SOLUTION PROPERTIES OF POLYURETHANE

Polyurethane was fractionated and the fractions were characterized by gel permeation chromatography (GPC) and viscometry. The intrinsic visc osities of polyurethane in ten solvents varying in their polarity were determined and are in the order of mineral spirit < acetone < cyclohe xane < cyclohexanone < xylene < ethyl benzene < toluene < benzene < me thyl ethyl ketone < tetrahydrofuran. The Mark-Houwink relations sugges ted that solvent blend MEK: n-heptane (1:3) is a poor solvent with an a value of 0.52 and tetrahydrofuran is a good solvent with an a value of 0.78. The weight average molecular weight has been estimated by an extrapolation technique based on a linear relationship between the vis cosity average molecular weight ($) over bar M(upsilon) and the Mark-H ouwink constant. The weight average molecular weights obtained from vi scosity studies were used to evaluate the unperturbed dimension of the chain.