CN118421060B - Polylactic acid biological composite plastic film and crystallization regulating and controlling method - Google Patents
Polylactic acid biological composite plastic film and crystallization regulating and controlling method Download PDFInfo
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Abstract
The invention relates to the technical field of green natural materials, in particular to a polylactic acid biological composite plastic film and a crystallization regulating and controlling method. The preparation method comprises the steps of firstly preheating an open mill to 170-200 ℃ in a melt blending mode, then adding polylactic acid into the open mill, fully stirring and melting, then adding cottonseed protein and maleic anhydride, fully mixing the materials, enabling the weight ratio of the polylactic acid to the cottonseed protein to the maleic anhydride to be 20:0.5-1.2:0.1-0.3, obtaining a mixed material, secondly preheating the mixed material to 170-200 ℃ in a flat vulcanization hot press, placing the mixed material into a template of the flat vulcanization hot press for molding, controlling the flat vulcanization hot press to cool the molded mixed material in a sectional cooling mode by using a cooling device, and cooling the sectional cooling mode to normal temperature by 2-10 ℃ per 5min when the temperature is reduced to 120-130 ℃ to obtain the polylactic acid biological composite plastic film.
Description
Technical Field
The invention relates to the technical field of green natural materials, in particular to a polylactic acid biological composite plastic film and a crystallization regulating and controlling method.
Background
The environmental pollution caused by petroleum-based plastics is seriously affecting the life and health of people, and as a green bio-based material capable of replacing petroleum-based plastics, polylactic acid (PLA) has been popularized in the fields of food packaging, drug delivery, tissue engineering and the like due to excellent transparency and mechanical properties. In order to improve the crystallinity of the polylactic acid, at present, the polylactic acid is combined with thermoplastic resin, polysaccharide or nano compound by means of in-situ grafting, blending modification and the like to provide effective nucleation sites for a polylactic acid matrix, promote heterogeneous nucleation of the polylactic acid and improve the crystallinity of the polylactic acid. Although the method can improve the crystallinity of the polylactic acid, the method has the problems of high cost and influence on degradation of the polylactic acid film.
Aiming at the problem, the use of amino acid to promote the nucleation of polylactic acid is disclosed at present, the requirement on the purity of the amino acid is high, and the problem of high cost still exists. The prior art discloses a starch-loaded polylactic acid crystallization nucleating agent which uses protein to replace amino acid as a nucleating agent, for example, a preparation method thereof disclosed in Chinese patent CN201710000859.6, wherein starch is used as the loaded polylactic acid crystallization nucleating agent, and the crystallization temperature is 95-105 ℃. The natural protein powder disclosed in Chinese patent CN201610097778.8 is used as an aliphatic polyester nucleating agent, and wool powder, cattle wool powder, feather powder, pig wool powder and silk powder are used as nucleating agents of polylactic acid, wherein the highest temperature of nucleation is 70.4-108 ℃.
However, the above-described technique has a disadvantage in that only the increase of protein is considered to promote nucleation of polylactic acid. However, the crystallization of the protein and the polylactic acid occurs at a lower temperature, so that the polylactic acid in the prior art can begin to crystallize after being cooled to the lower temperature, on the one hand, the cooling time is long, so that the whole crystallization process is slow, and on the other hand, the crystallization process of the protein and the polylactic acid is shorter, which can cause insufficient crystallization and affect the mechanical property or quality of the polylactic acid finished product.
Disclosure of Invention
The invention aims to provide a method for regulating and controlling the crystallinity of a polylactic acid biological composite plastic film, which is used for avoiding the defects in the prior art, and the preparation method selects cottonseed protein as a nucleating agent to effectively improve the crystallization of polylactic acid at a higher temperature, so that the polylactic acid can reach a crystallization point at the higher temperature, the crystallization process of the polylactic acid is effectively prolonged, and the performance of the polylactic acid biological composite film is improved.
