CN113817299A - PLA-based blending composite material with ion and chemical double-crosslinking structure and preparation method thereof - Google Patents

Abstract

The invention discloses a PLA-based blending composite material with an ion and chemical double cross-linking structure and a preparation method thereof, belonging to the technical and scientific fields of high polymer materials and being characterized in that the PLA-based blending composite material comprises the following raw materials in percentage by mass: PLA 60% -64%; 20% -22% of biodegradable polyester elastomer; 2% -5% of a three-arm star-shaped ionic chain extender; 4% -5% of an ionic polymer; 3% -6% of multi-wall carbon nano-tubes; 2 to 4 percent of hydrolysis resistant agent. Firstly, carbon nanotubes with different surface states, PLA and a three-arm star-shaped ionic chain extender are blended to prepare a blending filler master batch, and then the master batch is blended with a biodegradable polyester elastomer, so that the carbon tubes migrate to the biodegradable polyester elastomer with lower melt viscosity under the dual actions of dynamics and thermodynamics, and a concentration gradient of the carbon tubes is formed at the interface of the PLA and the biodegradable polyester elastomer. According to the invention, the three-arm star-shaped ionic chain extender is compounded with the ionomer, so that the compatibility of the blending components is improved, and simultaneously, a chemical crosslinking structure and an ionic crosslinking structure are constructed in the matrix of the blending composite material, so that the material is endowed with higher mechanical property and dielectric property.

Description

PLA-based blending composite material with ion and chemical double-crosslinking structure and preparation method thereof

Technical Field

The invention belongs to the technical and scientific fields of high polymer materials, particularly relates to a modified polylactic acid material, and particularly relates to a PLA-based blending composite material which has high dielectric constant, high flexibility and high strength and has an ionic and chemical double crosslinking structure, and a preparation method thereof.

Background

With the rapid development of electronic information technology, conductive polymers and high molecular dielectric materials with excellent dielectric properties gradually attract people's attention and are widely applied in the electronic information industry. However, the abandonment of the traditional polymer dielectric material and devices has great influence on the environment, so how to prepare the environment-friendly polymer dielectric material is a hotspot of industrial development and scientific research at present. Polylactic acid (PLA) is a research and development tool because of its natural and natural characteristicsAnd one of the main materials for replacing the traditional non-degradable petroleum-based materials in the industrial field, but the PLA material is brittle, and the conductivity of the PLA is poor, so that the application requirements of high-performance electronic devices cannot be met. At present, the toughness of the material is usually improved by introducing an elastomer, the electrical property of the material is enhanced by doping substances and non-substances, but the poor compatibility and interface interaction enable the strength of the PLA material to be obviously reduced while the toughness is improved, and at present, the degree of improving the electrical property of the PLA material by doping is limited, and the stability is poor. CN109912949A discloses a method for modifying and toughening PLA by using poly (butylene succinate) diol polyurethane prepolymer, and patent CN104194294A discloses a method for improving interfacial compatibility between PLA blend components by adding hyperbranched triazine, but the improvement degree of the above patent on PLA mechanical properties is limited, and the impact strength is not more than 10kJ/m²And does not relate to the electrical properties of the material. CN102943315A discloses PLA conductive fibers prepared from conductive fillers such as carbon black, carbon nanotubes, graphene, gas-phase carbon nanofibers, copper sulfide, cuprous sulfide, and cuprous iodide, but the materials prepared by this patent have the problems of uneven dispersion of fillers and generally low mechanical strength of composite materials, and the electrical properties of the above materials are mainly determined by the conductive fillers, but the influence of the ion interaction on the electrical properties of the materials is not involved, and the interaction between the fillers and the matrix and the dispersion state of the fillers in the matrix cannot be controlled.

Therefore, with the increasing environmental problems and the scientific development of polymer materials, a PLA-based blended composite material with high dielectric constant, high flexibility, and high strength and having an ionic and chemical double cross-linking structure has a wide prospect.

