Influence of Particle Surface Properties on Film Formation from Precipitated Calcium Carbonate/Latex Blends Jiansheng Tang, 1,3 Eric S. Daniels, 1,2 Victoria L. Dimonie, 1,2 Andrew Klein, 1,2 Mohamed S. El-Aasser 1,2 1 Emulsion Polymers Institute, Lehigh University, Iacocca Hall, 111 Research Drive, Bethlehem, Pennsylvania 18015 2 Department of Chemical Engineering, Lehigh University, Iacocca Hall, 111 Research Drive, Bethlehem, Pennsylvania 18015 3 NOVA Chemicals, 400 Frankfort Road, Monaca, Pennsylvania 15061 Received 11 September 2001; accepted 14 December 2001 Published online 14 August 2002 in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/app.11000 ABSTRACT: The surface properties of films prepared from a blend of precipitated calcium carbonate pigment (PCC) and poly(n-butyl methacrylate-co-n-butyl acrylate) [P(BMA/BA); T g = 0°C] latex were investigated in terms of the surface characteristics of the PCC and P(BMA/BA) latex particles. It was found that the presence of carboxyl groups on the P(BMA/BA) latex particles significantly improved the uniformity of the distribution of the PCC particles within the P(BMA/BA) copolymer matrix and the gloss of the resulting films. This phenomenon could be explained by an acid-base reaction between the PCC particles and the car- boxylated P(BMA/BA) latex particles. Studies on the influ- ence of the composition of PCC/P(BMA/BA) latex blends on the gloss and transparency of the films were also per- formed, which led to the determination of the critical pig- ment volume concentration (CPVC) of this system, which was found to be 42 vol %. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 891–900, 2002 Key words: blends; films; dyes/pigments; latexes; interfaces INTRODUCTION In the formulation studies, it was found that the op- posing -potential values of the PCC particles (posi- tive) and the P(BMA/BA) latex particles (negative) was the reason that stable PCC/P(BMA/BA) latex blends could not be obtained if no stabilizer is added. The addition of sodium polyacrylate (NaPA) to the PCC slurry changed the -potential of the PCC parti- cles from positive to negative, resulting in the forma- tion of a stable PCC/P(BMA/BA) latex blend. In latex coatings applications, pigments and extenders are added to a latex binder to achieve desired gloss, opacity, and color. Pigments can be organic or inorganic. In this article, film formation of blends of inorganic pig- ment and latex binder was studied. The inorganic pig- ment used in this work is precipitated calcium carbonate pigment (PCC) and the latex binder is poly(n-butyl methacrylate-co-n-butyl acrylate) [P(BMA/BA)] latex. As calcium carbonate pigments are heavily used in paper coatings, 1,2 the surface properties of the calcium carbon- ate pigmented latex films are very important. 3 Thus, academic research aimed at gaining an understanding of the relationship between various film formation param- eters and the properties of calcium carbonate pigmented latex films has been triggered. Of greatest interest in this research program is the study of the surface morphology and the surface properties of films obtained after drying blends of precipitated calcium carbonate pigment and P(BMA/BA) latex. One focus of this work is the inves- tigation of the influence of carboxyl groups that were present on the P(BMA/BA) binder particles on the sur- face properties of the PCC/P(BMA/BA) blend films. Although stabilizers are widely used in the formu- lation of pigmented latex coatings, 4–6 academic re- search on the mechanism through which the pigment stability is increased by the presence of suitable stabi- lizers is very limited. However, formation of a stable pigment/binder blend is a prerequisite for obtaining pigmented latex films and the investigation of the film properties. In this article, the effect of adding sodium polyacrylate (NaPA), which is commonly used in coat- ings formulations in preparing stable PCC/P(BMA/ BA) latex blends, was investigated. EXPERIMENTAL Materials n-Butyl methacrylate (BMA; Aldrich; reagent grade), n- butyl acrylate (BA; Aldrich; reagent grade), and methacrylic acid (MAA; Aldrich; reagent grade) mono- mers were used. All monomers were cleaned by passing them through an inhibitor removal column (Aldrich). Anionic and cationic ion exchange resins (AG 1-X4 and Correspondence to: M. S. El-Aasser. Journal of Applied Polymer Science, Vol. 86, 891–900 (2002) © 2002 Wiley Periodicals, Inc.