In order to achieve one of the above objects, the following technical solutions are provided:
The method for regulating and controlling the crystallinity of the polylactic acid biological composite plastic film comprises the following steps:
Firstly, preheating an open mill to 170-200 ℃ in a melt blending mode, adding polylactic acid into the open mill, fully stirring and melting, and then adding cottonseed protein and maleic anhydride to fully mix materials to obtain a mixed material, wherein the weight ratio of the polylactic acid to the cottonseed protein to the maleic anhydride is 20:0.5-1.2:0.1-0.3;
and secondly, adopting a flat vulcanizing hot press and preheating to 170-200 ℃, placing the mixed material into a template of the flat vulcanizing hot press for molding, and then controlling the flat vulcanizing hot press to cool the molded mixed material in a sectional cooling mode by using a cooling device, wherein the sectional cooling mode is that when the temperature is reduced to 120-130 ℃, the temperature is reduced to normal temperature by 2-10 ℃ per 5min, and the polylactic acid biological composite plastic film is obtained.
In some embodiments, the polylactic acid is put into an oven to be dried before being put into the open mill, the drying temperature is 40-55 ℃, and the drying time is 30-48 h.
In some embodiments, in the first step, the polylactic acid is stirred and melted in an open mill for 8-12 min.
In some embodiments, in the first step, the stirring time after adding the cottonseed protein and the maleic anhydride is 4-8 min.
In some embodiments, in step one, the mill is preheated to 180 ℃.
In some embodiments, in step one, the weight ratio of the polylactic acid, the cottonseed protein, and the maleic anhydride is 20:1:0.2.
In some embodiments, the step-down is performed by cooling to ambient temperature at 6 ℃ per 5 min.
In some embodiments, in step one, the cottonseed protein is added to the mill within 1 minute.
The method for regulating and controlling the crystallinity of the polylactic acid biological composite plastic film has the beneficial effects that:
(1) According to the method for regulating and controlling the crystallinity of the polylactic acid biological composite plastic film, cottonseed protein is used as a nucleating agent of the polylactic acid, the cottonseed protein is alkali-soluble plant protein and has high protein content, the alkali property of the cottonseed protein can effectively improve the compatibility of the cottonseed protein and the polylactic acid with high fat solubility, so that the cottonseed protein and the polylactic acid can be compatible quickly, and simultaneously, the high protein content of the cottonseed protein also provides richer crystallization nuclei, so that the crystallization rate between the cottonseed protein and the polylactic acid is further promoted, and therefore, when the polylactic acid is cooled and crystallized, the cottonseed protein and the polylactic acid begin to crystallize at a high temperature of 120 ℃, the polylactic acid can be crystallized in advance, the crystallization time is effectively prolonged, the cottonseed protein and the polylactic acid can be fully crystallized, and then the crystals are fully grown. The invention cools and crystallizes the crystallization material in a sectional cooling mode, so that the cooling and crystallization of each temperature stage are sufficient, the crystallization effect is further improved, and particularly when crystallization occurs at high temperature, the more stages can be cooled in sections, so that the cooling and crystallization are more sufficient.
(2) The method for regulating the crystallinity of the polylactic acid biological composite plastic film adopts a melt blending method to prepare the polylactic acid biological composite plastic film, and the melt blending method can blend cottonseed protein and polylactic acid uniformly without using a solvent and has the advantage of environmental protection.
(3) The method for regulating and controlling the crystallinity of the polylactic acid biological composite plastic film uses the cottonseed protein as a nucleating agent, has wide sources of the cottonseed protein and low cost, effectively replaces amino acid, and is suitable for large-scale production and application.
The polylactic acid biological composite plastic film is prepared by the method for regulating and controlling the crystallinity of the polylactic acid biological composite plastic film.
Drawings
FIG. 1 is an infrared spectrum of PLA/CPC polylactic acid bio-composite films of examples 1 to 4, polylactic acid films PLA and CPC of comparative example 1, a) full band, b) 3500-2500cm-1, c) 2000-1000cm-1, d) 1000-500 cm-1.
FIG. 2 is a DSC schematic diagram of PLA/CPC polylactic acid bio-composite films of examples 1 to 4 of the present invention, polylactic acid film PLA of comparative example 1, a) a first heating stage, b) a first cooling stage, c) a second heating stage.
Fig. 3 is a schematic view of isothermal crystallization of polylactic acid film PLA of comparative example 1 photographed at 0min, 5min, 10min and 15min in order.
