CN116218172A - Preparation method of blended polylactic acid biodegradable toughening composite material - Google Patents
Preparation method of blended polylactic acid biodegradable toughening composite material Download PDFInfo
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- CN116218172A CN116218172A CN202310066094.1A CN202310066094A CN116218172A CN 116218172 A CN116218172 A CN 116218172A CN 202310066094 A CN202310066094 A CN 202310066094A CN 116218172 A CN116218172 A CN 116218172A
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- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L67/00—Compositions of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Compositions of derivatives of such polymers
- C08L67/04—Polyesters derived from hydroxycarboxylic acids, e.g. lactones
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- C—CHEMISTRY; METALLURGY
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- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F283/00—Macromolecular compounds obtained by polymerising monomers on to polymers provided for in subclass C08G
- C08F283/02—Macromolecular compounds obtained by polymerising monomers on to polymers provided for in subclass C08G on to polycarbonates or saturated polyesters
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- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G64/00—Macromolecular compounds obtained by reactions forming a carbonic ester link in the main chain of the macromolecule
- C08G64/42—Chemical after-treatment
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- C08L2205/00—Polymer mixtures characterised by other features
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Abstract
The invention relates to a preparation method of a toughened composite material, in particular to a preparation method of a polylactic acid graft copolymer and a preparation method of a polylactic acid-polypropylene carbonate blend material. The invention has the advantages that the auxiliary grafting monomer is introduced in the preparation process of the graft copolymer to participate in the copolymerization process, which greatly improves the grafting rate of the grafting monomer on macromolecules, so that the compatibility of two materials is better, and the mechanical property of the blend is further improved. The invention has low cost and simple process, is environment-friendly, and widens the application range of the polylactic acid composite material in industry.
Description
Technical Field
The invention relates to a preparation method of a toughened composite material, in particular to a preparation method of a biodegradable toughened composite material of blend polylactic acid.
Background
Polylactic acid (PLA) is a biodegradable and biocompatible thermoplastic with high modulus, high strength, high transparency and excellent processability, which makes it widely used in modification studies of biodegradable materials. However, polylactic acid has some inherent weaknesses such as poor ductility and low tensile elongation at break, which greatly limits its application in various fields.
Polypropylene Carbonate (PPC) is a material synthesized from the "greenhouse gas" carbon dioxide and propylene oxide. This not only reduces the dependence on petroleum resources, but also effectively relieves the greenhouse effect. PPC has good toughness as a biodegradable material. This is complementary to PLA in mechanical properties. However, although both have some degree of compatibility due to their similar chemical structures, many studies have shown that this compatibility is very low, and thus the mechanical properties of the blend material cannot be satisfied. Therefore, there is a need to find a simple and effective way to improve the compatibility of PLA/PPC blends to increase their mechanical properties.
The invention patent application of the publication No. CN103254596B discloses a PLA/PPC biodegradable composite material and a preparation method thereof, and the performance of the composite material and the preparation method is improved by adding modified starch. However, the compatibilizer is not as high as the compatibilizer by using the modified starch.
Patent application publication No. CN108359230A discloses a method for preparing degradable PLA/PPC film, which improves the mechanical property of the blend by adding montmorillonite, but uses polycaprolactone to improve the compatibility of montmorillonite and matrix material due to poor compatibility of montmorillonite and polymer, and does not add graft to improve the compatibility of two matrixes.
The invention patent application of the published patent number CN109385059A discloses an antibacterial high-toughness PLA/PPC biodegradable composite material and a preparation method thereof, wherein the PLA/PPC biodegradable composite material is subjected to alkali treatment and then modified by a silanization reagent to improve toughness, so that the high-toughness PLA/PPC biodegradable composite material is prepared, but the operation process is complex and the cost is high.
Disclosure of Invention
The invention aims to provide a preparation method of a blended polylactic acid biodegradable toughening composite material, which comprises the steps of adding a plurality of grafting monomers and polylactic acid to form a graft, adding the graft to improve the compatibility and mechanical properties of the grafting monomers and the polylactic acid, and simultaneously using a blocking agent to carry out blocking treatment on the polypropylene carbonate to prevent the polypropylene carbonate from being thermally decomposed in the processing process, so as to improve the mechanical properties of the blend, and widen the application range of the polylactic acid composite material in industry.