Disclosure of Invention

The invention discloses a PLA-based blending composite material with an ion and chemical double cross-linking structure and a preparation method thereof, belonging to the technical and scientific fields of high polymer materials and being characterized in that the PLA-based blending composite material comprises the following raw materials in percentage by mass: PLA 60% -64%; 20% -22% of biodegradable polyester elastomer; 2% -5% of a three-arm star-shaped ionic chain extender; 4% -5% of an ionic polymer; 3% -6% of multi-wall carbon nano-tubes; 2 to 4 percent of hydrolysis resistant agent. Firstly, carbon nanotubes with different surface states, PLA and a three-arm star-shaped ionic chain extender are blended to prepare a blending filler master batch, and then the master batch is blended with a biodegradable polyester elastomer, so that the carbon tubes migrate to the biodegradable polyester elastomer with lower melt viscosity under the dual actions of dynamics and thermodynamics, and a concentration gradient of the carbon tubes is formed at the interface of the PLA and the biodegradable polyester elastomer. According to the invention, the three-arm star-shaped ionic chain extender is compounded with the ionomer, so that the compatibility of the blending components is improved, and simultaneously, a chemical crosslinking structure and an ionic crosslinking structure are constructed in the matrix of the blending composite material, so that the material is endowed with higher mechanical property and dielectric property.

The specific scheme is as follows:

a PLA-based blending composite material with an ion and chemical double-crosslinking structure is characterized in that the PLA-based blending composite material comprises the following raw materials in percentage by mass:

PLA 60％-64％；

20% -22% of biodegradable polyester elastomer; the biodegradable polyester elastomer is one or more polymers with high toughness, such as polybutylene terephthalate adipate (PBAT), Polycaprolactone (PCL), polypropylene carbonate (PPC) and the like;

2% -5% of a three-arm star-shaped ionic chain extender;

4% -5% of an ionic polymer; the ionic polymer is one or a mixture of ethylene-methacrylate copolymer with cation of sodium, potassium, magnesium or zinc;

3% -6% of multi-wall carbon nano-tubes; the multi-walled carbon nanotube is one or a mixture of more of a carbon nanotube with hydroxyl, amino and carboxyl grafted on the surface and a conventional multi-walled carbon nanotube without surface treatment;

2% -4% of an anti-hydrolysis agent; the main component of the hydrolysis resistant agent is one or more of polycarbodiimide and other imine compounds;

the three-arm star-shaped ionic chain extender is a three-arm star-shaped compound containing a quaternary ammonium ion ring structure and an epoxy group as shown in a formula II;

further, the melt mass flow rate of the PLA is 2g/10min-40g/10min at the temperature of 210 ℃ under the test condition that the load weight is 2.16kg, the flexural modulus is 100-150MPa, the elastic modulus is 3000-4000MPa, the tensile strength is 40-60MPa, the elongation at break is 4-10%, the melting point is 155-180 ℃, and the density is 1.2-1.3g/cm³。

Further, the elastomer has a density of 0.9 to 1.3g/cm³The melt mass flow rate is 3g/10min-43g/10min at a temperature of 190 ℃ under the test conditions of a load weight of 2.16 kg. The crystallization temperature is 50-115 ℃, the melting point is 60-130 ℃, the crystallinity is 25-40%, and the Shore hardness (A) is 40-90.

Further, the ionic polymer is one or a mixture of ethylene-methacrylate copolymer with cation of sodium, potassium, magnesium or zinc. The ionomer has a density of 0.92 to 1.22g/cm³The melt mass flow rate is 0.5g/10min-10g/10min under the test conditions of the temperature of 190 ℃ and the load weight of 2.16kg, and the melting point is 60-110 ℃.

Furthermore, the multi-walled carbon nanotube is one or a mixture of more of a carbon nanotube with hydroxyl, carboxyl and amino grafted on the surface and a conventional multi-walled carbon nanotube without surface treatment, the diameter is 4-6 nanometers, the purity is more than 98 percent, and the length is 10-20 micrometers.

Furthermore, the main component of the hydrolysis resistant agent is one or more of polycarbodiimide and other imine compounds. The molecular weight is 360-400g/mol, and the density is 1.02-1.05g/cm³The melting temperature is 60-100 ℃, and the content of carbodiimide is more than 12%.

