Fundamental investigations on the environmental stress cracking of vibration-welded thermoplastic-based nanocomposites

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Once thermoplastic products are under simultaneous effects of mechanical stress, i.e. external and internal stress, and an aggressive medium, the so-called environmental stress cracking (ESC) can be initiated, which leads to a premature catastrophic failure of the products. Premature failure of such products in service are often serious especially in the medical technology that can be life-threatening for the patients. Fundamental understanding of ESC behavior and improvement of ESC resistance are considered as great challenges for thermoplastic materials. It has been well established that increasing molecular weight and incorporation of nano-sized inorganic particles can both improve the ESC resistance of thermoplastics, and as a result, prolong their lifetime. Such thermoplastic products are often designed with welded parts, which are also susceptible to ESC. Till now, studies on the ESC behavior of welded products are quite sparse. The key objective of this research proposal is to investigate the effects of nanofillers with different geometries, spherical nanosilica and rod-like carbon nanotubes, on the ESC resistance of vibration-welded PP- and PC-based nanocomposites under influence of different ESC agents and ambient temperatures. More importantly, the effect of carbon nanotubes orientation within the weld region on the ESC behavior should be particularly considered. It is expected that the project outcome can contribute to a deep understanding of ESC behavior of the welded parts, and finally, a rational development of high ESC-resistant composite materials that exhibit longer lifetime and higher application safety.