Mechanical characterization of polyhedral oligomeric silsesquioxane/polypropylene blends

Abstract

Polypropylene blends with polyhedral oligomeric silsesquioxanes (POSS) bearing different alkyl groups were investigated to elucidate the effect of the alkyl group length on the mechanical behavior of the blends. In particular, blends of polypropylene (PP) with either octamethyl-POSS, octaisobutyl-POSS, or isooctyl-POSS were studied. Differential scanning calorimetry evidenced only minor changes in the degree of crystallinity compared to neat PP. Uniaxial tensile tests showed that the incorporation of octamethyl-POSS induces an increase in Young’s modulus and a reduction of the yield strength in comparison with unfilled PP. By contrast, upon the incorporation of octaisobutyl-POSS and isooctyl-POSS, both Young’s modulus and the yield strength were found to decrease by increasing the POSS content. It is suggested that POSS behave as particles having a siliceous hard-core surrounded by a hydrocarbon soft-shell, which limits the stress transfer from the matrix to the core in dependence on the length of the alkyl groups. Finally, the essential work of fracture method was employed to study the fracture behavior of octamethyl-POSS/PP blends, with different POSS contents (0, 3, and 10 wt %)

A novel functional MgO ∙ SiO2/polyhedral oligomeric silsesquioxane hybrids as an active filler of polypropylene

“…The structure and synthetic route to 1-(3-hydroxypropyl)dimethylsiloxy-3,5,7,9,11,13,15-hepta(isobutyl)pentacyclo-[9.5.1.1 3,9 .1 5,15 .1 7,13 ]octasiloxane (later called iBu-POSS) is shown in the Scheme 1 and in Table 1.…”

“…This kind of dependence may occur due to certain/limited amount of fi ller/nanofi ller in composite, above which a deterioration of properties is noted. Observations of this type were presented by Baldi 7 and Zhou 21 in their research. In Figure 4 the maximum fi lm strength, obtained in static stretching conditions, was presented.…”

“…The effect of chemical modifi cation of magnesium silicate surface on their physicochemical properties was determined. Functionalization was carried out with the use of different amount of (1-(3-hydroxypropyl)dimethylsiloxy-3,5,7,9,11,13,15-hepta(isobutyl)pentacyclo-[9.5.1.1 3,9 .1 5, 15 .1 7,13 ]octasiloxane). The polypropylene composites of 0.5, 1.0 and 1.5 wt.% modifi ed by 10 weight parts by the mass of the fi ller were also produced.…”

“…Reaction (1) Scheme 1. Reaction path for synthesis of 1-(3-hydroxypropyl)dimethylsiloxy-3,5,7,9,11,13,15-hepta(isobutyl)pentacyclo-[9.5.1.1 3,9 .1 5,15 .1 7,13 ] octasiloxane (E) to get (B) and hydrolysis of chloro-substituted silsesquioxane (B) yielding (C), followed by next condensation to receive (D), according to original procedure 14 . The fi nal step of the preparation of E is the most frequent method of silsesquioxane functionalization, i.e.…”

“…hydrosilylation (Scheme 1. Reaction (4)) of allyl alcohol with 1-hydrodimethylsiloxy-3,5,7,9,11,13,15-hepta(isobutyl)pen tacyclo[9.5.1.1 3,9 .1 5,15 .1 7,13 ]-octasiloxane (D) in the presence of Pt Karstedt catalyst…”