High-pressure phase behaviour of the system linear low density polyethylene + N-hexane + ethylene: Experimental results and modelling

Experimental bubble point curves, cloud point curves, and liquid-liquid-vapor boundary curves are presented for the linear low density polyethylene (LLDPE) + n-hexane + ethylene system. The experiments were conducted at process conditions (360-510 K and up to 15 MPa). The liquid-liquid-vapor boundary was measured up to a temperature where a three phase transition was no longer observed near a liquid-vapour critical point. The experiments were modeled with the modified Sanchez-Lacombe (MSL) EOS. Linearly temperature dependent binary interaction parameters were found for LLDPE + ethylene and LLDPE + n-hexane. The LLDPE + n-hexane binary interaction parameters were used to calculate the cloud points of two LLDPE + n-hexane systems reported by others. The LLDPE samples in these other systems had similar molecular structures but different molar mass distributions. The MSL equation provided a qualitative representation of the phase behavior of all three systems. This is an abstract of a paper presented at the AIChE Annual Meeting and Fall Showcase (Cincinnati, OH 10/30/2005-11/4/2005).