Polylactic acid foaming method

Abstract

The invention discloses a polylactic acid foaming method. The polylactic acid foaming method comprises the following steps that A, a gas-generating agent is dissolved into water to prepare a solution;B, monomer or oligomer, a thermal crosslinking agent are mixed with the aqueous solution of the step A to obtain an initial reaction mixed solution, and after the initial reaction mixed solution is frozen and dried in a freeze drying device, grinding is conducted; C, polylactic acid resin and the ground initial reaction mixture powder obtained in the step B are uniformly mixed; D, the uniformly mixed material in the step C is added into an extruder, process parameters of the extruder are set for melt extrusion, the gas-generating agent is heated and generated expansion during the extrusion process, and a polylactic acid melt displays a foaming state; and E, the polylactic acid melt in the step D is extruded through the extruder and the polylactic acid foaming material is obtained after cooling and shaping. The foaming method is simple and efficient, no special equipment is needed, the cost is low, the operation is easy, the control is easy, and the obtained foaming material is stablein quality, uniform in the foam size, and high in the foaming rate.

Description

technical field [0001] The invention relates to the technical field of polymer material processing, in particular to a polylactic acid foaming method. Background technique [0002] Polymer foam has properties such as low density, heat insulation, shock absorption and cushioning, and is widely used in fields such as cushioning and packaging. According to the different foaming agents used, the foaming process can be divided into chemical foaming and physical foaming. Microcellular foamed polymer refers to a polymer porous material with a cell size of 1-100 μm. Since the 1980s, microcellular foaming technology has been concerned by scientists all over the world. The microcellular foaming process usually uses supercritical carbon dioxide (CO 2 ) or nitrogen (N 2 ) as a blowing agent. [0003] Polylactic acid resin (PLA) is a biodegradable and renewable material. In addition, compared with other biodegradable polyester materials, PLA has many advantages such as good mechani...

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Problems solved by technology

[0004] However, because PLA is a crystalline material, its molecules have few long-chain branches and low melt strength, and the PLA melt is sensitive to temperature. As the temperature rises, the melt viscosity decreases a lot, which makes it impossible for the melt to wrap PLA when it is foamed. Bubbles prevent the escape of foaming agent, the foam film is unstable and easy to break, foam molding is difficult, and it is difficult to obtain a foaming material with high expansion ratio and uniform cells

[0005] Using supercritical carbon dioxide (CO 2 ) or nitrogen (N 2 ) as the foaming method of the foaming agent, often because the gas is released under the control of air pressure, it is easy to cause surface appearance defects; and equipment modification is required to increase gas generators, gas water pumping devices or flow adjustment devices, etc., equipment control is inconvenient, and the process complex and expensive to produce

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