43—The Shear and Young’s Moduli of Nylon 6.6 Monofilaments of Various Orientations and the Variation of Shear Modulus with Relative Humidity

Abstract

The dependence of the Young’s modulus and shear modulus of nylon 6.6 monofilaments on their degree of orientation has been measured at 25.0°C and 66% r.h. at a frequency of 6 c/min.Filaments of 6 different orientations ranging from nearly isotropic (birefringence 0.004) to highly oriented (birefringence 0.06) were used The orientation was produced by cold-drawing to various degrees. Filament diameters ranged from 0.09 mm (undrawn) to 0.04 mm (fully drawn)The shear modulus was measured by the torsional pendulum method and the Young’s modulus by a forced vibration method. The frequency of vibration in each case was 6 c/min.The variation of shear modulus with relative humidity in the range 0 to 93% was also measured for all 6 orientations.It was found that the Young’s modulus (at 66% r.h.) was the same for the undrawn and slightly drawn (draw ratio 1.4) filaments and then increased continually with draw ratio. For conditioned filaments, the values of the Young’s moduli were 8.6. 109 dyne cm-2 for undrawn filaments and 20.4. 109 dyne cm-2 for fully drawn filaments.At humidities greater than 40% r.h., the shear modulus increased with draw ratio, but at humidities less than 40% r.h. it decreased with draw ratio. At all humidities, unexplained divergences were shown by the filaments of draw ratio 1.4 and 2.35,. The shear modulus decreased steadily with increasing humidity at each draw ratio. For conditioned filaments, the shear modulus at 66% r.h. was 2.96,. 109 dyne cm-2 for undrawn and 3.59,. 109 dyne cm-2 for fully drawn filaments.