Polyacetals or simply acetals under the common trade name Delrin® differ from other polymers due to the presence of an oxygen heteroatom in their monomer giving an heterochain polymer. The basic polymer unit is usually formaldehyde [—CH—O—]n. Polyacetals resins are obtained by the polymerization of formaldehyde using trioxanes to give the homopolymer while copolymers are usually prepared by incorporating other monomers. The main properties of acetals include high melting point, elevate strength and stiffness, low friction coefficient, and high resistance to fatigue. Higher molecular weight increases toughness but reduces melt flow. The excellent dimensional stability and toughness of the acetal resins recommends their use for gears, pump impellers, other types of threaded connections such as plugs, mechanical uses. The material has an upper useful temperature limitation of ca. 105°C. The chemical resistance indicated in the literature shows a wide range of tolerance for various inorganic and organic products. As with many other resins, this formaldehyde polymer will not withstand strong acids, strong alkalis, or oxidizing media.
