Comparison of Vinyl Acetate Contents of Poly(Ethylene-co-Vinyl Acetate) Analyzed by IR, NMR, and TGA

Vinyl acetate (VA) contents of poly(ethylene-co-vinyl acetate) (EVA) analyzed by infrared spectroscopy (IR), nuclear magnetic spectroscopy (NMR), and thermogravimetric analysis (TGA) were compared. Four grade EVAs supplied by Aldrich Co. and four grade EVAs manufactured by DuPont Co. were used. For IR analysis, VA contents were determined using calibration curve (absorbance ratio of 1739 cm(-1) /2922 cm(-1) or 609 cm(-1) /1464 cm(-1)) of reference EVAs. Correlation coefficients of the calibration curves were not sufficiently high (r(2) <= 0.96). For NMR analysis, VA contents were determined using peaks of CH3, CH2, and CH. VA contents determined by NMR analysis were less than those marked by suppliers more than 10%. For TGA, VA contents were determined using weight loss through deacetylation. VA contents determined by TGA were slightly different with those marked by suppliers. Difference in the VA contents determined by different analytical methods was discussed, and difference in the analytical results according to the EVA suppliers was also examined.