Articles written in Sadhana

    • Effect of oven residence time on mechanical properties in rotomoulding of LLDPE


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      In rotational moulding of plastics, improving the mechanical properties without sacrificing the processibility is a challenging task. In this paper, an attempt has been made to investigate the effect of oven residence time on the mechanical properties of the rotationally moulded products made using linear low densitypolyethylene. Simulation studies were conducted using ROTOSIM software to analyze thermal transitions and phase changes during the process. Degree of curing of the polymers was also assessed and correlated with mechanical properties. Experiments were further conducted to obtain favourable oven residence time to obtain highest mechanical properties. Experimental investigation revealed that there exist regions where the part was ‘under-cured’ and mechanical properties were found to be inferior. It was also found that when parts were ‘overcured’, the mechanical properties were severely affected. A regime of favourable processing window was identified where the highest tensile, flexural and impact properties were noticed.

    • Effect of coir content on mechanical and thermal properties of LLDPE/coir blend processed by rotational molding


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      Rotational Molding is a unique polymer processing technique that gives an advantage of having stress free end product. Majorly, Linear Low Density Polyethylene (LLDPE) is preferred as a base resin for rotomolding. However, incorporation of additives becomes necessary to improve mechanical properties and viscoelasticity as incumbent for few applications. The present research makes an attempt to investigate the effect of coir fiber on rotationally moldable LLDPE. Based on preliminary processing experiments, 10% or less Coir inits powder form when mixed with LLDPE was found to account a better flow ability as a prerequisite for roto moldability. Hence, the effect of 3%, 5%, 7% and 10% Coir mixed with LLDPE was experimented for the roto molded product to determine the mechanical properties, viz. tensile, flexural, hardness and impact strength. Also, the rate of heat transfer was evaluated subjected to the data recorded for mold, oven and internal air temperature when processing LLDPE/Coir considering different weight percentages. Crystallinity of the blendwas examined based on DSC analysis for the distinguished percentage of coir incorporated in LLDPE. The experimental results depicted an improvised mechanical properties by 7% or less fiber addition, and beyond that,the properties were found to be regressed. The present work successfully engulfed Coir with LLDPE, producing a uniform distribution along the sides of the mold without applying any external pressure. Therefore, fiber integration in the rotomolding process is believed to be possible thus preserving homogeneous randomlydistributed fiber dispersion.

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