Viscosity Ratio Of Dispersed Phase Research Articles

Self‐reinforcing elastomer composites based on polyolefinic thermoplastic elastomer and thermotropic liquid crystalline polymer

AbstractIn situ reinforcing elastomer composites based on Santoprene thermoplastic elastomer, a polymerized polyolefin compound of ethylene–propylene–diene monomer/polypropylene, and a thermotropic liquid crystalline polymer (TLCP), Rodrun LC3000, were prepared using a single‐screw extruder. The rheological behavior, morphology, mechanical, and thermal properties of the blends containing various LC3000 contents were investigated. All neat components and their blends exhibited shear thinning behavior. With increasing TLCP content, processability became easier because of the decrease in melt viscosity of the blends. Despite the viscosity ratio of dispersed phase to the matrix phase for the blend system is lower than 0.14, most of TLCP domains in the blends containing 5–10 wt % LC3000 appeared as droplets. At 20 wt % LC3000 or more, the domain size of TLCP became larger because of the coalescence of liquid TLCP threads that occurred during extrusion. The addition of LC3000 into the elastomer matrix enhanced the initial tensile modulus considerably whereas the extensibility of the blends remarkably decreased with addition of high TLCP level (>.20 wt %). The incorporation of LC3000 into Santoprene slightly improved the thermal resistance both in nitrogen and in air. Dynamic mechanical analysis results clearly showed an enhancement in dynamic moduli for the blends with 20–30 wt % LC3000. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

In Situ Reinforcing Elastomer Composite Based on Polyolefinic Thermoplastic Elastomer and Thermotropic Liquid Crystalline Polymer

In situ reinforcing elastomer composites based on Santoprene thermoplastic elastomer, a polymerized polyolefin compound of ethylene-propylene-diene monomer (EPDM)/polypropylene (PP), and a thermotropic liquid crystalline polymer (TLCP), Rodrun LC3000, were prepared using a single-screw extruder. The rheological behavior, morphology, mechanical and thermal properties of the blends containing various LC3000 contents were investigated. All neat components and their blends exhibited shear thinning behavior. With increasing TLCP content, processability became easier because of the decrease in melt viscosity of the blends. Despite the viscosity ratio of dispersed phase to the matrix phase for the blend system is lower than 0.14, most of TLCP domains in the blends containing 5-10 wt% LC3000 appeared as droplets. At 20 wt% LC3000 or more, the domain size of TLCP became larger due to the coalescence of liquid TLCP threads that occurred during extrusion. The addition of LC3000 into the elastomer matrix enhanced the initial tensile modulus considerably whereas the extensibility of the blends remarkably decreased with addition of high TLCP level (>20wt%). The results obtained from thermogravimetric analysis suggested that the incorporation of LC3000 into Santoprene slightly improved the thermal resistance both in nitrogen and in air.

A study on weld line morphology and mechanical strength of injection molded polystyrene/poly(methyl methacrylate) blends

AbstractIn this work, the mechanical strength and weld line morphology of injection molded polystyrene/poly(methyl methacrylate) (PS/PMMA) blends were investigated by scanning electron microscopy (SEM) and mechanical property test. The experimental results show that the tensile strength of PS/PMMA blends get greatly decreased due to the presence of the weld line. Although the tensile strength without the weld line of PS/PMMA (70/30) is much higher than that of the PS/PMMA (30/70) blend, their tensile strength with weld line shows reversed change. The viscosity ratio of dispersed phase over matrix is a very important parameter for control of weld‐line morphology of the immiscible polymer blend. In PS/PMMA (70/30) blend, the PMMA dispersed domains at the core of the weld line are spherically shaped, which is the same as bulk. While in the PS/PMMA (30/70) blend, the viscosity of the dispersed PS phase is lower than that of the PMMA matrix, the PS phase is absent at the weld line, and PS particles are highly oriented parallel to the weld line, which is a stress concentrator. This is why weld line strength of PS/PMMA (30/70) is lower than that of PS/PMMA (70/30) blend. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1856–1865, 2002; DOI 10.1002/app.10450

Interrelationships between Rheological, Morphological, and Mechanical Properties of Polystyrene/Liquid Crystalline Polymer Blends

The effects of the viscosity ratio of dispersed phase to matrix on the rheological, morphological, and mechanical properties of blends of polystyrene and two rheologically different liquid crystalline polymers (LCPs) were investigated. Two different rheological behaviors are obtained by blending polystyrene (PS) and two different LCPs: one is the case that the viscosity of dispersed phase is lower than that of matrix phase as observed in PS/Rodrun blends, and another one is the case that the viscosity of dispersed phase is higher than that of matrix phase as observed in PS/Vectra blends. Scanning electron micrographs of fracture surfaces of injection-molded samples show that the finely distributed LCP fibril structure is observed for PS/Rodrun blends where the viscosity of the dispersed LCP phase is lower than that of the polystyrene matrix phase, whereas dispersed LCP phase in PS/Vectra blends show the spherical form of LCP domains. Mechanical properties of injection molded specimens show that the modulus of PS/Rodrun blends shows a strong positive deviation from the simple additive rule, whereas the modulus of PS/Vectra blends follows the simple additive rule of mixture. These mechanical properties are well consistent with the morphological characteristics of the PS/LCP blends.

The effect of the viscosity ratio of dispersed phase to matrix on the rheological, morphological, and mechanical properties of polymer blends containing a LCP

The effect of the viscosity ratio of the dispersed LCP phase to the polystyrene/poly(phenylene oxide) (PS/PPO) thermoplastic matrix on the rheological, morphological, and resultant mechanical properties of the LCP blends was investigated. The viscosity of PS/PPO is largely dependent on the blend composition, so that different levels of viscosity ratios of dispersed LCP phase to PS/PPO thermoplastic matrix are obtained by using PS/PPO premixtures of different blend ratios as a thermoplastic matrix. When the viscosity of the LCP dispersed phase is lower than that of the thermoplastic matrix, finely distributed fibril structure of LCP is obtained. Tensile modulus of injection molded specimens show a positive deviation from the additive rule when the viscosity ratio (η LCP /η matrix ) is smaller than unity. These improvements in tensile modulus are attributed to the formation of finely distributed LCP fibrils.