FIG. 4 is a schematic diagram of isothermal crystallization of the PLA/CPC5 polylactic acid bio-composite film of example 1 photographed at 0min, 5min, 10min and 15min in sequence.
FIG. 5 is a schematic diagram of isothermal crystallization of PLA/CPC10 of example 2 sequentially photographed at 0min, 5min, 10min and 15 min.
FIG. 6 is a schematic diagram of isothermal crystallization of example 4PLA/CPC20 sequentially photographed at 0min, 5min, 10min and 15 min.
Fig. 7 is a scanning electron microscope picture of the polylactic acid film PLA of comparative example 1 and the polylactic acid film PLA of example 2/CPC 10, wherein a) is the polylactic acid film PLA of comparative example 1 and b) is the polylactic acid film PLA of example 2/CPC 10.
Detailed Description
Preferred embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. While the preferred embodiments of the present invention are shown in the drawings, it should be understood that the present invention may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
The method for regulating and controlling the crystallinity of the polylactic acid biological composite plastic film disclosed by the embodiment comprises the following steps:
Firstly, preheating an open mill to 170-200 ℃, preferably 180 ℃, and then adding polylactic acid into the open mill and fully stirring and melting, wherein the stirring and melting time is preferably 8-12 min.
And heating the mixture to 170-200 ℃ by an open mill to enable the cottonseed protein and the polylactic acid to be melted and mixed.
And then adding cottonseed protein and maleic anhydride to fully mix the materials, wherein the stirring time is 4-8 min, and the maleic anhydride is used as a solubilizer, so that the cottonseed protein and polylactic acid can fully form a uniform phase. The weight ratio of the polylactic acid to the cottonseed protein to the maleic anhydride is 20:0.5-1.2:0.1-0.3, preferably 20:1:0.2, so as to obtain a mixed material.
Wherein, the cottonseed protein is added into the open mill within 1min, so as to avoid the flying of the cottonseed protein.
And secondly, preheating the mixed material to 170-200 ℃ by adopting a flat vulcanizing hot press, placing the mixed material into a template of the flat vulcanizing hot press for molding, and controlling the flat vulcanizing hot press to cool the molded mixed material in a sectional cooling mode by using a cooling device, wherein the sectional cooling mode is that when the temperature is reduced to 120-130 ℃, the temperature is reduced to normal temperature by 2-10 ℃ per 5min, so as to obtain the polylactic acid biological composite plastic film. Preferably, the sectional temperature rising mode is that the temperature is reduced to normal temperature at 6 ℃ per 5 min.
The flat vulcanizing hot press is preheated to the temperature of the open mill, so that phase change of mixed materials is avoided, and as the protein used in the invention is cottonseed protein, the crystallization point of the cottonseed protein is about 120 ℃, after the temperature is reduced to about 120-130 ℃ near the crystallization point, the temperature is gradually reduced by using a cooling device, and the temperature is maintained for a certain time, so that crystallization can be ensured to be sufficient in each cooling stage, and the crystallization effect is improved.
The flat vulcanizing hot press gradually crystallizes the mixed materials in a gradual heating mode, so that the crystallinity is effectively improved.
In this embodiment, before the polylactic acid is put into the open mill, the polylactic acid is put into an oven for drying, the drying temperature is 40-55 ℃, and the drying time is 30-48 hours.
The polylactic acid removes moisture through the drying effect of the oven.
According to the method for regulating and controlling the crystallinity of the polylactic acid biological composite plastic film, cottonseed protein is used as a nucleating agent of the polylactic acid, the cottonseed protein is alkali-soluble plant protein and has high protein content, the alkali property of the cottonseed protein can effectively improve the compatibility of the cottonseed protein and the polylactic acid with high fat solubility, so that the cottonseed protein and the polylactic acid can be compatible quickly, and meanwhile, the high protein content of the cottonseed protein also provides richer crystallization nuclei, so that the crystallization rate between the cottonseed protein and the polylactic acid is further promoted, and when the cottonseed protein and the polylactic acid are cooled and crystallized, the cottonseed protein and the polylactic acid begin to crystallize at a high temperature of 120 ℃, so that the whole polylactic acid can be crystallized in advance, the crystallization time is effectively prolonged, the cottonseed protein and the polylactic acid can be fully crystallized, and then the crystals can be fully grown, therefore, the density of the whole polylactic acid biological composite plastic film is good, the mechanical property of the film is better, the crystallization material is cooled and crystallized in a sectional cooling mode, so that the crystallization effect is fully cooled at each temperature stage, and the crystallization effect is further improved, and especially when the crystallization occurs at high temperature, the crystallization stage, the more stages are cooled and more than full crystallization stage. The melt blending method is adopted to prepare the polylactic acid biological composite plastic film, and the melt blending method can blend cottonseed protein and polylactic acid uniformly without using a solvent, so that the method has the advantage of environmental protection. The cottonseed protein is used as a nucleating agent, has wide sources and low cost, effectively replaces amino acid, and is suitable for large-scale production and application.
