MECHANICAL PROPERTIES OF THE BIAXIALLY STRETCHED NYLON-6 FILMS PREPARED BY DRY-PROCESS

Abstract

In the previous paper of this series, the molecular orientation and crystallization of biaxially stretched Nylon-6 films at high temperatures were reported. The present study deals with the changes in mechanical properties of the biaxially stretched Nylon-6 films. The specimens, stretching devices and stretching conditions are same as described in the previous report.The static mechanical properties of the stretched films such as tensile strength, elongation at break, Young's modulus and F_??_, value were measured at 20°C under 65% R. H. using an Autograph tensile tester. The dynamic properties i.e. the temperature dependencies of tan δ and dynamic modulus E′ as well as dynamic loss E′ were measured at 100Hz using a Viscoelastic Junior Spectrometer.The following results were obtained;(1) The mechanical properties of the films uniaxially stretched with free width differ only in the transverse direction in those of constant width. For the machine direction, these properties were found to be similar to general tendency of the change.(2) The mechanical properties of the simultaneous-biaxially stretched films were same in both directions machine and transverse regardless of their stretch-ratio as observed for other polymer films (e. g. PVC, PP and PET films).(3) The films stretched by different processes show characteristic changes in dynamic viscoelastic properties due to the changes in degree of orientation and crystallinity. For the biaxially stretched films, the strain which the molecular chain suffers is greater than that of uniaxially stretched ones for the same stretch ratio.