Izod notched impact strength copolymers

The use of core-shell impact modifiers combined with styrene-hydrogenated poly butadiene block copolymers in sPS is described by Rohm and Haas [24]. The core of the former type is of polybutadiene or its copolymer, the shell consists predominately of polystyrene. Rohm and Haas found that a synergistic effect is present and that the Izod notched impact strength is higher when both rubber types are used instead of only one. 

Figure 3.56 Izod notched impact strength vs. temperature for Celanese Hostaform acetal copolymer resins after 1000 h storage in air at temperature [5],...

Figure 2.15 shows the variation in standard Izod impact strength (1 mm notch tip radius) with temperature for the same range of materials. By far the most temperature sensitive is the low-melt-index polypropylene (PP) copolymer. It is interesting to compare the sharp fall-off in notched impact strength with this material between 23°C and 0°C with the steady values obtained for falling weight impact strength for the same temperature range (Figure 2.16). The removal of points of stress concentration is thus the most vital factor governing the impact performance at tanperatures of 90°C and below.

Figure 14.9 Effect of various impact modifiers (25wt%) on the notched Izod impact strength of recycled PET (as moulded and annealed at 150°C for 16 h) E-GMA, glycidyl-methacrylate-functionalized ethylene copolymer E-EA-GMA, ethylene-ethyl acrylate-glycidyl methacrylate (72/20/8) terpolymer E-EA, ethylene-ethyl acrylate EPR, ethylene propylene rubber MA-GPR, maleic anhydride grafted ethylene propylene rubber MBS, poly(methyl methacrylate)-g-poly(butadiene/styrene) BuA-C/S, poly(butyl acrylate-g-poly(methyl methacrylate) core/shell rubber. Data taken from Akkapeddi etal. [26]...

Figure 17. Notched Izod impact strength of PVC-VC/PE graft copolymer alloys and proportion of unbroken specimens hammer 10 ft-lb...

Figure 18. Influence of the gelling time on the Izod impact strength (notched) of a PVC/PE graft copolymer alloy (87% Solvic 239 + 13% VC/LD PE (50-50) graft copolymer) hammers 3 ft-lb, 10 ft-lb...

Resin. A styrene/acrylonitrile (SAN) copolymer, Tyril 870, manufactured by the Dow Chemical Co. was used. The resin came as ys-inch pellets and had a reported tensile strength of 9500 psi and an Izod impact strength of 0.35 ft-lb/inch of notch. 

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. 

Since the homopolymer PMMA as well as the MMA-rich copolymers are quite brittle, exhibiting low elongation to break 5%) and low notched Izod impact strength (typically < 15 J/m), there was a need to blend suitable impact modifiers that would improve the ductihty and impact strength of these resins without sacrificing the transparency, rigidity and weatherabihty characteristics. 

Commercial impact modified PPE/PA blends exhibit notched Izod impact strengths ranging from 175 to 500 J/m at room temperature. They also differ in their ductile brittle transition temperature and low temperature impact behavior. The type of nylon used (PA-6 or PA-66 or copolymer type), its end group concentrations and molecular weight, and more importantly, the nature of the rubber modifier used (compatible... 

The cost and usefulness of co-additives might be considered as coimter-remedies for restoring properties. For example 5% silicone modifier additions have been shown to nearly double notched Izod impact strength in PP compounds, potentially raising the impact of an FR-PP to near the level of neat PP. Or, given that PP copolymers require more phosphorous FR than homopolymers, a materials selector might choose a less-expensive, impact-modified homopolymer FR-PP instead. This attention to property interactions can save costs, as long as the FR is not interfered with by the chosen modifier [5-13, 5-19). 

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