This research work is divided into two parts. The main objective of the first part was to study and compare the microstructure developed in the case of polypropylene (PP)-talc composite drawn at an elevated temperature to that of neat PP drawn under similar processing conditions. For a given die geometry, the final draw ratio of both of the die drawn materials increased with draw rate, and plateaued at higher draw rates. The ratio of final void fraction to particle fraction in the case of die drawn PP-talc composite with an initial filler loading of 7.5 vol. % (or 20 wt. %), was found to be higher (2.26 vs. 1.81) than that of the die drawn composite with an initial filler loading of 16.5 vol. %. Microscopic analysis of the drawn materials revealed that the voids in both cases were stretched in the drawing direction and the void volume fractions also leveled above an actual draw ratio (DR) of 7. Voids of higher aspect ratios were observed in the die drawn composite that had lower loading of talc. The average void length in the drawing direction had grown 4-6 times that of the particle length.The steps of annealing and subsequent drawing led to a 12-15 % increase in crystallinity of the matrix phase, for both die drawn neat PP as well as die drawn PP-talc-20 wt. % composite. Die-drawing led to formation of well developed texture elements of type (110)[001] and (010)[001]. These textures sharpened with DR in both the materials. For a given draw rate, debonding and void growth in the drawn composite resulted in less developed crystal orientation than drawn neat PP of comparable draw ratio. In the case of die drawn neat PP, the predominant texture type was (110)[001], whereas in the case of die drawn composite it was of type (010)[001]. The void growth in drawn PP-talc-20 wt. % composite progressed with the crystal orientation of the matrix phase, and both of them plateaued above a DR of 7. Despite saturation in void growth as well as crystal orientation, the tensile modulus of the drawn composite increased with DR. For the highest draw rate studied using a wedge die of nominal draw ratio 2, the tensile modulus attained for drawn PP-talc-20 wt. % composite was 3 times that of undrawn neat PP. The second part of the research work was motivated by the aim of developing nanocomposites of high molecular weight high density polyethylene (HMW-HDPE) with enhanced mechanical properties and improved or similar processability as that of the base resin. This was achieved by adding a small percentage of organoclay with appropriate compatibilizers to the base resin, and using appropriate mixing conditions. Complete exfoliation of the dispersed clay could be achieved with much lower loadings of compatibilizer than those reported in the literature. Injection molded bars of a let-down formulation with 5 wt. % organoclay showed a modulus increase of 19 %. Extensional melt flow tests on nanocomposites with 3 wt. % organoclay showed a similar level of strain hardening to that of neat HMW-HDPE. Despite the strain hardening ability and good dispersion of the organoclay, blown film samples obtained with HMW-HDPE nanocomposites did not show much improvement in the mechanical properties. For similar film thicknesses, all the mechanical properties except the tensile modulus of this material were lower than that of neat HMW-HDPE. The anisotropic orientation of exfoliated platelets during the film blowing operation was found to be a likely cause.
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