Vulcanization techniques

The finished dry rubber and latex based rubber products can be vulcanized by several techniques depending on the type of rubber compound (dry rubber compound/latex compound), size of the finished product, and its shape and structure. Moulded rubber products are vulcanized by press curing using compression, transfer, or injection moulding presses. The vulcanization techniques other than moulding may be grouped into batch and continuous methods. The batch methods include the use of autoclaves, hot air/gas oven, and hot liquid/ water bath. Rubber products may be vulcanized at room temperature by cold curing either by immersion of rubber products in a carbon disulphide solution of sulphur chloride (SjCy, or by exposure to its vapour. 

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Compatibilization along with dynamic vulcanization techniques have been used in thermoplastic elastomer blends of poly(butylene terephthalate) and ethylene propylene diene rubber by Moffett and Dekkers [28]. In situ formation of graft copolymer can be obtained by the use of suitably functionalized rubbers. By the usage of conventional vulcanizing agents for EPDM, the dynamic vulcanization of the blend can be achieved. The optimum effect of compatibilization along with dynamic vulcanization can be obtained only when the compatibilization is done before the rubber phase is dispersed. 

Ghosh et al. (32) had developed a new vulcanization technique to mitigate the cure-rate mismatch of NR/EPDM blends by introducing a multifunctional additive, namely, DIPDIS. In order to control the curative diffusion from the nonpolar to polar elastomer, EPDM has made more polar through its reaction with DIPDIS. Although EPDM used in the investigation has a low unsaturation content (5%), it will react with DIPDIS and yield rubber-bound intermediates as shown in Fig. 15.2 (32). It was... 

Figure 27.5 Structure of the networks formed by the four vulcanization techniques (a) DCP, (b) EV, (c) mixed, (d) CV (left) and mole percent -hexane uptake of natural rubber with different crosslinking systems (right). (Reprinted from ref. 26 with the permission of Copyright 1997 John Wiley and Sons, Inc.)...

Sulphur-curing grades are usually preferred by the rubber industry as they make use of established technology, but two other vulcanization techniques are also well established as they produce elastomers with certain superior properties these are crosslinking with peroxide or diisocyanate. Peroxide curing can be universally used as it has a free radical-type... 

The poly(methyl methacrylate) molecules were dispersed in the natural rubber matrix, or vice versa, to form spherical droplets, as observed by optical photographs or scanning electron microscopy. The compatible natural rubber/poly(methyl methacrylate) blends had been made by the addition of the graft copolymer of natural rubber-gr t-poly(methyl methacrylate) as the compatibilizing agent due to its ability to enhance the interfacial adhesion between the two homopolymers. Moreover, Nakasorn and coworkers reported that natural rubber-gr i -poly(methyl methacrylate) could be blended with poly(methyl methacrylate) via a dynamic vulcanization technique with a conventional sulfur vulcanization system. The natural rubber-gra/t-poly(methyl methacrylate) was synthesized by a semi-batch emulsion polymerization technique via different bipolar redox initiation systems, i.e. cumene hydroperoxide and tetraethylene pentamine. ... 

The thermal stability of NR and carboxylated styrene butadiene rubber (XSBR) lattices and their blends were studied by thermogravimetric methods by Stephen et The thermal degradation and ageing properties of these individual lattices and their blends were investigated with special reference to blend ratio and vulcanization techniques. As already described, as the XSBR content in the blends increased, their thermal stability was also found to increase. Among sulphur and radiation-vulcanized samples, radiation cured possessed higher thermal stability due to the higher thermal stability of carbon carbon crosslinks. 

Curing is achieved either by random radical crosslinking of polysiloxanes by heating with peroxides or by room temperature vulcanization techniques making use of reactive end groups of the precursors. 

A second group of room temperature vulcanization techniques have been developed based upon linear polysiloxane chains terminated by hydroxyl groups. Curing can be achieved by two ways which both make use of hydrolyzation reactions of labile Si T R bonds. Two-component vulcanization RTV-2. 

In this section, the mixing behavior of BR rubber and rubber particles as a tracer was studied in a three-dimensional internal mixer with the rotor wing having the most effective distribution of rubber. As the mixing behavior of a three-dimensional internal mixer cannot be observed, it was investigated using a vulcanization technique (Gondoh et al., 1995). 

Investigations of the species to be found in the vapours and mists from vulcanization have been mainly confined to the last ten years, and the current understanding can be attributed largely to laboratory studies. An essential ingredient of much of this work has been gas clu-omatog-raphy with on-line mass spectrometry (GC/MS) and the development of vulcanization techniques which can most effectively exploit this instrumentation has been described and reviewed.The gas transfer mould already described (Figs 10 and 11) represents the latest stage in the evolution of these techniques. ... 

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