Example 1
The embodiment discloses a method for regulating and controlling the crystallinity of a polylactic acid biological composite plastic film,
Step one, polylactic acid (PLA) is dried in a 50 ℃ oven for 48 hours for standby,
Preheating an open mill to 180 ℃ in advance by adopting a melt blending processing mode, and then fully stirring and melting polylactic acid (20 g) and Cottonseed Protein (CPC) (1 g) with certain content on the open mill for about 10min, and fully stirring a trace amount of maleic anhydride (0.2 g) serving as a compatibilizer by using a stirring cutter to uniformly stir materials for 5min;
And thirdly, preheating the flat vulcanizing hot press to 180 ℃, transferring the mixed materials to a required template while the mixed materials are hot, and controlling the flat vulcanizing hot press to cool the formed mixed materials in a sectional cooling mode by using a cooling device, wherein the sectional cooling mode is that when the temperature is reduced to 120-130 ℃, the temperature is reduced to normal temperature at 6 ℃ per 5min, and the polylactic acid biological composite plastic film is obtained.
And fourthly, decompressing and taking out after waiting for full cooling to obtain the polylactic acid/cottonseed protein plastic, and marking as PLA/CPC5.
Example 2
The embodiment discloses a method for regulating and controlling the crystallinity of a polylactic acid biological composite plastic film,
Step one, polylactic acid (PLA) is dried in a 50 ℃ oven for 48 hours for standby,
Preheating an open mill to 180 ℃ in advance by adopting a melt blending processing mode, and then fully stirring and melting polylactic acid (20 g) and Cottonseed Protein (CPC) (2 g) with certain content on the open mill for about 10min, and fully stirring a trace amount of maleic anhydride (0.2 g) serving as a compatibilizer by using a stirring cutter to uniformly stir materials for 5min;
And thirdly, preheating the flat vulcanizing hot press to 180 ℃, transferring the mixed materials to a required template while the mixed materials are hot, and controlling the flat vulcanizing hot press to cool the formed mixed materials in a sectional cooling mode by using a cooling device, wherein the sectional cooling mode is that when the temperature is reduced to 120-130 ℃, the temperature is reduced to normal temperature at 6 ℃ per 5min, and the polylactic acid biological composite plastic film is obtained.
And fourthly, decompressing and taking out after waiting for full cooling to obtain the polylactic acid/cottonseed protein plastic, and marking as PLA/CPC10.
Example 3
Step one, polylactic acid (PLA) is dried in a 50 ℃ oven for 48 hours for standby,
Preheating an open mill to 180 ℃ in advance by adopting a melt blending processing mode, and then fully stirring and melting polylactic acid (20 g) and Cottonseed Protein (CPC) (3 g) with certain content on the open mill for about 10min, and fully stirring a trace amount of maleic anhydride (0.2 g) serving as a compatibilizer by using a stirring cutter to uniformly stir materials for 5min;
And thirdly, preheating the flat vulcanizing hot press to 180 ℃, transferring the mixed materials to a required template while the mixed materials are hot, and controlling the flat vulcanizing hot press to cool the formed mixed materials in a sectional cooling mode by using a cooling device, wherein the sectional cooling mode is that when the temperature is reduced to 120-130 ℃, the temperature is reduced to normal temperature at 6 ℃ per 5min, and the polylactic acid biological composite plastic film is obtained.
And fourthly, decompressing and taking out after waiting for full cooling to obtain the polylactic acid/cottonseed protein plastic, and marking as PLA/CPC15.
