Preparation and characterization of some unusual elastomeric and plastics composites

This work focused on examining the structure-property relationships of filled and unfilled elastomers and plastics. Some of the factors that influence the final properties of these systems are: molecular weight, % isotactic pentad content, shape and structure of the filler particles, surface modification of the filler particles, polymer-filler interaction, particle size, pore size, surface area, etc. The five parts in this dissertation are as follows:; Chapter 1. Thermal and mechanical tests of thermoplastic elastomeric polypropylenes (EPP) prepared by the metallocene catalysts showed that they were multiphase, tough elastomeric materials. The moduli and strengths of the unfilled EPPs increased with increase in % isotactic pentad content and increase in molecular weight. Preliminary tests on filled EPPs showed that layered silicates (clays) gave better reinforcement than silica fillers because of the higher aspect ratio of the former.; Chapter 2. The mechanical properties of poly (methyl acrylate) composites prepared by using a silane coupling agent designed to suppress the bonding between the silica and the elastomeric matrix were much poorer than those of the corresponding composite having a silane giving strong interfacial bonding, and thus documenting the effects of these interactions on the reinforcement of a typical elastomeric material.; Chapter 3. The polystyrene/Vycor blends and pseudo interpenetrating polymer networks (PIPN) did not exhibit any reinforcing ability due to the large particle size of the Vycor filler. The PS/zeolite PIPNs showed reinforcement whereas the PS/zeolite blends did not. The PIPN samples gave larger tensile strength values relative to the corresponding blends. This could possibly be due to increased interfacial interactions in the PIPNs.; Chapter 4. Poly(dimethylsiloxane) (PDMS) composites, reinforced by in situ silica precipitation, were prepared by a two-step process. Ultraviolet/visible spectroscopy was used to make quantitative visual observation that the composites were highly transparent. The filler particles gave pronounced increases in mechanical properties of the composites, thus demonstrating excellent reinforcing capabilities.; Chapter 5. PDMS composites were prepared using different types of fumed silica. With increase in the surface area (decreasing particle size) and silica loadings, the mechanical properties increased irrespective of the silica used. Incorporating silane coupling agents also increased the tensile properties of the composites.