Further, a preparation method for preparing the PLA-based blended composite material is characterized by comprising the following steps: firstly, performing vacuum drying on PLA, a biodegradable polyester elastomer and an ionomer at 60 ℃ for 12 hours to remove water, controlling the water content of all materials to be lower than 200ppm, then adding the PLA, a multi-walled carbon nanotube and a three-arm star-shaped ionic chain extender into a high-speed mixer in proportion, blending at the rotating speed of 4000-. And then the master batch, the biodegradable polyester elastomer, the ionomer, the anti-hydrolysis agent and the like are fully mixed in a high-speed mixer with the rotating speed of 2000-4000r/min, then melt-extruded in a double-screw extruder with the temperature of 130-200 ℃, and air-cooled and granulated at the temperature of 30-40 ℃ to obtain the PLA-based blending composite material with the ionic and chemical double-crosslinking structure.

Further, the method also comprises a step of preparing the three-arm star-shaped ionic chain extender, and specifically comprises the following steps:

step a, adding an ammonium hydroxide aqueous solution into a flask provided with a thermometer and a stirring device, then dropwise adding propargyl bromide into the aqueous solution, reacting at room temperature for 3 hours, and precipitating ammonium bromide, wherein the solution is yellow in color; then stirring the mixture at room temperature for 24 hours, raising the temperature to 50 ℃, continuing stirring for 48 hours, and finishing the reaction after the propargyl bromide completely reacts; the product is subsequently extracted 3 times with diethyl ether and dried over sodium sulfate, and finally the residue is purified by column chromatography with a diethyl ether/hexane volume ratio of 1: 1;

and b, adding the tripropargylamine prepared in the step a into a flask containing a mixed solvent of N, N, N' -pentamethyl divinyl triamine (PMDETA) and N, N-dimethyl formamide (DMF), heating to 90 ℃, slowly dropwise adding 3- (azidomethyl) -2, 2-dimethyl-ethylene oxide, and reacting for 48 hours. After the reaction is finished, cooling the reactant to room temperature, pouring the reactant into deionized water, extracting the reactant with DMF for multiple times, extracting the reactant twice with deionized water and saturated NaCl solution respectively, extracting and washing the reactant with anhydrous Na₂SO₄Drying overnight, filtering, and evaporating the solvent under reduced pressure to obtain a compound (I);

step c, slowly dropwise adding dimethyl sulfate into the compound (I) prepared in the step b, and stirring and reacting at the constant temperature of 60 ℃ for 24 hours; and (3) cooling to room temperature after the reaction is finished, adding deionized water, standing, precipitating a solid, performing suction filtration, washing with deionized water, recrystallizing with methanol-water, and drying. Preparing a compound (II), namely the three-arm star-shaped ionic chain extender;

the invention has the following beneficial effects:

1) the three-arm star-shaped ionic chain extender is a three-arm star-shaped compound simultaneously containing quaternary ammonium ions and epoxy groups, and the ionic elements in the chain extender can improve the reaction efficiency of the epoxy groups and terminal hydroxyl and terminal carboxyl in PLA and biodegradable polyester in the blending process, so that a chemical crosslinking structure is formed in a matrix, and the compatibility of the PLA and an elastomer is improved. Meanwhile, quaternary ammonium cation and counter ion can interact with cation and counter ion in the ionomer through static electricity, hydrogen bond and the like to form an ionic crosslinking structure in a polymer matrix. The chemical and ionic crosslinking structure endows the material with high toughness and strength.

2) Under the catalytic action of the three-arm star-shaped ionic chain extender, active groups on the surface of the functionalized carbon nano tube can respectively perform physical/chemical actions with PLA, the biodegradable polyester elastomer and the chain extender, so that the dispersion performance of the functionalized carbon nano tube in a matrix is improved, and the electrical property of the material is improved. In addition, the three-arm star-shaped ionic chain extender and an ionic crosslinking network formed by ionic elements in the ionomer and the conjugation of the ionic elements and the carbon tubes can strengthen the interaction between the carbon tubes and the matrix and further improve the electrical property of the PLA-based composite material from the material body.

