Vu Thevu, Nikaeen Peyman, Chirdon William, Khattab Ahmed, Depan Dilip
Institute of Materials Research and Innovation, Department of Chemical Engineering, University of Louisiana at Lafayette, P.O. Box 43675, Lafayette, LA 70504-4130, USA.
Laboratory of Composite Materials, Department of Mechanical Engineering, University of Louisiana at Lafayette, P.O. Box 43675, Lafayette, LA 70504-4130, USA.
Biomimetics (Basel). 2020 Nov 17;5(4):61. doi: 10.3390/biomimetics5040061.
To understand the interrelationship between the microstructure and degradation behavior of poly(lactic acid) (PLA), single-walled carbon nanotubes (CNTs) were introduced into PLA as nucleating agents. The degradation behavior of PLA-CNT nanocomposites was examined under accelerated weathering conditions with exposure to UV light, heat, and moisture. The degradation mechanism proceeded via the Norrish type II mechanism of carbonyl polyester. Differential scanning calorimetry (DSC) studies showed an increase in glass transition temperature, melting temperature, and crystallinity as a result of the degradation. However, pure PLA showed higher degradation as evidenced by increased crystallinity, lower onset decomposition temperature, embrittlement, and a higher number of micro-voids which became broader and deeper during degradation. In the PLA-CNT nanocomposites, CNTs created a tortuous pathway which inhibits the penetration of water molecules deeper into the polymer matrix, making PLA thermally stable by increasing the initial temperature of mass loss. CNTs appear to retard PLA degradation by impeding mass transfer. Our study will facilitate designing environmentally friendly packaging materials that display greater resistance to degradation in the presence of moisture and UV light.
为了解聚乳酸（PLA）的微观结构与降解行为之间的相互关系，将单壁碳纳米管（CNT）作为成核剂引入PLA中。在暴露于紫外线、热和湿气的加速老化条件下，研究了PLA-CNT纳米复合材料的降解行为。降解机理通过羰基聚酯的Norrish II型机理进行。差示扫描量热法（DSC）研究表明，降解导致玻璃化转变温度、熔点和结晶度升高。然而，纯PLA表现出更高的降解程度，表现为结晶度增加、起始分解温度降低、脆化以及在降解过程中微孔数量增加且变得更宽更深。在PLA-CNT纳米复合材料中，CNT形成了一个曲折的路径，抑制了水分子深入聚合物基体的渗透，通过提高初始质量损失温度使PLA具有热稳定性。CNT似乎通过阻碍传质来延缓PLA的降解。我们的研究将有助于设计在存在湿气和紫外线的情况下具有更高抗降解性的环保包装材料。
