CN114957945A

CN114957945A - Thermoplastic elastomer material and preparation method thereof

Info

Publication number: CN114957945A
Application number: CN202210643272.8A
Authority: CN
Inventors: 徐进; 梅仁杰; 许丽华; 许明明
Original assignee: Wuxi Institute of Technology
Current assignee: Wuxi Institute of Technology
Priority date: 2022-06-09
Filing date: 2022-06-09
Publication date: 2022-08-30

Abstract

The invention discloses a thermoplastic elastomer material and a preparation method thereof, belonging to the technical field of high polymer materials, wherein the thermoplastic elastomer material is uniformly mixed according to a proportion, added into a medium-speed mixer and uniformly stirred together; uniformly mixing, discharging, adding into a double-screw extruder, extruding, blending, plasticizing and extruding, wherein the double-screw extruder is heated from a feed hopper to a die in a linear gradient manner at the temperature of 200-220 ℃, and the rotating speed of a screw is 120 r/min; the invention improves the toughness of PLA and does not reduce the rigidity of PLA.

Description

Thermoplastic elastomer material and preparation method thereof

Technical Field

The invention relates to the technical field of high polymer materials, in particular to a thermoplastic elastomer and a preparation method thereof.

Background

High molecular polymers play an important role in human life and production due to their unique properties, but the use of high molecular polymers brings a series of environmental problems, for example, the high molecular polymer raw material is mainly derived from petroleum, and it takes a lot of time to degrade in the natural environment after use, which puts a great strain on the environment. With the improvement of environmental awareness, the existing polymer materials begin to develop towards good biocompatibility and degradability.

Polylactic acid (PLA) is produced from renewable resources such as corn, sugarcane, beet and the like through biotransformation and polymerization, can be biodegraded after use, has good biocompatibility, can be directly buried in soil for degradation, generates carbon dioxide which enters organic matters of the soil or is absorbed by plants, cannot cause greenhouse effect, has the potential of replacing the traditional petrochemical polymer, but has limited application due to the influence of D-type isomers and slow crystallization speed due to brittleness of the PLA.

Disclosure of Invention

Aiming at the technical defects, the invention aims to provide a preparation method of a thermoplastic elastomer material, which is characterized in that the thermoplastic elastomer material is uniformly mixed according to the proportion, added into a medium-speed mixer and uniformly stirred together; uniformly mixing, discharging, adding into a double-screw extruder, extruding, blending, plasticizing and extruding, wherein the double-screw extruder is heated from a feed hopper to a die in a linear gradient manner at the temperature of 200-220 ℃, and the rotating speed of a screw is 120 r/min;

the thermoplastic elastomer material comprises: in terms of mass fraction, the content of the active carbon,

65-90 parts of PLA;

10-20 parts of TPEE (thermoplastic polyester elastomer);

3-5 parts of a compatilizer;

the compatilizer is one or more of PLA grafted glycidyl methacrylate and PLA grafted maleic anhydride; the interfacial adhesion of PLA and TPEE is very small, TPEE has very good elasticity and thermoplasticity, the TPEE and the PLA can be mixed to modify the PLA, but the TPEE and the PLA are directly mixed, the TPEE is distributed in a PLA matrix in a spherical particle state along with the increase of the amount of the TPEE, the compatibility of the TPEE and the PLA is poor, and the modification purpose cannot be achieved; in the invention, the thermoplastic elastomer material is heated in a double-screw extruder in a linear gradient heating mode at 200-220 ℃ from a feed hopper to a die, the thermoplastic elastomer material is heated in a linear gradient manner, so that the TPEE is more uniformly dispersed in the PLA matrix, the particle size of the TPEE which does not react with the compatilizer is smaller and more uniformly dispersed, fine particles can be formed in the PLA matrix, and the fine particles are helpful for absorbing impact energy, thereby increasing the impact resistance, forming a net structure between the TPEE and the compatilizer to modify the PLA, and simultaneously, as the amount of the TPEE is more than that of the compatilizer, the excessive fine particles formed by the TPEE can promote heterogeneous nucleation, thereby accelerating the crystallization speed when the PLA matrix is cooled, and reducing the influence on the rigidity of the PLA during modification.

