(The) rheological properties of filled and reinforced polymer systems

Abstract

A study has been carried out on the rheological properties of filled polyethylene, filled polypropylene, reinforced polypropylene, and reinforced nylon 6. The mechanical properties have also been investigated. Calcium carbonate and chopped strand E-glass fiber are the filler and reinforcing material used. For calcium carbonate, three coupling agents, stearic acid, a titanate type, and a silane type, are tested. For the glass fiber, three silane type coupling agents are examined. The rheological properties are measured by a capillary rheometer and a dynamic spectrometer. An Instron universal testing machine is used for the mechanical properties. The microphotograph technique is also employed to help result explanations. A twin-screw extruder and a twin-screw Plasti-Corder are used for compounding calcium carbonate and glass fiber. For the reinforced polypropylene, a chemical modification has been accomplished by use of maleic anhydride (MA) and an initiator. In calcium carbonate filled high density polyethylene system, complex viscosity was increased with increasing filler level. From the plot against loss modulus, the storage modulus was decreased slightly with increasing filler content. From the same plot, however, effects of coupling agent and temperature on storage modulus were diminished. Compounding with calcium carbonate did not improve tensile strength. Elongation at break was decreased with increasing calcium carbonate content. The coupling agent showed almost no effect on tensile strength but a rather big improvement in elongation at break. This notable difference between the untreated and treated systems in elongation, however, seems to be related with dispersion state of filler. In the calcium carbonate filled polypropylene systems, effects of coupling agent and filler content on the viscosity and first normal stress difference were clearly seen. In steady shear, the filler increased the viscosity but decreased the first normal stress difference. Inc...