The invention aims at realizing the following technical scheme:
the preparation method of the blended polylactic acid biodegradable toughening composite material is a preparation method of a polylactic acid graft copolymer and a polypropylene carbonate blending material; the preparation method comprises the following preparation steps:
(1) Uniformly mixing the dried polypropylene carbonate and an auxiliary agent, adding the mixture into a double-screw extruder, setting the heating temperature of the double-screw extruder to be 130-150 ℃ and the rotating speed of the double-screw extruder to be 40-60r/min, taking materials, and drying for later use;
(2) Dissolving an initiator in a mixed solution of an auxiliary agent and acetone, and respectively adding a proper amount of auxiliary grafting monomer into the mixed solution; then fully mixing the mixture with polylactic acid according to the mass ratio; after the acetone is completely volatilized, preparing a graft copolymer by using a double-screw extruder, cooling the product, and granulating for later use; mixing conditions: the temperature is 170-180 ℃, the rotating speed is 40-60r/min, and the time is 6-10min;
(3) Uniformly mixing the dried polylactic acid and the materials in the step 1 and the step 2, and adding the mixture into a double-screw extruder, wherein the double-screw extruder is set to have a heating temperature of 160-200 ℃ and a rotating speed of 40-80 rpm;
(4) Granulating the raw materials extruded by the double-screw extruder in the step (3), and drying for later use;
the blending material comprises the following raw material components:
60-90 parts of polylactic acid;
10-40 parts of polypropylene carbonate;
0-10 parts of grafting monomer;
0-40 parts of auxiliary grafting monomer;
0-5 parts of initiator.
The auxiliary agent is one or two of Maleic Anhydride (MAH) and Glycidyl Methacrylate (GMA).
The grafting-assisting monomer is one or more of styrene (St), methyl Methacrylate (MMA), vinyl acetate, acrylic acid, alpha-methyl styrene (AMS) and epoxy resin (EP).
The initiator is one or two of dibenzoyl peroxide (BPO), dicumyl peroxide (DCP), azodiisobutyronitrile (AIBN), acrylamide (AM), tert-butyl peroxybenzoate, lauroyl peroxide, diisopropyl peroxydicarbonate and potassium persulfate.
The invention has the advantages and effects that:
1. according to the invention, a grafting-assisting monomer of a material for improving the toughness of the PLA/PPC blend is added, the grafting-assisting monomer is added, a graft is prepared by a melt reaction extrusion method, and epoxy groups and polyester hydroxyl groups or carboxyl groups in the auxiliary agent form a copolymer between two phases through nucleophilic substitution reaction, so that the interfacial tension is reduced, the binding force between the two phases is enhanced, the grafting degree of the monomer is improved, and side reactions during the grafting reaction are inhibited by adding the grafting-assisting monomer.
2. The two raw materials of the invention are all biodegradable materials, so that the white pollution problem can be reduced. To improve the phase separation of the two materials, a variety of graft copolymers were prepared. According to the invention, the auxiliary grafting monomer is introduced in the preparation process of the graft copolymer to participate in the copolymerization process, so that the grafting rate of the grafting monomer on macromolecules is greatly improved, the compatibility of two materials is better, and the mechanical property of the blend is further improved. The invention has low cost and simple process, is environment-friendly, and widens the application range of the polylactic acid composite material in industry.
Drawings
FIG. 1 is a comparative picture of crystallinity for thermal performance testing in examples of the present invention.
Detailed Description
The present invention is described in detail below by way of specific examples, which are given herein for further illustration only and are not to be construed as limiting the scope of the invention, as many insubstantial modifications and adaptations of the invention will be apparent to those skilled in the art in light of the foregoing disclosure.
Examples 1 to 4 are examples of graft copolymers according to the invention, respectively. The present invention will be described in detail with reference to examples.
Example 1
3 parts of grafting monomer
Initiator 0.15 part
The specific implementation steps are as follows:
dissolving an initiator in a mixed solution of an auxiliary agent and acetone, uniformly mixing the mixed solution with polylactic acid according to a certain mass ratio, and preparing a graft copolymer by a double screw extruder after the acetone is completely volatilized. The temperatures of the zone I, the zone II, the zone III, the zone IV, the zone V, the zone VI and the machine head in the extruder are respectively set to 165 ℃, 175 ℃, 160 ℃, the screw speed is 70r/min, and the feeding speed is 8.0r/min. The extruded bars are granulated after being cooled in water and placed in a vacuum oven at 60 ℃ for 12 hours for standby.
