Bookbinding and the Conservation of Books
A Dictionary of Descriptive Terminology

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synthetic resins

A group of complex, partially amorphous, organic semi-solid or solid substances that are produced by chemical reaction or by polymerization of relatively simple compounds. Synthetic resins are comparable to natural resins in various physical properties but are considered to be superior to them in that they are more uniform, possess greater clarity, durability, flexibility and resistance to chemical change. The synthetic resins include: 1) formaldehyde condensation products of phenol, urea, and melamine; 2) reaction products of polyhydric alcohols and polybasic acids (alkyd and polyester resins); 3) polymerization products of acrylic acid and its derivatives (acrylic resins) or styrene (polystyrene): and 4) polymers of butadiene and its derivatives, or copolymers, with other materials (synthetic elastomers, etc.).

According to the manner in which they react to heat and pressure, synthetic resins are classified broadly as being either thermoplastic or thermosetting. Although the cellulose polymers, cellulose acetate, cellulose nitrate, and ethyl cellulose, are prepared from natural materials and, therefore. do not conform to the definition of a synthetic resin, they are nonetheless classed along with them. These resins also find use in papermaking as adhesives in coating and laminating. as barrier materials, and as agents to impart special properties to paper, e.g., improved wet and dry strength. Synthetic resins are also used extensively in the application of finishes to the grain surface of leather. (17 , 306 )

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