in modulus and elongation this indicates susceptibility to acid hydrolysis from the fact that the reduction was much higher in the case of the 5 crosslinked sample the amide linkage which is beta to a hydroxyl may be especially susceptible to acid hydrolysis if the urethane linkage were the weak point of the network a more substantial decrease in the tensile strength of the 10 crosslinked sample would probably have been observed exposure to ph 8 is not as detrimental the 10 crosslinked sample showed a general hardening as indicated by the slightly increased tensile strength the marked increase in tensile modulus and a considerable reduction in elongation the last two entries in the table indicate the thermal stability of the 10 hmdi crosslinked sample when the samples were prepared for this phase of the study they were subjected to three 15 min press cycles at 150 u00b0 c although the shear was not severe the ability of the material to withstand a lengthy thermal exposure is demonstrated by the small decrease in tensile strength and elongation and the slight increase in modulus of dry samples the wet samples showed no change in modulus a small increase in tensile strength and a small reduction in elongation films of the.