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High pressure forming method for increasing crystallinity of polylactic acid

A technology of high-pressure molding and polylactic acid, which is applied in the field of polymer materials, can solve problems such as unreported and uneven dispersion, and achieve the effects of broadening the application range, high production efficiency, easy control and popularization and application

Inactive Publication Date: 2013-02-27
SICHUAN UNIV
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

Among them, adding crystallization nucleating aids (such as talc, montmorillonite, starch, etc.) is the most commonly used method (Sarazin P, et al. Polymer, 2008, 49: 599-609), which accelerates the process of polymer Nucleation rate to improve crystallinity, but the problem with this method is that the nucleating agent will agglomerate in a large amount in the polymer during the actual operation, so the dispersion is not uniform
In summary, high-pressure molding is very beneficial to the improvement of polymer crystallinity, but so far, research on high-pressure crystallization of polylactic acid has not been reported.

Method used

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  • High pressure forming method for increasing crystallinity of polylactic acid
  • High pressure forming method for increasing crystallinity of polylactic acid
  • High pressure forming method for increasing crystallinity of polylactic acid

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Experimental program
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Embodiment 1～13

[0021] (1) Drying: first place the polylactic acid particles in a vacuum oven, evaporate and remove internal moisture under vacuum conditions, the oven temperature is 60°C, and the drying time is 12 hours until the moisture weight content is less than 0.01%;

[0022] (2) High-pressure molding: first place the dried polylactic acid particles in a high-pressure mold, then raise the temperature to 185°C, and maintain it for a long enough time until the heat history is completely eliminated, and then slowly cool at a rate of 2.5°C / min until molding temperature (120-185° C.), and then apply a pressure of 300-1500 MPa and maintain it for 0.5-24 hours for isothermal crystallization, and finally release the pressure after the temperature drops to room temperature. In order to prevent polylactic acid from degrading under high temperature and pressure, the samples need to be molded in a nitrogen-protected environment. The specific molding temperature and pressure are shown in Table 1. ...

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Abstract

The invention discloses a high pressure forming method for increasing crystallinity of polylactic acid. The method is as below: placing dried polylactic acid particles in a high pressure die; first heating to 185 DEG C and maintaining for long enough to completely eliminate the thermal history; slowly cooling with a speed of 2.5 DEG C / min to a forming temperature (120-185 DEG C); applying a pressure of 300-1500MPa and maintaining for 0.5- 24 h for isothermal crystallization; and eventually releasing pressure until temperature decreases to room temperature. A polylactic acid product prepared by the method gains significantly improved crystallinity behavior, crystallinity as high as 66.3%, and obviously improved heat resistance and mechanical properties. The invention can further broaden application value and use range of polylactic acid.

Description

technical field [0001] The invention belongs to the technical field of polymer materials, and in particular relates to a high-pressure molding method for improving the crystallinity of polylactic acid. Background technique [0002] Polylactic acid (PLA) is made of starch raw materials extracted from renewable plant resources (such as corn), which can be completely degraded by microorganisms in nature after use, and finally generate carbon dioxide and water without polluting the environment. It is recognized Environmentally friendly materials (Auras R, et al. Macromolecular Bioscience, 2004, 4: 835-864). In addition, polylactic acid is a widely used engineering plastic. Because of its good melt processability, mechanical strength and suitable barrier properties, it has very broad prospects in the field of actual product applications. However, due to the slow crystallization kinetics of polylactic acid, it often shows an amorphous state after the usual extrusion or injection ...

Claims

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Application Information

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IPC IPC(8): B29C43/02B29B13/06B29K67/00
Inventor 李忠明张进雷军
Owner SICHUAN UNIV
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