about 90 minutes in the polymerization of the ion exchange obtained salt heat up from about 230 u00b0 c to about 265 u00b0 c took place in about 65 minutes and the salt was held at between about 265 u00b0 270 u00b0 c for about 90 minutes from ion from exchange control obtained salt salt______________________________________relative viscosity rv 10 7 8 7 cooh ends 10 sup 6 gm polymer 268 5 434 nh sub 2 ends 10 sup 6 gm polymer 175 5 175difference of ends 93 259dta peaks melting point u00b0 c 256 257 freeze point u00b0 c 227 226______________________________________ relative viscosity rv is conventionally defined as the ratio of absolute viscosity of an 8 4 weight percent polyamide solution in 90 formic acid to the absolute viscosity of the 90 formic acid solution at 25 u00b0 c for small size samples as in these experiments the relative viscosity of a 0 42 weight polyamide solution was measured and converted to the conventional rv by the following empirically developed correlation for 66 nylon the molecular weight of the polyamide produced from the ion exchange obtained salt measured by relative viscosity was slightly lower than the control because of greater end group imbalance the salt obtained from.