Crystallinity: 2.4
Example 2
3 parts of grafting monomer
Initiator 0.15 part
6 parts of auxiliary grafting monomer
The specific implementation steps are as follows:
dissolving an initiator in a mixed solution of an auxiliary agent and acetone, then respectively adding a proper amount of auxiliary grafting monomer St,
then evenly mixing the polymer with polylactic acid according to a certain mass ratio, and preparing the graft copolymer by a double screw extruder after the acetone is completely volatilized. The temperatures of the zone I, the zone II, the zone III, the zone IV, the zone V, the zone VI and the machine head in the extruder are respectively set to 165 ℃, 175 ℃, 160 ℃, the screw speed is 70r/min, and the feeding speed is 8.0r/min. The extruded bars are granulated after being cooled in water and placed in a vacuum oven at 60 ℃ for 12 hours for standby.
Crystallinity: 4.2
Example 3
3 parts of grafting monomer
Initiator 0.15 part
6 parts of auxiliary grafting monomer
The specific implementation steps are as follows:
dissolving an initiator in a mixed solution of an auxiliary agent and acetone, respectively adding a proper amount of auxiliary grafting monomer AMS, uniformly mixing with polylactic acid according to a certain mass ratio, and preparing a graft copolymer by a double-screw extruder after the acetone is completely volatilized. The temperatures of the zone I, the zone II, the zone III, the zone IV, the zone V, the zone VI and the machine head in the extruder are respectively set to 165 ℃, 175 ℃, 160 ℃, the screw speed is 70r/min, and the feeding speed is 8.0r/min. The extruded bars are granulated after being cooled in water and placed in a vacuum oven at 60 ℃ for 12 hours for standby.
Crystallinity: 3.6
Example 4
3 parts of grafting monomer
Initiator 0.15 part
6 parts of auxiliary grafting monomer
The specific implementation steps are as follows:
dissolving an initiator in a mixed solution of an auxiliary agent and acetone, respectively adding a proper amount of auxiliary grafting monomer EP, uniformly mixing with polylactic acid according to a certain mass ratio, and preparing a graft copolymer by a double-screw extruder after the acetone is completely volatilized. The temperatures of the zone I, the zone II, the zone III, the zone IV, the zone V, the zone VI and the machine head in the extruder are respectively set to 165 ℃, 175 ℃, 160 ℃, the screw speed is 70r/min, and the feeding speed is 8.0r/min. The extruded bars are granulated after being cooled in water and placed in a vacuum oven at 60 ℃ for 12 hours for standby.
Crystallinity: 2.8
After the co-grafting monomer is introduced into the grafting reaction system, the grafting rate of the graft copolymer is improved.
Effect examples 1 to 9
Effect examples 1 to 5 are effect examples of applying the graft copolymers of examples 1 to 4 of the present invention to PLA/PPC compatibilization modification, respectively. Specifically, 5 to 10 parts of the graft copolymer of examples 1 to 4 were dispersed in 30 to 50 parts of polypropylene carbonate and 40 to 80 parts of polylactic acid, respectively, to obtain modified polylactic acid/polypropylene carbonate of effect examples 1 to 5. Effect example 5 the preparation and test methods were the same as in effect example 1 except that no graft was added unlike in effect example 1. The inventors measured Izod notched impact strength according to GB/T1843/1-A using a GT-7045-MD impact tester. Tensile properties were measured using a tensile tester (Instron 3365, USA) according to GB/T1040-1BA at a crosshead speed of 25 mm/min. Effect examples 1-5 the component proportions of polylactic acid and the results of mechanical property tests are shown in table 1.
TABLE 1 Effect examples 1-5 polylactic acid/Poly (propylene carbonate) component ratio and mechanical Property test results
By comparing effect examples 1-5, it was found that the introduction of the grafting monomer improved the compatibility of PLA with PPC to some extent, thereby improving the impact strength and elongation at break of the blend. After PPC blending, the toughness of the PLA blend is improved. To further improve the mechanical properties of the blend, PLA-g-GMA graft copolymer was used as a reactive compatibilizer. The PLA-g-GMA graft copolymer improves the toughness of the blend to some extent due to the slightly improved compatibility between PLA and PPC. After the comonomer is introduced into the PLA-g-GMA graft copolymer, the grafting degree of the PLA-g-GMA graft copolymer can be well improved, and the higher the grafting degree is, the more epoxy groups can react with PLA or PPC end groups, and the better the interface compatibility between the PLA and the PPC is. As the compatibility of the blend increases, the degree of physical entanglement of the molecular chains of the blend increases, intermolecular forces increase, and interfacial tension decreases. At the same time, stress can be effectively transferred from the PLA phase to the PPC phase, improving the toughness of the blend.
