The relationship between emulsion freeze‐thaw stability and polymer glass transition temperature. I. A study of the polymers and copolymers of methyl methacrylate and ethyl acrylate

Abstract

AbstractEmulsion polymers and copolymers of ethyl acrylate‐methyl methacrylate containing varying amounts of methacrylic acid were subjected to three freeze‐thaw cycles, following adjustment to a pH of about 9.5 with NH3. The minimum amount of acid required to obtain resistance to freezing and thawing was determined. Values for the glass temperature, (Tg) and minimum film formation temperature (MFT) of the polymer were correlated with the minimum required acid content, indicating that more acid is required as the glass temperature decreases. If a polymer is exceptionally hard so that its particles resist irreversible contact under large forces, it would be expected that little or no acid would be required to obtain freeze‐thaw stability. On the other hand, if the polymer particle is so soft (low Tg) as to readily form aggregates, then very high acid amounts would be required. A plot of minimum weight per cent of acid versus Tg or MFT should, therefore, be hyperbolic approaching zero acid at very high Tg values and approaching very high acid levels at very low Tg values. This is indeed the characteristic of the plot of the experimental data.