Preferably, the PLA grafted glycidyl methacrylate is prepared by grafting a glycidyl methacrylate chain segment on the surface of PLA, the PLA grafted maleic anhydride is prepared by grafting a maleic anhydride chain segment on the surface of PLA, and the graft polymerization method is a melt grafting method, specifically, the PLA grafted glycidyl methacrylate is prepared by taking PLA and glycidyl methacrylate as raw materials, taking dibenzoyl peroxide as a catalyst, blending, adding into a double-screw extruder, and extruding, melting, grafting and copolymerizing at 210 ℃; PLA grafted maleic anhydride takes PLA and maleic anhydride as raw materials, dicumyl peroxide as a catalyst, the materials are uniformly mixed and then extruded through double screw reaction, and the extrusion, the melting, the grafting and the copolymerization are carried out at the temperature of 170-200 ℃.

Preferably, the grafting degree of the PLA grafted glycidyl methacrylate is between 1.2% and 1.8%, and the grafting degree of the PLA grafted maleic anhydride is between 1.2% and 2%.

Preferably, the weight average molecular weight of the PLA is more than or equal to 190000g/mol, and the content of the D-lactic acid is less than or equal to 2.0%.

Preferably, the weight average molecular weight of the PLA is 190000g/mol, and the content of the D-lactic acid is less than or equal to 1.4 percent.

Preferably, the TPEE is a block copolymer having polybutylene terephthalate as a crystalline segment and polyether diol as an amorphous segment.

On the basis of the scheme, in order to further increase the crystallization speed of the PLA, the invention also adds a nucleating agent to promote heterogeneous nucleation so as to promote the crystallization speed, and preferably, the thermoplastic elastomer material also comprises 0.4-1 part of the nucleating agent; the nucleating agent is one or more of zinc oxide, zinc stearate and sodium citrate, wherein the sodium citrate can effectively reduce the condition that the sodium citrate cannot be uniformly mixed in the PLA matrix, and the crystallization speed of the PLA-based thermoplastic elastomer is improved by adding the nucleating agent.

Another object of the present invention is to provide a thermoplastic elastomer material prepared by the method for preparing a thermoplastic elastomer, which is characterized by weighing, by weight, the following components in parts by weight:

65-90 parts of PLA;

10-20 parts of TPEE;

3-5 parts of a compatilizer;

adding into a medium-speed mixer, and uniformly stirring; uniformly mixing, discharging, adding into a double-screw extruder, extruding, blending, plasticizing and extruding, wherein the double-screw extruder heats from a feed hopper to a die in a linear gradient of 200-220 ℃, and the rotating speed of a screw is 120 r/min; preferably, the weight ratio of the compatilizer to the TPEE is 1: 3-1: 7, the amount of compatibilizer is greater than the amount of TPEE.

The compatilizer is one or more of PLA grafted glycidyl methacrylate and PLA grafted maleic anhydride.

The weight average molecular weight of the PLA is not less than 190000g/mol, the content of the D-lactic acid is not more than 2.0%, and more preferably, the weight average molecular weight of the PLA is 190000g/mol, and the content of the D-lactic acid is not more than 1.4%.

The TPEE is a block copolymer with polybutylene terephthalate as a crystalline segment and polyether glycol as an amorphous segment.

Preferably, the thermoplastic elastomer material further comprises 0.4-1 part of a nucleating agent; the nucleating agent is zinc oxide or zinc stearate; one or more of sodium citrate.

The invention has the beneficial effects that: 1. according to the thermoplastic elastomer material, the TPEE elastomer is added into the PLA, when the proportion of the TPEE is increased, the TPEE elastomer is uniformly dispersed in a PLA matrix in a spherical particle form, the toughening efficiency is not as good as the toughening effect of a net structure, and if the net-shaped TPEE toughening PLA is used, the TPEE cannot promote the heterogeneous nucleation of the PLA due to the existence of the net structure, so that the crystallization speed of the PLA is greatly reduced; 2. a small amount of compatilizer is used, the amount of the TPEE in the PLA matrix is increased, a linear gradient heating blending mode is adopted, the dispersed particle size of a large amount of TPEE which does not react with the compatilizer in the PLA matrix is small due to linear gradient heating blending, and the TPEE with small particle size can promote PLA heterogeneous nucleation so as to accelerate the crystallization speed of the PLA and further achieve the aim of modification; 3. the invention improves the toughness of PLA and does not reduce the rigidity of PLA.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a graph of semi-crystallization half-crystallization time vs. temperature at isothermal crystallization for the blended thermoplastic elastomers obtained in example 3, example 9, and comparative examples 1 and 2 of the present invention, and the test Differential Scanning Calorimeter (DSC) model is DSC-200.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Before mixing, the required raw materials are dried in a vacuum oven at the temperature of 60 ℃, wherein the drying period of PLA and the compatilizer is 12 hours, and the drying period of TPEE is 4 hours; the types of the double-screw extruder used in the embodiment of the invention are as follows: the Rondol Microlab 400 has a screw diameter of 10 mm and a length/diameter ratio of 20, and the temperatures from the feed hopper to the discharge hopper are respectively set to be 200-. The Charpy impact tester is Ceast resin Impactor with the test standard of ISO 179-1, the tensile tester is Instron 5565A, and the test standard is ISO 527-2.