3) In the aspect of processing technology, firstly, carbon nanotubes with different surface states are mixed with PLA and a three-arm star-shaped ionic chain extender at a high speed, in the high-speed mixing process, the polymer surface is subjected to micro-melting under the action of strong friction force, and the chain extender and the filler are coated on the surface of the micro-melted polymer and subjected to chain extension and coupling reaction. And then, preparing the filler master batch by melt extrusion and temperature-controllable hot air drying processes, wherein the master batch is dried in a hot air environment, the moisture content is extremely low, and the PLA can be pre-crystallized. When the master batch and the biodegradable polyester elastomer are subjected to melt blending and extrusion, the PLA crystal can regulate and control the aggregation structure of the biodegradable polyester, and the carbon tube can migrate to the biodegradable polyester elastomer with lower melt viscosity under the dual actions of dynamics and thermodynamics, so that the concentration gradient of the carbon tube is formed at the interface of the PLA and the biodegradable polyester elastomer, and the controllable dispersion of inorganic fillers such as the carbon tube and the like in a matrix is realized. Finally, the compatibility of the blending components is improved, and simultaneously, a chemical crosslinking structure and an ionic crosslinking structure are constructed in the matrix of the blending composite material, so that the material is endowed with higher mechanical property and dielectric property.

4) The PLA blending composite material has high toughness and rigidity, and excellent dielectric property, and has wide prospects in the aspects of electrode materials, electromagnetic shielding materials, sensor materials, electrochromic materials and the like.

Drawings

FIG. 1a is a flow chart of a synthetic structure of a three-arm star-shaped ionic chain extender, FIG. 1b is a structural formula of an intermediate (I), and FIG. 1c is a structural formula of a product (II)

FIG. 2 three-armed star-shaped ionic chain extender¹H-NMR spectrum

FIG. 3 TEM morphologies of various examples and comparative examples

Detailed Description

The present invention will be described in more detail below with reference to specific examples, but the scope of the present invention is not limited to these examples.

The following examples used the raw materials:

PLA is polylactic acid, the MFR of which is 7g/10min under the test conditions of the temperature of 210 ℃ and the load weight of 2.16kg, the elongation at break is 6 percent, the notch impact strength is 0.3J/m, and the melting point is175 ℃ and a density of 1.22g/cm³4032D from Nature Works, USA is selected.

PBAT polybutylene adipate terephthalate with a density of 1.2g/cm³The MFR is 43g/10min under the test conditions of the temperature of 190 ℃ and the load weight of 2.16kg, and is selected from Guangzhou Jinfa science and technology Co.

PCL: polycaprolactone with a density of 1.146g/cm³The MFR is 3g/min at 160 ℃ under the test conditions with a load weight of 2.16kg, 6500 from Perstorp, Sweden is used.

The three-arm star-shaped ionic chain extender is as follows: a three-arm star-shaped compound containing a quaternary ammonium ion ring structure and an epoxy group is prepared by the following steps:

step a, adding an ammonium hydroxide aqueous solution into a flask provided with a thermometer and a stirring device, then dropwise adding propargyl bromide into the aqueous solution, reacting at room temperature for 3 hours, and precipitating ammonium bromide, wherein the solution is yellow in color; then stirring the mixture at room temperature for 24 hours, raising the temperature to 50 ℃, continuing stirring for 48 hours, and finishing the reaction after the propargyl bromide completely reacts; the product is subsequently extracted 3 times with diethyl ether and dried over sodium sulfate, and finally the residue is purified by column chromatography with a diethyl ether/hexane volume ratio of 1: 1;

and b, adding the tripropargylamine prepared in the step a into a flask containing a mixed solvent of N, N, N' -pentamethyl divinyl triamine (PMDETA) and N, N-dimethyl formamide (DMF), heating to 90 ℃, slowly dropwise adding 3- (azidomethyl) -2, 2-dimethyl-ethylene oxide, and reacting for 48 hours. After the reaction is finished, cooling the reactant to room temperature, pouring the reactant into deionized water, extracting the reactant with DMF for multiple times, extracting the reactant twice with deionized water and saturated NaCl solution respectively, extracting and washing the reactant with anhydrous Na₂SO₄Drying overnight, filtering, and evaporating the solvent under reduced pressure to obtain a compound (I);

