An umbrella term used to describe a family of thermoplastic materials that are the result of polymerizing or co-polymerizing vinyl monomers with a carbonyl or nitrile group attached, including but not limited to Acrylic acid, Methacrylic acid, or Acrylonitrile. The generic description of these materials is represented as: (CH2=CHCO2R), with R representing the organic group. Acrylic polymers were first prepared in 1880 by the Swiss chemist Georg W.A. Kahlbaum. In 1901, in Germany, Otto Röhm described his acrylate synthesis work in “Polymerization products of acrylic acid”, his doctoral thesis then later patented the process in 1915. Polymethyl methacrylate was first marketed by Rohm and Haas in Germany in 1927. Acrylics have been sold by Rohm & Haas, ICI in England and DuPont in the U.S. since 1931 as glass substitutes (Plexigum®, Plexiglas®, Perspex® and Lucite® ) and as adhesives, varnishes, and paint media (Acryloid® F-10, Lucite® 44, Acryloid® B-72). Magna solvent-soluble acrylic artist paints were first sold in 1947 by Bocour, while Liquitex, an acrylic emulsion paint, was first marketed in 1954. The first Acrylic fiber, Orlon®, was introduced in 1950.
Synonyms and Related Terms
acrylics; acrylate; methacrylate; résine acrylique (Fr.); resina acrilica (It.); polímero acrílico (Esp.); resina acrílica (Esp.); acrílico (Esp.); resina acrílica (Port.)
Examples: Acryloid® [Rohm & Haas];Plexigum® [Rohm & Haas]; Lucite® [DuPont]; Paraloid® [Rohm & Haas]; Elvacite® [DuPont]; Plexiglas® [Rohm & Haas]; Perspex®; Magna [Bocour]; Liquitex [Permanent Pigments]; Shiva [Shiva]; Hyplar Acrylic Colors[Grumbacher]; Aqua-tec [Bocour]
- Paints, coatings, and adhesives
- Fabrics, textile and leather finishes
- Windows and clear glazing
- Mounts and display cases
Acrylates are considered to be stable to light and aging but the monomers will irritate the skin and eyes. Some resins are combustible but often slow-burning and self-extinguishing.
Some acrylate polymers crosslink, which is why only specific ones are recommended for use as coatings in conservation. Iso-Amyl Methacrylate, sometimes referred to 27H in conservation publications, was infamously shown to crosslink after it had been promoted for use as a paint varnish.
Some acrylic pressure sensitive adhesives that are designed NOT to dry, may give off acetic acid and acrylic acid; both are corrosive.
Dust is flammable
Physical and Chemical Properties
Acrylic resins range from soft, tacky materials to hard solids that are glossy, optically clear and have good shock and water resistance. Acrylics tend to be stable to outdoor weathering and resistant to some chemicals including mild acids and bases.
Soluble in mineral spirits, turpentine, aromatic hydrocarbons, chlorinated hydrocarbons, esters, and ketones.
Insoluble in water, ethanol.
Softening points (Tg in C) are:
- polymethyl methacrylate (105-125)
- polyethyl methacrylate (65)
- poly iso-butyl methacrylate (48)
- poly n-butyl methacrylate (22)
- polymethyl acrylate (9)
- polyethyl acrylate (-24)
Refractive Index = 1.5
Resources and Citations
- Feller, R.L., N. Stolow, and E.H. Jones. 1985. On picture varnishes and their solvents. Revised and enlarged ed. Washington, D.C.: National Gallery of Art.
- R. J. Gettens, G.L. Stout, Painting Materials, A Short Encyclopaedia, Dover Publications, New York, 1966 Comment: Refractive index range from 1.482 to 1.521
- C.V.Horie, Materials for Conservation, Butterworth-Heineman, London, 1997
- G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971
- Encyclopedia Britannica, http://www.britannica.com Comment: Acrylic polymers - polymethyl acrylate first made in 1880 by the Swiss chemist Georg W.A.Kahlbaum; acrylic polymers described in depth by by Otto Rohm in 1901
- Ralph Mayer, A Dictionary of Art Terms and Techniques, Harper and Row Publishers, New York, 1969 (also 1945 printing)
- ASTM, "Standard Terminology Relating to Paint, Varnish, Lacquer and Related Products", Annual Book of ASTM Standards, Section 6, Paints, Related Coatings and Aromatics, ASTM, D16, 7-Jan, Jul-96
- Matt Roberts, Don Etherington, Bookbinding and the Conservation of Books: a Dictionary of Descriptive Terminology, U.S. Government Printing Office, Washington DC, 1982
- The Dictionary of Art, Grove's Dictionaries Inc., New York, 1996 Comment: Acrylic painting - acrylics discovered by Otto Rohm-1880, patented 1915
- Reed Kay, The Painter's Guide To Studio Methods and Materials, Prentice-Hall, Inc., Englewood Cliffs, NJ, 1983
- Michael McCann, Artist Beware, Watson-Guptill Publications, New York City, 1979
- Theodore J. Reinhart, 'Glossary of Terms', Engineered Plastics, ASM International, 1988 Comment: Website Hyperlink