Example 4
Step one, polylactic acid (PLA) is dried in a 50 ℃ oven for 48 hours for standby,
Preheating an open mill to 180 ℃ in advance by adopting a melt blending processing mode, and then fully stirring and melting polylactic acid (20 g) and Cottonseed Protein (CPC) (4 g) with certain content on the open mill for about 10min, and fully stirring a trace amount of maleic anhydride (0.2 g) serving as a compatibilizer by using a stirring cutter to uniformly stir materials for 5min;
And thirdly, preheating the flat vulcanizing hot press to 180 ℃, transferring the mixed materials to a required template while the mixed materials are hot, and controlling the flat vulcanizing hot press to cool the formed mixed materials in a sectional cooling mode by using a cooling device, wherein the sectional cooling mode is that when the temperature is reduced to 120-130 ℃, the temperature is reduced to normal temperature at 6 ℃ per 5min, and the polylactic acid biological composite plastic film is obtained.
And fourthly, decompressing and taking out after waiting for full cooling to obtain the polylactic acid/cottonseed protein plastic, and marking as PLA/CPC20.
Comparative example 1
The embodiment discloses a method for regulating and controlling the crystallinity of a polylactic acid biological composite plastic film,
Step one, polylactic acid (PLA) is dried in a 50 ℃ oven for 48 hours for standby,
Preheating an open mill to 180 ℃ in advance by adopting a melt blending processing mode, and then fully stirring and melting a certain content of polylactic acid (20 g) on the open mill for about 10min and a trace of maleic anhydride (0.2 g) serving as a compatibilizer, and simultaneously stirring by using a stirring knife to fully and uniformly stir the materials for 5min;
And thirdly, preheating the flat vulcanizing hot press to 180 ℃, transferring the mixed materials to a required template while the mixed materials are hot, and controlling the flat vulcanizing hot press to cool the formed mixed materials in a sectional cooling mode by using a cooling device, wherein the sectional cooling mode is that when the temperature is reduced to 120-130 ℃, the temperature is reduced to normal temperature at 6 ℃ per 5min, and the polylactic acid biological composite plastic film is obtained.
And fourthly, decompressing and taking out after waiting for full cooling, and obtaining the polylactic acid plastic.
And (3) effect verification:
1. Infrared spectrum testing:
Respectively carrying out infrared detection on the polylactic acid biological composite membrane of the embodiment 1-4, the polylactic acid membrane of the comparative example 1 and Cottonseed Protein (CPC) in the whole wave band, 3500-2500cm -1 sections, 2000-1000cm -1 sections and 1000-500cm -1 sections, wherein the detection structure is shown in figure 1:
The ester group (c=o) carbon skeleton stretching of PLA in fig. 1 (C) can be observed at 1755cm -1 and 1078cm -1, and the enhancement effect is evident, indicating that the increase of ester groups may be related to CPC amide bond content and the like. In addition, 1458cm -1 and 1358cm -1 are assigned to the hydrocarbon stretching vibration (C-H), and 1084cm -1 is assigned to the stretching vibration (C-O) due to the carbon-oxygen single bond. With the increase of the protein content, the peak value is gradually enhanced, which indicates that the cottonseed protein and the polylactic acid are uniformly mixed. Meanwhile, some high molecular polymers exhibit absorption of the polymer backbone in the infrared low frequency region. In fig. 1 (d), 870cm -1 and 754cm -1 are allocated to the crystalline and amorphous regions of polylactic acid, and the peak value becomes gradually strong, which is closely related to the crystallinity, crystallization speed, etc. of PLA. The absorption of CPC at 3295cm -1 observed in fig. 1 (b) is attributable to the vibration of the N-H bond and O-H bond, but is not apparent in the composite, indicating that after sufficient mixing of cottonseed protein with polylactic acid, physical interaction enhancement of cottonseed protein with polylactic acid occurs, resulting in polylactic acid/cottonseed protein plastic.