step c, slowly dropwise adding dimethyl sulfate into the compound (I) prepared in the step b, and stirring and reacting at the constant temperature of 60 ℃ for 24 hours; and (3) cooling to room temperature after the reaction is finished, adding deionized water, standing, precipitating a solid, performing suction filtration, washing with deionized water, recrystallizing with methanol-water, and drying. Preparing a compound (II), namely the three-arm star-shaped ionic chain extender;

the ionomers used were:

surlyn 8920: is an ethylene-methacrylic acid copolymer containing sodium ions: the density was 0.95g/cm³The MFR was 0.9g/10min at 190 ℃ under the test conditions of a load weight of 2.16kg, the melting point was 88 ℃ and 8920 from DuPont, USA.

The multi-walled carbon nanotubes used were:

MWCNTs: the purity is 95%, the length is 10-20 microns, and XFM01 is selected from Jiangsu Xiancheng nano material science and technology Limited.

MWCNT-COOH: the purity is 95%, the length is 10-20 microns, and XFM33 is selected from Jiangsu Xiancheng nano material science and technology Limited.

MWCNT-OH: 98 percent of purity and 10 to 20 microns of length, and XFM68 of Jiangsu Xiancheng nano material science and technology Limited is selected.

The hydrolysis resistant agent is:

hyadimide 100: the chemical composition is polymerized carbodiimide with the density of 1.05g/cm³The melting temperature is 100 ℃, and Hyadimide 100 of Rhein-Schafer Germany is selected.

Hyadimide 1001: the chemical component is an imine compound with the density of 1.02g/cm³The melting temperature is 60-80 ℃, and Hyadimide 1001 of Rhein-Schafer Germany is selected.

The traditional chain extenders used were:

ADR: the molar mass is 5500g/mol, the epoxy equivalent is 445g/mol, the glass transition temperature is 56 ℃, and German BASF 4300 is selected.

The mass percentage ratio of each raw material in the following examples is shown in table 1.

TABLE 1 materials and amounts (in weight percent) of PLA-based blended composites

Example 1

In this embodiment, the materials and formulation of the PLA-based blended composite material are shown in table 1, and the preparation method comprises the following steps:

firstly, performing vacuum drying on PLA, a biodegradable polyester elastomer and an ionomer at 60 ℃ for 12 hours to remove water, controlling the water content of all materials to be lower than 200ppm, then adding the PLA, a multi-wall carbon nano tube and a three-arm star-shaped ionic chain extender into a high-speed mixer in proportion, blending at the rotating speed of 4000r/min, stopping blending when the surface of the PLA is softened and slightly melted and the carbon nano tube and the three-arm star-shaped ionic chain extender are coated on the surface of the PLA, then adding the mixture into a double-screw extruder at the temperature of 140-210 ℃ for melt blending extrusion, and granulating after air cooling at the temperature of 40-50 ℃ to obtain the blended filler master batch. And then the master batch, the biodegradable polyester elastomer, the ionomer, the anti-hydrolysis agent and the like are fully mixed in a high-speed mixer with the rotating speed of 3000r/min, then the mixture is subjected to melt extrusion in a double-screw extruder with the temperature of 130-200 ℃, and air cooling granulation is performed at the temperature of 30-40 ℃ to obtain the PLA-based blending composite material with the ionic and chemical double-crosslinking structure.

