Abstract:

Based on the effects of crosslinking agent on the rheological properties of polylactic acid (PLA), the cellular structure of crosslinked PLA foams was investigated via batch foaming. The results showed that when adding the crosslinking agent to the PLA, its loss tangent and complex viscosity in low frequency region and its melt strength and extensional viscosity increased. In the initial cell growth stage, the cell wall was stretched, which dramatically increased the high complex viscosity of the crosslinked PLA slowed down the cell growth rate. In the later cell growth stage, the melt strength and extensional viscosity and so increased the strength of the cell wall. Then, cell coalescence was abviously reduced and the cellular structure of the crosslinked PLA foam samples was more regular and uniform. The amount of gas loss decreased because of the high melt strength of the crosslinked PLA, which resulted in an increased expansion ratio of the PLA foam samples. The PLA foam had a maximum volume expansion ratio of 41 when adding 0.4 phr crosslinking agent.

Key words: polylactic acid, supercritical fluid, polymer processing, crosslinking agent, rheology, cellular structure

摘要：

在研究交联剂对聚乳酸(PLA)流变性能影响的基础上,采用间歇发泡方法研究交联PLA发泡材料的泡孔结构。结果表明,交联剂可提高低频区PLA的损耗角正切和复数黏度以及PLA的熔体强度和拉伸黏度。交联PLA的复数黏度高,使泡孔长大初期的长大速率较低;泡孔长大后期泡孔壁被拉伸时,熔体强度和拉伸黏度的急剧提高使泡孔壁强度增加而不会被撕裂,大大减小泡孔的合并,形成较均匀且较规则的泡孔结构。交联PLA高的熔体强度可明显减少发泡时二氧化碳扩散至空气中的量,从而增加PLA发泡样品的体积膨胀率;加入0.4 phr的交联剂时,样品的体积膨胀率最大(达41)。

关键词: 聚乳酸, 超临界流体, 聚合物加工, 交联剂, 流变学, 泡孔结构