property and preparation method thereof - Google Patents

Polylactic acid thermoplastic composite material with high mechanical property and preparation method thereof Download PDF

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CN116041926A
CN116041926A CN202310214666.6A CN202310214666A CN116041926A CN 116041926 A CN116041926 A CN 116041926A CN 202310214666 A CN202310214666 A CN 202310214666A CN 116041926 A CN116041926 A CN 116041926A
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polylactic acid
modified
continuous glass
composite material
glass fiber
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竺亚斌
李沛沛
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Ningbo Baoting Biological Technology Co ltd
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Ningbo Baoting Biological Technology Co ltd
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/04—Reinforcing macromolecular compounds with loose or coherent fibrous material
    • C08J5/06—Reinforcing macromolecular compounds with loose or coherent fibrous material using pretreated fibrous materials
    • C08J5/08—Reinforcing macromolecular compounds with loose or coherent fibrous material using pretreated fibrous materials glass fibres
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2367/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
    • C08J2367/04—Polyesters derived from hydroxy carboxylic acids, e.g. lactones
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00—Use of organic ingredients
    • C08K5/16—Nitrogen-containing compounds
    • C08K5/20—Carboxylic acid amides
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K7/00—Use of ingredients characterised by shape
    • C08K7/02—Fibres or whiskers
    • C08K7/04—Fibres or whiskers inorganic
    • C08K7/14—Glass
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K9/00—Use of pretreated ingredients
    • C08K9/02—Ingredients treated with inorganic substances
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K9/00—Use of pretreated ingredients
    • C08K9/08—Ingredients agglomerated by treatment with a binding agent

Abstract

The invention discloses a polylactic acid thermoplastic composite material with higher mechanical property and a preparation method thereof, wherein the composite material comprises 25-45% of a resin matrix and 55-75% of a reinforcement according to mass percentage, wherein the resin matrix is modified polylactic acid, the reinforcement is modified continuous glass fiber, and the modified polylactic acid is grafted with the modified continuous glass fiber through chemical bonds. The polylactic acid thermoplastic composite material with high mechanical property is adopted, and the continuous glass fiber and the polylactic acid are modified to be connected through chemical bonds, so that the interface bonding is tighter, and the mechanical property of the composite material is further improved.

Description

Polylactic acid thermoplastic composite material with high mechanical property and preparation method thereof
Technical Field
The invention relates to the technical field of composite material preparation, in particular to a polylactic acid thermoplastic composite material with higher mechanical property and a preparation method thereof.
Background
Because of the high mechanical properties of composite materials, great attention is paid to the possibility of manufacturing lightweight and strong structures and components. Typically, composite materials are made by a reinforced composite material technique consisting of two different components. One is a polymer matrix, which typically acts as a continuous phase. The other component is reinforcing fibers or nanoparticles, typically as a discontinuous phase. While the polymer matrix can be divided into thermoset and thermoplastic polymers. Wherein the thermoplastic polymer is a powder or a solid at room temperature and exhibits liquid-like behavior at its melting temperature.
Currently, thermoplastic composites are in great demand because they can be produced in high yields and are easy to manufacture. In addition, thermoplastic composites have been applied to various high performance and lightweight structural materials in the aerospace, automotive, sporting goods and transportation industries, and have partially replaced conventional thermoset composites, thanks to good processing convenience, heat resistance, excellent mechanical properties and restorability.
Polylactic acid is a thermoplastic resin which can be completely biodegraded, and has the advantages of reproducibility, innocuity, harmlessness and good biocompatibility. However, polylactic acid has inherent disadvantages such as low toughness, poor air permeability, poor heat resistance, poor impact resistance, etc., which limit its application range.
Fiber reinforced thermoplastic composites are a broad class of thermoplastic composites, and the fiber reinforcement may be continuous glass fibers, carbon fibers, metal fibers, etc., with continuous fibers being one type of continuous long fibers that have been used in thermoplastic composites to further enhance their mechanical properties. At present, continuous glass fibers are widely used for preparing continuous glass fiber reinforced composite materials due to their excellent properties such as light weight, high strength, high modulus and high temperature resistance.
Impregnation and shaping preparation of continuous fiber reinforcement with thermoplastic polymer matrices is a challenge due to the high melt viscosity of the thermoplastic polymer matrix and the non-uniform distribution of continuous fibers in the thermoplastic polymer matrix. In addition, the polymer matrix belongs to an organic material, the continuous glass fiber belongs to an inorganic material, and the physical and chemical properties of the organic material and the inorganic material are greatly different, so that the adhesion at an interface in the compounding process of the organic material and the inorganic material is not tight enough, and the mechanical property of the composite material is low.
Disclosure of Invention
The invention aims to provide a polylactic acid thermoplastic composite material with higher mechanical property and a preparation method thereof, so as to solve the problems of insufficient uniform mixing of a polymer matrix and continuous glass fibers and insufficient tight adhesion of the polymer matrix and the continuous glass fibers.
In order to achieve the aim, the invention provides a polylactic acid thermoplastic composite material with higher mechanical property, which comprises 25-45% of a resin matrix and 55-75% of a reinforcing body according to mass percentage, wherein the resin matrix is modified polylactic acid, the reinforcing body is modified continuous glass fiber, and the modified polylactic acid is grafted with the modified continuous glass fiber through chemical bonds.
