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- 저자 : R. Pantani (검색결과 2 건)
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Crystallization of Syndiotactic Polystyrene under High Pressure and Cooling Rate
A. Sorrentino,R. Pantani,G. Titomanlio 한국고분자학회 2010 Macromolecular Research Vol.18 No.11
This study examined the effect of both pressure and cooling rate on crystallization kinetics of syndiotactic polystyrene (sPS). To that purpose, a homemade apparatus that can solidify polymer samples under cooling rates and pressures comparable to those achieved in common industrial processes, was employed. The morphology of the solidified samples was analyzed by pressure, volume, and temperature (PVT) test, densitometry, infrared (IR) spectroscopy, and X-ray diffraction. The results showed that the overall final crystallinity degree gradually decreases with increasing cooling rate, whereas the kinetics of the α and β forms are influenced in different ways by the pressure. A Kolmogoroff-Avrami-Evans kinetics model based on a modified Hoffman-Lauritzen approach was introduced for the description of the pressure effects. The results showed a good agreement between the experimental data and model prediction in all ranges of conditions investigated.
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V. Speranza,U.Vietri,R.Pantani 한국고분자학회 2011 Macromolecular Research Vol.19 No.6
The quality of the molded parts depends on the processing conditions, which creates a continuous demand for advanced techniques for monitoring and controlling the process. Temperature and pressure transducers are being used increasingly in industry. Therefore, the use of their measurements to obtain indications concerning the product quality could overcome the traditional resistance of industry to introduce new sensors in their production. The aim of this paper was to select a parameter, which can be identified by adopting pressure and temperature transducers, to correlate with the quality. To this goal, several series of injection molding tests were conducted by adopting a general purpose PS, changing the holding pressure and time, injection time, mould and injection temperature, nozzle length,gate and cavity thickness. The pressure histories and temperature evolution at the interface with the mould at several positions along the flow-path were measured by means of pressure-temperature transducers. The samples were measured after molding, and dimensional accuracy was assumed to be the target quality parameters. The mean solidification pressure, namely the average along the thickness direction of the pressures at which each layer solidifies, is a key parameter for quality control. A procedure not requiring simulation of the entire injection molding test and based on the knowledge of both the local pressure evolution, mold temperature and the polymer thermal diffusivity has been developed to evaluate the local solidification profile.
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