Solubility of ethylene, 1-butene and 1-hexene in polyethylenes

The gravimetric method was used to measure the solubility of ethylene, 1-bu tene and 1-hexene for four polyethylene samples with different crystallinit ies and branching structures. Buoyancy corrections were made for polymer sw elling; it was found that polymer volume varied approximately linearly with the amount of olefin sorbed. The solubility of ethylene, at temperatures o f 30-90 degreesC and pressures up to 3.5 MPa, was well described by Henry's law; Coefficients of Henry's law were in the range of 0.005 -0.014 (g C2H4 )/(g of amorphous PE . MPa). The coefficients decreased with increasing tem perature and increasing crystallinity. The solubility of 1-butene and 1-hex ene, measured over the same temperature range and at pressures up to about 90% of the vapour pressures, did not follow Henry's law; these olefins were much more soluble than ethylene in all four types of polyethylene. Olefin solubility, based oil amount of amorphous polyethylene, decreased with incr easing polyethylene crystallinity and was also a function of the type of br anching. (C) 2001 Elsevier Science Ltd. All rights reserved.