The preparation method of the polylactic acid thermoplastic composite material with higher mechanical property comprises the following steps:
step one: adding 55-75% of modified polylactic acid into a charging barrel according to the mass percentage, setting the processing temperature to be 180-220 ℃, carrying out melt extrusion by a double screw extruder, and entering an impregnation die;
step two: according to the mass percentage, 25-45% of modified continuous glass fiber passes through a guide wheel and is fully immersed in melted modified polylactic acid in an immersion mould;
step three: the traction speed is regulated to 3-9 r/min, the tension force is 1-20N, and the dipping modified continuous glass fiber bundles containing the modified polylactic acid are extracted from the dipping mold and pass through a cooling bath to form the composite material.
Preferably, the processing temperature is 220 ℃.
Preferably, the working tension is 11N.
Preferably, the traction speed is 3 rpm.
Preferably, the content of the modified continuous glass fiber is 40%.
Preferably, the method for preparing the modified continuous glass fiber comprises the following steps:
(1) Activating the continuous glass fiber to obtain a hydroxylated continuous glass fiber with hydroxyl groups on the surface;
(2) And (3) reacting the hydroxylated continuous glass fiber with amino-terminated hyperbranched polysiloxane at 80 ℃ for 8 hours, and washing and drying to obtain the modified continuous glass fiber.
Preferably, the mass ratio of hydroxylated continuous glass fibers to amino-terminated hyperbranched polysiloxanes is 100:10.
Preferably, the activation process of the step (1) is to soak the continuous glass fiber in hydrogen peroxide, heat up to 80-100 ℃, react for 5-8 hours, wash and dry to obtain the hydroxylation continuous glass fiber.
Preferably, the preparation process of the amino-terminated hyperbranched polysiloxane in the step (2) comprises the steps of adding KH-550, water and ethanol into a three-neck flask, slowly dropwise adding trimethylchlorosilane into the system, reacting for 5-8 hours at 50 ℃, adjusting the pH value to be neutral, removing salt and distilling under reduced pressure to obtain the amino-terminated hyperbranched polysiloxane.
Preferably, the mass ratio of KH-550, water and ethanol is 1:2:10.
Preferably, the mass ratio of KH-550 to trimethylchlorosilane is 1:1.2.
Preferably, sodium ethoxide is used to adjust the pH.
Preferably, the modified polylactic acid is prepared by uniformly mixing polylactic acid, polyisocyanate, polyol and nucleating agent.
Preferably, the weight ratio of polylactic acid, polyisocyanate, polyol and nucleating agent is 100:2-10:0.1-0.3:0.1-0.5.
Preferably, the polyisocyanate comprises at least one of toluene diisocyanate, hexamethylene diisocyanate, triisocyanate.
Preferably, the polyol comprises at least one of ethylene glycol, butylene glycol, glycerol.
Preferably, the nucleating agent is an amide compound, and the amide compound comprises at least one of ethylene bis-stearamide, ethylene hydroxy bis-stearamide and 1,3, 5-benzene tricarboxamide.
The invention principle of the invention:
in the process of modifying continuous glass fiber, hydrogen peroxide is firstly adopted to activate the continuous glass fiber to enable the surface of the continuous glass fiber to have active hydroxyl groups, KH-550 and trimethylchlorosilane are then adopted to react to generate polysiloxane with hyperbranched structure, active amino groups are circumferentially arranged on the surface of the continuous glass fiber, and finally the hydroxyl groups on the surface of the continuous glass fiber are reacted with part of the amino groups on the surface of the polysiloxane to enable the polysiloxane to be grafted on the surface of the continuous glass fiber. In the process, on one hand, hyperbranched structures are formed on the surface of the continuous glass fiber, and on the other hand, after polysiloxane is grafted, amino groups remain on the surface of the continuous glass fiber, so that the subsequent chemical reaction is facilitated.
In the process of modifying the polylactic acid, the polyisocyanate, the polyol and the nucleating agent are mixed with the polylactic acid, and the polyisocyanate and the polyol are subjected to polymerization reaction while the polylactic acid reacts with the surface of the modified continuous glass fiber, so that structures between all branches in the surface of the modified continuous glass fiber and the hyperbranched structure are filled, an infiltration area is formed on the surface of the hyperbranched structure and the surface of the modified glass fiber, the adhesiveness between the inorganic material continuous glass fiber and the organic material polylactic acid resin matrix is improved, and the inorganic material continuous glass fiber and the organic material polylactic acid resin matrix are connected through chemical bonds, so that the interface adhesion is tighter, and the mechanical property of the composite material is improved.
Therefore, the polylactic acid thermoplastic composite material with higher mechanical property and the preparation method thereof have the following beneficial effects:
(1) Continuous glass fiber reinforced polylactic acid thermoplastic composite materials are successfully prepared by a pultrusion method, and the tensile strength of the composite materials is increased along with the increase of the processing temperature and the content of the continuous glass fibers, but the tensile strength of the composite materials is not excessively high. The pultrusion manufacturing method is a low-cost and high-strength method, so that the industrial application of the composite material has ideal performance, and the possibility is provided for the reasonable design of the continuous glass fiber reinforced polylactic acid thermoplastic composite material and the specific application of the pultrusion preparation.
