n-Butyl acrylate
The classic soft monomer: butyl acrylate brings flexibility and low-temperature film formation to latex paints, elastomeric coatings and adhesives.
n-Butyl acrylate is the butyl ester of acrylic acid (molecular weight about 128.2 g/mol), a clear liquid with a sharp odor. Its homopolymer has a glass transition temperature of about −54 °C, making it soft and rubbery at room temperature.
BA is copolymerized with hard monomers such as MMA or styrene to set the hardness of acrylic latex binders for architectural paints, elastomeric wall and roof coatings, caulks and pressure-sensitive adhesives. It also appears in solution acrylics and acrylic polyols.
Like other acrylates, BA polymerizes through its C=C double bond by free radicals, usually in emulsion at the factory. Increasing the BA share lowers the copolymer’s Tg and minimum film-forming temperature, improving flexibility and crack resistance but increasing tack and dirt pickup.
BA monomer is flammable, irritating and a skin sensitizer. It is shipped with inhibitor and needs air in the headspace to keep the inhibitor working. Residual monomer in finished latex products is kept low.
MMA makes films hard and BA makes them soft. Adjusting the ratio tunes the copolymer Tg for the climate and use.
Only trace residual monomer, typically very low. Raw monomer handling is where the main hazards lie.
