Polystyrene rheological effects

Hong, B. K. and Jo, W. H. (2000) Effects of molecular weight of SEBS triblock copolymer on the morphology, impact strength, and rheological property of syndiotactic polystyrene/ ethylene-propylene rubber blends. Polymer, 41, 2069-2079. 

S. Chang, T. Xie, and G. Yang, Effects of polystyrene-encapsulated magnesium hydroxide on rheological and flame-retarding properties of HIPS composites, Polym. Degrad. Stab., 91(12) 3266-3273, December 2006. 

Chuai CZ et al. (2004) The effect of compatibilization and rheological properties of polystyrene and poly(dimethylsiloxane) on phase structure of polystyr-ene/poly(dimethylsiloxane) blends. J Polym Sci Part B Polym Phys 42(5) 898—913... 

Anionic polymerization, however, can be used to produce high molecular weight narrow distribution polystyrene. If all the chains are initiated at the same time and the temperature is kept low to minimize chain transfer, molecular weight distributions very close to monodisperse can be produced. The commercial uses of these polymers seem to be limited to instrument calibrations and laboratory studies of the effects of molecular weight on rheology and physical properties. However, anionic polymerization as a potential commercial method for producing polystyrene has been extensively studied by Dow and others. The potential for high polymerization rates, complete conversion of... 

Unlike radical polymerization, branched polystyrenes having a variety of controlled structures have been synthesized (Figure 24.10). This is because termination can be precisely controlled. The branched polystyrenes synthesized using anionic chemistry have been used to study the effect of branch structure on rheology [15]. As will be discussed in the next section, branch architecture (like those presented in Figure 24.10) can influence the rheological properties of polystyrene resins. 

Very few studies have been performed investigating the effect of branching on the extensional rheological properties of polystyrenes. Such investigations can be valuable because many of the fabrication operations associated with commercial applications of polystyrene include operations in which the polystyrene melt undergoes an extensional deformation. Some examples are extruded foam sheet, blown film, oriented (tentered) sheet, and thermoforming. The types of deformations associated with these processing operations are best described as... 

In spite of this evidence of possibly poor mixing, some noticeable changes were found in the rheology and thermal stability of polystyrene. In comparing two polystyrene blends, one with 5% of polymer 3 and the other with 0.1 % (control), the melt viscosity of the 5% blend was about 50% at 180 °C and 80% at 120 °C, respectively. The effect was more drastic at higher temperatures and higher shear rates. The addition of polymer 3 also seemed to improve the thermal stability of polystyrene. When the molten blend polymer was kept at 180 °C for some time, the melt viscosity of the 0.1% blend increased, whereas that of the 5% blend remained constant. 

The effect of overall molecular weight or the number of blocks on rheological properties for the samples from the second fractionation can be illustrated as a plot of reduced viscosity vs. a function proportional to the principal molecular relaxation time (Figure 2). This function includes the variables of zero shear viscosity, shear rate, y, and absolute temperature, T, in addition to molecular weight, and allows the data to be expressed as a single master curve (10). All but one of the fractions from the copolymer containing 50% polystyrene fall on this... 

Studies on the morphology and on the melt rheological, tensile, and impact properties were carried out on ternary blend of iPP with two of the following polymers low and high density polyethylene, styrene-b-ethylene butylene-b-styrene triblock copolymer, polystyrene, and acrylonitrile-butadiene-styrene terpolymer (30-33). The results are interpreted for the effect of each individual component by comparing the ternary blends with the respective iPP-based binary blends as the reference systems. 

GRT particles of sizes of lower than 500 xm and between 500-1000 trm were blended with a postconsumer PP and high impact polystyrene (HIPS) at ratios of 90/10 and 70/30 (Montagna and Santana, 2012). The rheological, physical, and mechanical properties of blends were measured. The addition of GRT reduced the mechanical properties with the reduction being dependent on the particle size. The incorporation of GRT particles into the recycled HIPS and PP matrix led to a decrease and an increase of viscosity, respectively. The extent of the effect was dependent on particle size. 

Su et al. (2001a, b) have prepared blends of PBT with hydroxy-functionalized polystyrenes which differed in the number of hydroxy groups per chain. The effects of triphenyl phosphite and titanium butoxide on PBT chain degradation and copolymer formation were studied. Blends were characterized by FTIR, DSC, GPC, morphology, rheology, and mechanical properties. 

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