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An experimental study of structure development in melt spinning polyetherimide (PEI) and polyarylate (PAR) is presented. PEI was melt spun at 320° and 350°C and PAR at 310° and 340°C to drawdown ratios of up to 1 000. The melt spun fibers were found to be totally amorphous but to have significant levels of birefringence which increased with draw-down ratio. The birefringence was found to vary linearly with the spinline stress for both polymers and the data was independent of the melt spinning temperature. The proportionality constants are interpretable as equivalent to stress optical constants for the corresponding melts and have values of 9 400 Brewsters for the PEI and 7 400 Brewsters for the polyarylate. The mechanical properties of the melt spun fibers were determined in uniaxial extension. It was found that Young's modulus and tensile strength increased with spinline stress or birefringence while elongation to break decreased. The mechanical properties were found to be similar to polyether ether ketone, poly-p-phenylene sulfide, and polyethylene terephthalate in similar correlations, but as compared to polypropylene at the same spinline stress had higher Young's modulus and tensile strength but lower elongation to break. We were not able to successfully draw these materials over a hot plate at temperatures above their glass transition temperature.

Orientation and Mechanical Property Development in the Melt Spinning of Fibers from Polyetherimide and Polyarylate