Quantitative Determination of Vinyl Acetate Content in Ethylene Vinyl Acetate Copolymers Using Multiple Internal Reflection Spectroscopy

The vinyl acetate content in ethylene vinyl acetate (EVA) copolymers is presently being determined by either elemental analysis, saponification, solution or direct transmission infrared analysis of the resin. The major drawbacks of these methods are the time involved and the relative dependence of results on sample handling. Considerably more time is involved if the resin in question is part of a laminated film. Multiple internal reflection (MIR) spectroscopy has been used for qualitative identification of laminated films and coatings, but quantitative analyses had to be done by first separating the film from the laminate and then analyzing for comonomer content by one of the methods previously mentioned or another suitable procedure. The MIR method described in this paper allows for rapid, quantitative determination of vinyl acetate in EVA copolymer resins with minimal sample handling. If the resin is the outer layer of a multi-layered laminate, separation of the layers before analysis is not necessary.