Management of both toughness and stiffness of polypropylene nanocomposites using poly(5-hexen-1-ol-co -propylene) and silica nanospheres

We developed novel polypropylene (PP)/silica nanocomposites using PP and silica nanospheres (SNSs) combined with poly(5-hexen-1-ol-co-propylene) (PPOH), which is a functionalized PP containing hydroxyl groups that was assumed to play a role as not only an elastomer but also an interface modifier. Since the affinity between the PP matrix and silica filler was expected to be improved by blending with PPOH, its influence on the mechanical properties, structure, and toughness of the ternary composites was examined in detail to provide a better understanding of the role of the matrix-filler affinity on the mechanical properties. The dispersity of the SNSs in the fabricated PP/PPOH/SNS nanocomposite was improved by increasing the hydroxyl group content of PPOH due to the enhanced affinity between PPOH and the SNSs. The SNSs in the composite with PPOH containing 6.4 mol% hydroxyl groups (PPOH6.4) were almost dispersed in the microscale domain, while the SNSs in the composite with 1.3 mol% hydroxy groups (PPOH1.3) were considerably aggregated. The toughness of the nanocomposite was noticeably improved by blending PPOH6.4 without a significant loss of stiffness. In contrast, the toughness was hardly improved using PPOH1.3. Therefore, both the fine dispersion of the SNSs and the excellent affinity between PPOH6.4 and the SNSs contributed to the good balance of toughness and stiffness of the PP/PPOH/SNS nanocomposite.