Study of Kinetics and Properties of PBR/Nano filler Based Composites Prepared via in- situ Process Using Ziegler Natta Polymerization Systems

Abstract

Literature studies envisage that polybutadiene rubber based nano composites are mostly prepared by either using solution method or melt compounding method. But, solution process is economically infeasible and not environmentally benign due to major waste of solvent, while melt intercalation solves the problem associated with solution method, however poor dispersion of nanofillers is observed because of weak interaction between the polymer and nanofillers. This ultimately reduces rubber properties substantially. On the other hand, the advantage of in situ approach lies in the better exfoliation achieved compared to melt and solution methods. Therefore, the objective of the present work is to improve dispersion of nanofillers into rubber matrix by in situ method during polymerization reaction. The research interest on multi-wall carbon nanotube (MWCNT) and nano silica (NS) has been increased enormously because of the possible large scale production of these materials. In our earlier study, ex situ polybutadiene rubber (PBR) based nano composites were studied and further investigated their physico-mechanical, morphological and thermal properties. Finally the filler concentration in the composites based on their mechanical and thermal properties improvement were optimized. Among the various nanofillers used in ex situ process, MWCNT & NS have been chosen for further investigation. In this present work, batch solution polymerizations were performed to study the effect of nanofillers loading on the kinetics of the stereospecific polymerization of 1, 3-butadiene catalysed by Ziegler-Natta catalytic systems and properties of the synthesised in situ nano composites. To study the kinetics of polymerization, conversion, yield, viscosity average molecular weight, exothermicity of the reactions were measured. The effect of nano filler concentration showed that adding nanofillers causes no consolidated change in the kinetics curve, whereas there is an optimum dose of MWCNT loading wherein the monomer conversion and yield reached to its maximum level. However, increasing nano silica content results showed no such improvement for Ni based systems, but showed improvement in Co based systems. Moreover the nanofillers did not have any significant effect on microstructure. The best improvement of mechanical and other important properties like hardness; heat build-up etc. was achieved for nano composites containing 0.5 phr MWCNT.