ANALYSIS OF AUTOHESION AND PHYSICO-MECHANICAL PROPERTIES (MULTIFUNCTIONAL BEHAVIOR) OF THE COAGULUM FROM THE LATEX OF EUPHORBIA CADUCIFOLIA HAINES VIS-À-VIS COMPARISON AGAINST SYNTHETIC RESINS IN NATURAL RUBBER COMPOUNDS

Abstract

ABSTRACT Soft and tacky mass recognized as whole coagulum (Cog) and its toluene soluble fraction (TE) obtained through coagulation of latex of Euphorbia caducifolia Haines has been investigated in this article as green tackifier cum multifunctional agent in natural rubber (NR) based gum compounds. It was observed that inclusion of TE and Cog in the formulations increased tack strength over the control compound (without TE and Cog). At the same loading, autohesion for natural and commercial coumarone indene resin was found comparable. However, phenol formaldehyde (non–heat reactive octyl phenol formaldehyde) resin demonstrated highest tack strength among all the NR compositions studied. Presence of various functional groups such as esters/carboxylic acid, carbon–carbon unsaturation, and so on, in natural resin activated the system and reduced the activation energy barrier for curing. The optimized composition with 5 phr TE showed nearly 5% reductions in activation energy over the control compound. However, no such cure acceleration was displayed by Cog. Unaged tensile properties of the compounds with natural resin at similar proportions to commercial resins were found comparable. Retention of tensile properties after aging for the vulcanizates with TE was better than those with the commercial resins. For Cog, however, the retention of elongation at break and tensile strength were slightly higher compared with tensile modulus.