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Download or read book Study of Factors Influencing Structure of Precipitated Silica written by and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Subtle changes in synthesis and processing of reinforcing fillers are known to have substantial impact on mechanical properties of elastomers. The task of linking the synthetic process with resulting structure and final properties is difficult because reinforcing fillers are complex structures, spanning over 6 decades in length scales. Ultra Small angle X-ray scattering (USAXS) and light scattering (LS) are effective tools to characterize these colloidal structures. In the first section of this work, the role of drying technique on structure of precipitated silica was studied. By using LS and USAXS, the effect of drying on morphology of both, aggregate / (nanoscale) and agglomerate / (micron scale) structure was established. The gentle process of oven drying leads to weakly interpenetrated aggregates, which are clustered in agglomerates. The agglomerate size exceeds 50æm in radius of gyration. Spray drying on the other hand produces agglomerates of order of 10æm, with minimal interpenetration of aggregates. On dispersion in rubber, the fillers look identical in aggregate regime. The interpenetration of aggregates was attributed to the rate of drying. The powders show marginal difference in degree to which agglomerates break on milling in rubber. From scanning electron micrographs, the size of agglomerates formed during spray drying was found to be less than the size of those formed during oven drying. The effect of drying on agglomerate strength was investigated by sonication and LS. For the same amount of sonication energy, it was observed that the agglomerates in solutions (silica never dried) broke down dramatically as compared to dried powders. Finally, the mechanical properties of rubber filled with never-dried silica, spray-dried silica and oven-dried silica powder, were compared. It was observed that the never-dried silica filled rubber and spray dried powder give far better properties than the oven dried rubber because of facile dispersion and less interpenetration of agglomerates. It was concluded that the process of drying leads to strong bonds in the agglomerates, making them hard to disperse. In the second part of this work, the possibility of in-situ modification of silica structure was investigated. 3-mercapto propyl tri-ethoxy silane was added as a surface- modifying agent and different samples were synthesized by varying the amount of silane. USAXS study revealed decreasing trend in what seems to be the interpenetration of aggregates, with increase in the amount of silane added. Light scattering revealed a slight decrease in size of particles, with increasing amount of silane. SEM showed suppression of clusters by adding silane. It was concluded that in-situ modification changes the silica structure on the aggregate and agglomerate scale.