(2) The amino-terminated hyperbranched polysiloxane molecules are grafted on the surface of the modified continuous glass fiber, so that amino is provided for the surface of the continuous glass fiber, the amino can react with polylactic acid organic materials, the adhesiveness between the continuous glass fiber and polylactic acid is increased through chemical bonds, the hyperbranched polysiloxane molecules are provided, the infiltration area between the continuous glass fiber and the polylactic acid is increased, a polymer resin matrix is formed between the hyperbranched polysiloxane molecules in the reaction process of the polylactic acid, and the mechanical property of the composite material is integrally improved.
The technical scheme of the invention is further described in detail through the drawings and the embodiments.
Drawings
FIG. 1 is a process flow diagram of a method of preparing a composite material of the present invention;
FIG. 2 is a schematic representation of the composite material of the present invention (left a) and structure (right b);
FIG. 3 is a schematic diagram of the melt impregnation of the present invention;
FIG. 4 shows SEM images (a, b) of pure polylactic acid and SEM images (c, d) of composite materials in the present invention.
FIG. 5 is a graph of tensile strength versus processing temperature for a composite;
FIG. 6 is a graph of tensile strength versus composite material at different processing tensions;
FIG. 7 is a graph of tensile strength versus traction speed for a composite material;
FIG. 8 is a graph comparing tensile strength of composites made with varying amounts of modified continuous glass fibers;
FIG. 9 is a TGA comparison graph of composites of varying modified continuous glass fiber content;
FIG. 10 is a graph of storage modulus versus composite materials of pure polylactic acid and varying modified continuous glass fiber content.
Fig. 11 is a graph showing tensile strength comparisons of fourteen to sixteen embodiments.
Detailed Description
The following further describes the technical solution of the present invention through the drawings and examples, and it should be noted that the present example provides detailed implementation and specific operation procedures on the premise of the technical solution, but the present invention is not limited to the present example.
Polylactic acid powder in the embodiment of the invention is purchased from Nature works Inc. of America. Continuous glass fibers (S4C 10-800) were purchased from Nanj continuous glass fiber research institute, inc.
Description of the preferred embodiments
Referring to fig. 1, a polylactic acid thermoplastic composite material with higher mechanical properties comprises, by mass, 32% of modified continuous glass fibers and 68% of modified polylactic acid.
The preparation method of the polylactic acid thermoplastic composite material with higher mechanical property comprises the following steps:
step one: according to the mass percentage, 42.5g of modified polylactic acid is added into a charging barrel, the processing temperature is set to be 180 ℃, the mixture is melted and extruded by a double-screw extruder, and enters an impregnation die, and the principle of melt impregnation is shown in figure 3.
Step two: 20g of modified continuous glass fiber is passed through a guide wheel according to mass percent, and molten modified polylactic acid is fully impregnated in an impregnation die.
The specific preparation process of the modified polylactic acid comprises the steps of uniformly mixing polylactic acid, polyisocyanate, polyol and nucleating agent to obtain the modified polylactic acid, wherein the weight ratio of the polylactic acid to the polyisocyanate to the polyol to the nucleating agent is 100:5:0.2:0.3, the polyisocyanate is toluene diisocyanate, the polyol is ethylene glycol, and the nucleating agent is ethylene bis stearamide.
The preparation method of the modified continuous glass fiber comprises the following steps:
(1) Soaking continuous glass fibers in hydrogen peroxide, heating to 80 ℃, reacting for 6 hours, washing and drying to obtain hydroxylated continuous glass fibers;
(2) Adding KH-550, water and ethanol into a three-neck flask, slowly dropwise adding trimethylchlorosilane into the system, wherein the mass ratio of KH-550 to water to ethanol is 1:2:10, the mass ratio of KH-550 to trimethylchlorosilane is 1:1.2, reacting at 50 ℃ for 6 hours, adjusting the pH value to be neutral by using sodium ethoxide, removing salt and distilling under reduced pressure to obtain the amino-terminated hyperbranched polysiloxane;
and (3) reacting the hydroxylated continuous glass fiber with amino-terminated hyperbranched polysiloxane for 8 hours at the temperature of 80 ℃, and washing and drying to obtain the modified continuous glass fiber, wherein the mass ratio of the hydroxylated continuous glass fiber to the amino-terminated hyperbranched polysiloxane is 100:10.
Step three: the drawing speed was adjusted to 3 rpm, the tension was 1N, and the dip-modified continuous glass fiber strands containing the modified polylactic acid were drawn out of the dip mold and passed through a cooling bath to form a composite material, the physical and structural diagram of which is shown in FIG. 2.
Second embodiment
Referring to fig. 1, a polylactic acid thermoplastic composite material with higher mechanical properties comprises, by mass, 32% of modified continuous glass fibers and 68% of modified polylactic acid.
