Core-shell polymers of methyl methacrylate-styrene system were prepared by sequential emulsion polymerization in the presence of sodium dodecyl benzene sulfonate(SDBS) as an emulsifier using ammonium persulfate(APS) in an initiator and the characteristics of these core-shell polymers were evaluated. Core-shell composite latex has the both properties of core and shell components in a particle, whereas polymer blends or copolymers show a combined physical properties of two homopolymers. This unique behavior of core-shell composite latex can be used in various industrial fields. However, in preparation of core-shell composite latex, several unexpected matters are observed, for examples, particle coagulation, low degree of polymerization, and formation of new particles during shell polymerization. To solve this matters, we study the effects of surfactant concentrations, initiator concentrations, and reaction temperature on the core-shell structure of PMMA-PSt and PSt-PMMA. Particle size and particles distribution were measured by using particle size analyzer, and the morphology of the core-shell composite latex was observed by using transmission electron microscope. Glass temperature was also measured by using differential scanning calorimeter. To identify the core-shell structure, pH of the composite latex solutions was measured.

This paper presents the application of integrated mathematical programming approach for the design of cellular manufacturing. The proposed approach is carried out in two phases: The first phase concerning exceptional elements(EEs) in cell formation and th

Ultra-fine copper powders with particle size about 150 nm were synthesized from copper hydroxide slurry by wet method using hydrazine as reduction agent and several sur factants at below . The particle size distribution and dispersion of synthesized powders as function of temperature, feeding rate of reduction and especially, sur factants were character ized by XRD, BET, PSA and SEM by this process.

The purpose of this study is to execute the investigation of injurious factors causing muscle-skeletal diseases at an automotive glass manufacturing company and, on the basis of the results, to enhance productivity by the improvement of working environment. By using an survey and an ergonomic evaluation method, symptoms of muscle-skeletal diseases of workers and working postures at each process were analyzed, and quantitative evaluation of muscle-skeletal disease risk against each process was performed. Based on the result of the evaluation, to enhance the working environment, improvement of worktable, working space, tools, and outfit was suggested, and induction of mechanical system was also suggested. Suggested improvement plan was applied to the workplace step by step and it is confirmed that improvement plan not only removes the injurious factors of muscle-skeletal diseases but also is effective to enhance productivity.

ISO 9000 quality standards families were established in 1987 and have been started to implement Korean industry since early 1990s. ISO 9000 standards families of 1987 were revised in 1994 and 2000, respectively, by request of world wide certification bodi