Example 2

The materials and formulation of the PLA-based blended composite material of this example are shown in Table 1, and the preparation process is the same as that of example 1

Example 3

The materials and formulation of the PLA-based blended composite material of this example are shown in Table 1, and the preparation process is the same as that of example 1

Comparative example 1

The materials and formulation of PLA-based blended composite material of this comparative example are shown in Table 1, and the preparation process is the same as that of example 1

Comparative example 2

The materials and formulation of PLA-based blended composite material of this comparative example are shown in Table 1, and the preparation process is the same as that of example 1

Comparative example 3

The materials and formulation of PLA-based blended composite material of this comparative example are shown in Table 1, and the preparation process is the same as that of example 1

Comparative example 4

The raw materials and the formula of the PLA-based blended composite material in the comparative example are shown in Table 1, and the preparation method comprises the following steps:

PLA, biodegradable polyester elastomer, ionomer were first vacuum dried at 60 ℃ for 12 hours to remove water, controlling the water content of all materials below 200 ppm. PLA, biodegradable polyester elastomer, ionomer, carbon nano tube, chain extender and anti-hydrolysis agent are added into a high-speed mixer with the rotating speed of 2000r/min in proportion for full mixing, and then melt extrusion granulation is carried out in a double-screw extruder with the temperature of 130-200 ℃ to prepare the material.

Comparative example 5

The materials and formulation of PLA-based blended composite material of this comparative example are shown in Table 1, and the preparation process is the same as that of comparative example 4.

Test and results

The materials prepared in the above examples and comparative examples were cut to prepare test specimens, wherein the test methods were:

tensile strength: testing according to ISO527 standard, and the speed is 50 mm/min;

elongation at break: testing according to ASTM D638, with a speed of 10 mm/min;

notched impact strength: the pendulum mass is 0.668kg, the speed is 0.46m/s and the pendulum energy is 4J according to the test of the ASTM D256 standard;

conductivity: testing according to GB/T11007 standard;

dielectric constant: the frequency range is 20Hz-2 MHz and the temperature range is 30-80 ℃ according to the test of ASTM A893 standard.

The test results are shown in table 2, with example 3 having the best overall performance. The performance of example 1 is inferior to that of example 3 under the condition of the same content of the carbon nanotubes, because the content of the three-arm star-shaped ionic chain extender is lower than that of example 3, and the regulation effect on the carbon nanotubes is not obvious. In example 2, compared with example 3, the reduction of the content of the carbon nanotubes not only reduces the electrical property, but also reduces the mechanical property of the material, which shows that the filler carbon nanotubes have a reinforcing effect on the material. Comparative example 1 does not use any chain extender and has poor performance. Comparative example 3 only uses the traditional chain extender ADR, and finds that the interfacial dispersion state is difficult to control and the comprehensive performance of the material is poor. Comparative example 2 introduces a three-arm star-shaped ionic chain extender on the basis of the above, and the effect of regulating and controlling is found to be achieved, but the performance is poorer than that of example 3. In conclusion, the superiority of the formulation designed in example 3 is shown.

The examples 2 and 3 have the same formula as the comparative examples 4 and 5 but different preparation processes, and have larger performance difference. The reason is that the traditional blending method is difficult to realize the controllable dispersion of the carbon tube in the matrix, and embodies the superiority of the preparation process.

The TEM appearances of different samples are shown in FIG. 3, and in example 3, the carbon nanotubes are uniformly dispersed at the interface of two phases to play a role in adhesion and increase the interaction between the two phases. In example 1, the content of the three-arm star-shaped ionic chain extender is low, so that the carbon nanotube can be regulated to a certain extent, and a small amount of aggregation can still be seen. In example 2, the effect of adhesion between the two phases at the interface was insufficient because the content of carbon nanotubes was small, and the reinforcing effect was insufficient. Comparative example 1a large amount of agglomeration of carbon nanotubes in the polyester elastomer was seen because no chain extender was added. Comparative example 3 using a conventional chain extender ADR, it was found that carbon nanotubes were dispersed in a polyester elastomer, but it was difficult to play a role in migration control. Comparative example 2 on the basis of the above, a part of the three-arm star-shaped ionic chain extender is added, and the carbon nanotube is found to begin to migrate, but the effect is not obvious enough. In conclusion, the formulation of example 3 is superior.

The carbon nanotubes in comparative examples 4 and 5, which use the conventional blending process, are dispersed randomly, and can be agglomerated both inside the polyester elastomer and at the interface of two phases, which has adverse effects on the properties of the material. Thereby showing the superiority of the material preparation process.

