Determination of bound styrene in insoluble emulsion polymerised styrene‐butadiene copolymers

Bound styrene is determined in insoluble emulsion polymerised styrene‐butadiene copolymers by measurement of the 10.3 μm/13.2 μm absorbence ratio using the baseline method. This ratio is obtained from the infra‐red spectrogram of the copolymer. The styrene content is then determined from a standard curve. The standard curve is constructed from absorbence ratios of 10.3 μm/13.2 μm derived from the infra‐red spectrograms of cast films of styrene‐butadiene latices over a range of compositions in which the bound styrene has been determined by nitration of the isolated and extracted copolymers. Styrene content based on nitration is determined from standard curves relating styrene concentration to spectrophotometric absorbence measurements at wavelengths of 285.0 nm, 273.8 nm and 265.0 nm. The source of the styrene for these curves is NBS standard rubber #1500.