CN114230986A - Stereo composite crystal reinforced biodegradable material - Google Patents
Stereo composite crystal reinforced biodegradable material Download PDFInfo
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- CN114230986A CN114230986A CN202210001543.XA CN202210001543A CN114230986A CN 114230986 A CN114230986 A CN 114230986A CN 202210001543 A CN202210001543 A CN 202210001543A CN 114230986 A CN114230986 A CN 114230986A
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- 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
- C08L67/02—Polyesters derived from dicarboxylic acids and dihydroxy compounds
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L2201/00—Properties
- C08L2201/06—Biodegradable
Abstract
The invention provides a stereo composite crystal enhanced biodegradable material, belonging to the field of biodegradable high polymer materials. It has solved the problem that prior art has not high intensity. The stereo composite crystal reinforced biodegradable material is characterized by comprising the following components in parts by mass: 85-95 parts of poly (butylene adipate terephthalate) (PBAT), 5-15 parts of polylactic acid (PLA) with high stereocomplex crystal content and 0.1-3 parts of chain extender. The stereo composite crystal reinforced biodegradable material has high strength.
Description
Technical Field
The invention relates to the technical field of biodegradable high polymer materials, in particular to a stereo composite crystal enhanced biodegradable material and a preparation method thereof.
Background
Abuse of traditional petroleum-based plastics has caused serious environmental pollution problems in the last hundred years. The biodegradable polyester is used as an environment-friendly material, has good biocompatibility and excellent processing performance and mechanical property, is widely applied to the fields of biomedicine, agricultural production, oil exploitation and the like, and is expected to become a substitute of the traditional plastic. Among various marketable biodegradable polyesters, poly (butylene adipate terephthalate) (PBAT) has good thermal stability, moderate mechanical properties, relatively low price, softness and transparency, and is similar to low-density polyethylene, so that the poly (butylene adipate terephthalate) (PBAT) has good prospects in applications such as packaging films, agricultural films and the like.
However, the mechanical strength of PBAT is not high, and it is difficult to meet the requirements of more application occasions, and it is often necessary to enhance and modify it in practical applications. For example, the tensile strength of PBAT materials can be increased by blending with polylactic acid (PLA) without affecting the degradability of the material. However, the large amount of PLA is added, so that the toughness of the material is sacrificed, and the elongation at break is reduced. As the PBAT and the PLA are thermodynamically incompatible systems, the main reason influencing the elongation at break of the PBAT/PLA blend material is that the phase interface is separated to form cavities in the stretching process, and the formation of a large number of cavities directly leads to the fracture of the material under low strain.
In order to improve the mechanical properties of the PBAT/PLA blend material, the compatibility of the PLA and PBAT can be improved, for example by adding a reactive compatibilizer. In addition, the mechanical strength of the PLA phase in the blend can be improved, so that the PBAT modulus can be greatly enhanced by using less PLA, and the phase interface is reduced, thereby ensuring better toughness of the material. Lactic acid has two optical isomers because it contains one chiral carbon in the molecule. When poly-L-lactic acid (PLLA) and poly-D-lactic acid (PDLA) are blended or stereoblock copolymerized, a stereocomplex crystal can be formed, and the melting point of the stereocomplex crystal is about 50 ℃ higher than that of single PLLA or PDLA homogeneous crystal. And compared with a homogeneous crystalline material, the stereo composite crystalline material has higher strength and modulus, faster crystallization speed and excellent solvent resistance. The literature reports the use of PLA containing stereocomplex crystallites to increase the modulus of PBAT materials (Colloid polym.sci.2020,298, 463-475). However, due to the fact that formation of stereocomplex crystals requires one-to-one pairing of PLLA and PDLA at the molecular level, PLA with higher stereocomplex crystal content cannot be obtained usually by simple melt blending, and further improvement of the mechanical properties of PBAT/PLA blended materials is limited. In order to make PLA have a high content of stereocomplex crystals, it is known in the literature to blend at a temperature lower than the melting point of the stereocomplex crystals, but since PLA is solid, it has poor flowability during processing, which is not conducive to uniform dispersion with PBAT, and the product is difficult to melt process repeatedly. Therefore, the provision of a novel PBAT/PLA blending material with excellent mechanical properties and a preparation method thereof have important significance.
