An increase in the tensile strength of BA/MMA/AA/IPO copolymer cured latex film is attributed to the amide-ester cross-linkages formed by chemical reaction of AA and IPO units between latex particles. Amide-ester formation in this copolymer is not a linear function of temperature. Cross-linking between latex particles causes decreased mobility of remaining AA and IPO units, and further heating is required in order for the copolymer to again become fluid enough so that remaining AA and IPO units can react to form amide-ester linkages. An IR method is given for the quantitative analysis of SIPO copolymers.
