Gel-containing polymers are used in many industrial applications, such as coatings, plastic additives, personal care, and adhesives, and their gel fraction and crosslinking density are among the key factors in determining their application performance.  The most common way of analyzing the gel fraction and crosslinking density is the gravimetric gel fraction/swell ratio test, where the polymer solution is centrifuged to isolate the gel content from the serum phase for gel fraction determination. The swell ratio is defined as weight ratio of the swollen gel to dry gel.  Higher swell ratio indicates lower crosslinking density.  However, the gravimetric method is very time-consuming and often lacks precision, especially for samples with low gel fractions.  In this study, a series of polyacrylic copolymers with different levels of gel fraction and swell ratio were synthesized using emulsion polymerization with various types of crosslinkers and crosslinker loading levels.  To develop a fast and robust method for gel fraction and swell ratio measurement, we utilized an asymmetric flow field flow fractionation (AFFFF) technique to separate the sample soluble fraction from its gel fraction and gauged the swell ratio by using the ratio of the gel size (Rg^3) to molecular weight (Mw) measured from on-line multi-angle light scattering (MALS) detector.  Our results showed good correlation of the gel fraction and swell ratio between the AFFFF method and the gravimetric gel fraction swell ratio method and demonstrated that AFFFF can be used as a fast and robust way to determine the polymer gel fraction and swell ratio.

Analysis of gel fraction and swell ratio of polyacrylic copolymers using asymmetric flow field flow fractionation

2019 Fall National Meeting

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