Novel analytical method for determination of contents of backbone and terminal/branch vinyl acetate groups of poly(ethylene-co-vinyl acetate) using deacetylation reaction

Vinyl acetate (VA) groups in poly(ethylene-co-vinyl acetate) (EVA) exist in backbone, terminal, and branch positions. The VA moieties were converted to carbon-carbon double bonds (∼CH=CH∼) by deacetylation reaction. By deacetylation, the backbone VA group was converted to 1,4-unit (∼CH2CH=CHCH2∼) while the terminal and branch ones were converted to 1,2-unit (∼CH=CH2). A novel analytical method for determination of ratio of backbone and terminal/branch VA contents was developed using off-line pyrolysis and transmission-Fourier transform infrared spectroscopy (FTIR). The analytical method included sample preparation of deacetylated EVA coated on NaCl window for transmission-FTIR analysis and calculation of backbone and terminal/branch VA contents using quantitative analysis of 1,4- and 1,2-units of the deacetylated EVA. Influence of deacetylation conditions (pyrolysis temperatures and times) on degree of deacetylation and other side reactions was also investigated, and proper deacetylation condition was suggested. From the experimental results, proper off-line pyrolysis condition of EVA coated on NaCl window was 300 °C for 60-80 min. The novel analytical method was reliable with the experimental error of below 5%.