STUDIES ON STRUCTUR-PROPERTY-PERFORMANCE-RELATIONSHIP OF VARIOUS POLYTHYLENE GRADES

Abstract

The project work described in the dissertation consists of three parts. 1. HDPE Raffia Grade: Total 7 HDPE raffia grades were collected from various manufacturers. Industrial trials for raffia tape manufacturing were done in one of the leading raffia manufacturing industry using different HDPE raffia grades. During the trials it was observed that HD/R/I-018, HD/R/I-022 and HD/R/I-025 grades failed to perform well at higher line speeds of 300 Mt/min and many problems (like higher tape breakage, higher power consumption etc) were encountered while no such problems were encountered in HD/R/G grade which was able to run at a line speed 300 Mt/min. Some other established raffia grades HD/R/R-027, HD/R/R-067 and HD/R/H were also found to be performing well. Therefore, to ascertain the root cause of the problems encountered in case of HD/R/I-018, HD/R/I-022 and HD/R/I-025 grades, structure-property-performance-relationship for HDPE raffia grades was studied. Various characterization techniques like MFI, MFR, Power Law curve, Parallel Plate Rheometer, High Temperature–Gel Permeation Chromatography, Dynamic Mechanical Analysis and Differential Scanning Calorimetry were used. It was found that HD/R/I-022 and HD/R/I-025 had higher melt viscosity than HD/R/G leading to higher power consumption. HD/R/I-018, HD/R/I-022 and HD/R/I-025 grades had different concentration of very high molecular weight fractions and low molecular weight fractions as compared to HD/R/G. It was observed that even slight changes in these fractions, had resulted in widely different processing behaviours of the resins. 2. HDPE Large Blow Molding Grade: Total 5 HDPE raffia grades were collected from various manufacturers. Processing trials were done in one of the leading manufacturing industry in INDIA with HDPE large blow molding grades HD/LBM1/024, HD/LBM1/111, HD/LBM1/121, HD/LBM1/125 and HD/LBM2/571 to produce primarily large capacity (220 litre) Lring barrels. During the trails it was observed that HD/LBM2/571 grade was performing well with no difficulty and product quality was observed within the customer’s requirement. But with HD/LBM1/024, HD/LBM1/111, HD/LBM1/121 and HD/LBM1/125 grades various problems (like rough inner surface, decrease in product weight etc with HD/LBM1/024 and HD/LBM1/111 and uneven L-ring formation at the bottom of the barrel, short molding etc with HD/LBM1/121 and HD/LBM1/125) were observed during the process and in the product manufactured. Therefore, to ascertain the root cause of the problems encountered in case of HD/LBM1/024, HD/LBM1/111, HD/LBM1/121 and HD/LBM1/125 grades, structureproperty- performance-relationship for HDPE large blow molding grades was studied. Various characterization techniques like MFI, MFR, Capillary Rheometer, Parallel Plate Rheometer, High Temperature–Gel Permeation Chromatography and Differential Scanning Calorimetry were used. Wide differences in extensional viscosity values for HD/LBM1/024, HD/LBM1/111, HD/LBM1/121 and HD/LBM1/125 grades as compared to HD/LBM2/571 were observed. It was found that HD/LBM1/024, HD/LBM1/111, HD/LBM1/121 and HD/LBM1/125 grades had lack of very high molecular weight fractions, varying low molecular fractions and absence of high extensional viscosity which plays an important role during large blow molding processes while HD/LBM2/571 had ideal set of properties for large blow molding process for manufacturing L-ring barells (220 litre).3. LLDPE Blown Film Extrusion Grade: Total 2 LLDPE (1-butene based) blown film extrusion grades were collected along with density, MFI, dart impact, tensile strength at break, % elongation at break and tear strength values. Both the grades had nearly similar MFI @ 2.16kg and density values. But there were appreciable differences in the properties of both the grades. Thus both the grades were tested by using various characterization techniques like High Temperature-Gel Permeation Chromatography, 13C-Nuclear Magnetic Resonance spectroscopy, Crystallization Analysis Fractionation and Differential Scanning Calorimetry, to ascertain the root cause for difference in properties and structure-property-relationship was studied for each LLDPE grade. It was found that different property values could be attributed to different concentration of the comonomer present and widely different comonomer composition distribution in polymer chains for both the grades.