Preparation and properties of soapless poly(styrene–butyl acrylate–acrylic acid)/SiO2 composite emulsion

Abstract

Soapless emulsion polymerization of styrene-butyl acrylate-acrylic acid was carried out using single or combined polymerizable emulsifiers, such as hydroxypropyl methacrylate sodium sulfate (HPMAS), sodium vinyl sulfate, and vinyl alkylphenol polyether sulfates (NRS-10), in the presence of colloidal nano-SiO2 solution in order to obtain films with high degree of hardness and water-resistance. Monomer conversion, formation of coagulum, viscosity, particle size, size distribution, and surface tension of the emulsions, as well as the film properties, were determined and compared with those of an emulsion prepared with the conventional emulsifier sodium dodecyl sulfate and polyoxyethylene octylphenol ether. Emulsions prepared from a mixture of two polymerizable emulsifiers NRS-10 and HPMAS (1:1, weight ratio) have presented high monomer conversion, low coagulum, and small particle sizes. When the emulsifier level increased within a certain level, the monomer conversion increased but particles size decreased. Increased amounts of reactive emulsifiers led to low monomer conversion, large amount of coagulum and small particle sizes. With the increase of nano-SiO2 the particle sizes and the viscosity of the emulsion also increased. The introduction of reactive emulsifiers improved the water-resistance of the resulting films, and the addition of nano-SiO2 increased the hardness of the coatings. Under optimal conditions, the coatings made from emulsions produced from a combination of reactive emulsifiers such as NRS-10 and HPMAS (1:1, weight ratio) at 2 % level (based on monomer weight) exhibited remarkable hardness, adhesion force and water-resistance.