Semi-crystalline/amorphous latex blends for coatings with improved mechanical performance

Multiphase latex particles containing semi-crystalline domains can be used to reinforce the mechanical properties of coatings made using emulsion polymers, but their synthesis can be challenging. In this work, we show that simple latex blends involving a semi-crystalline phase can also lead to significantly improved mechanical performance. A series of amorphous and semi-crystalline polymer latexes are synthesized and the mechanical properties of films cast from blends of the latexes are measured. By tailoring the particle size of the latexes, it is shown that blends can result in improved mechanical performance. This effect is related to the film microstructure, which is demonstrated through simulations of packed blends of latex particles that show the particle size and relative weight fraction govern the statistical probability of contact between amorphous and semi-crystalline particles. By balancing the continuity of contact between semi-crystalline latex particles, which leads to stiffer films, and the low T-g amorphous latex, which improves elongation at break, films can be obtained with simultaneously improved stiffness and toughness. The improvement in mechanical properties can also be seen in practical measures relevant to coatings, such as blocking resistance, where the latex blends showed substantial improvement compared to the amorphous latexes.