Polypropylene‐POSS Nanocomposites: Morphology and Crystallization Behaviour

Abstract

Nanocomposites of isotactic polypropylene (PP) with polyhedral oligomeric silsesquioxanes (POSS) [RSiO1,5]8 having different alkyl substituents (R = methyl, isobutyl, isooctyl) were obtained by melt blending and analysed with electron microscopy, optical microscopy and DSC calorimetry. The influence of POSS structure on the morphological characteristics, the crystallization and melting behaviour of PP/POSS composites was investigated with varying the filler amount. The crystallization kinetics of the composites from the melt, examined both in isothermal and non‐isothermal conditions, demonstrated that the nucleation activity of the examined POSS can be related to the length of alkyl substituents which, depending on the loading amount, affect the filler dispersion in the PP matrix and the growth of polymer crystals.

Polyethylene/polyhedral oligomeric silsesquioxanes composites: Electrical insulation for high voltage power cables

“…POSS dispersion within LDPE matrix was previously shown to be influenced by the chain length of POSS' alkyl groups . Similar findings were reported in studies dealing with PP/POSS composites (Fina et al, 2005b;Pracella et al, 2006). As can be seen, the compatibility between OmPOSS and LDPE is low, leading to micron-sized crystalline aggregates for both 1 wt% and 5 wt% filler contents (Figure 5.3 (a,b)).…”

“…In PP-based systems, increased Tons and Tc values and accelerated crystallization resulted from the addition of 3-30 wt% OmPOSS. On the other hand, decreased Tons and Tc values and retarded crystallization were found with the addition of 3-6 wt% OibPOSS and 3-10 wt% IoPOSS (Fu et al, 2001;Pracella et al, 2006). These results show that the influence of POSS on the crystallization behavior of polymers depends, at least to a certain degree, on the type of polymer concerned, as well as on the type and concentration of POSS.…”

Morphology and crystallization kinetics of polyethylene/long alkyl-chain substituted Polyhedral Oligomeric Silsesquioxanes (POSS) nanocomposite blends: A SAXS/WAXS study

“…Figure 8B shows ln(t 1/2 ) plotted as a function of 1/T. The linear form of the plots for PE and PE-POSS blends all lie on similar slopes, which confirms a consistent Arrhenius type of temperature dependence during crystallization [23,38]. The normalised quiescent crystallization curves in Figure 7, were used to obtain Avrami plots.…”

“…However, at higher loadings the POSS molecules aggregate and are less dispersed in the matrix reducing their effect on the crystallization process. Pracella [23] also reported on the morphology and crystallization behaviour of PP-POSS blends, having different alkyl substituents (methyl, isobutyl, isooctyl). The results showed that the length of alkyl substituent groups on the POSS molecule played a fundamental role in determining the dispersion degree and crystallization process of PP from the melt.…”

“…Indeed, a few have detailed the effects of chain length of POSS substituent groups on these characteristics, but the POSS substituent groups have been relatively short, the longest being isooctyl [12,23,25]. The crystal structure and packing morphology of the POSS molecules themselves have not been comprehensively characterised and therefore any influence of these characteristics once blended in the host polymer, have not been taken into account.…”