Example 1:

weighing in proportion: 90 parts of PLA; TPEE 17 parts; 5 parts of a compatilizer; adding the mixture into a medium-speed mixer, and uniformly stirring the mixture; uniformly mixing, discharging, adding into a double-screw extruder, extruding, blending, plasticizing and extruding, wherein the double-screw extruder is heated in a linear gradient manner at the temperature of 200-220 ℃ from a feed hopper to extrusion, and the rotating speed of a screw is 120 r/min; the compatilizer is PLA grafted glycidyl methacrylate; PLA weight average molecular weight is 200000g/mol, and D-lactic acid content is 2.0%; TPEE is a block copolymer of polybutylene terephthalate as a crystalline segment and polyether diol as an amorphous segment.

Example 2:

weighing in proportion: 90 parts of PLA; TPEE 17 parts; 3 parts of a compatilizer; adding the mixture into a medium-speed mixer, and uniformly stirring the mixture; uniformly mixing, discharging, adding into a double-screw extruder, extruding, blending, plasticizing and extruding, wherein the double-screw extruder is heated in a linear gradient manner at the temperature of 200-220 ℃ from a feed hopper to extrusion, and the rotating speed of a screw is 120 r/min; the compatilizer is PLA grafted glycidyl methacrylate; PLA weight average molecular weight is 200000g/mol, and D-lactic acid content is 1.4%; TPEE is a block copolymer of polybutylene terephthalate as a crystalline segment and polyether diol as an amorphous segment.

Example 3:

weighing in proportion: 90 parts of PLA; TPEE 17 parts; 3 parts of a compatilizer; adding the mixture into a medium-speed mixer, and uniformly stirring the mixture; uniformly mixing, discharging, adding into a double-screw extruder, extruding, blending, plasticizing and extruding, wherein the double-screw extruder is heated in a linear gradient manner at the temperature of 200-220 ℃ from a feed hopper to extrusion, and the rotating speed of a screw is 120 r/min; the compatilizer is PLA grafted glycidyl methacrylate; the weight-average molecular weight of PLA is 190000g/mol, and the content of D-lactic acid is 1.4%; TPEE is a block copolymer of polybutylene terephthalate as a crystalline segment and polyether diol as an amorphous segment.

Example 4:

weighing in proportion: 85 parts of PLA; 16 parts of TPEE; 5 parts of a compatilizer; adding the mixture into a medium-speed mixer, and uniformly stirring the mixture; uniformly mixing, discharging, adding into a double-screw extruder, extruding, blending, plasticizing and extruding, wherein the double-screw extruder is heated in a linear gradient manner at the temperature of 200-220 ℃ from a feed hopper to extrusion, and the rotating speed of a screw is 120 r/min; the compatilizer is PLA grafted maleic anhydride; the weight-average molecular weight of PLA is 190000g/mol, and the content of D-lactic acid is 1.4%; TPEE is a block copolymer of polybutylene terephthalate as a crystalline segment and polyether diol as an amorphous segment.

Example 5:

weighing in proportion: 75 parts of PLA; 12 parts of TPEE; 3 parts of a compatilizer; adding the mixture into a medium-speed mixer, and uniformly stirring the mixture; uniformly mixing, discharging, adding into a double-screw extruder, extruding, blending, plasticizing and extruding, wherein the double-screw extruder is heated in a linear gradient manner at the temperature of 200-220 ℃ from a feed hopper to extrusion, and the rotating speed of a screw is 120 r/min; the compatilizer is PLA grafted glycidyl methacrylate; the weight-average molecular weight of PLA is 190000g/mol, and the content of D-lactic acid is 1.4%; TPEE is a block copolymer of polybutylene terephthalate as a crystalline segment and polyether diol as an amorphous segment.