2. Differential pressure scanning calorimeter (DSC) analysis
Differential pressure scanning calorimeter (DSC) analysis and detection structures of the polylactic acid bio-composite films of examples 1 to 4 and the polylactic acid film of comparative example 1 are shown in FIG. 2 and Table 1:
TABLE 1
During the first heating, no glass transition and no cold crystallization peak were detected, and a melting peak was observed only around 170 ℃, indicating that the material melted around 170 ℃, where the crystallization zone completely disappeared and the material entered the molten state. At a cooling rate of 10 ℃ per minute, no cold crystallization peak was detected during the cooling process as well. After the heat history is removed and the second heating is performed, a "plateau" appears near 60 ℃, which is an indication of the glass transition, which means the process by which the material changes from normal to high-elastic state, and the glass transition temperature decreases with increasing cottonseed protein content, which is believed to be related to the toughness of the material. A cold crystallization peak appeared near 120 ℃ and a melting peak appeared near 164 ℃, and both the cold crystallization temperature and the melting temperature gradually decreased as cottonseed protein increased. From this Differential Scanning Calorimetric (DSC) analysis, it is known that PLA/CPC has a crystallization temperature in the vicinity of 120℃and a relatively high crystallization temperature.
3. Analysis of crystallization Effect
The polylactic acid bio-composite films of examples 1 to 4 and the polylactic acid film of comparative example 1 were subjected to crystallization analysis,
Sample preparation, namely obtaining polylactic acid biological composite films of examples 1-4 and polylactic acid films of comparative example 1 as samples, respectively performing treatments of dissolving in 10ml of chloroform solution and uniformly dispersing by ultrasonic, and then observing crystallization and morphology under a polarizing microscope. Specifically, 1ml of the sample solution was taken, dropped onto a heating stage and warmed up to 200 ℃ for 3min, then cooled down to 120 ℃ at a rate of 10 ℃/min, and kept at that temperature for 15min while photographing and capturing the growth behavior of the crystal using a polarizing microscope.
As shown in FIG. 4, after cottonseed protein was added as a filling matrix, crystallization behavior was observed near the isothermal crystallization point, and at 5min, a large crystal growth area was seen in the screen, and after 10min, the crystal was slowly grown and gradually occupied the entire screen, and within 15min, the crystal growth was substantially completed and the shape was maintained. The crystal shape is diamond or cross, and the crystal shape is regular and mutually embedded into a whole. Compared with pure polylactic acid (PLA), the PLA/CPC5 of the composite material example 1 added with the cottonseed protein shows a faster crystallization rate, which indicates that after the cottonseed protein is added, the cottonseed protein can start to rapidly enter crystallization under the high temperature condition, thereby being beneficial to fully growing the crystals.
Further, as shown in fig. 7, after cottonseed protein was added as a filler, improvement in compatibility was observed under a scanning electron microscope. In particular, the sample of PLA/CPC10 of example 2 clearly shows fewer cracks and a smoother and more uniform interface than pure PLA, again indicating that cottonseed protein is effective in promoting polylactic acid nucleation.
After 10min, as shown in fig. 5, the crystal grew slowly and gradually occupied the entire screen, the nucleation density increased, the grain size was slightly smaller, the number of grains was large, and the crystal growth was substantially completed and the shape was maintained unchanged within 15 min. The crystal shape is mostly 'diamond' or 'cross', and the arrangement is regular, and the POM of PLA/CPC10 of example 2 is embedded into one body, and the CPC with 10% content provides a large number of nucleation sites, which is beneficial to heterogeneous nucleation of PLA, and the nucleation barriers are reduced to the minimum, so that PLA macromolecular chains are more easy to be orderly arranged near the CPC to form crystalline phases.
As shown in fig. 6, excessive CPC addition can lead to stacking and dispersion irregularities, PLA begins to agglomerate to lower surface energy, at which time nucleation sites decrease, intuitively causing the morphology of the crystal to become larger and more "loose".
As shown in fig. 3, the crystallization rate of a single polylactic acid material is relatively slow, and no crystals have occurred within 15 minutes from 0 minutes. This phenomenon can be attributed to the fact that polylactic acid of a single component does not have many nucleation sites, and according to the nucleation theory, the nucleation barrier of polylactic acid is high at this time, so that the activation energy required for nucleation growth is large, and the effects of slow crystallization speed and low crystallinity are objectively caused.
