Moisture effect on structure and mechanical property of nylon 6 as studiedby the time-resolved and simultaneous measurements of FT-IR and dynamic viscoelasticity under the controlled humidity at constant scanning rate

Time-resolved simultaneous measurement of infrared spectra and complex Youn g's modulus was made for nylon 6 films by using the combined system of FT-I R spectrometer and dynamic viscoelastometer under the control of humidity s canned at a constant rate and at a constant temperature. The complex Young' s modulus of nylon 6 films annealed at various temperatures was found to de crease with increasing relative humidity. This behavior could be reproduced well by applying the complex mechanical model of the crystalline and amorp hous phases with the humidity dependence of the amorphous modulus taken int o consideration. The moisture effect on the infrared bands of crystalline a nd amorphous phases was investigated, from which the moisture-induced disor dering in the crystalline region was speculated. The complex Young's modulu s was measured at the various strain frequencies under the stepwisely-scann ed humidity at 35 degreesC, from which the master curves of the real and im aginary parts of the modulus could be produced successfully. The humidity d ependence of the thus evaluated shift factor was found to be fitted quite w ell to the theoretical equation concerning the free volume in the amorphous region. The characteristic features of the dynamic viscoelatometer system used in this experiment were also investigated in detail.