The preparation method of the polylactic acid thermoplastic composite material with higher mechanical property comprises the following steps:
step one: according to the mass percentage, 42.5g of polylactic acid is added into a charging barrel, the processing temperature is set to 190 ℃, the polylactic acid is melted and extruded by a double-screw extruder, and enters an impregnation die, and the principle of melt impregnation is shown in figure 3.
Step two: 20g of modified continuous glass fiber is passed through a guide wheel according to mass percent, and molten modified polylactic acid is fully impregnated in an impregnation die. The preparation method of the modified continuous glass fiber and the modified polylactic acid is the same as that of the first embodiment.
Step three: the drawing speed was adjusted to 3 rpm, the tension was 1N, and the dip-modified continuous glass fiber strands containing the modified polylactic acid were drawn out of the dip mold and passed through a cooling bath to form a composite material, the physical and structural diagram of which is shown in FIG. 2.
Description of the preferred embodiments
Referring to fig. 1, a polylactic acid thermoplastic composite material with higher mechanical properties comprises, by mass, 32% of modified continuous glass fibers and 68% of modified polylactic acid.
The preparation method of the polylactic acid thermoplastic composite material with higher mechanical property comprises the following steps:
step one: according to the mass percentage, 42.5g of polylactic acid is added into a charging barrel, the processing temperature is set to be 200 ℃, the polylactic acid is melted and extruded by a double-screw extruder, and enters an impregnation die, and the principle of melt impregnation is shown in figure 3.
Step two: 20g of modified continuous glass fiber is passed through a guide wheel according to mass percent, and molten modified polylactic acid is fully impregnated in an impregnation die. The preparation method of the modified continuous glass fiber and the modified polylactic acid is the same as that of the first embodiment.
Step three: the drawing speed was adjusted to 3 rpm, the tension was 1N, and the dip-modified continuous glass fiber strands containing the modified polylactic acid were drawn out of the dip mold and passed through a cooling bath to form a composite material, the physical and structural diagram of which is shown in FIG. 2.
Fourth embodiment
Referring to fig. 1, a polylactic acid thermoplastic composite material with higher mechanical properties comprises, by mass, 32% of modified continuous glass fibers and 68% of modified polylactic acid.
The preparation method of the polylactic acid thermoplastic composite material with higher mechanical property comprises the following steps:
step one: according to the mass percentage, 42.5g of modified polylactic acid is added into a charging barrel, the processing temperature is set to be 210 ℃, the modified polylactic acid is melted and extruded by a double-screw extruder, and enters an impregnation die, and the melt impregnation principle is shown in figure 3.
Step two: 20g of modified continuous glass fiber is passed through a guide wheel according to mass percent, and molten modified polylactic acid is fully impregnated in an impregnation die. The preparation method of the modified continuous glass fiber and the modified polylactic acid is the same as that of the first embodiment.
Step three: the traction speed is regulated to be 3 revolutions per minute, the tension force is 1N, the immersed modified continuous glass fiber bundles containing the modified polylactic acid are extracted from the immersed mould and are subjected to cooling bath, and the modified continuous glass fiber reinforced polylactic acid thermoplastic composite material is formed, and the physical and structural diagram of the composite material is shown in figure 2.
Description of the preferred embodiment
Referring to fig. 1, a polylactic acid thermoplastic composite material with higher mechanical properties comprises, by mass, 32% of modified continuous glass fibers and 68% of modified polylactic acid.
The preparation method of the polylactic acid thermoplastic composite material with higher mechanical property comprises the following steps:
step one: according to the mass percentage, 42.5g of modified polylactic acid is added into a charging barrel, the processing temperature is set to 220 ℃, the polylactic acid is melted and extruded by a double-screw extruder, and enters an impregnation die, and the principle of melt impregnation is shown in figure 3.
Step two: 20g of modified continuous glass fiber is passed through a guide wheel according to mass percent, and molten modified polylactic acid is fully impregnated in an impregnation die. The preparation method of the modified continuous glass fiber and the modified polylactic acid is the same as that of the first embodiment.
Step three: the drawing speed was adjusted to 3 rpm, the tension was 1N, and the dip-modified continuous glass fiber strands containing the modified polylactic acid were drawn out of the dip mold and passed through a cooling bath to form a composite material, the physical and structural diagram of which is shown in FIG. 2.
Description of the preferred embodiment six
Referring to fig. 1, a polylactic acid thermoplastic composite material with higher mechanical properties comprises, by mass, 32% of modified continuous glass fibers and 68% of modified polylactic acid.
The preparation method of the polylactic acid thermoplastic composite material with higher mechanical property comprises the following steps:
step one: according to the mass percentage, 42.5g of modified polylactic acid is added into a charging barrel, the processing temperature is set to 220 ℃, the polylactic acid is melted and extruded by a double-screw extruder, and enters an impregnation die, and the principle of melt impregnation is shown in figure 3.
Step two: 60g of modified continuous glass fiber is passed through a guide wheel according to mass percent, and molten modified polylactic acid is fully impregnated in an impregnation die. The preparation method of the modified continuous glass fiber and the modified polylactic acid is the same as that of the first embodiment.