Disclosure of Invention
The invention aims to solve the technical problem of overcoming the defects in the prior art and provides a stereo composite crystal reinforced biodegradable material and a preparation method thereof.
In order to solve the technical problem, the solution of the invention is as follows:
a biodegradable material with reinforced stereo complex crystal is provided, which is composed of poly adipic acid/butylene terephthalate (PBAT) and polylactic acid (PLA) with high content of stereo complex crystal.
The invention further provides a method for preparing the stereo complex crystal reinforced biodegradable material, and the material is prepared by a two-step melt blending method. The preparation method comprises the following steps:
(1) in the presence of a chain extender, equal amounts of poly-L-lactic acid (PLLA) and poly-D-lactic acid (PDLA) are melted and blended to prepare PLA with high stereocomplex crystal content.
(2) In the presence of a chain extender, PBAT and PLA with high stereocomplex crystal content are melted and blended according to a certain proportion.
In the present invention, the chain extender is selected from any one of Joncryl ADR 4300, Joncryl ADR 4368 and Joncryl ADR 4370.
In the invention, the mass fraction of the chain extender in the step (1) is 0.1-2%.
In the invention, the melt blending refers to drying and mixing the raw materials, extruding the raw materials by a single-screw extruder or a double-screw extruder, and granulating the raw materials.
In the invention, the raw materials are dried in an oven at 60-90 ℃ for 10-12h under the drying condition, the operating temperature of the single-screw extruder or the double-screw extruder is 230-250 ℃, and the screw rotating speed is 10-60 r/min.
Description of the inventive principles:
in the invention, the principle of enhancing the mechanical property of the material is that on one hand, PLA is dispersed in PBAT to bear stress by utilizing the higher modulus of PLA relative to PBAT. On the other hand, the specific stereocomplex crystal of PLA is utilized to further improve the modulus of the crystal phase. The formation of stereocomplex crystals requires hydrogen bonds to be formed between the molecular chains of PLLA and PDLA to be closely packed, however, the PLLA and PDLA chains tend to separate in a molten state, even to form microphase separation structures, and thus the formation of stereocomplex crystals by the interaction therebetween is not facilitated. The copolymerization molecular chain containing PLLA and PDLA chains can be obtained by utilizing the chain extension reaction, so that the uniform distribution of the two molecular chains is promoted, the two molecular chains are not separated in a molten state, more opportunities are provided for interaction to form hydrogen bonds and stereo composite crystals, and the advantages can be kept in the subsequent repeated melting processing. Therefore, when the chain extender is added during melt blending of the PLLA and the PDLA, the PLA with higher stereoregular composite crystal content can be obtained.
Compared with the prior art, the invention has the following technical advantages:
(1) the invention reduces the dosage of PLA by improving the content of PLA stereocomplex crystals, thereby effectively improving the mechanical strength of PBAT without obviously losing the toughness of the material.
(2) The material has the advantages of simple preparation process, no complex requirements on equipment and process, low production cost, easy large-scale industrial production and no pollution.
Drawings
FIG. 1 is a DSC curve of the PLA used in examples 2, 4-6 and comparative example 1 during temperature increase at a rate of 10 deg.C/min after melt cooling.
Fig. 2 is a stress-strain curve in the uniaxial tensile test at room temperature for example 2 and comparative examples 1 to 4.
Detailed Description
The present invention will be described in further detail with reference to specific embodiments below:
the raw materials used in the present invention are illustrated below: PBAT is available from Zhejiang Xin rich pharmaceutical Co., Ltd, and has a butanediol terephthalate unit molar content of 45% and a weight average molecular weight of 71.2 kg/mol. PLLA and PDLA were obtained from Pond Poulak, a weight average molecular weight of 150-200kg/mol and an optical purity of more than 98%. The chain extender was purchased from basf, germany under the designation Joncryl ADR 4368.
The preparation method of the stereo composite crystal reinforced biodegradable material comprises the following steps:
(1) under the condition of the existence of a chain extender, equal amount of PLLA and PDLA are melted and blended to prepare PLA with high stereocomplex crystal content.
