Grafted rubber concentrate

Laser fight scattering was described by one of us (2) for measuring the phase structure of an MBAS plastic as a function of graft rubber concentration. The data were analyzed with the Debye-Bueche expression (I, 2)... 

The next step is the polymerization of styrene and acrylonitrile in the presence of the rubber latex. Part of the polymerized styrene-acrylontrile is grafted on to the rubber. This grafted rubber concentrate is then either mixed with additional emulsion-prepared styrene-co-acrylonitrile (SAN) copolymer and then coagulated or first isolated and then compounded with SAN. 

In addition to blending with SPMI copolymers, PMI can be incorporated into ABS using mass, emulsion [46-50] or suspension [42] free radical polymerization techniques. The high heat ABS resin can be completely produced by mass polymerization, or mass polymerized PMI-SAN can be blended with (emulsion polymerized) SAN-grafted rubber concentrates and/or conventional mass ABS. Sumitomo Naugatuck determined an empirical relation for the compatibility of SAN/SAN-PMI blends based on the polar monomers in each component [51]. Figure 15.4 shows that the miscibility window with SANs becomes wider with increasing PMI level in the terpolymer [52]. 

To design a resin with the property enhancements of AN without the cross-linking problem, it was found that SMA copolymers and terpolymers could be blended with ABS resins to form miscible blends with properties of HHABS. A fundamental look at the miscibility of SMA copolymers with SAN copolymers indicated that the optimum thermodynamic interaction occurs when the AN content of the SAN is nearly equal to the MA content of the SMA [72]. Kim et al. also found low impact strengths at all modifier levels when blending SMA with SAN-g-polybutadiene (GRC = grafted rubber concentrate) [73]. Blends of SMA with SAN and GRC (SAN + GRC = emulsion ABS) exhibited ductility behavior similar to HHABS. The impact strengths of the polymers were 2-5 ft-lb/in, in a notched Izod test at ambient temperature. 

Ramsteiner et al. [32] investigated the rubber toughening of PS AN. In ASA-containing particles with a diameter of ca 0.5 xm and at a graft rubber concentration of 50 wt %, the distance between the rubber particles is small enough for... 

The TEM images (Figure 25.7) show the rubber particles (a) MSP 1, (b) MSP2, and (c) MSP 3 mixed into the S/DPE matrix containing 15 % DPE. Figure 25.8 shows the morphology of MSP 1 in S/DPE(30). The blends were injection moulded to dumbbell test pieces. In all cases the grafted rubber concentration was 36 wt%. These rubber particles consist of 40 % styrene as the outer shell, for compatibility with the S/DPE copolymer, and 60 % crosslinked butyl acrylate rubber as the... 

The crosslinkable epoxy thermoplastic modified with 5 wt % grafted rubber concentrate (CET-GRC) was prepared according to published procedure (5). The rubber domains are nominally 0.1 micron in diameter and consist of a core-shell structure with a 0.03 micron diameter polystyrene seed. Blocks of the CET-GRC were cryo-polished at -90°C using a diamond knife to provide a smooth face for SPM imaging. Some of these surfaces were post stained in OSO4 vapors by suspending the polished blocks in sealed containers over an aqueous solution of... 

ABS and HIPS. The yield stress vs. W/t curves of ABS and HIPS are very similar. They are somewhat surprising because the yield stresses reach their respective maximum values near the W/t (or W/b) where plane strain predominates. This behavior is not predicted by either the von Mises-type or the Tresca-type yield criteria. This also appears to be typical of grafted-rubber reinforced polymer systems. A plausible explanation is that the rubber particles have created stress concentrations and constraints in such a way that even in very narrow specimens plane strain (or some stress state approaching it) already exists around these particles. Consequently, when plane strain is imposed on the specimen as a whole, these local stress state are not significantly affected. This may account for the similarity in the appearance of fracture surface electron micrographs (Figures 13a, 13b, 14a, and 14b), but the yield stress variation is still unexplained. 

The experimental data on the Pn of homopolystyrene, the efficiency of polystyrene grafting to rubber, and the dependence of styrene polymerization on rubber concentration were compared with the calculated data, with up to 8% of styrene conversion at T = 100 °C. 

Fractionation of PS-EPDM Raw Polymerizates. Determination of the Components Grafted Rubber + Free Rubber. A few grams of material in the form of beads were placed in contact with a large excess of methyl ethyl ketone the resultant dispersion was centrifuged. The solid, which consisted of graft copolymer and free rubber, was dried and weighed. The supernatant was concentrated and then precipitated with excess methanol the precipitate consisted of practically pure PS. 

Oommen et al. had studied melt rheological behaviour of the blends between NR and poly(methyl methacrylate) based on the effect of blend ratio, processing conditions and graft copolymer concentration as a function of shear stress and temperature. It was clarified that the viscosity of the blends increased with the increase of the amount of NR. On the other hand, the flow behaviour of the blends was found to be influenced by dynamic vulcanization of the rubber phase. 

The kinetics of graft copolymerization substantially correspond to those of styrene homopolymerization except at low rubber concentrations and at high conversions due to cross-linking reactions [34]. Figure 9 illustrates a schematic of a network of polybutadiene and polystyrene [35]. 

The y-radiation-induced grafting of diethylene glycol dimethacrylate and its mixture with (3-hydroxy ethyl methacrylate in ethanol-water systems onto silicone rubber has been reported [ 164]. The grafting yield increases as the radiation dose, concentration of monomer and concentration of transfer agent increase. At the same radiation dose, the degree of grafting decreases, as the dose level increases. However, at the same dose rate, the grafhng level increases with radiation dose. 

There are three principal families of styrene containing polymers, which are used to make commercial plastic products. The first family is pure polystyrene, the second family comprises random copolymers, and the final family consists of polystyrene chains grafted to blocks of rubbery polymers. There are also synthetic rubbers that contain significant concentrations of styrene, but these are outside the scope of this book. 

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