BENCHMARKING STUDY OF VARIOUS COMMERCIAL POLYPROPYLENE RAFFIA GRADES AVAILABLE IN INDIAN MARKET

Abstract

Under this research work ten different commercially available polypropylene homopolymer Raffia grades were taken. The main objective of this study was to establish „Structure-Property-Performance‟ relationship. “Performance” refers to their processability and runnability at higher line speed (Extrusion Tape Line). Therefore, trial runs were conducted on these PP raffia grades in order to analyze their performances. It was found that some grades, namely, PP/R/R-036 & PP/R/H-031 run very well at higher line speeds of 415mt/min and 365mt/min respectively, when compared to other grades, namely, PP/R/I-071, PP/R/I-075 and PP/R/I-027. The major problems found with PP/R/I-071, PP/R/I-075 and PP/R/I-027 grades during the trial run were the tape breakage, higher power consumption, higher water carry-over etc. Therefore, to ascertain the root cause of the inferior performance of PP/R/I-071, PP/R/I-075 and PP/R/I-027 a detailed “Benchmarking” study on these PP-raffia grades, were undertaken. Each grade was characterized in detailed using MFI & MFR, Capillary Rheometer, Differential Scanning Calorimetry, Oxygen Index Test, Dynamic Mechanical Analyzer, Dynamic Rotational Rheometer and HT-GPC techniques. On comparing the characteristics of these grades it was found that the PP/R/R-036 and PP/R/I-089 grades were having the good combination of higher modulus; low melt viscosity, higher melt elasticity and high crystallinity, than other grades, mainly due to the differences in various aspects such as high molecular weight tail, high and low molecular weight fractions at very low concentration, molecular weight distribution. Polypropylene raffia grades such as PP/R/R-036 and PP/R/I-089 have very limited high molecular weight tail with moderately broad molecular weight distribution. It is worth mentioning here that PP/R/I-075, PP/R/I-071 and PP/R/I-027 comparatively have very high molecular weight tail. These long molecular weight fractions will reduce the overall crystallinity by reducing the enthalpy. In addition to that, grades with comparatively broad molecular weight distribution have shown better processability and flowability. The presence of high molecular weight fractions at low concentration also play detrimental role during the orientation and annealing process, as in the case of PP/R/R-036 and PP/R/I-089 in the tape extrusion process.