Physical and relaxation properties of flame-sprayed ethylene-methacrylic acid copolymer

A range of physical and chemical properties of flame-sprayed ethylenemethac rylic acid copolymer (EMAA) were assessed, following different processing c onditions. Coatings were produced at a range of specific temperatures by va rying the propane flow rate and gun traverse rate. The flame spraying proce ss oxidizes the EMAA copolymer during processing, the extent of oxidation i ncreasing with greater deposition temperatures. Coatings were scanned using dielectric relaxation spectroscopy at a frequency range from 10(2) to 10(6 ) Hz over a temperature interval of -20 to 85 degrees C. The glass transiti on temperature (usually denoted as the beta' relaxation in this system), is attributed to the microBrownian motion of long chain segments in the amorp hous phase and is found to decrease with increasing deposit temperature. Th e oxidation process appears to reduce the position of the beta' relaxation due to chain scission. The molecular weight for the EMAA powder was reduced from 22,693 g/mol to 9302 g/mol when deposited at 271 degrees C as shown b y gel permeation chromatography. Despite the decrease in chain length, the activation energies for beta'relaxation increased with increasing coating t emperatures. This is attributed to the increased polarity of the oxidized c oatings resulting in greater intermolecular association, which outweighs th e decreased chain length.