Nanocomposites of synthetic styrene‐co‐butadiene rubber and three types of organoclay fillers were prepared by melt‐compounding and characterized by small‐angle X‐ray scattering (SAXS), differential calorimetry and stretching calorimetry. The in‐rubber structure of the organoclay particles is characterized by different degrees of intercalation with interlayer distances ranging from 3.1–4.8 nm. In contrast to the pristine rubber, all nanocomposites exhibited irreversibility of both mechanical work and heat effects in stretching/contraction cycles at fairly low elongations. Moreover, at the same filler loading both the mechanical reinforcement effect and the magnitude of specific heat effects proved strongly dependent on the degree of intercalation. In the range of low elongations, significantly earlier onsets of the heat inversion phenomenon (compared to theoretically expected), as well as the overshoots of exothermal heat effects in contraction above the endothermal heat effects in stretching for nanocomposites, suggested the contribution of structural rearrangements at the rubber/filler interface by the mechanism of chain slippage operative in both stretching and contraction regimes. In the range of high elongations, the thermoelastic behavior of nanocomposites could be accounted for quantitatively by the model, which assumed explicitly the contributions of local strain amplification for the rubber matrix and of successive decay of nanoparticle clusters with increasing strain, generating the exothermal effects of external friction between nanoparticles.Dependency on relative elongation of specific mechanical work (squares) and specific heat effects (circles) for the pristine rubber.magnified imageDependency on relative elongation of specific mechanical work (squares) and specific heat effects (circles) for the pristine rubber.
Poly(vinylidene fluoride) (PVDF) and its blends with polyaniline (PANI) doped with dodecylbenzene sulfonic acid (DBSA) were characterized by electrical conductivity, differential scanning calorimetry (DSC) and X-ray scattering techniques.The onset of an infinite cluster (InC) of conducting, highly anisometric PANI/ DBSA particles in PVDF/(PANI/DBSA) blends was observed at the percolation threshold as low as w à % 3.5 wt.%. The small angle X-ray scattering (SAXS) data confirmed the expected spatial organization of PANI/DBSA needles into fractal-like structures above w à . A slight decrease of both the DSC and the wide-angle X-ray scattering (WAXS) degrees of crystallinity of PVDF with the PANI/DBSA mass content w was explained by strong interactions at the PVDF/(PANI/DBSA) interface resulting in the loss of crystallizability of a fraction of sterically immobilized chains of PVDF in boundary layers around PANI/DBSA particles. The available data suggest that the conductive paths within InC of PANI/DBSA in PVDF/(PANI/DBSA) blends were formed primarily by the end-to-end contacts of PANI/DBSA fibrils.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.