Effect examples 6 to 10 are effect examples of applying the graft copolymers of examples 1 to 4 of the present invention to PLA/PPC compatibilization modification, respectively. Specifically, 5 to 10 parts of the graft copolymer of examples 1 to 4 were dispersed in 30 to 50 parts of polypropylene carbonate and 40 to 80 parts of polylactic acid, respectively, to obtain modified polylactic acid/polypropylene carbonate of effect examples 1 to 5. Effect example 6 the preparation and test methods were the same as in effect example 7 except that no graft was added unlike in effect example 7. The inventors pressed the PLA/PPC blend into a film about 80 μm thick using a flat vulcanizing machine and tested the haze and transmittance of the blend using a haze meter (CS-700). Effect examples 6-10 the component proportions of polylactic acid and the results of the optical property tests are shown in table 2.
TABLE 2 Effect examples 6-10 polylactic acid/Poly (propylene carbonate) component ratio and optical Property test results
After the PLA-g-GMA graft copolymer is incorporated into the blend, the haze of the blend decreases. And the haze of the blend is further reduced after the co-grafted monomer is introduced into the PLA-g-GMA graft copolymer. This is mainly due to the effect of the degree of crystallization of the polymer, and generally the more internal crystals, the greater the haze. After the co-grafting monomer is introduced into the grafting reaction system, the crystallinity of the blend gradually decreases, and thus the haze of the blend decreases. On the other hand, the incorporation of the graft copolymer did not have a significant effect on the transmittance of the blend, which fluctuated in the range of 91.6-92.5%. Therefore, after the co-grafting monomer is introduced into the grafting reaction system, the haze of the blend can be reduced on the premise of keeping the high transmittance of the blend, and finally, the above embodiment is only used for illustrating the technical scheme of the present invention and not limiting the protection scope of the present invention, although the present invention is described in detail with reference to the preferred embodiment, it should be understood by those skilled in the art that the technical scheme of the present invention can be modified or replaced equivalently without departing from the spirit and scope of the technical scheme of the present invention.
Claims (4)
1. The preparation method of the blended polylactic acid biodegradable toughening composite material is characterized in that the preparation method of the composite material is a polylactic acid graft copolymer and a preparation method of a blend material of the polylactic acid graft copolymer and polypropylene carbonate; the preparation method comprises the following preparation steps:
(1) Uniformly mixing the dried polypropylene carbonate and an auxiliary agent, adding the mixture into a double-screw extruder, setting the heating temperature of the double-screw extruder to be 130-150 ℃ and the rotating speed of the double-screw extruder to be 40-60r/min, taking materials, and drying for later use;
(2) Dissolving an initiator in a mixed solution of an auxiliary agent and acetone, and respectively adding a proper amount of auxiliary grafting monomer into the mixed solution; then fully mixing the mixture with polylactic acid according to the mass ratio; after the acetone is completely volatilized, preparing a graft copolymer by using a double-screw extruder, cooling the product, and granulating for later use; mixing conditions: the temperature is 170-180 ℃, the rotating speed is 40-60r/min, and the time is 6-10min;
(3) Uniformly mixing the dried polylactic acid and the materials in the step 1 and the step 2, and adding the mixture into a double-screw extruder, wherein the double-screw extruder is set to have a heating temperature of 160-200 ℃ and a rotating speed of 40-80 rpm;
(4) Granulating the raw materials extruded by the double-screw extruder in the step (3), and drying for later use;
the blending material comprises the following raw material components:
60-90 parts of polylactic acid;
10-40 parts of polypropylene carbonate;
0-10 parts of grafting monomer;
0-40 parts of auxiliary grafting monomer;
0-5 parts of initiator.
2. The method for preparing the blended polylactic acid biodegradable toughening composite material according to claim 1, wherein the auxiliary agent is one or two of Maleic Anhydride (MAH) and Glycidyl Methacrylate (GMA).
3. The preparation method of the blended polylactic acid biodegradable toughening composite material according to claim 1, wherein the grafting-assisting monomer is one or more of styrene (St), methyl Methacrylate (MMA), vinyl acetate, acrylic acid, alpha-methylstyrene (AMS) and epoxy resin (EP).
4. The method for preparing the blended polylactic acid biodegradable toughening composite material according to claim 1, wherein the initiator is one or two of dibenzoyl peroxide (BPO), dicumyl peroxide (DCP), azobisisobutyronitrile (AIBN), acrylamide (AM), tert-butyl peroxybenzoate, lauroyl peroxide, diisopropyl peroxydicarbonate and potassium persulfate.
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| CN202310066094.1A CN116218172A (en) | 2023-02-06 | 2023-02-06 | Preparation method of blended polylactic acid biodegradable toughening composite material |
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| CN202310066094.1A CN116218172A (en) | 2023-02-06 | 2023-02-06 | Preparation method of blended polylactic acid biodegradable toughening composite material |
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