CHARACTERIZATION OF THE RHEOLOGICAL BEHAVIOR OF UHMWPE GELS USING PARALLEL-PLATE RHEOMETRY

The effects of shear flow, temperature, and gel concentration on the r heological behavior of the ultrahigh-molecular-weight polyethylene (UH MWPE) gel in gel spinning process were investigated. The gel point was determined using parallel plate rheometry in rotation mode with contr olled stress. Likewise, the flow curves at various temperatures were d etermined with controlled shear rate from 10(-2) to 10 s(-1). Whereas the shear storage modulus (G') was obtained in oscillation mode with c ontrolled strain from I to 100%. The result shows that the gel point o f the UHMWPE gel increases with increasing gel concentration. The resu lt from the strain sweep indicates that G' of the gel is 1.5 x 10(3) P a, and it exhibits a plateau at low strain, but it is reduced with inc reasing strain. At low shear rates, for temperatures above gel point, all flow curves exhibit a plateau, then go down with increasing shear rate. Studying contributions from UHMWPE gel concentration, temperatur e, and shear rate for rheological view, we found that spinning at 6% U HMWPE (MW : 1.4 x 10(6) g/mol) gel and 140 degrees C gives the best ef fect on formation of fiber structure. (C) 1998 John Wiley & Sons, Inc.