Tesfaye Melakuu, Patwa Rahul, Gupta Arvind, Kashyap Manash Jyoti, Katiyar Vimal
Department of Chemical Engineering, Indian Institute of Technology Guwahati, Guwahati, 781039, Assam, India.
Department of Chemical Engineering, Indian Institute of Technology Guwahati, Guwahati, 781039, Assam, India.
Int J Biol Macromol. 2017 Aug;101:580-594. doi: 10.1016/j.ijbiomac.2017.03.085. Epub 2017 Mar 18.
In this study, the effect of silk nanocrystals (SNCs) on the thermal and rheological properties of poly (lactic acid) (PLA) under repetitive extrusion process is investigated. The presence of SNCs facilitates the crystallization process and delaying the thermal degradation of PLA matrix. This leads to the reduction in cold crystallization peak temperature with lower crystallization half-time and higher growth rate. The substantial improvement in nucleation density observed through Polarized Optical Microscope (POM) proves the nucleating effect of SNC in all processing cycles. Moreover, the rheological investigation (complex viscosity, storage and loss modules values) revealed the stabilizing effect of SNC and the drastic degradation of neat PLA (NPLA) in third and fourth cycle is observed to be fortified by the presence of SNC. Cole-Cole plot and cross over frequencies have been correlated with the molar mass distribution of PLA and PLA-Silk composite during processing, which is further supported by the intrinsic viscosity measurement and acid value analysis. This investigation suggests that the melt viscosity and thermal properties of PLA can be stabilized by addition of silk nanocrystals.
在本研究中，研究了丝纳米晶体（SNCs）在重复挤出过程中对聚乳酸（PLA）热性能和流变性能的影响。SNCs的存在促进了结晶过程，并延缓了PLA基体的热降解。这导致冷结晶峰值温度降低，结晶半衰期缩短，生长速率提高。通过偏光显微镜（POM）观察到的成核密度的显著提高证明了SNC在所有加工循环中的成核作用。此外，流变学研究（复数粘度、储能模量和损耗模量值）揭示了SNC的稳定作用，并且观察到在第三和第四循环中纯PLA（NPLA）的剧烈降解因SNC的存在而得到加强。Cole-Cole图和交叉频率与加工过程中PLA和PLA-丝复合材料的摩尔质量分布相关，这进一步得到特性粘度测量和酸值分析的支持。该研究表明，添加丝纳米晶体可以稳定PLA的熔体粘度和热性能。
