Degradable Plastics Are Vulnerable to Cracks

• 作者: Xuxu Yang Jason Steck Jiawei Yang Yecheng Wang Zhigang Suo
• 来源期刊: 工程（英文）
• 年，卷（期）: 2021,（5）
• 所属期刊栏目: Green Chemical Engineering:Soft Matter—Letter
• 页码范围: 624-629
• 页数: 6页
• 语种: 英文

摘要

A plastic may degrade in response to a trigger.The kinetics of degradation have long been characterized by the loss of weight and strength over time.These methods of gross characterization,however,are mis-leading when plastic degrades heterogeneously.Here,we study heterogeneous degradation in an extreme form:the growth of a crack under the combined action of chemistry and mechanics.An applied load opens the crack,exposes the crack front to chemical attack,and causes the crack to outrun gross degradation.We studied the crack growth in polylactic acid(PLA),a polyester in which ester bonds break by hydrolysis.We cut a crack in a PLA film using scissors,tore it using an apparatus,and recorded the crack growth using a camera through a microscope.In our testing range,the crack velocity was insensi-tive to load but was sensitive to humidity and pH.These findings will aid the development of degradable plastics for healthcare and sustainability.