In Blends with Rubber Compounds

The investigations and studies presented in this section are concerned with the blending of waste rubber powder or crumb, which has not been through any devulcanisation processes of the type described in Chapter 4, into rubber compounds to produce new products. The rubber crumb in question may or may not have been surface-activated by one of the processes described in Chapter 6, Section 6.6. The properties of the resulting blends will depend upon whether this activation has taken place or not, as well as upon some of the variables already listed at the start of Section 7.2, namely the origin and type of rubber crumb, the proportion of rubber crumb in the blend, and 

Guzman and co-workers [27] investigated whether it is possible to use waste tyre crumb as a replacement for zinc oxide as an activator in the sulfur vulcanisation of natural rubber (NR). They used the unsaturated organic compound squalene as a model compound for NR in their work, and followed the course of the vulcanisation reaction using the analytical technique high-performance liquid chromatography. The results confirmed that waste rubber crumb was an alternative to zinc oxide as an activator in the curing of NR compounds by sulfur-based cure systems. 

Chandra and Pillai [28] used a low-molecular-weight recycled rubber as a processing aid in a number of tyre tread formulations and compared its performance with other commercial process aids. This process aid (Ecoreen T) is shown to function as well as or even better than depolymerised NR or similar process aids. The same workers also reported on the use of new products with low viscosity that are produced by blending low-molecular-weight virgin polymers with recycled butyl rubber [29]. When these products 

As has been shown in Chapter 6, in addition to crumb from waste tyres, it is possible to commercially source crumb from a number of other rubber types, e.g., fluorocarbon rubber. Shell [30] has carried out a study whereby micropowder from vulcanised fluorocarbon, silicone and nitrile wire insulation rubber has been put back into wire compounds using an open mill. The loadings chosen were those that maximised the performance and economic efficiency of the formulations. 

Workers in Brazil [31] have investigated the properties of revulcanised SBR that has been recovered from scrap rubber. Their work involved compounding the recovered SBR with an aromatic oil and different conventional ruhher cure systems. The curing behaviour of these compounds was then evaluated using a rubber process analyser. 

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