Enhanced Segmental Dynamics of Poly(lactic acid) Glasses during Constant Strain Rate Deformation
Enhanced Segmental Dynamics of Poly(lactic acid) Glasses during Constant Strain Rate Deformation
复制标题
DOI：
10.1021/acs.macromol.9b01363
复制
发表时间：
2019-09-10
期刊：
影响因子：
5.5
通讯作者：
Ediger, M. D.
中科院分区：
文献类型：
--
作者：
Bennin, Trevor;Ricci, Josh;Ediger, M. D.
采用探针重取向法研究了温度和形变对聚乳酸（PLA）玻璃链段动力学的综合影响。在T-g - 15 K和T-g - 25 K之间的温度下，在PLA玻璃上进行恒定应变速率变形，应变速率在6 × 10（-6）和3 × 10（-5）s（-1）之间。相对于未变形状态，变形使段弛豫时间减少多达30倍。在postyield制度的节段弛豫时间与局部应变率通过幂律，与那些报道的轻度交联的PMMA的指数相似。的Kohlrausch-Williams-Watts指数，β（KWW），通常解释的分段弛豫时间的分布的宽度，从未变形状态的postyield政权的变化，表明显着收窄的弛豫谱。我们观察到β（KWW）与PLA的变形诱导的节段流动性增加相关，如PMMA所报告的那样。PLA和PMMA对变形的类似反应表明，所观察到的效应是恒定应变速率变形对聚合物玻璃的分段动力学的一般后果。
The combined effects of temperature and deformation on the segmental dynamics of poly(lactic acid) (PLA) glasses were investigated by using probe reorientation measurements. Constant strain rate deformations, with strain rates between 6 x 10(-6) and 3 x 10(-5) s(-1), were performed on PLA glasses at temperatures between T-g - 15 K and T-g - 25 K. Deformation decreases the segmental relaxation time by up to a factor of 30 relative to the undeformed state. The segmental relaxation time in the postyield regime is related to the local strain rate via a power law, with exponents similar to those reported for lightly cross-linked PMMA. The Kohlrausch-Williams-Watts exponent, beta(KWW), commonly interpreted in terms of the width of the distribution of segmental relaxation times, changes from the undeformed state to the postyield regime, indicating a significant narrowing of the relaxation spectrum. We observe that beta(KWW) is correlated to the deformation-induced increase of segmental mobility for PLA, as was reported for PMMA. The similar responses of PLA and PMMA to deformation suggest that the observed effects are the generic consequences of constant strain rate deformation on the segmental dynamics of polymer glasses.