PS—PE blends

The formation of the polyalloy results in improvement in the performance of the blends. This system is similar to the production of high-impact polystyrene (HIPS) where a rubber is dissolved in styrene monomer and then polymerized in the usual way. Even though the impact strength of the compatibilized PS-PE blend was higher than that of PS, it was much less than that of HIPS. In another study. Van Ballegooie and [55] have confirmed... 

The validity of the theoretical assumptions was evaluated by comparing the two models predictions with the experimentally measured drop diameter at different axial positions in the twin screw extruder. Experimentally, after the extrusion reached steady state, the screw rotation was stopped and the molten blend was quenched within a specially designed extruder barrel. It was estimated that the PS/PE blends were quenched within 7-10 sec. The second model predicted well the morphology evolution of non-compatibUized blends of PS in PE, and their inverse of PE in PS (see Figure 9.16 in Chapter 9). 

The PS/PE blends compatibiUzed by a block copolymer have been offered commercially (Neo-polen ) and are primarily used for packaging [Utracki, 1993]. Dow has aimounced plans to commercialize ethylene-styrene copolymers employing single-site metallocene catalysts. High styrene versions of these copolymers could have interest as a compatibiUzer for PO/PS blends [Grande, 1997]. 

The study of electroconductive polymer systems, based on conductive particles and polymer blends, has been quite intensive during the recent past. Gubbels et al. [149] studied the selective localization of CB particles in multiphase polymeric materials (PS and PE). According to these results, the percolation threshold may be reduced by the selective localization of CB. The minimum resistivity was obtained when double percolation (phase and particle percolation) exists in the PS-PE blend. In addition, it was found that the percolation threshold may be obtained at very low particle concentrations, provided that CB is selectively localized at the interface of the blend components. Soares et al. [150] found that the type of CB (i.e., different surface areas) does not affect the conductivity of the blend with 45/55 PS/PIP (polyisoprene) composition. 

Heikens et al. 1 >1 observed, in the case of 75/25 PS/PE blends having 0%, 1%, 7% of added graft copol3nner, that the dimensions of the PE domains decrease with increasing copolymer concentrations. Similar results were obtained for the same systems by Paul and for PS/Polydiene 1, for PVC/PE 1 >1, and for Poly-amide/Polyolefin blends by several reserach groups. 

Effect of 5% by weight added PS-PE copolymers on the impact strength of PS/PE blends at different compositions. PE content 0 - 25%. The structures of BC-1, BC-2 and BC-3 block copolymers and those of GC-1, GC-3 and GC-4 graft copolymers are reported in Scheme 1,... 

Neopolen Polystyrene/polyethylene, PS/PE, blend BASF Plastics... 

Polystyrene/poly(2,6-dimethyl 1,4-phenylene ether), except for Styroblend WS that is PS/PE blend. Styroblend FR has flame retardant properties. 

Table 1 contains comparison of FR (flame retardant), HT (high temperature) and WS (PS/PE) blends. 

The ratio of polymer viscosity values, imder which a substantial drop in local interfacial CB concentration is observed, differs for various polymer pairs. The greater is the difference in wetting forces of polymers, the more times the viscosity of the second (having higher wetting force) polymer, can exceed the viscosity of the preliminarily filled polymer. So, this ratio is about four for the PE + PMMA blend, and about two for the PS+PE blend. The best conditions for particles to localize at the interface are provided when viscosity of the second polymer is slightly lower than that of a preliminarily filled polymer component. 

The effect of bcp on the range of cocontinuity is not well understood in this study, we investigated the effect of an optimal bcp [6] on the range of cocontinuity of PS/PE blends using SEM with a novel image analysis technique. 

Figure 1 shows SEM micrographs at various compositions (30, 35, 70, and 75 wt% PS) of PS/PE blends without bcp. (a) and (d) have droplet morphologies, while (b) and (c) show the presence of continuous domains. The compositions in (b) and (c) represent the boundaries of cocontinuity, where the blend morphology transitions from droplet to cocontinuous. Further image analysis was used to quantify this transition. 

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