The analysis of the test data shows that the mechanical property of the PLA-based blended composite material is greatly improved, and the following reasons exist: (1) the epoxy group in the chain extender reacts with hydroxyl and carboxyl in PLA and the elastomer, the quaternary ammonium ion and the ionomer play a role in promoting the reaction, the compatibility between the two phases is improved, and the force is uniformly transmitted when the chain extender is acted by the force. (2) After the chain extender is added, the material forms chemical crosslinking, the interaction between ions forms ionic crosslinking, and the two have synergistic action, so that a large amount of energy is absorbed when force is applied to the material, and meanwhile, the rigidity and the toughness of the material are improved. (3) The space structure contains a large number of annular structures, and the strength of the material is improved.

The analysis of the test data shows that the electrical property of the PLA-based blended composite material is greatly improved, and the following reasons exist: (1) ions and the carbon nano tubes form ion interaction, so that the carbon nano tubes are uniformly dispersed; (2) a specific processing technology induces the carbon nano tube to migrate between two phases, so as to achieve the purposes of thermodynamic and kinetic regulation and control; (3) the presence of the ionic crosslinked network in the matrix further improves the electrical properties of the material.

Therefore, the tensile strength, elongation at break, notch impact strength, conductivity and dielectric constant results in each embodiment and the comparative example show that the material overcomes the problem of material strength reduction while toughening polylactic acid by adding the biodegradable polyester elastomer, the three-arm star-shaped ionic chain extender, the ionomer, the multi-wall carbon nanotube and the hydrolysis resistance agent for compounding, simultaneously endows the material with excellent electrical property, expands the application range and the field of the polylactic acid composite material, and has wide prospects in special fields such as electrode materials, electromagnetic shielding materials, sensor materials, electrochromic materials and even stealth materials.

TABLE 2 Performance test results for each PLA-based blended composite example

While the present invention has been described in detail with reference to the preferred embodiments, it should be understood that the above description should not be taken as limiting the invention.

Claims (8)

1. A PLA-based blending composite material with an ion and chemical double-crosslinking structure is characterized in that the PLA-based blending composite material comprises the following raw materials in percentage by mass:

PLA 60％-64％；

20% -22% of biodegradable polyester elastomer; the biodegradable polyester elastomer is one or more polymers with high toughness, such as polybutylene terephthalate adipate (PBAT), Polycaprolactone (PCL), polypropylene carbonate (PPC) and the like;

2% -5% of a three-arm star-shaped ionic chain extender;

4% -5% of an ionic polymer; the ionic polymer is one or a mixture of ethylene-methacrylate copolymer with cation of sodium, potassium, magnesium or zinc;

3% -6% of multi-wall carbon nano-tubes; the multi-walled carbon nanotube is one or a mixture of more of a carbon nanotube with hydroxyl, amino and carboxyl grafted on the surface and a conventional multi-walled carbon nanotube without surface treatment;

2% -4% of an anti-hydrolysis agent; the main component of the hydrolysis resistant agent is one or more of polycarbodiimide and other imine compounds;

the three-arm star-shaped ionic chain extender is a three-arm star-shaped compound containing a quaternary ammonium ion ring structure and an epoxy group as shown in a formula II;

2. the PLA-based blended composite of claim 1, wherein: the melt mass flow rate of the PLA is 2g/10min-40g/10min under the test conditions that the temperature is 210 ℃ and the load weight is 2.16kg, the flexural modulus is 100-150MPa, the elastic modulus is 3000-4000MPa, the tensile strength is 40-60MPa, the elongation at break is 4-10%, the melting point is 155-180 ℃, and the density is 1.2-1.3g/cm³。

3. The PLA-based blended composite according to any one of claims 1-2, wherein: the density of the elastomer is 0.9-1.3g/cm³The melt mass flow rate is 3g/10min-43g/10min at a temperature of 190 ℃ under the test conditions of a load weight of 2.16 kg. The crystallization temperature is 50-115 ℃, the melting point is 60-130 ℃, the crystallinity is 25-40%, and the Shore hardness (A) is 40-90.

