An experimental study was carried out to investigate the effects of coupling agents on the rheological properties, processability, and mechanical properties of highly filled polypropylenes (PP). Inorganic fillers used were CaCO, and glass beads, and coupling agents used were two silane coupling agents, N-octyl triethoxy silane and y-aminopropyl triethoxy silane, and one titanate coupling agent, isopropyl triisostearoyl titanate. It was found that the addition of the coupling agents to the PP-CaCO, (50 wt percent) decreased the melt viscosity and increased the melt elasticity (first normal stress difference). However, the addition of the silane coupling agents to the PP-glass beads (50 wt percent) affected the rheological properties of the melts quite differently. The N-octyl triethoxy silane had relatively little effect on either the melt viscosity or the melt elasticity, whereas the y-aminopropyl triethoxy silane increased the melt viscosity and decreased the melt elasticity. The CaC0,-or glass bead-filled polypropylenes, with and without coupling agents, were injection-molded and the mechanical properties of the molded specimens were measured by the use of an Instron testing machine. It was found that the effect on the tensile strength and percent elongation of the filled polypropylenes depended upon the specific coupling agent utilized. A melt-spinning study was also carried out to investigate the effect of coupling agents on the spinnability (defined as the maximum draw-down ratio) of the PP-CaCO, system, and on the mechanical properties of the melt-spun fibers. It was found that the spinnability of the PP-CaC0, was enhanced considerably by the addition of the coupling agents, and that the tensile strength of the melt-spun fibers was also improved by their addition. Scanning electron micrographs were taken of the fracture surface of injection-molded specimens and an attempt was made, with the aid of photomicrographs, to explain the mechanical properties of molded specimens observed experimentally.

An experimental study was carried out to investigate the effects of titanate coupling agents on the rheological properties of p articulate‐filled polyolefin melts. Inorganic fillers used were CaCO3, talc, and fiberglass, and polyolefins used were high‐density polyethylene (HOPE) and polypropylene (PP). It was found that the addition of the coupling agent TTS to the PP‐CaCO3 and PP‐fiberglass systems reduced the melt viscosity considerably, whereas the addition of the coupling agent ETDS‐201 to the PP‐talc and HDPE‐talc systems affected the melt viscosity very little. Also carried out was an injection molding study to investigate the effects of different inorganic fillers and the titanate coupling agents used on the mechanical properties of the injection molded specimens. It was found that addition of titanate coupling agents generally resulted in reduced modulus and tensile strength, and increased elongation and impact strength of the filled systems. The PP‐CaCO3‐TTS and HDPE‐talc‐ETDS 201 systems were found to have impact strength improved by approximately 100 percent with the addition of a titanate coupling agent. The PP‐CaCO3‐TTS samples have ultimate tensile elongation approaching that of virgin PP.

Rheological behavior of dispersed two‐phase polymer melts has been investigated by means of a capillary rheometer. The two‐phase systems chosen for study were blends of two polymers: high‐density polyethylene and polystyrene, which are incompatible in the molten state. In order to investigate the state of dispersion, photographs were taken of the microstructure of extrudate samples, showing that the polystyrene forms long fibers or droplets as a discrete phase dispersed in the polyethylene which forms a continuous phase. Measurements were made of the axial pressure distributions of the two‐phase molten polymers flowing through circular tubes, which permit one, according to the theory advanced by Han, to determine viscous and elastic properties of the melts. Also measured was melt die swell ratio. It has been found from the two independent experimental techniques that there exist a maximum and/or minimum elastic property at a certain blending ratio, and that the elastic property decreases first with L/D ratio of a capillary and then levels off.

SynopsisAn experimental study of foam extrusion was carried out to determine the effect of processing variables on the quality of the foam produced. For the study, the chemical blowing agent azodicarbonamide was used, together with an activator and a nucleating agent, to produce thermoplastic foams of low-density polyethylenes. The quality of foam was determined from photomicrographs and the tensile properties of extrudate samples. It was found that the percent elongation correlates with the foam density and that the cell structure (cell size and its distribution) correlates with the ultimate tensile properties of the foam produced. Also, an experimental study was carried out to observe the growth of gas bubbles as the polymer melt containing a blowing agent flows through a rectangular channel constructed of quartz. This experiment helped us to interpret the curued pressure profile of the polymer melt containing a blowing agent as the melt approaches the die exit, whereas the polymer without a blowing agent shows a linear pressure profile.

SynopsisResins having different rubber particle sizes were prepared by polymerizing impact polystyrene using different agitation rates but keeping all other parameters constant. Also, samples were made varying the amount and type of rubber and type of agitation. The impact and tensile properties of the prepared resins are studied in relation to existing theories of rubber particle reinforcement. The particle size dependence of energy absorption in impact (high intensity) and tensile (low intensity) testing appear to be opposite in nature. Energy absorption increases with increasing particle size in the high-intensity mode and decreases in low-intensity testing. Different mechanisms are, therefore, postulated to be operative in each of these two test methods.