Step three: the drawing speed is regulated to 3 revolutions per minute, the tension is 6N, the immersed modified continuous glass fiber bundles containing the modified polylactic acid are extracted from the immersing mould and pass through a cooling bath to form a composite material, and the real object and the structure diagram are shown in figure 2.
Embodiment seven
Referring to fig. 1, a polylactic acid thermoplastic composite material with higher mechanical properties comprises, by mass, 32% of modified continuous glass fibers and 68% of modified polylactic acid.
The preparation method of the polylactic acid thermoplastic composite material with higher mechanical property comprises the following steps:
step one: according to the mass percentage, 42.5g of modified polylactic acid is added into a charging barrel, the processing temperature is set to 220 ℃, the polylactic acid is melted and extruded by a double-screw extruder, and enters an impregnation die, and the principle of melt impregnation is shown in figure 3.
Step two: 20g of modified continuous glass fiber is passed through a guide wheel according to mass percent, and molten modified polylactic acid is fully impregnated in an impregnation die. The preparation method of the modified continuous glass fiber and the modified polylactic acid is the same as that of the first embodiment.
Step three: the drawing speed was adjusted to 3 rpm and the tension was 11N, and the dip-modified continuous glass fiber strands containing the modified polylactic acid were drawn from the dip mold and passed through a cooling bath to form a composite material, the physical and structural diagram of which is shown in fig. 2.
Description of the preferred embodiment eight
Referring to fig. 1, a polylactic acid thermoplastic composite material with higher mechanical properties comprises, by mass, 32% of modified continuous glass fibers and 68% of modified polylactic acid.
The preparation method of the polylactic acid thermoplastic composite material with higher mechanical property comprises the following steps:
step one: according to the mass percentage, 42.5g of modified polylactic acid is added into a charging barrel, the processing temperature is set to 220 ℃, the polylactic acid is melted and extruded by a double-screw extruder, and enters an impregnation die, and the principle of melt impregnation is shown in figure 3.
Step two: 20g of modified continuous glass fiber is passed through a guide wheel according to mass percent, and molten modified polylactic acid is fully impregnated in an impregnation die. The preparation method of the modified continuous glass fiber and the modified polylactic acid is the same as that of the first embodiment.
Step three: the drawing speed was adjusted to 3 rpm, the tension was 16N, and the dip-modified continuous glass fiber strands containing the modified polylactic acid were drawn out of the dip mold and passed through a cooling bath to form a composite material, the physical and structural diagram of which is shown in fig. 2.
Description of the preferred embodiments
Referring to fig. 1, a polylactic acid thermoplastic composite material with higher mechanical properties comprises, by mass, 32% of modified continuous glass fibers and 68% of modified polylactic acid.
The preparation method of the polylactic acid thermoplastic composite material with higher mechanical property comprises the following steps:
step one: according to the mass percentage, 42.5g of modified polylactic acid is added into a charging barrel, the processing temperature is set to 220 ℃, the polylactic acid is melted and extruded by a double-screw extruder, and enters an impregnation die, and the principle of melt impregnation is shown in figure 3.
Step two: 20g of modified continuous glass fiber is passed through a guide wheel according to mass percent, and molten modified polylactic acid is fully impregnated in an impregnation die. The preparation method of the modified continuous glass fiber and the modified polylactic acid is the same as that of the first embodiment.
Step three: the drawing speed was adjusted to 3 rpm and the tension was 20N, and the dip-modified continuous glass fiber strands containing the modified polylactic acid were drawn from the dip mold and passed through a cooling bath to form a composite material, the physical and structural diagram of which is shown in fig. 2.
Description of the preferred embodiments
Referring to fig. 1, a polylactic acid thermoplastic composite material with higher mechanical properties comprises, by mass, 32% of modified continuous glass fibers and 68% of modified polylactic acid.
The preparation method of the polylactic acid thermoplastic composite material with higher mechanical property comprises the following steps:
step one: according to the mass percentage, 42.5g of modified polylactic acid is added into a charging barrel, the processing temperature is set to 220 ℃, the polylactic acid is melted and extruded by a double-screw extruder, and enters an impregnation die, and the principle of melt impregnation is shown in figure 3.
Step two: 20g of modified continuous glass fiber is passed through a guide wheel according to mass percent, and molten modified polylactic acid is fully impregnated in an impregnation die. The preparation method of the modified continuous glass fiber and the modified polylactic acid is the same as that of the first embodiment.
Step three: the drawing speed was adjusted to 7 rpm and the tension was adjusted to 11N, and the dip-modified continuous glass fiber strands containing the modified polylactic acid were drawn from the dip mold and passed through a cooling bath to form a composite material, the physical and structural diagram of which is shown in fig. 2.
Description of the invention eleven
Referring to fig. 1, a polylactic acid thermoplastic composite material with higher mechanical properties comprises, by mass, 32% of modified continuous glass fibers and 68% of modified polylactic acid.
The preparation method of the polylactic acid thermoplastic composite material with higher mechanical property comprises the following steps:
step one: according to the mass percentage, 42.5g of modified polylactic acid is added into a charging barrel, the processing temperature is set to 220 ℃, the polylactic acid is melted and extruded by a double-screw extruder, and enters an impregnation die, and the principle of melt impregnation is shown in figure 3.
