Effects of chemical modifications on the rheological and the expansion behavior of polylactide (PLA) in foam extrusion
Effects of chemical modifications on the rheological and the expansion behavior of polylactide (PLA) in foam extrusion
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DOI：
10.1515/epoly-2019-0030
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发表时间：
2019-01
期刊：
影响因子：
3.7
通讯作者：
T. Standau;S. Castellón;Agathe Delavoie;C. Bonten;V. Altstädt
中科院分区：
文献类型：
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作者：
T. Standau;S. Castellón;Agathe Delavoie;C. Bonten;V. Altstädt
摘要 众所周知，聚丙交酯（PLA）由于熔体强度低而难以发泡。因此，文献中描述了许多提高发泡性的方法。然而，实际上仅在有限数量的出版物中测定了熔体强度。本研究通过添加化学改性剂来改变PLA的流变行为，从而提高其在泡沫挤出过程中的发泡性能。首次描述了过氧化二枯基改性 PLA 在泡沫挤出中的应用。两种改性都会导致熔体强度明显增加。此处，用过氧化二异丙苯改性的 PLA 的增幅最高。此外，观察到用过氧化物改性的 PLA 的应变硬化。在泡沫挤出中使用纯聚乳酸和改性聚乳酸实现了低密度泡沫。纯 PLA 的密度为 45 kg/m3，而过氧化物改性的 PLA 显示出最高的膨胀率，密度降低至 32 kg/m3。这两种修改都会导致更均匀的泡孔结构和更高的抗压强度。在这里，与纯 PLA 泡沫相比，过氧化物改性的发泡 PLA 表现出了出色的性能，即使密度降低了 30%，压缩强度却是其两倍 (151 Pa)。
Abstract It is well known that polylactide (PLA) is difficult to foam due to its low melt strength. Thus, many ways were described in the literature to enhance the foamability. However, the melt strength was actually determined only in a limited number of publications. In this study, the addition of chemical modifiers was used to change the rheological behavior of PLA and thereby improve its foamability in foam extrusion process. For the first time the use of dicumyl peroxide modified PLA in foam extrusion is described. Both modifications lead to a distinct increase in melt strength. Here, the highest increase was shown for the PLA modified with dicumyl peroxide. Furthermore, strain hardening was observed for PLA modified with the peroxide. Low density foams were achieved for neat and modified PLA in foam extrusion. Neat PLA showed a density of 45 kg/m3, while the peroxide modified PLA showed the highest expansion with a density reduction down to 32 kg/m3. Both modifications result in a more uniform cell structure and an improved compression strength. Here, the foamed, peroxide modified PLA showed outstanding performance compared to neat PLA foam with twice the compression strength (151 Pa) even at a 30% lower density.