Example 6:

weighing in proportion: 65 parts of PLA; 10 parts of TPEE; 3 parts of a compatilizer; adding the mixture into a medium-speed mixer, and uniformly stirring the mixture; uniformly mixing, discharging, adding into a double-screw extruder, extruding, blending, plasticizing and extruding, wherein the double-screw extruder is heated in a linear gradient manner at the temperature of 200-220 ℃ from a feed hopper to extrusion, and the rotating speed of a screw is 120 r/min; the compatilizer is PLA grafted glycidyl methacrylate; the weight-average molecular weight of PLA is 190000g/mol, and the content of D-lactic acid is 1.4%; TPEE is a block copolymer of polybutylene terephthalate as a crystalline segment and polyether diol as an amorphous segment.

Example 7:

weighing in proportion: 75 parts of PLA; 12 parts of TPEE; 3 parts of a compatilizer; 0.4 part of nucleating agent; adding into a medium-speed mixer, and uniformly stirring; uniformly mixing, discharging, adding into a double-screw extruder, extruding, blending, plasticizing and extruding, wherein the double-screw extruder is heated in a linear gradient manner at the temperature of 200-220 ℃ from a feed hopper to extrusion, and the rotating speed of a screw is 120 r/min; the compatilizer is PLA grafted glycidyl methacrylate; the weight-average molecular weight of PLA is 190000g/mol, and the content of D-lactic acid is 1.4%; TPEE is a segmented copolymer with polybutylene terephthalate as a crystalline segment and polyether diol as an amorphous segment, and a nucleating agent is sodium citrate.

Example 8:

weighing in proportion: 75 parts of PLA; 12 parts of TPEE; 3 parts of a compatilizer; 0.9 part of nucleating agent; adding the mixture into a medium-speed mixer, and uniformly stirring the mixture; uniformly mixing, discharging, adding into a double-screw extruder, extruding, blending, plasticizing and extruding, wherein the double-screw extruder is heated in a linear gradient manner at the temperature of 200-220 ℃ from a feed hopper to extrusion, and the rotating speed of a screw is 120 r/min; the compatilizer is PLA grafted glycidyl methacrylate; the weight-average molecular weight of PLA is 190000g/mol, and the content of D-lactic acid is 1.4%; TPEE is a segmented copolymer with polybutylene terephthalate as a crystalline segment and polyether diol as an amorphous segment, and a nucleating agent is sodium citrate.

Example 9:

weighing in proportion: 90 parts of PLA; 20 parts of TPEE; 5 parts of a compatilizer; adding the mixture into a medium-speed mixer, and uniformly stirring the mixture; uniformly mixing, discharging, adding into a double-screw extruder, extruding, blending, plasticizing and extruding, wherein the double-screw extruder is heated in a linear gradient manner at the temperature of 200-220 ℃ from a feed hopper to extrusion, and the rotating speed of a screw is 120 r/min; the compatilizer is PLA grafted glycidyl methacrylate; the weight-average molecular weight of PLA is 190000g/mol, and the content of D-lactic acid is 1.4%; TPEE is a block copolymer of polybutylene terephthalate as a crystalline segment and polyether diol as an amorphous segment.

Comparative example 1:

weighing in proportion: 90 parts of PLA; TPEE 17 parts; 3 parts of a compatilizer; adding the mixture into a medium-speed mixer, and uniformly stirring the mixture; uniformly mixing, discharging, adding into a double-screw extruder, extruding, blending, plasticizing and extruding, wherein the temperature from a feed hopper to the extrusion of the double-screw extruder is set to 200-; the compatilizer is PLA grafted glycidyl methacrylate; the weight-average molecular weight of PLA is 190000g/mol, and the content of D-lactic acid is 1.4%; TPEE is a block copolymer of polybutylene terephthalate as a crystalline segment and polyether diol as an amorphous segment.

