Modeling of tensile modulus of polyolefin- layered silicate nanocomposites: modified micro-mechanical and statistical methods

摘要

Applicability and subsequent modification of various composite models for the prediction of the relative tensile modulus of polyolefin nanocomposites has been studied. A number of models, such as the modified Halpin-Tsai, Guth, Mori-Tanaka, Hui and Shia and Takay-anagi models, as well as factorial and mixture designs, were considered. Various assumptions in the models, such as uniform shape and size of filler (i.e., complete exfoliation), alignment, as well as interfacial bonding between the components, restrict their application for the prediction of the nanocomposite modulus. The modified Guth model and Halpin-Tsai model, with the O_m concept, were developed further to incorporate the modulus reduction factors for polyolefin nanocomposites. This allowed the generation of master curves of the modulus reduction factor as a function of the aspect ratio of the filler in the composite. It was observed that the Mori Tanaka model, modified by constructing models of various representative volume elements (RVEs) of the underlying structure of the nanoclay filled polymers, matched the experimental values of the tensile modulus of polyolefin nanocomposites. The modified Hui and Shia model, incorporating the non-bonding interfacial effects, as well as the three component modified Takayanagi model, were also able to predict the tensile modulus of polyolefin nanocomposites efficiently. Factorial and mixture designs did not require the conventionally used assumptions and satisfactorily reflected the material behavior, and were specific to the particular components used to generate nanocomposites. These models were also helpful in predicting the aspect ratio of the filler in the composites, when synergistically combined with other modified models.