Sulfur content rubber study

The efficacy of polyurethane and styrene butadiene rubber (SBR) as binders for ground rubber prepared from waste tires was compared to a formulation of a compound developed without binder. Without binder, the effect of both sulfur and accelerator content on tensile properties are studied, as well as the effect of ageing on these properties [29]. The suggested uses of the unbound product include rubber blocks, and ballast mats for railway applications. 

Saturated and monoene alcohols and acetates are quite stable in rubber septa. In general in traps in field applications, they neither hydrolyse nor oxidize (5, 25). However, several studies showed that conjugated dienes isomerize in rubber to ultimately form an equilibrium mixture (25-28). At equilibrium the content is 65-70% EE, 2-5% ZZ and the percentages of EZ and ZE are comparable to each other (27, 28). The exact values depend on the position of the double bonds. Because non-pheromone isomers may decrease or prevent trap catch, the useful life of a lure may be determined by this factor. Complete equilibration only requires about a month (27. 28) The reason for the rapid isomerization appears to be a combination of sunlight and catalysis by the sulfur used to cure the rubber (26-28). An alternate synthetic-elastomeric septum is available which reduces the rate of isomerization by about 8-fold (28). 

SBR/PVC blends with nitrile rubber (NBR) as a compatibilizer show improved mechanical properties at lower cost than NBR/PVC. i This was the conclusion of studies using a divinylbenzene cross-linked, hot-polymerized emulsion polymer with 30% bound styrene and a cold-polymerized emulsion polymer with 23% boimd styrene PVC with inherent viscosity from 0.86 to 1.4 NBR with Mooney viscosity from 30 to 86 acrylonitrile content of 23.5, 32.6, and 39.7% and ZnO, stabilizers, sulfur, and accelerators. ... 

The adhesion of RFL-coated tire cords to rubber can be adversely affected if the dipped cords are exposed to ozone, UV light, nitrogen oxides, sulfur dioxide, or air before vulcanization into rubber. lyengar proposed that ozone exposure of RFL reduces adhesion because ozone attacks the double bonds of the butadiene component of the rubber latex and impairs its cocuring with the solid rubber compound. Infrared studies by Solomon reinforced this argument. When typical RFL films were exposed to ozone, the IR spectrum showed an increase in IR absorption at 1720 cm corresponding to an increase in the carbonyl content in the exposed film. An RFL film with no ozone exposure did not show this absorption at 1720 cm The increased carbonyl content is due to the reaction of some double bonds in the rubber with ozone and therefore, would leave fewer unsaturation sites for rubber crosslinking and adhesion. 

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