SANS AND SWELLING ASSESSMENT OF THE STRUCTURAL-PROPERTIES OF THE THERMOPLASTIC ELASTOMERS SANTOPRENE(TM) AND SARLINK(TM)

Two thermoplastic polyolefin elastomers, Santoprene(TM) 281-82 and Sar link(TM) 3280, were studied by small-angle neutron scattering (SANS) a nd swelling. Sorption was performed in 3% (volume/volume) aqueous acet ic acid (HAc) solutions at 65 degrees C. Increase in mass and volume w ere followed separately. For SANS studies, swelling was also performed in D2O solutions of HAc. Samples were subjected to mechanical fatigue , causing mainly shear stresses. A Sarlink variety with partly deutera ted mineral oil was prepared to study by SANS the influence of fatigue on distribution of the oil. Absorption of the HAc solution follows Ty pe I Fickian diffusion. Diffusion coefficients D, calculated in three ways, revealed a discrepancy between values obtained from measurements of mass or volume increase. D values were of a 10(-13) m(2)/s order o f magnitude. Influence of fatigue on D was not significant, although s aturation liquid uptake differed markedly between fatigued and control samples. Also, remarkable differences between control Sarlink and San toprene in saturation uptake were observed. From SANS experiments, no influence of fatigue on void size or distribution, or on distribution of mineral oil, could be observed. However, marked differences between control Sarlink and Santoprene was observed when data were interprete d in terms of fractal dimensions of phase boundaries. (C) 1996 John Wi ley & Sons, Inc.