CANCELLED: A Process for Preparation of Carbon Black /Silica/ Nanoclay Masterbatches From Fresh Natural Rubber Latex

A process for preparation of carbon black /silica/ nanoclay masterbatches from fresh natural rubber latex

 

 K.K. Sasidharan,  Rosamma Alex, James Jacob and Thomas Kurian

 Rubber Research Institute of India, Kottayam, Pin-686009

    Abstract

            A process for production of carbon black/silica/nanoclay ternary filler masterbatch from fresh natural rubber (NR) latex was standardized. The filler, nano clay at doses varying from 3-10 parts per hundred rubber (phr) along with carbon black and silica at a dose of 25/25 phr was incorporated in fresh NR latex by a modified coagulation process. The coagulum, containing fillers was dried at 70 ⁰C in an air oven to get latex filler masterbatch which was processed further in the conventional way. The compounds prepared from the masterbatch were vulcanized as per standard methods and used for determining mechanical and dynamic properties.

           The latex mixed with filler dispersions, coagulated immediately on addition of acids. The master batch compounds containing only silica/carbon black showed higher level of vulcanization as compared to the corresponding dry mixes.  The vulcanization level of nanoclay incorporated mixes increased as the content of   nanoclay increased. The mechanical properties like tensile strength, modulus, tear strength, abrasion resistance and hardness increased with proportion of nanoclay in the mixes   up to 5 phr and with further amount the change was only marginal. The heat build-up values for the tri-filler masterbatches that contained 5 to 10 phr nanoclay was similar to the 25/25 carbon black/silica master batch.  

Lower tan delta values were observed for all the master batches containing nanoclay in the ranges 3-10 phr compared to the control dry mix containing 25/25 carbon black/silica, showing better polymer filler interaction. Within the nanoclay containing mixes the lowest tan delta peak height was observed for the ternary mix containing 5 phr nanoclay. The tan delta values at 60⁰C are lower for all the master batches than the dry rubber mix containing 25/25 carbon black/silica. The tri-filler system containing 5 phr nanoclay showed the  lowest tan delta  at 60⁰C  and  the  highest  storage modulus  within the different ternary filler masterbatches.

The improvement in mechanical properties and dynamic properties shown by the silica/carbon black/ nanoclay master batches over the conventional mill mixed   compounds was attributed to factors related to filler dispersion and higher level of vulcanization. Better filler dispersion was evidenced from the result of filler dispersion data obtained using Dispersion Analyzer and nanoclay exfoliation observed from X-Ray diffractograms. Better polymer –filler interaction and good filler dispersion was also revealed from dynamic mechanical analysis.

The rubber mixes containing carbon black/silica/nanoclay tri-filler system      prepared by a modified coagulation process from fresh natural rubber latex has specific beneficial properties over the conventional dry rubber based mixes that can find application in a variety of rubber products and specifically tyres. 

 Keywords:  carbon black, latex master batch, natural rubber latex, silica, nanoclay

 

For correspondence Email: sasidharan@technologist.com; sasidharankri@gmail.com