Investigation of colored lump formation inside the silos during the production of polypropylene copolymer.

Polypropylene (PP) is one of the most widely used commodity plastic materials worldwide in terms of the production and its consumption. At commercial scale, PP is produced in various grades like homopolymer and copolymer (random and impact) by the polymerization of propylene and mixture of propylene-ethylene monomers using Ziegler–Natta catalysts and alkyl aluminum as co-catalysts. The present study deals with the colored lump formation of polypropylene random copolymer (PPCP) during storage at large scale and its probable route cause analysis for the lump formation. The lump samples were collected and characterized using FTIR, TGA, DSC and molecular weight determination and compared with pure PPCP. FTIR data show all the signature peaks of PPCP with additional > C=O stretching near 1720 cm−1 in colored lump sample, TG analysis revealed degradation of PPCP polymer and formation of volatile organic compounds in the temperature range 200–250 °C, the DSC analysis of the colored lump and pure PPCP showed that the melting peak was broader for colored lump of PPCP (i.e., PPCP_Y) which is an indicative that polymer molecules were having different chain length and the molecular weight analysis showed that the colored sample was having very low molecular weight with some bimodal character as compared to pure polymer. Based on these data and observations, the possible reason for the colored lump formation was also discussed. [ABSTRACT FROM AUTHOR]