Step two: 20g of modified continuous glass fiber is passed through a guide wheel according to mass percent, and molten modified polylactic acid is fully impregnated in an impregnation die. The preparation method of the modified continuous glass fiber and the modified polylactic acid is the same as that of the first embodiment.
Step three: the drawing speed was adjusted to 9 rpm and the tension was adjusted to 11N, and the dip-modified continuous glass fiber strands containing the modified polylactic acid were drawn from the dip mold and passed through a cooling bath to form a composite material, the physical and structural diagram of which is shown in fig. 2.
Twelve examples of embodiment
Referring to fig. 1, a polylactic acid thermoplastic composite material with higher mechanical properties comprises, by mass, 36% of modified continuous glass fibers and 64% of modified polylactic acid.
The preparation method of the polylactic acid thermoplastic composite material with higher mechanical property comprises the following steps:
step one: according to the mass percentage, 42.5g of modified polylactic acid is added into a charging barrel, the processing temperature is set to 220 ℃, the polylactic acid is melted and extruded by a double-screw extruder, and enters an impregnation die, and the principle of melt impregnation is shown in figure 3.
Step two: 23.90g of modified continuous glass fiber is passed through a guide wheel and molten modified polylactic acid is sufficiently impregnated in an impregnation die in percentage by mass. The preparation method of the modified continuous glass fiber and the modified polylactic acid is the same as that of the first embodiment.
Step three: the drawing speed was adjusted to 3 rpm and the tension was 11N, and the dip-modified continuous glass fiber strands containing the modified polylactic acid were drawn from the dip mold and passed through a cooling bath to form a composite material, the physical and structural diagram of which is shown in fig. 2.
Description of the preferred embodiments
Referring to fig. 1, a polylactic acid thermoplastic composite material with higher mechanical properties comprises 40% of modified continuous glass fibers and 60% of modified polylactic acid by mass percent.
The preparation method of the polylactic acid thermoplastic composite material with higher mechanical property comprises the following steps:
step one: according to the mass percentage, 42.5g of modified polylactic acid is added into a charging barrel, the processing temperature is set to 220 ℃, the polylactic acid is melted and extruded by a double-screw extruder, and enters an impregnation die, and the principle of melt impregnation is shown in figure 3.
Step two: 28.33g of modified continuous glass fiber was passed through a guide wheel and the molten modified polylactic acid was sufficiently impregnated in an impregnation die in mass percent. The preparation method of the modified continuous glass fiber and the modified polylactic acid is the same as that of the first embodiment.
Step three: the drawing speed was adjusted to 3 rpm and the tension was 11N, and the dip-modified continuous glass fiber strands containing the modified polylactic acid were drawn from the dip mold and passed through a cooling bath to form a composite material, the physical and structural diagram of which is shown in fig. 2.
Fourteen embodiments
The difference from the thirteenth embodiment is that: in the second step, the melt modified polylactic acid is directly impregnated with unmodified continuous glass fibers.
Description of the preferred embodiment fifteen
The difference from the embodiment case thirteenth is that: in the second step, the molten polylactic acid is directly impregnated with the modified continuous glass fiber.
Sixteen embodiments
The difference from the thirteenth embodiment is that: in the preparation process of the polysiloxane in the second step, only KH-550 is added, and no trimethylchlorosilane is added.
Referring to fig. 4, left a and right d show SEM micrographs of the tensile fracture surfaces of the pure polylactic acid and the composite material prepared in the thirteenth embodiment, respectively. As shown in the left and right figures, the stretch-broken morphology of the neat polylactic acid was smooth. As shown in the graph left c and the graph right d, the modified continuous glass fiber is uniformly dispersed and wraps the polylactic acid matrix, and the modified continuous glass fiber and the polylactic acid have good interfacial compatibility. This is important for composites having higher tensile strength than the pure polylactic acid matrix.
Referring to fig. 5, the tensile strength of the composite material at different processing temperatures was analyzed. The tensile strength is greater and greater with increasing processing temperature, and the composite material prepared at 220 ℃ has the highest tensile strength, because the viscosity of polylactic acid is lower and lower with increasing temperature, and the flowability is better and better. Therefore, the processing temperature of the pultrusion process is 220 ℃, the modified polylactic acid is easy to be immersed into the modified continuous glass fiber bundles, and the dipping effect is good, so that the composite material with the highest tensile strength is manufactured at 220 ℃.
Referring to fig. 6, the effect of process tension on the tensile strength of the composite is shown. It can be seen that the tensile strength of the composite increases and then decreases with increasing tension. In particular, when Zhang Ligu is set at 11N, the tensile strength is maximized. The following two points are the reasons why the tensile strength reaches a peak when the tension is fixed at 11N: i) When the tension is less than 11N, the partially modified continuous glass fiber cannot be completely straightened, which makes it difficult to jointly bear higher loads during the pultrusion process. In addition, the modified continuous glass fiber bundles are not fully unfolded, so that the molten modified polylactic acid is difficult to fully permeate into the glass fiber bundles, the impregnation effect is poor, and the tensile strength of the composite material is low; ii) when the tension is greater than 11N, the friction between the modified continuous glass fiber and the tension device increases, and part of the glass fiber breaks, so that the content of the active modified continuous glass fiber in the composite material decreases in the process of drawing and extruding, and the tensile strength tends to decrease under higher tension.
