Rheological investigation of interactions between sorbitol and polyhedral oligomeric silsesquioxane in development of nanocomposites of isotactic polypropylene
Sorbitol-type nucleating agents can be used to aid dispersion of polyhedral oligomeric silsesquioxane (POSS) molecules in isotactic polypropylene (iPP) and to promote self-assembly of POSS molecules into nanoparticles. In this paper, the interactions between a sorbitol-type nucleating agent and POSS molecules were investigated using polarized optical microscopy and rotational rheometry. Dibenzylidene sorbitol (DBS), a nucleating agent of iPP, was used in conjunction with two non-reactive POSS—trisilanolphenyl-POSS (ph-TPOSS) and octaisobutyl-POSS (bu-MPOSS). DBS formed three-dimensional fibrillar networks in iPP upon cooling from a homogeneous state. These fibrillar networks were characterized as gels using oscillatory shear rheometry. Trisilanolphenyl-POSS was incompatible with iPP but offered strong hydrogen bonding possibility with DBS; bu-MPOSS, on the other hand, was compatible with iPP but did not produce significant interactions with DBS. It was found that as low as 0.5 wt % of ph-TPOSS molecules in a ternary compound with 0.7 wt % DBS subdued fibrillar network formation by DBS and altered the rheological properties of the compounds. No such effect was seen in compounds of bu-MPOSS, although viscosity showed strong reduction. The storage modulus vs loss modulus data provided much better indication of changes of morphology in iPP/POSS and iPP/DBS/POSS compounds than loss tangent vs oscillatory frequency plots.
Jana, Sadhan, "Rheological investigation of interactions between sorbitol and polyhedral oligomeric silsesquioxane in development of nanocomposites of isotactic polypropylene" (2010). Polymer Engineering Faculty Research. 701.