Friction and scratch resistance of polyamide 6 modified with ionomeric ethylene/methacrylic acid copolymer

Ethylene/methacrylic acid copolymer Surlyn((R)) 9020 (SU) was used to reduce the crystallinity of polyamide 6 (PA6). Differential scanning calorimetry was used to calculate the change in crystallinity of a modified polymer: four cases of SU weight fractions (5, 15, 20, and 30%) were considered. The fracture morphology was studied by use of scanning electron microscopy. With the increasing fraction of SU the structure transformed into a fine crystalline one. The effect of reduction in crystalline fraction on friction and scratch resistance of PA6 was investigated. The static and dynamic coefficients of friction decreased with respect to the increase in weight fraction of SU. With the addition of SU, the scratch resistance was found to decrease as well, whereas the healing (i.e., recovery of material after a scratch was made) of the material was found to increase. SU hindered crystallization of PA6, and with higher content of SU plastification of material occurred. Results from thermomechanical tests confirmed that conclusion: the Young's modulus E decreases and the thermal expansion coefficient alpha(L) increases with the addition of SU. (C) 2004 Wiley Periodicals, Inc.