As calculated by the crystallinity, the crystallinity of the PLA/CPC10 composite is maximum, and the crystallinity is reduced when the content of the cottonseed protein is continuously increased, because the ratio of the polylactic acid is reduced due to excessive cottonseed protein, and the excessive cottonseed protein is easy to generate aggregation effect, so that nucleation sites are reduced, and the crystallinity is influenced.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (6)
1. The method for regulating and controlling the crystallinity of the polylactic acid biological composite plastic film is characterized by comprising the following steps of:
Firstly, preheating an open mill to 170-200 ℃ in a melt blending mode, adding polylactic acid into the open mill, fully stirring and melting, and then adding cottonseed protein and maleic anhydride to fully mix materials to obtain a mixed material, wherein the weight ratio of the polylactic acid to the cottonseed protein to the maleic anhydride is 20:2:0.2;
Step two, adopting a flat vulcanization hot press and preheating to 180 ℃, and placing the mixed material into flat vulcanization heat
And (3) molding in a mold plate of a press, and then controlling the flat vulcanizing hot press to cool the molded mixed material in a sectional cooling mode by using a cooling device, wherein the sectional cooling mode is that when the temperature is reduced to 120 ℃, the temperature is reduced to normal temperature at 6 ℃ per 5min, and the polylactic acid biological composite plastic film is obtained.
2. The method for regulating and controlling the crystallinity of the polylactic acid bio-composite plastic film according to claim 1, wherein the polylactic acid is put into an oven for drying before being put into the open mill, the drying temperature is 40-55 ℃, and the drying time is 30-48 h.
3. The method for regulating and controlling the crystallinity of the polylactic acid bio-composite plastic film according to claim 1, wherein in the first step, the polylactic acid is stirred and melted in an open mill for 8-12 min.
4. The method for regulating and controlling the crystallinity of the polylactic acid bio-composite plastic film according to claim 1, wherein in the first step, stirring time after cottonseed protein and maleic anhydride are added is 4-8 min.
5. The method for controlling the crystallinity of the polylactic acid bio-composite plastic film according to claim 1, wherein in the first step, the cottonseed protein is added into the open mill within 1 min.
6. The polylactic acid bio-composite plastic film is characterized by being prepared by the method for regulating and controlling the crystallinity of the polylactic acid bio-composite plastic film according to any one of claims 1-5.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
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| CN104530670A (en) * | 2014-12-22 | 2015-04-22 | 南京林业大学 | Fibroin/polylactic acid blend material and melt-blending preparation method thereof |
| CN114045038A (en) * | 2021-12-31 | 2022-02-15 | 广东工业大学 | A kind of cottonseed protein composite material and its preparation method and application |
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| CN101445608B (en) * | 2008-12-29 | 2010-12-29 | 南京林业大学 | Copolymer of fibroin and poly L-lactic acid, solid phase polymerization preparation method and application thereof |
| CN101486806A (en) * | 2009-02-17 | 2009-07-22 | 四川大学 | Natural polymer / degradable polymer composite material and preparation thereof |
| CN101851424B (en) * | 2009-03-31 | 2011-08-10 | 西南科技大学 | Thermoplastic plant protein/polylactic acid blend material and preparation method thereof |
| US8524811B2 (en) * | 2009-04-28 | 2013-09-03 | Kimberly-Clark Worldwide, Inc. | Algae-blended compositions for thermoplastic articles |
| CN105238074A (en) * | 2015-11-18 | 2016-01-13 | 沈阳化工大学 | Preparation method of urea modified cottonseed protein plastic |
| CN110655795A (en) * | 2019-10-25 | 2020-01-07 | 仲恺农业工程学院 | A kind of cottonseed protein/PVA composite membrane and preparation method thereof |
| CN114381865A (en) * | 2022-01-21 | 2022-04-22 | 广东工业大学 | Vegetable protein composite nanofiber membrane as well as preparation method and application thereof |
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| CN104530670A (en) * | 2014-12-22 | 2015-04-22 | 南京林业大学 | Fibroin/polylactic acid blend material and melt-blending preparation method thereof |
| CN114045038A (en) * | 2021-12-31 | 2022-02-15 | 广东工业大学 | A kind of cottonseed protein composite material and its preparation method and application |
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