Mina , M. F. and Asano , T. and Dafader , N. C. and Akhtar, F. and Yoshida , S. and Tohyama , N. and Imaizumi , K. (2004) Effect of monomers in the structural modification of natural rubber during grafting with gamma-ray irradiation. JOURNAL OF MACROMOLECULAR SCIENCE-PHYSICS , B43 (2). pp. 297-307. ISSN 0022-2348
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Nonirradiated latex (NIL), irradiated latex (IL) and the latex grafted separately with monomers such as styrene, butyl methacrylate (BMA), methyl methacrylate (MMA), and cyclohexyl methacrylate (CHMA) were prepared from natural rubber obtained by Bangladesh Forest Industries Development Corporation, Bangladesh. Morphology and mechanical properties of the six different rubber films were observed by mechanical testing, optical microscopy, and x-ray diffraction methods. An inhomogeneous electron density is developed as a consequence of cross-linking and grafting during irradiation. The resultant structure includes density fluctuation of several nanometers to microns as revealed by small-angle x-ray scattering (SAXS) and microscopy. The rubber elasticity is enhanced due to the network structure, resulting in high tensile strength and high elongation in the IL. Aggregation of the grafted latex increases tensile strength and decreases elongation. Consequently, the greater the population of aggregates in the grafted film, the lower the elongation values. The mechanical properties and corresponding structures are explained by a polymer gel theory using a spring model. Considering numbers of junction N and the average length of the spring L with the spring constant k, the tensile strength (T) is proportional to NkL(max). As the elongation at break (E) depends on L-max (the maximum length of L), the relative value of N can be estimated from the mechanical results by (T/E)(3/5). The experimental results are well explained by the gel theory. Existence of large-sized aggregates by grafting and homopolymerization increases stiffness and brittleness of the rubber material.
|Subjects:||Physical Science > Nanophysics|
Physical Science > Nano objects
Material Science > Nanochemistry
Material Science > Nanostructured materials
|Divisions:||Faculty of Engineering, Science and Mathematics > School of Physics|
Faculty of Engineering, Science and Mathematics > School of Chemistry
|Deposited On:||19 Oct 2010 06:27|
|Last Modified:||19 Oct 2010 06:27|
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