Experimental Study on Mechanical Properties of Epoxy/MWCNT Nanocomposites—Effects of Acid Treatment, Pressured Curing, and Liquid Rubber

Abstract

The unique properties of carbon nanotube (CNT) have made it very attractive as reinforcement in polymer nanocomposites in the hope of effectively improving the mechanical properties. In order to explore the effects of three appealing influencing factors, i.e., acid treatment, pressured curing, and liquid rubber (LR) on mechanical properties of nanocomposites, tensile tests, and single-edge notched bending (SENB) tests are carried out for four types of CNT-reinforced nanocomposites. Compared with type I of nanocomposites using pristine multiwalled carbon nanotube (MWCNT) as reinforcement for epoxy, which are termed as Epoxy/MWCNT, type II of Epoxy/MWCNT-COOH nanocomposites with acid-treated MWCNTs as reinforcement, show obvious improvement on tensile properties and fracture toughness. This positive effect of acid treatment can be attributed to better dispersion of CNTs and stronger interface based on the corresponding fracture surfaces. For type III of P-Epoxy/MWCNT-COOH nanocomposites under pressured curing, although the voids in samples are decreased effectively and the interface is strengthened, there is no expected positive results because of severe CNTs agglomeration. For type IV of P-Epoxy/LR/MWCNT-COOH nanocomposites, addition of LR results in at least around a threefold increase in fracture toughness compared with that of P-Epoxy/MWCNT-COOH, indicating the amazing effect of LR. The present work provides much more choices for fabricating specific CNT-reinforced nanocomposites with desired properties by reasonably combining proper fabrication conditions including acid treatment, pressured curing, liquid rubber with polymer matrix, and reinforcement loading.