Comparative example 2:

weighing in proportion: 90 parts of PLA; TPEE 17 parts; adding the mixture into a medium-speed mixer, and uniformly stirring the mixture; uniformly mixing, discharging, adding into a double-screw extruder, extruding, blending, plasticizing and extruding, wherein the double-screw extruder is heated in a linear gradient manner at the temperature of 200-220 ℃ from a feed hopper to extrusion, and the rotating speed of a screw is 120 r/min; the compatilizer is PLA grafted glycidyl methacrylate; the weight-average molecular weight of PLA is 190000g/mol, and the content of D-lactic acid is 1.4%; TPEE is a block copolymer of polybutylene terephthalate as a crystalline segment and polyether diol as an amorphous segment.

Table 1, table of example data:

table 2, table of performance test data of examples:

as shown in Table 2, the impact resistance of the thermoplastic elastomer of the present invention is improved by introducing a small amount of a compatibilizer to partially react with the TPEE elastomer to form a network structure.

In the thermoplastic elastomer material, the amount of the TPEE is larger than that of the compatilizer, the TPEE which does not react with the compatilizer is dispersed in the PLA matrix, and the dispersed small TPEE particles can absorb part of impact energy when the PLA matrix is impacted, so that the toughness of the thermoplastic elastomer material is improved.

The thermoplastic elastomer material adopts a linear gradient heating melt blending mode in the melt blending stage, the dispersed particle size of the TPEE in the PLA matrix is smaller, the TPEE with small particle size can be used as a crystal nucleus to promote the heterogeneous nucleation of the PLA so as to accelerate the crystallization speed of the PLA (figure 1), and the rigidity of the PLA matrix is not influenced while the toughness of the PLA is ensured to be improved.

The percent strain before fracture of the inventive thermoplastic elastomer as measured by the tensile stress-strain test is reported in table 2, and the data shows that the inventive thermoplastic elastomer transitions from brittle fracture to ductile fracture upon the addition of TPEE and a compatibilizer.

Part of the compatilizer reacts with the TPEE elastomer to form a reticular structure, so that the viscoelasticity of the thermoplastic elastomer is increased, the TPEE with small particle size is dispersed in the PLA matrix, and the nucleation sites are increased, so that the thermoplastic elastomer is convenient for subsequent foaming.

The invention takes PLA as a matrix, and the PLA can be biodegraded after being used and has small pressure on the environment.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.

Claims

1. A method for preparing thermoplastic elastomer material is characterized in that,

uniformly mixing thermoplastic elastomer materials according to a ratio, adding the mixture into a medium-speed mixer, and uniformly stirring the mixture; uniformly mixing, discharging, adding into a double-screw extruder, extruding, blending, plasticizing and extruding, wherein the double-screw extruder is heated from a feed hopper to a die in a linear gradient manner at the temperature of 200-220 ℃, and the rotating speed of a screw is 120 r/min;

the thermoplastic elastomer material comprises: 65-90 parts of PLA (polylactic acid) by mass fraction; 10-20 parts of TPEE; 3-5 parts of a compatilizer; the compatilizer is one or more of PLA grafted glycidyl methacrylate and PLA grafted maleic anhydride.

2. The method for preparing a thermoplastic elastomer material according to claim 1, wherein the PLA grafted glycidyl methacrylate is grafted glycidyl methacrylate segments on the surface of the PLA, the PLA grafted maleic anhydride is grafted maleic anhydride segments on the surface of the PLA, and the graft polymerization method of the compatibilizer is a melt-grafting method.

3. The process for the preparation of a thermoplastic elastomeric material according to claim 2, wherein the degree of grafting of said PLA grafted glycidyl methacrylate is comprised between 1.2% and 1.8% and the degree of grafting of said PLA grafted maleic anhydride is comprised between 1.2% and 2%.

4. The process for producing a thermoplastic elastomer material according to claim 1, wherein said TPEE is a block copolymer having polybutylene terephthalate as a crystalline segment and polyether diol as an amorphous segment.

5. The process for preparing a thermoplastic elastomer material according to claim 1, wherein the weight average molecular weight of PLA is 190000g/mol or more and the D-lactic acid content is 2.0% or less.

6. The method of claim 5, wherein the weight average molecular weight of the PLA is 190000g/mol, and the D-lactic acid content is 1.4% or less.

7. The method for producing a thermoplastic elastomer material according to claim 1, wherein the thermoplastic elastomer material further comprises 0.4 to 1 part of a nucleating agent; the nucleating agent is one or more of zinc oxide, zinc stearate and sodium citrate.

8. A thermoplastic elastomer material obtained by the process for producing a thermoplastic elastomer material as claimed in any one of claims 1 to 7.