(2) In the presence of a chain extender, PBAT and PLA with high stereocomplex crystal content are melted and blended according to a certain proportion.
The melt blending method is that the raw materials are added into a single-screw extruder or a double-screw extruder, mixed for 3min at 250 ℃, and then extruded and granulated.
The following examples are presented to enable those skilled in the art to more fully understand the present invention and are not intended to limit the invention in any way.
In examples 1 to 6, the PLA content and the amount of the chain extender used in blending PLLA/PDLA were changed in this order. In comparative examples 1 and 2, no chain extender was added during blending of PLLA/PDLA, in comparative example 3, no chain extender was added during the two-step blending, and in comparative example 4, a pure PBAT material was used without PLA enhancement.
Specific embodiments of examples 1 to 6 and comparative examples 1 to 4 are shown in Table 1.
Table 1: PLA content of examples 1-6 and comparative examples 1-4, amount of chain extender used in two-step melt blending
In the present invention, the materials involved can be characterized by the following analytical instruments, including in particular:
differential scanning calorimeter (DSC,214Polyma, NETZSCH, Germany): the PLLA/PDLA blended sample is heated to 250 ℃ at the speed of 50 ℃/min from room temperature in the nitrogen atmosphere, the temperature is kept for 3min to eliminate the thermal history, then the temperature is reduced to-70 ℃ at the speed of 10 ℃/min, the temperature is kept for 3min at-70 ℃, and then the temperature is heated to 250 ℃ at the speed of 10 ℃/min.
Universal material testing machine (Shenzhen Sansi SANS-UTM 4204): and (3) carrying out unidirectional tensile test on the samples at room temperature to obtain a stress-strain curve and mechanical property data, wherein the initial distance between the clamps is 15mm, the tensile rate is 10mm/min, and each group of samples is repeatedly subjected to tensile test for at least 5 times to obtain an average result.
And (3) analyzing experimental data:
from the results of DSC analysis (fig. 1), unless a chain extender is added at the time of blending PLLA with PDLA (comparative example 1), the resulting PLLA/PDLA blend after melt-cooling shows only a very weak melting peak of stereocomplex crystals (about 220 ℃) during the subsequent temperature rise by DSC, while melting of homogeneous crystals (about 175 ℃) is mainly observed. When the mass parts of the chain extender added during the blending of the PLLA and the PDLA are gradually increased (examples 2 and 4-6), the melting peak area of the stereocomplex crystal of the obtained PLLA/PDLA blend is gradually increased and the melting peak area of the homogeneous crystal is gradually reduced in a DSC temperature rise curve after the melting and cooling of the PLLA/PDLA blend, which indicates that the application of the chain extender effectively promotes the formation of the stereocomplex crystal in the PLLA/PDLA blend.
From the analysis of the stress-strain curve results (fig. 2 and table 2), the young's modulus and yield strength of the material are improved when 10% PLA is added (comparative example 3) compared to pure PBAT without PLA (comparative example 4), but limited by the compatibility of PBAT with PLA, and comparative example 3 breaks at early stages of stretching, with an elongation at break of only 140%. If 1.1% of the chain extender is used in blending PBAT/PLA (comparative example 1), the elongation at break of the material will be effectively increased, but the effect of improving the young's modulus and yield strength will not be significant. If a chain extender is also used when blending PLLA/PDLA, the Young modulus and the yield strength of the material are respectively increased from 30.9MPa and 5.0MPa to 36.2MPa and 5.7MPa as the dosage of the chain extender is increased from 0.05% to 1% (examples 2 and 4-6), and the elongation at break is slightly reduced from 940% to 900%, so that the material still maintains better strength and toughness, because the strength of PLA is increased due to the increase of the content of the stereo composite crystals. The Young's modulus and yield strength of example 2 are similar to those of comparative example 2, and the elongation at break is much larger than that of comparative example 2, which shows that when the PBAT is reinforced by PLA with high stereocomplex crystal content, the reinforcing effect of PLA with low stereocomplex crystal content close to 15% can be realized by 10% of PLA, and the toughness of the PBAT can be maintained by adding a small amount of PLA.
