Rubber recovery from centrifuged natural rubber latex residue using sulfuric acid

Waste latex sludge from centrifuged residue, which is a null by-product of concentrated latex manufacturing, was digested to retrieve the rubber by using sulfuric acid. It was found that the acid concentration and digestion time have an effect on the amount and purity of the retrieved rubber. Sulfuric acid at concentrations of more than 10% by weight with a digestion time of 48 hours completely digested waste latex sludge and gave rubber 10% by weight. The quality of the retrieved rubber was examined for Mooney viscosity (MV), plasticity retention index, nitrogen content, and ash content. The average molecular weight of the retrieved rubber, using gel permeation chromatography, was lower than that of normal natural rubber (NR) which corresponds with the MV and initial plasticity (Po). The molecular structure from Fourier transform infrared spectroscopy (FT-IR) indicated that the retrieved rubber surface is wet composed with hydroxyl functional ended group. The residue solution was evaporated and crystallized. The structure of crystals was determined using power X-ray diffractometer.