Popcorning-type cracking failure in thermohyperelastic packaging materials in the presence of “wet” and “dry” cavities  

作　　者：LI ZhiGang SHU XueFeng 

机构地区：[1]Department of Mechanics,Taiyuan University of Technology [2]Institute of Applied Mechanics and Biomedical Engineering,Taiyuan University of Technology

出　　处：《Science China Chemistry》2013年第3期624-628,共5页中国科学（化学英文版）

基　　金：supported by the National Natural Science Foundation of China (Grant No. 11172195);the Natural Science Foundation of Shanxi Province,China (Grant No. 2012011019-4)

摘　　要：Thermal cracking occurs in the plastic packaging materials due to the presence of moisturized micro-cavities in the material.The moisture resident in the micro-cavities gives rise to the internal vapor pressure that drives the thermal expansion of micro-cavities as temperature rises.The plastic packaging materials are considered a class of thermo-hyperelastic materials,thus allowing the micro-cavities to thermally expand to the substantial extent before the cracking failure.The micro-cavities can be moisture-abundant(i.e.,wet) or substantially dry when cracking occurs.Cracking appears to be almost certain in the presence of wet cavities.The possibility of cracking in dry cavities turns to be two-sided:when the initial volume fraction of the micro-cavities is relatively small,cracking cannot occur in the dry cavities regardless of the phase transition temperature;when the initial cavity volume fraction is relatively large,cracking tends to occur in the dry cavities especially when the phase transition temperature is large.Because of the two-sided cracking possibility,the dry-cavity cracking mode presents a scenario that might reveal the mechanism of popcorning-type cracking failure in plastic packaging materials.Thermal cracking occurs in the plastic packaging materials due to the presence of moisturized micro-cavities in the material. The moisture resident in the micro-cavities gives rise to the internal vapor pressure that drives the thermal expansion of mi- cro-cavities as temperature rises. The plastic packaging materials are considered a class of thermo-hyperelastic materials, thus allowing the micro-cavities to thermally expand to the substantial extent before the cracking failure. The micro-cavities can be moisture-abundant （i.e., wet） or substantially dry when cracking occurs. Cracking appears to be almost certain in the presence of wet cavities. The possibility of cracking in dry cavities turns to be two-sided： when the initial volume fraction of the mi- cro-cavities is relatively small, cracking cannot occur in the dry cavities regardless of the phase transition temperature; when the initial cavity volume fraction is relatively large, cracking tends to occur in the dry cavities especially when the phase tran- sition temperature is large. Because of the two-sided cracking possibility, the dry-cavity cracking mode presents a scenario that might reveal the mechanism of popcorning-type cracking failure in plastic packaging materials.

关 键 词：plastic packaging materials popcorning-type cracking failure micro-cavities 

分 类 号：TB484.3[一般工业技术—包装工程] O343[理学—固体力学]