Film formation of hard‐core/soft‐shell latex particles

Abstract Multiphase latex particles can be used to overcome some of the limitations with regards to the mechanical properties of films cast from homogeneous latexes while maintaining a reasonably low minimum film formation temperature (MFFT). In this work, we focus on the synthesis and film formation behavior of a series of hard‐core/soft‐shell latexes with varying compositions. It is shown that below a hard‐core content of around 60 wt% the MFFT is almost exclusively dependent on the glass transition temperature of the polymer that forms the soft‐shell. Above hard‐core contents of 60 wt% there is an abrupt increase of the MFFT and film formation is significantly restricted. This behavior is ascribed to the packing behavior of the hard phase. It is shown that the MFFT can be decreased by the use of blends of core‐shell particles of different size such that the packing fraction of the hard domains is improved. This is demonstrated by the counterintuitive result that a blend of two latexes with high MFFT can result in a latex with significantly reduced MFFT. The mechanical properties of the resulting films are also explored in order to determine the limits of hard‐core/soft‐shell systems with regards to their use in coatings applications.