Referring to fig. 7, the effect of traction speed on the tensile strength of the composite is shown. It can be seen that the tensile strength of the composite gradually decreases with increasing traction speed, which can be explained by considering the following two reasons. First, the higher drawing speed has shorter impregnation time, and the molten polylactic acid is difficult to completely impregnate into the glass fiber bundles, so that the impregnation effect of the composite material is poor, and the modified continuous glass fiber and the polylactic acid matrix cannot effectively share external load at the high drawing speed. Second, if the melted polylactic acid does not sufficiently impregnate the modified continuous glass fiber bundles, this means that a portion of the glass fibers are exposed at the surface, rubbed against the rotating rod, broken and entangled around the rotating rod. Thus, in the tensile strength test, the content of effectively modified continuous glass fibers in the composite that can withstand external loads is reduced, resulting in lower tensile strength at higher traction speeds. Thus, during the pultrusion process, the pulling speed was fixed at 3 revolutions per minute.
Referring to fig. 8, analysis of the effect of varying amounts of modified continuous glass fibers on the tensile strength of the composite material shows that the tensile strength of the composite material increases gradually with increasing glass fiber content. The tensile strength of the pure PLA matrix was 45.3MPa, with the tensile strength being maximum when the maximum content of modified continuous glass fibers reached about 40.0 weight percent. It can be concluded that the tensile strength of the composite is greater than that of pure polylactic acid due to the introduction of the modified continuous glass fibers. Typically, continuous glass fibers have relatively high tensile strength and modulus, and once incorporated into a modified polylactic acid matrix, act as a backbone, and can withstand much higher external loads than a pure polylactic acid matrix. In addition, the continuous glass fibers are continuously present in the polylactic acid matrix, and once the composite is subjected to an external load, the modified continuous glass fibers can effectively transfer the load, thereby also helping the composite to obtain greater tensile strength.
Referring to fig. 9, thermogravimetric analysis of the composite materials of case seven, case twelve and case thirteen revealed that the modified continuous glass fiber was between 30wt% and 40 wt% in accordance with the raw material mass ratio.
Referring to fig. 10, the storage modulus of the composite material of pure polylactic acid and different modified continuous fiber contents. It is not difficult to find that the storage modulus of the composite material is gradually increased with the increase of the content of the modified continuous glass fiber, and the storage modulus is increased to 17.5GPa at maximum and is 68 times of the storage modulus of the pure polylactic acid. As shown, the thirteen composites had the highest modified continuous glass fiber content and storage modulus, indicating that they were more resistant to external deformation and more rigid. Furthermore, as the temperature is further increased, the storage modulus of pure PLA and composite materials shows a decreasing trend. This is because as the temperature further increases to the glass transition temperature of the polylactic acid matrix, the molecular segments of the polylactic acid start to move, pushing the polylactic acid matrix from the glassy state to the elastic state, resulting in a rapid decrease in storage modulus.
Referring to fig. 11, there is a graph of tensile strength versus fourteen, fifteen and sixteen. As can be seen from the tensile strength of the thirteenth embodiment and the fourteenth embodiment, when the unmodified continuous glass fiber is used in the fourteenth embodiment, the continuous glass fiber is an inorganic nonmetallic material, and the interfacial contact between the continuous glass fiber and the polylactic acid is greatly different due to the physical and chemical properties between the continuous glass fiber and the polylactic acid, so that the overall tensile strength of the continuous glass fiber is improved compared with that of pure polylactic acid, but compared with the thirteenth embodiment, the tensile strength of the continuous glass fiber is obviously reduced, the surface of the continuous glass fiber is modified, the interfacial connection between the continuous glass fiber and the modified polylactic acid can be increased, and the amino groups on the surface of the modified continuous glass fiber and active groups (hydroxyl groups) in the modified polylactic acid are chemically reacted.
From the tensile strength of the thirteenth embodiment and the fifteen embodiment, it can be seen that when the fifteen embodiment is added with polylactic acid, and the modified polylactic acid is not used, that is, the polyisocyanate, the polyol and the nucleating agent are not added, and the surface of the modified continuous glass fiber is subjected to chemical reaction, only the polylactic acid is reacted, the hydroxyl end groups of the polylactic acid are partially reacted with the amino groups on the surface of the fiber, but the reaction is insufficient, so that the grafting of the polylactic acid and the amino groups is not compact, and the tensile strength is reduced.
