A novel pressure-volume-temperature apparatus for polymer melts and solids.

摘要

A novel PvT was developed to aid in computer simulations for injection molding. The apparatus was designed, fabricated, and tested. The development process required: (1) Metal selection, (2) A robust mechanical design to withstand temperatures up to 350{dollar}spcirc{dollar}C and pressures up to 20,000 psi, (3) Heat exchanger design to achieve rapid cooling rates, (4) Sensor selection to facilitate temperature measurements with accuracy of {dollar}pm1spcirc{dollar}C and volume measurements with an accuracy of 0.001 cm{dollar}sp3{dollar}, and (5) Set up of Data Acquisition system. The sensors were strategically placed to allow accurate measurements of the actual polymeric sample. The temperature measurements were made with the temperature probe embedded in the polymeric material, which is not accomplished by any apparatus generating hydrostatic states of stress. Cooling rates were achieved up to 30{dollar}spcirc{dollar}C/min, which is seven times greater than any apparatus generating hydrostatic pressure.; Three materials tested were (1) Polystyrene (PS) (2) Polyethylene-terphthalate (PET), and (3) A PS-PET blend. Polystyrene was tested at a cooling rate of 4{dollar}spcirc{dollar}C/min to calibrate the apparatus. PS showed a glass transition between 90{dollar}spcirc{dollar}C to 105{dollar}spcirc{dollar}C which correlates well with Differential Scanning Calorimeter measurements. PET was tested at 30{dollar}spcirc{dollar}C/min. PET showed multiple transitions: (a) Melt, (b) Pre-melt, and (c) Glass. A Thermo-gravimetric analysis was performed to study the degradation behavior of PET and PS as a function of time. No degradation was observed until fifteen minutes which is a very long time as compared to the time the polymer is exposed to such temperatures in the PvT apparatus.; The rapid cooling rates and the mode of measurement make it the most unique apparatus of its time. The data from such an apparatus would be very beneficial in computer simulations of the injection molding process. The apparatus with improvement in the heat exchange system has a potential to achieve cooling rates similar to that observed in an injection molding process. This would open up a new dimension in the simulation technology thus making the mold design process and process control very economical and efficient.