Solving the film formation dilemma: blends of soft core–hard “shell” particles

Abstract

The use of soft core–hard “shell” polymer particles is an alternative to overcome the film formation dilemma (achieving, at the same time, good film formation at a low temperature and good mechanical properties at a usually higher service temperature). In this article, blends of soft core–hard “shell” particles of different sizes have been prepared, and it has been observed that by adding tiny amounts of small particles (e.g., 1 wt %) to big particles, film formation can be substantially improved (lower minimum film formation temperature (MFFT) and higher critical cracking thickness (CCT)). Furthermore, mechanical properties of the films are also improved (higher elongation at break and toughness, maintaining Young’s modulus and the stress at break) without affecting the water sensitivity of the film. It has been found that the viscoelastic properties of the small particles must be similar to those of the large ones in order to have a significant effect.