Derivatives of 4,4'-azobis-4-cyanopentanoic acid were prepared using its diacid chloride and various hydroxyl and amino compounds. The objective was to obtain substances that would act both as initiators for different modes of free-radical polymerisation and also as stabilisers for emulsion polymerisation reactions carried out in the absence of added conventional surfactant. During the preparation of the above compounds, it was discovered that 4,4'-azobis-4-cyanopentanoyl chloride appears to exist in two different forms called I and II. These forms yielded two different forms of esters when reacted with straight-chain aliphatic alcohols. These esters are called 'esters A' and 'esters B', respectively. Surprisingly, the esters A were found to act as effective initiator/stabilisers for the emulsion polymerisation of styrene in the absence of conventional surfactant. Unfortunately, during the course of the investigation, it was suddenly found to be impossible to prepare further batches of acid chloride I, and most subsequent attempts to prepare acid chloride I met with failure. The efforts which had been made to try to prepare acid chloride I and to elucidate possible structural differences between I and II that might account for the observed phenomena are described in detail. The rest of this work is concerned with the study of the behaviour of esters derived from acid chloride II and a range of fatty-alcohol ethoxylates. Results are given for the use of these derivatives as both initiators and stabilisers for the emulsion polymerisation of styrene in the absence of added conventional surfactant. The effects of temperature, initiator concentration and the total volume of water upon the rate of polymerisation were studied. Also, the effects of these variables upon the shapes of the conversion-versus-time curves obtained when the esters were used as initiator/stabilisers were investigated. The surfactant properties of some of the initiator/stabilisers have also been investigated. The kinetics of the decomposition of these initiator/stabilisers is also included.

Produced by existing size reduction technologies, rubber crumb is the most valuable type of recycled material. However, only a limited amount of untreated crumb can be used in new tyres due to significant property loss. The de-vulcanisation process offers the potential for providing high quality recycled material that can be used as a substitute for virgin rubber. Rubber materials produced during industrial trials that formed the development stages of the novel DeVulCO”2 de-vulcanisation technology, were used in this work. A practical way to characterise de-vulcanised and re-vulcanised waste tyre materials and blends with virgin compound was established. This work showed that simple to obtain and understand parameters, acquired from tests that are commonly used in the rubber industry, such as Mooney viscosity, Mooney relaxation and curing can be successfully used to indicate the efficiency of the de-vulcanisation process and hence, to assist the research and development stages of the de-vulcanisation process and to assure quality control. Good correlation was evident between these parameters and the network characterisation parameter (Vr) obtained from the swelling measurements that are known to be a reliable guide but are more time consuming to perform. In this work, the Mooney relaxation test was successfully extended to characterise some de-vulcanised compounds (automotive weather strip and clothing tape). In addition, the swollen-state 1H-NMR technique was successfully applied to characterise de-vulcanised and subsequently re-vulcanised “closed-loop” tyre materials. A new tool to measure the efficiency of the de-vulcanisation process has been devised, based on a comparison of the peak areas in the olefinic region of rubber extracts analysed by the liquid 1H-NMR technique. This technique is capable of characterising different components of a rubber blend (e.g. NR, BR) and is suitable for carbon black filled compounds. The results of this work have confirmed the potential of the DeVulCO”2 technology and have indicated that up to 20% of de-vulcanisate can be blended with virgin tyre compound without significant deterioration of the key performance properties.

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