Paraloid B-72 or B-72 is a

thermoplastic A thermoplastic, or thermosoftening plastic, is any plastic polymer material that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling. Most thermoplastics have a high molecular weight. The polymer chains as ...

resin that was created by

Rohm and Haas Rohm and Haas Company is a US manufacturer of specialty chemicals for end use markets such as building and construction, electronic devices, packaging, household and personal care products. Headquartered in Philadelphia, the company is organiz ...

for use as a surface coating and as a vehicle for flexographic ink. Subsequently, it has found popular use as an adhesive by

conservator-restorer A conservator-restorer is a professional responsible for the Conservation-restoration of cultural heritage, preservation of artistic and cultural artifacts, also known as cultural heritage. Conservators possess the expertise to preserve cultural ...

s, specifically in the conservation and restoration of ceramic objects, glass objects, the preparation of

fossils A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

, the hardening of piano hammers, and can also be used for labeling museum objects.

Uses

B-72 is a durable and non-yellowing acrylic resin, which can be described chemically as an

ethyl methacrylate Ethyl methacrylate is the organic compound with the formula C2H5O2CC(CH3)=CH2. A colorless liquid, it is a common monomer for the preparation of acrylate polymer An acrylate polymer (also known as acrylic or polyacrylate) is any of a group of ...

–

methyl acrylate Methyl acrylate is an organic compound, more accurately the methyl ester of acrylic acid. It is a colourless liquid with a characteristic acrid odor. It is mainly produced to make acrylate fiber, which is used to weave synthetic carpets. It is a ...

copolymer In polymer chemistry, a copolymer is a polymer derived from more than one species of monomer. The polymerization of monomers into copolymers is called copolymerization. Copolymers obtained from the copolymerization of two monomer species are som ...

. It is soluble in

acetone Acetone (2-propanone or dimethyl ketone) is an organic compound with the chemical formula, formula . It is the simplest and smallest ketone (). It is a colorless, highly Volatile organic compound, volatile, and flammable liquid with a charact ...

ethanol Ethanol (also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound with the chemical formula . It is an Alcohol (chemistry), alcohol, with its formula also written as , or EtOH, where Et is the ps ...

toluene Toluene (), also known as toluol (), is a substituted aromatic hydrocarbon with the chemical formula , often abbreviated as , where Ph stands for the phenyl group. It is a colorless, water Water is an inorganic compound with the c ...

, and

xylene In organic chemistry, xylene or xylol (; IUPAC name: dimethylbenzene) are any of three organic compounds with the formula . They are derived from the substitution of two hydrogen atoms with methyl groups in a benzene ring; which hydrogens are su ...

s, among other solvents and solvent mixtures.Phenix, A. 1992. Solvents for Paraloid B-72. Conservation News 48:21–3. One of the major advantages of B-72 as a consolidant is that it is stronger and harder than

polyvinyl acetate Polyvinyl acetate (PVA, PVAc, poly(ethenyl ethanoate)), commonly known as wood glue (a term that may also refer to other types of glues), PVA glue, white glue, carpenter's glue, school glue, or Elmer's Glue in the US, is a widely available adh ...

without being extremely brittle. This adhesive is more flexible than many of the other typically used adhesives and tolerates more stress and strain on a join than most others. The major drawbacks to using B-72 are related to its handling properties: as in the case of other acrylic resins it is difficult to apply as an adhesive and to manipulate with precision. The most suitable solvent for B-72 is acetone. However, solvent mixtures with various proportions of acetone, ethanol, and toluene are frequently used to alter the working time of the resin and to produce slightly different properties (hardness and flexibility, e.g.) in the set resin. Unlike

cellulose nitrate Nitrocellulose (also known as cellulose nitrate, flash paper, flash cotton, guncotton, pyroxylin and flash string, depending on form) is a highly flammable compound formed by nitrating cellulose through exposure to a mixture of nitric acid and ...

, B-72 does not need additives like

plasticizer A plasticizer ( UK: plasticiser) is a substance that is added to a material to make it softer and more flexible, to increase its plasticity, to decrease its viscosity, and/or to decrease friction during its handling in manufacture. Plasticizer ...

s to stabilize its durability. Fumed

colloidal silica Colloidal silicas are suspensions of fine amorphous, nonporous, and typically spherical silica particles in a liquid phase. It may be produced by Stöber process from Tetraethyl orthosilicate (TEOS). Properties Usually they are suspended in an ...

can be added to help with the workability of the resin. Research shows that the silica better distributes the stress and strain that occurs during evaporation of a solvent and during the setting of the adhesive film. Because of its transparency and versatility, conservators, led by Stephen Koob of the

Corning Museum of Glass The Corning Museum of Glass is a museum in Corning (city), New York, Corning, New York, United States, dedicated to the art, history, and science of glass. It was founded in 1951 by Corning Incorporated, Corning Glass Works and currently has a ...

, have recently begun to use cast sheets of B-72 as a fill material in glass objects.

References

{{Reflist Conservation and restoration of cultural heritage Adhesives Brand name materials Acrylate polymers Copolymers