A rapid separation method for gel content determination in pressure sensitive adhesive dispersions and acrylic-based latices for an industrial setting.

A rapid method has been developed for determining gel content in industrial samples such as water-borne pressure sensitive adhesives (PSAs) and acrylic-based latices. The method is based on thermal field-flow fractionation (ThFFF) and evaporative light scattering detection (ELSD). Results are compared to those obtained using a centrifugation-based gravimetric method. Sample preparation was an important aspect of the developed analysis. Although the latices and PSA are similar in chemistry, they required different handling and sample preparation procedures. The PSA sample, with its sub-ambient glass transition temperature (Tg), formed visible macro-gels, if it was added directly to tetrahydrofuran (THF). No macro-gels were formed, if the PSA was pre-diluted in water and then suspended in THF. By using this new sample preparation procedure and ThFFF total analysis time was reduced from days to a few hours. The gel content in water-borne pressure sensitive adhesives and acrylic-based latices varied from 5 to 51% with an average relative standard deviation (RSD) of 11%.