The crystallization of polymers under pressure has recently attracted particular interest for being a powerful method of obtaining different crystal structures and morphologies. A specific molecular conformation may indeed induce remarkable changes in polymer solvent resistance and mechanical performance. In this work an experimental apparatus was designed and developed to investigate the effects of pressure and cooling rate on polymer samples. The apparatus, based on the confining fluid technique, is able to impose constant external pressures and different cooling rates during the solidification of polymer samples. In its current configuration, the device can reach 1250 bars and a maximum cooling rate of 40 degrees C/s (measured at 200 degrees C) with water at 5 degrees C as a cooling medium. Preliminary results obtained with Syndiotactic Polystyrene confirm that, in addition to thermal history, external pressure is indeed a significant factor for inducing changes in crystalline polymeric structures. The stable orthorhombic beta form is favored for specimens solidified under pressure, whereas the overall final crystallinity degree (alpha and beta forms) gradually decreases with both cooling rate and pressure.
A novel apparatus for solidification of polymer samples under simultaneous high pressures and high cooling rates
Sorrentino A;
2005
Abstract
The crystallization of polymers under pressure has recently attracted particular interest for being a powerful method of obtaining different crystal structures and morphologies. A specific molecular conformation may indeed induce remarkable changes in polymer solvent resistance and mechanical performance. In this work an experimental apparatus was designed and developed to investigate the effects of pressure and cooling rate on polymer samples. The apparatus, based on the confining fluid technique, is able to impose constant external pressures and different cooling rates during the solidification of polymer samples. In its current configuration, the device can reach 1250 bars and a maximum cooling rate of 40 degrees C/s (measured at 200 degrees C) with water at 5 degrees C as a cooling medium. Preliminary results obtained with Syndiotactic Polystyrene confirm that, in addition to thermal history, external pressure is indeed a significant factor for inducing changes in crystalline polymeric structures. The stable orthorhombic beta form is favored for specimens solidified under pressure, whereas the overall final crystallinity degree (alpha and beta forms) gradually decreases with both cooling rate and pressure.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