4. A PLA-based blended composite as claimed in any one of the preceding claims 1-3, wherein: the ionic polymer is one or a mixture of ethylene-methacrylate copolymer with cation of sodium, potassium, magnesium or zinc. The ionomer has a density of 0.92 to 1.22g/cm³The melt mass flow rate is 0.5g/10min-10g/10min under the test conditions of the temperature of 190 ℃ and the load weight of 2.16kg, and the melting point is 60-110 ℃.

5. The PLA-based blended composite material according to any of the above claims 1 to 4, wherein: the multi-wall carbon nano tube is one or a mixture of more of a carbon nano tube with hydroxyl, carboxyl and amino grafted on the surface and a conventional multi-wall carbon nano tube without surface treatment, the diameter is 4-6 nanometers, the purity is more than 98 percent, and the length is 10-20 micrometers.

6. The PLA-based blended composite material according to any of the above claims 1 to 5, characterized in that: the main component of the hydrolysis resistant agent is one or more of polycarbodiimide and other imine compounds, the molecular weight is 360-400g/mol, and the density is 1.02-1.05g/cm³The melting temperature is 60-100 ℃, and the carbonized material is carbonizedThe amine content is greater than 12%.

7. A preparation method for preparing the PLA-based blended composite material as described in any one of claims 1 to 6, which is characterized by comprising the steps of: firstly, performing vacuum drying on PLA, a biodegradable polyester elastomer and an ionomer at 60 ℃ for 12 hours to remove water, controlling the water content of all materials to be lower than 200ppm, then adding the PLA, a multi-walled carbon nanotube and a three-arm star-shaped ionic chain extender into a high-speed mixer in proportion, blending at the rotating speed of 4000-. And then the master batch, the biodegradable polyester elastomer, the ionomer, the anti-hydrolysis agent and the like are fully mixed in a high-speed mixer with the rotating speed of 2000-4000r/min, then melt-extruded in a double-screw extruder with the temperature of 130-200 ℃, and air-cooled and granulated at the temperature of 30-40 ℃ to obtain the PLA-based blending composite material with the ionic and chemical double-crosslinking structure.

8. The preparation method according to claim 7, further comprising preparing the three-arm star-shaped ionic chain extender, specifically comprising the steps of:

step a, adding an ammonium hydroxide aqueous solution into a flask provided with a thermometer and a stirring device, then dropwise adding propargyl bromide into the aqueous solution, reacting at room temperature for 3 hours, and precipitating ammonium bromide, wherein the solution is yellow in color; then stirring the mixture at room temperature for 24 hours, raising the temperature to 50 ℃, continuing stirring for 48 hours, and finishing the reaction after the propargyl bromide completely reacts; the product is subsequently extracted 3 times with diethyl ether and dried over sodium sulfate, and finally the residue is purified by column chromatography with a diethyl ether/hexane volume ratio of 1: 1;

step b, adding the tripropargylamine prepared in the step a into a solution containing N, N, N'In a flask containing a mixed solvent of N' -Pentamethyldivinyltriamine (PMDETA) and N, N-Dimethylformamide (DMF), the temperature was raised to 90 ℃ and 3- (azidomethyl) -2, 2-dimethyl-oxirane was slowly added dropwise thereto, followed by reaction for 48 hours. After the reaction is finished, cooling the reactant to room temperature, pouring the reactant into deionized water, extracting the reactant with DMF for multiple times, extracting the reactant twice with deionized water and saturated NaCl solution respectively, extracting and washing the reactant with anhydrous Na₂SO₄Drying overnight, filtering, and evaporating the solvent under reduced pressure to obtain a compound (I);

step c, slowly dropwise adding dimethyl sulfate into the compound (I) prepared in the step b, and stirring and reacting at the constant temperature of 60 ℃ for 24 hours; and (3) cooling to room temperature after the reaction is finished, adding deionized water, standing, precipitating a solid, performing suction filtration, washing with deionized water, recrystallizing with methanol-water, and drying. Preparing a compound (II), namely the three-arm star-shaped ionic chain extender;

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