Table 2: young's modulus, yield strength and elongation at break of examples 1-6 and comparative examples 1-4
The results show that the chain extender is added when the PLLA and the PDLA are blended, so that the content of the stereospecific composite crystal can be effectively improved, the mechanical strength of the PBAT/PLA blended material is further improved, the toughness is not obviously lost, and the PBAT/PLA blended material has potential application value in the fields of biodegradable polymer films and the like.
Finally, it should be noted that the above-mentioned list is only a specific embodiment of the present invention. It is obvious that the present invention is not limited to the above embodiments, but many variations are possible. All modifications which can be derived or suggested by a person skilled in the art from the disclosure of the present invention are to be considered within the scope of the invention.
Claims (6)
1. A stereo composite crystal enhanced biodegradable material is characterized by comprising the following components in parts by mass: 85-95 parts of poly (butylene adipate terephthalate) (PBAT), 5-15 parts of polylactic acid (PLA) with high stereocomplex crystal content and 0.1-3 parts of chain extender.
2. The stereocomplex crystal-enhanced biodegradable material according to claim 1, wherein said high stereocomplex crystal content PLA comprises equal amounts of poly-L-lactic acid (PLLA) and poly-D-lactic acid (PDLA), and a chain extender, wherein the chain extender accounts for 0.1% -2% of the total mass of the PLLA and the PDLA.
3. The stereocomplex crystallization-enhanced biodegradable material according to claim 1 or 2, characterized in that the chain extender is selected from any one of Joncryl ADR 4300, Joncryl ADR 4368 or Joncryl ADR 4370.
4. A preparation method of a stereo complex crystal reinforced biodegradable material is characterized by comprising the following steps:
(1) under the condition of the existence of a chain extender, equal amount of PLLA and PDLA are melted and blended to prepare PLA with high stereocomplex crystal content.
(2) In the presence of a chain extender, PBAT and PLA with high stereocomplex crystal content are melted and blended according to a certain proportion.
5. The method for preparing the stereocomplex crystallographically enhanced biodegradable material according to claim 4, characterized in that it comprises the steps of: drying and mixing the raw materials, extruding by adopting a single-screw extruder or a double-screw extruder, and granulating.
6. The method for preparing the stereocomplex crystallization-enhanced biodegradable material as claimed in claim 5, wherein the drying condition of the raw material is drying in an oven at 60-90 ℃ for 10-12h, the operating temperature of the single-screw extruder or the twin-screw extruder is 230-250 ℃, and the screw rotation speed is 10-60 r/min.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114773810A (en) * | 2022-06-04 | 2022-07-22 | 元嘉生物科技(浙江)有限公司 | High-performance polylactic acid-based 3D printing wire rod and preparation method thereof |
| CN115028976A (en) * | 2022-06-07 | 2022-09-09 | 杭州德泓科技有限公司 | Stereo composite interface compatibilization polylactic acid blending material and preparation method thereof |
| CN115746525A (en) * | 2022-11-29 | 2023-03-07 | 浙江金晟环保股份有限公司 | Low-crystallinity rapidly-degradable PLA/PBAT composite material and preparation method thereof |
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Patent Citations (4)
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| CN103965493A (en) * | 2014-05-09 | 2014-08-06 | 四川大学 | Method for preparing high molecular weight vertical structure composite polylactic acid with melt stability characteristics |
| CN106916421A (en) * | 2017-04-07 | 2017-07-04 | 常州大学 | One kind enhancing is poly-（Terephthalic acid (TPA) butanediol co adipic acid butanediols）Ester degradable material |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114773810A (en) * | 2022-06-04 | 2022-07-22 | 元嘉生物科技(浙江)有限公司 | High-performance polylactic acid-based 3D printing wire rod and preparation method thereof |
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| CN115028976A (en) * | 2022-06-07 | 2022-09-09 | 杭州德泓科技有限公司 | Stereo composite interface compatibilization polylactic acid blending material and preparation method thereof |
| CN115746525A (en) * | 2022-11-29 | 2023-03-07 | 浙江金晟环保股份有限公司 | Low-crystallinity rapidly-degradable PLA/PBAT composite material and preparation method thereof |
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