Mithun Bhattacharya

Influence of Different Nanofillers and their Dispersion Methods on the Properties of Natural Rubber Nanocomposites

Abstract The effects of varying morphological and chemical constitution of nanofillers and various dispersion methods on natural rubber nanocomposites prepared by conventional processing techniques were determined by incorporating various nanofillers like montmorillonite, sepiolite (SP), hectorite, carbon nanofiber (F) and expanded graphite. When compared with the gum, SP filled (4 phr) nanocomposite exhibited an increment of 26% in the modulus and F (6phr) increased the tear strength by 18%, over the gum. Nanofiller dispersion was enhanced by various compatibilization and dispersion techniques which helped SP introduce 56 and F 113% increment in the modulus of the nanocomposites, over the gum rubber vulcanizate. It also rendered 28% improvement in the tear strength of F filled system. Deeper insights into the material properties were obtained through dynamic mechanical and swelling studies. Property-morphology correlation of the hybrids was performed through X-ray Diffraction, Atomic Force Microscopy and...

Exfoliation of Nanolayer Assemblies for Improved Natural Rubber Properties: Methods and Theory

Natural rubber (NR)-based nanocomposites were prepared by conventional processing techniques using various natural and modified nanoclays. For modified montmorillonite (Cloisite® 15A), the 300% modulus, tensile, and tear strength exhibited substantial increments of over the gum due to better dispersion. The unmodified montmorillonite clay (Cloisite® Na+) failed to improve the above properties significantly. The limitations of Cloisite® Na+-based NR nanocomposites prepared by the conventional method were alleviated using latex blending technique. Pre-exfoliated aqueous suspension of Cloisite® Na+ was blended with NR latex under special conditions and cured by pre-vulcanization as well as conventional curing. These showed predominantly exfoliated morphology along with substantially improved physical and mechanical properties. A simple theory based on effective surface area factor was proposed to account for the structure—property correlations.

Correlation of Vulcanization and Viscoelastic Properties of Nanocomposites Based on Natural Rubber and Different Nanofillers, with Molecular and Supramolecular Structure

Abstract Elastomer nanocomposites reinforced with low volume fraction of nanofillers, such as nanoclays and carbon nanofibers, have long been known to possess significantly improved mechanical, thermal, dynamic mechanical, flame retardant, and barrier properties. The present work attempts to evaluate the effect of nanofillers (like modified and unmodified montmorillonite, sepiolite, carbon nanofiber, and carbon black) and their amount on vulcanization, as well as dynamic and rheological properties in the prevulcanization and postvulcanization stages. Upon using organomodified nanoclay, optimum cure time was reduced and cure rate index increased; whereas, in comparison, carbon nanofiber resulted in a slower cure. The influence of loading of some representative nanofillers on natural rubber was studied through qualitative description of critical dynamic viscoelastic parameters, which indicated the formation of supramolecular structure even at low volume fraction. The nanocomposite vulcanizates showed solidl...

Liquid Silicone Rubber Vulcanizates: Network Structure - Property Relationship and Cure Kinetics

Liquid silicone rubber (LSR) vulcanizates have been prepared from vinyl-end capped polydimethylsiloxane (PDMS) and polymethylhydrogenosiloxane (PMHS) in presence of platinum catalyst using solution casting technique. The science involving synthesis of usable silicone rubber by curing with polymethylhydrogenosiloxane has been studied in details. The effects of vinyl content of PDMS and the ratio of hydride crosslinker to vinyl concentration on crosslink density, mechanical, dynamic-mechanical and thermal properties have been discussed. It has been found that at optimum level of crosslinker, the LSR vulcanizate shows a maximum crosslink density with highest improvement in mechanical and thermal properties. The amount of crosslinker required, depends upon the number of vinyl functionality per unit length of the polymer chain and the chemical composition of the hydride crosslinker. This study makes a novel attempt to determine cure kinetics of PDMS by using Fourier Transform Infrared spectroscopy. Measurements have been done at three different temperatures and found to follow the first order reaction with respect to consumption of vinyl (C=C) and silyl hydride groups (Si-H). The activation energy and kinetic parameters have been determined as well.