| The Chlorinated Natural Rubber (CNR), which is prepared by,the chlorinated modification of crumb natural rubber (NR) with solution or directly from latex. With such excellent properties as film-forming, quick-drying, acid-proof, alkali-proof, wear-resistant, aging-resistant, corrosion-resistant in sea water, inflame-retarding, insulativity and highthermal stability, has extensively been used in the production of paints, adhesives, additive of print ink and products of acid-proof and alkali-proof.,etc, and become one of the most important industrial derivatives of natural rubber.There are mainly two kinds of method for production of CNR. One is the traditional solution process, in which CNR was prepared by dissolving the NR crumb in tetrachloromethane, then chloridized. This process, however, has been prohibited in some developed countries and will in developing countries because of high operation cost and the intensive environment pollution of tetrachloromethane. Other is latex technics by directly inputting chlorine to chloridize stabilited natural rubber latex. It is a new preparation technology for CNR with the advantages of low pollution, simple technics and low cost. CNR prepared by natural rubber latex has become one of hotspots in rubber modification researche field in our country. The structure and properties of products by two methods have obvious differences. The stability of the CNR from latex is weaker than that of CNR by solution, Especially in wet condition, CNR prepared from latex has high sensitivity of heat and prone to tending to release HC1 once effected by heat, light, oxygen and acid, so that it will result in variation ofthe molecular structure and properties. Therefore, it is the key to study the rule of effects of different heated course on molecular structure and propertis, and to reveal the dynamic relationship between drying conditions and the structure and properties.In this thesis, the effects of the drying condition in the thin layer on CNR from latex on drying rate, molecular structure and properties have been researched systematically with various advanced investigation methods.The results of FTIR showed that although basic structure between CNR prepared from latex and by solution are similar, the fine structures are different. It can be regarded as the essential reason for the difference in stability between them.Degradation and stability of CNR are usually characterized by HC1 content escaped. Mensurating conductance is a simple method to determine the amount of HC1 escaped. Among factors of the temperature, granularity, atmosphere and methods for preparation, temperature has an obvious effect on HC1 escaped, especially in oxygen atmosphere. The activation energy of high-speed reaction period was smaller in oxygen than that in nitrogen, which show that HC1 escaped in oxygen was easier than in nitrogen. But under low temperature, either in oxygen or in nitrogen, HC1 escaped was too little to affect the quality and application of CNR.The moisture diffusion features in chlorir ated natural rubber granules during their drying process have beer studied by means of thermogravimetry. The results showed that there are significant influences on the diffusion coefficient by moisture content and drying temperature butlittle by granularity and air flux. Diffusion coefficient increases with reducing of the moisture content; Diffusion coefficient value varys in the range of 0.005-0.05 mn2.min"1 and increases with the increasing of the drying temperature exponentially.The drying process of material for chlorinated natural rubber granules from latex has also been studied by means of thermogravimetry. The results showed that the drying process could be divided into three stages: accelerated stage, constant stage, and decelerated stage. The temperature is of more obvious influence on the rate of drying than drying air velocity. A model derived from experiment data was adopted to describe the whole drying progress.The experiments of thin layer dryingof CNR were carried out o... |
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