Role of silane crosslinking on the properties of melt blended metallocene polyethylene-g-silane/clay nanocomposites at various clay contents

摘要

A study to investigate matrix properties and their interaction with loaded nanoclay was designed under controlled clay dispersion. Metallocene polyethylene grafted vinyltriethoxy silane (mPE-g-silane) was served as the matrix, with or without silane crosslinking (grafting and post crosslinking with catalyst versus only grafting without catalyst), to assess the strength of commercial organoclay (20A)-filled nanocomposites prepared via a melt mixing. According to X-ray diffraction and transmission electron microscopy analyses, all nanocomposites achieved similar dispersion degrees at specific clay contents mainly due to the silane interaction with the dispersed clay via hydrogen bonding and/or chemical bonding. Chemical bonding of grafted silane with clay was inferred based on the slightly higher crosslinking degree with increasing clay content for crosslinked cases. For uncrosslinked cases, the crosslinking degree was virtually zero regardless of clay content. The dynamic mechanical properties revealed enhanced interaction between mPE-g-silane and clay with increasing clay content based on the increased glass transition temperatures. Young's modulus of nanocomposites with crosslinked cases showed higher values in comparison with uncrosslinked cases at a specific clay content, indicating the significance of matrix crosslinking effect and the effective interfacial interaction between silane and clay especially at higher clay content. To the authors' best knowledge, this is the first study which generally maintains similar clay dispersions through the effect of uncrosslinking (only grafting) and crosslinking (grafting and post crosslinking), and then probes the effect of matrix properties and interfacial interactions at the large deformation state (tensile test) and small deformation state (cutting test).