From the tensile strength of the thirteen embodiments and the sixteenth embodiments, it can be seen that when no trimethyl siloxane is added in the sixteenth embodiments, the tensile strength is reduced, mainly because no trimethyl siloxane is added, KH-550 directly reacts with hydroxyl groups on the surface of the modified continuous glass fiber, KH-550 does not form amino-terminated hyperbranched polysiloxane which is the same as that of the thirteenth embodiments, amino-terminated hyperbranched polysiloxane is grafted on the surface of the continuous glass fiber, wherein the amino-terminated hyperbranched polysiloxane can provide more reaction sites for the surface of the continuous glass fiber on one hand, and can provide more dense chemical branches on the other hand, and can form a polymer between the surface of the modified continuous glass fiber and the chemical branches when the subsequent chemical reaction with polylactic acid, polyisocyanate and polyalcohol occurs, and the polymer can serve as a wetting area and a connecting area between a polylactic acid matrix and the continuous glass fiber, so that interface bonding between the polylactic acid matrix and the continuous glass fiber is improved. When the hyperbranched structure is not formed, the continuous glass fiber and the polylactic acid matrix are connected by using only the chemical chain of KH-550, and the tensile strength is reduced, which indicates that the hyperbranched structure improves the adhesiveness between the two.
Therefore, the polylactic acid thermoplastic composite material with higher mechanical property and the preparation method thereof, which are disclosed by the invention, are prepared by using the continuous glass fiber reinforced polylactic acid thermoplastic composite material obtained by the preparation method of low-cost and high-strength pultrusion, and the physical property of a polylactic acid matrix is effectively enhanced due to good interfacial compatibility between the continuous glass fiber and the polylactic acid.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention and not for limiting it, and although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that: the technical scheme of the invention can be modified or replaced by the same, and the modified technical scheme cannot deviate from the spirit and scope of the technical scheme of the invention.

Claims (10)

1. A polylactic acid thermoplastic composite material with higher mechanical property is characterized in that: the composite material comprises, by mass, 25-45% of a resin matrix and 55-75% of a reinforcing body, wherein the resin matrix is modified polylactic acid, the reinforcing body is modified continuous glass fibers, and the modified polylactic acid is grafted with the modified continuous glass fibers through chemical bonds.
2. The method for preparing the polylactic acid thermoplastic composite material with higher mechanical property according to claim 1, which is characterized in that: the method comprises the following steps:
step one: adding 55-75% of modified polylactic acid into a charging barrel according to mass percentage, setting the processing temperature to be 180-220 ℃, carrying out melt extrusion by a double screw extruder, and entering an impregnation die;
step two: according to the mass percentage, 25-45% of modified continuous glass fiber passes through a guide wheel and is fully immersed in melted modified polylactic acid in an immersion mould;
step three: the traction speed is regulated to 3-9 r/min, the tension force is 1-20N, and the dipping modified continuous glass fiber bundles containing the modified polylactic acid are extracted from the dipping mold and pass through a cooling bath to form the composite material.
3. The method for preparing the polylactic acid thermoplastic composite material with higher mechanical property according to claim 2, which is characterized in that: the preparation method of the modified continuous glass fiber comprises the following steps:
(1) Activating the continuous glass fiber to obtain a hydroxylated continuous glass fiber with hydroxyl groups on the surface;
(2) And (3) reacting the hydroxylated continuous glass fiber with amino-terminated hyperbranched polysiloxane at 80 ℃ for 8 hours, and washing and drying to obtain the modified continuous glass fiber.
4. The method for preparing the polylactic acid thermoplastic composite material with higher mechanical property according to claim 3, which is characterized in that: the activation process of the step (1) is to soak the continuous glass fiber in hydrogen peroxide, heat up to 80-100 ℃, react for 5-8 hours, wash and dry to obtain the hydroxylation continuous glass fiber.
5. The method for preparing the polylactic acid thermoplastic composite material with higher mechanical property according to claim 4, which is characterized in that: adding KH-550, water and ethanol into a three-neck flask, slowly dropwise adding trimethylchlorosilane into the system, reacting at 50 ℃ for 5-8 hours, adjusting the pH value to be neutral, removing salt, and distilling under reduced pressure to obtain the amino-terminated hyperbranched polysiloxane.
6. The method for preparing the polylactic acid thermoplastic composite material with higher mechanical property according to claim 2, which is characterized in that: the specific preparation process of the modified polylactic acid comprises the step of uniformly mixing polylactic acid, polyisocyanate, polyol and nucleating agent to obtain the modified polylactic acid.
7. The method for preparing the polylactic acid thermoplastic composite material with higher mechanical property according to claim 6, which is characterized in that: the weight ratio of the polylactic acid to the polyisocyanate to the polyol to the nucleating agent is 100:2-10:0.1-0.3:0.1-0.5.
8. The method for preparing the polylactic acid thermoplastic composite material with higher mechanical property according to claim 6, which is characterized in that: the polyisocyanate includes at least one of toluene diisocyanate, hexamethylene diisocyanate, and triisocyanate.
9. The method for preparing the polylactic acid thermoplastic composite material with higher mechanical property according to claim 6, which is characterized in that: the polyalcohol comprises at least one of ethylene glycol, butanediol and glycerol.
10. The method for preparing the polylactic acid thermoplastic composite material with higher mechanical property according to claim 6, which is characterized in that: the nucleating agent is an amide compound, and the amide compound comprises at least one of ethylene bis-stearamide, ethylene hydroxy bis-stearamide and 1,3, 5-benzene tricarboxamide.
CN202310214666.6A 2023-03-08 2023-03-08 Polylactic acid thermoplastic composite material with high mechanical property and preparation method thereof Pending CN116041926A (en)

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