EFFECT OF ORIENTATION AND CRYSTAL-STRUCTURE ON DAMPING PROPERTIES FOR NYLON-6 AND AROMATIC POLYAMIDE BLENDS

By using the resonance frequency method of mechanical impedance measurement, blends of an aliphatic polyamide (nylon 6) and an aromatic polyamide (MXD 6) were found to show superior damping properties. The damping property, represented by loss factor (eta), increased as the proportion of MXD 6 in the blend increased. Moreover, eta measured at a high temperature (80 degrees C) reached a maximum when the MXD 6 content was about 20 wt%. Significantly, the crystallinity as measured by X-ray diffraction remained unchanged regardless of the MXD 6 content. The glass transition point measured with the dynamic visco-elastic property tan 6 increased consistently as the proportion of MXD 6 increased. However, light scattering showed that the phase length was about 0.1 mu m at 20 wt% of MXD 6 and was shorter than that of neat nylon 6 (0.5 mu m), indicating the changes in the phase structure and orientation of crystals in the blend. These results show that the crystal structure and orientation of neat nylon 6 are more ordered than those of the blends with MXD 6, but the damping property of nylon 6 is inferior to that of the blends, This is ascribable to the disorderedness in the crystal structure and orientation on adding MXD 6. These observations on orientation and crystal structure should contribute to the improvement of the damping property in the blends of nylon 6 and MXD 6.