Colorless, highly transparent, thermoplastic, synthetic resins made by the polymerization of acrylic derivatives, chiefly from the esters of acrylic acid, CH 2:CH COOH, and methacrylic acid, CH 2:C(CH 3) COOH, ethyl acrylate and methyl acrylate. Glacial acrylic acid is the anhydrous monomer with less than 2% moisture. It can be esterified directly with an alcohol. Vinyl acrylic acid, CH 2:CHCH:CHCOOH, with a melting point of 80 C, is made from acrolein and malonic acid. It polymerizes on heating.
The resins vary from soft, sticky semisolids to hard, brittle solids, depending upon the constitution of the monomers and upon the polymerization. They are used for adhesives, protective coatings, finishes, laminated glass, transparent structural sheet, and molded products. Acrylic resins, or acrylate resins, are stable and resistant to chemicals. They do not cloud or fade in light when used as laminating material in glass and are used as air-curing adhesives to seal glass to metals or wood. Water-based acrylics are used for the formulation of caulks and sealants. They have better adhesion and weather resistance than butyl rubbers and dry more quickly. The sealants usually contain about 80% solids. A hydrogel sealant of acrylates and water, developed at Germany's Fraunhofer Institute, automatically seals underground pipe joints by swelling on water contact in the event of a leak from a crack in service.
Most acrylic plastics are based on polymers of methyl methacrylate, which may be...
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