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Spherulite Growth In Poly Propylene Experiment

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Title: Spherulite Growth In Poly Propylene Questionnaire Figure (A): Spherulite growth rate (?m/min) in Polypropylene melting at different temperatures. (See Appendices 1.1) 1. Temperature (?C) Spherulite growth rate (?m/min) 130 0.023 128 0.035 126 0.038 124 0.057 2. The observed variation of growth rate with temperature The size shape regularity of the crystals depend on their growth conditions, such factor as temperature and growth rate being important. The thickness of the lamellar depends on the crystallization temperature and any subsequent annealing treatment (Hendra 1976). According to the graph (appendix 2.2) higher the temperature gives lower the spherulite growth rate. However it is clearly observed that spherulite can grow bigger then phase-separated domains in rapid cooling process. ...read more.


The disappearance of a polymer crystalline phase at the melting point is accomplished by changes in physical properties, since crystalline melting point may be determined by noting the temperature of disappearance of the last traces of crystallinity as evidence by birefringence observed between crossed polarized on a hot stage microscope. 5. Appearance of slowly crystallized and quenched sample According to the graph it is found that crystallization take place with respect to time and also it is found that mobility of chains are restricted in quenched sample. The development of crystallinity in polymer is not instantaneous. According to the graph spherulite growth is the function of time at temperature below the crystalline melting point. As the temperature is lowered, the rate of crystallization increases, so the mobility of the molecules decreases. ...read more.


The behavior of the polymer melt during rapid cooling in the mould determines, to a great extent, the quality and usability of a final product. Technical raw materials are often equipped with nucleating agents in order to obtain crystallization within the desired temperature range and at the required rate. At slow cooling rate, larger crystals were formed, whereas at fast cooling rate, smaller crystals appeared together. Slowly crystallized samples had a broader distribution of crystal size. Crystallization temperatures had a similar effect as cooling rate. At higher crystallization temperatures, larger crystals and a broader crystal size distribution were found. Agitation rate had a marked effect on crystal size. Higher agitation rates lead to smaller crystal size. Cooling rate was the most influential parameter in crystal thermal behavior and composition. Slowly crystallized samples showed a broader melting diagram and an enrichment of long-chain. Crystallization behavior was more related to processing conditions of injection moulding. ...read more.

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