Preparation and properties of melt blended metallocene polyethylene/silica nanocomposites: modifier effects

Metallocene polyethylene (mPE)/silica ternary nanocomposites were prepared via a melt mixing approach using two types of modifiers, mPE-g-MA (maleic anhydride) or linear low density polyethylene (LLDPE)-g-MA. Transmission electron microscopy revealed a similar degree of silica dispersion status for mPE/silica with or without modifiers to suggest the similar compatibility for mPE with modified silica, as evidenced by a similar change on the master curves over the corresponding frequency range and silica content in Cole-Cole plots. Silica and the modifiers served as nucleating agents to increase the crystallization temperature of mPE. Two visible crystallization temperatures or melting temperatures corresponding to mPE and LLDPE-g-MA, respectively, were still observable for LLDPE-g-MA modified cases, but not for mPE-g-MA modified cases. LLDPE-g-MA modified cases rendered the highest Young's modulus and cutting strength due to the induced yielding from the high crystalline LLDPE-g-MA. Cutting strength of the LLDPE-g-MA modified case was approximately 34% larger than that of the mPE-g-MA modified case at 10 phr silica. By contrast, mPE-g-MA modified cases rendered the highest tear strength due to its high flexibility to provide more physical entanglements. Strength of investigated nanocomposites varied under different deformation behaviors to signify the importance of interphase and matrix variation at similar silica dispersion status.