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

The gravimetric method was used to measure the solubility of ethylene, 1-butene and 1-hexene for four polyethylene samples with different crystallinities and branching structures. Buoyancy corrections were made for polymer swelling; it was found that polymer volume varied approximately linearly with the amount of olefin sorbed. The solubility of ethylene, at temperatures of 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 temperature and increasing crystallinity. The solubility of 1-butene and 1-hexene, 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 increasing polyethylene crystallinity and was also a function of the type of branching. (C) 2001 Elsevier Science Ltd. All rights reserved.