Rubber formulation Abrasion resistance

Epoxies have an excellent resistance to abrasion. The abrasion resistance of a particular system depends upon the type of formulation and conditions. For example coatings have the capacity to resist abrasion from rubber wheels, whereas screed floorings, repair mortar and self-levelling floors can resist thousands of cycles from steel wheels. 

Tensile strengths of chlorosulfonated polyethylene rubber (CSM) vulcanisates are around 3.5 MPa, depending upon formulation. In resilience, the elastomer compares favourably with other synthetic elastomers, though generally its resilience is lower than NR vulcanisates. Flex and abrasion resistance are very good and CSM will not support combustion. 

Fillers are added to the elastomer in order to add bulk, lower cost and/or to improve physical properties such as hardness, strength and abrasion resistance. Typical fillers are materials such as carbon black, talc, china clay and whiting. Carbon black has been shown to contain polynuclear aromatics (PNAs) and there is concern regarding their carcinogenicity (Lee and Hites, 1976). However, despite extra controls there has been a move away from the use of carbon black as a filler in applications involving the primary packaging of parenterals. Its use continues as a pigment or colourant in rubber formulations but at substantially lower levels than that as a filler. 

The British Standard offers three standard rubbers in addition to the DIN standard formulation. All results for the three non-ISO methods are expressed as an abrasion resistance index. 

The use of silica in rubber mixes cannot be considered as new at all, because this filler has been used in rubber formulations since the beginning of the 20th century (Voet et al., 1977). Silicas are not reinforcing fillers in the proper sense, because silica-reinforced mixes exhibit much lower mechanical properties, particularly considering modulus at break and abrasion resistance. So silicas weren t used as reinforcing fillers but mainly in association with carbon black. 

Carbonated nitrile rubber (XNBR) incorporates up to 10% of a third comonomer with organic acid functionality. When compared to NBR, XNBR has improved abrasion resistance and strength. XNBR can be difficult to process, and it requires special formulation to prevent sticking to mixer surfaces and premature vulcanization. 

Polybutadiene and natural rubber are blended in tire sidewalls to improve fatigue resistance, cut growth resistance, and improve abrasion resistance to minimize the effect of curb scuffing. Figure 4.7 shows atomic force micrographs (AFMs) of the model tire sidewall compound formulation given in Table 4.8. Many tire compounds are composed of two or more elastomer blends. Depending on the types of elastomers these blends may be ... 

Blends of halobutyl or brominated poly(isobutylene-co-p-methylstyrene) with high diene rubbers are used in tire sidewalls and tread compoimds (137-139). In sidewalls, ozone resistance, crack cut growth, and appearance are critical to their performance. Properly formulated blends with high diene rubbers that exhibit phase cocontinuity yield excellent sidewalls (140). The property balance for tire tread compounds can be enhanced by the incorporation of a more damping halobutyl or brominated poly(isobutylene-co-p-methylstyrene) rubber phase (141). Improvements in wet-, snow-, and ice-skid resistances and in dry traction without compromises in abrasion resistance and rolling resistance for high performance tires can be accomplished by using bromobutyl or brominated poly(isobutylene-co-p-methylstyrene) up to 30 pbr in tread compoimds (142). 

Sizing/coating/pigmenting is the domain of the high end formulations. Synthetic polymers like Hypalon give outstanding abrasion resistance, nitrile rubbers... 

Figure 3.5 shows a plot of hardness against volume fraction of filler [ISAF (intermediate super abrasion furnace) black] in the vulcanizate base on the rubber compound formulations shown in Table 3.1. Hardness is defined as the resistance to surface indentation as measured under specified conditions. It is a non-destructive test that measures the reversible deformation when an... 

Compared with similar natural rubber compositions of the same hardness, styrene butadiene rubber (SBR) formulations are characterized by lower tensile strength, elongation, and resilience, lower resistance to tear, flexing, abrasion, ozone, and sunlight, and higher permanent set. The freeze resistance and permeability to gases of styrene butadiene are equivalent to those of comparable natural rubber, and so are the electrical characteristics. 

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