Highly Reinforced Poly(lactic acid) Foam Fabricated by Formation of a Heat-Resistant Oriented Stereocomplex Crystalline Structure,ACS Sustainable Chemistry & Engineering

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Highly Reinforced Poly(lactic acid) Foam Fabricated by Formation of a Heat-Resistant Oriented Stereocomplex Crystalline Structure
ACS Sustainable Chemistry & Engineering ( IF 7.1 ) Pub Date : 2021-09-03 , DOI: 10.1021/acssuschemeng.1c04862
Ruiguang Li ₁ , Xiaowen Zhao ₁ , Phil Coates ₂ , Fin Caton-Rose ₂ , Lin Ye ₁

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Avoiding disorientation of oriented poly(l-lactide) (PLLA) during foaming remains challenging for preparing highly reinforced PLLA foams with an oriented structure. By utilizing the melting-temperature difference of stereocomplex (SC)/homo-crystallite (HC) crystals, PLLA/poly(d-lactide) (PDLA) blend foams with an oriented crystalline structure were prepared via solid-phase hot drawing and the supercritical CO₂ foaming technology. Incorporating both SC crystals and molecular orientation promoted PLLA crystallization, and highly oriented HC/SC crystals formed after drawing. By subsequent foaming, HC crystals mainly formed. For the oriented pure PLLA sample, serious disorientation occurred after foaming, while for the oriented PLLA/PDLA blend foam, with increasing PDLA content, orientation retention of the HC/SC crystal increased sharply to 70.4/87.8%. Much more fibrillar structures formed on the cell wall of foams, indicating that forming the SC crystal was significant to maintain the orientation structure of PLLA during foaming. By increasing the PDLA content and draw ratio, the dissolved CO₂ amount increased, while CO₂ escape was hindered, resulting in a dense cell structure. Highly oriented PLLA/PDLA foams exhibited superior heat resistance and mechanical strength.

中文翻译：

通过形成耐热定向立体复合物晶体结构制备的高强度聚乳酸泡沫

在发泡过程中避免取向聚（l-丙交酯）（PLLA）的取向对于制备具有取向结构的高度增强的 PLLA 泡沫仍然具有挑战性。利用立体络合物（SC）/均晶（HC）晶体的熔融温度差异，通过固相热拉伸和超临界制备具有取向晶体结构的PLLA/聚（d-丙交酯）（PDLA）共混泡沫。 CO ₂发泡技术。SC晶体和分子取向的结合促进了PLLA结晶，拉伸后形成了高度取向的HC/SC晶体。通过随后的发泡，主要形成HC晶体。对于取向的纯PLLA样品，发泡后发生严重的取向紊乱，而对于取向的PLLA/PDLA共混泡沫，随着PDLA含量的增加，HC/SC晶体的取向保留率急剧增加，达到70.4/87.8%。在泡沫的细胞壁上形成了更多的原纤维结构，表明形成 SC 晶体对于在发泡过程中保持 PLLA 的取向结构具有重要意义。通过增加 PDLA 含量和拉伸比，溶解的 CO ₂量增加，而 CO ₂逃逸受到阻碍，导致细胞结构致密。高度取向的 PLLA/PDLA 泡沫表现出优异的耐热性和机械强度。

更新日期：2021-09-20

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