Polyester resins

Any polymer whose repeating units are linked together by ester bonds is called a polyester. According to this broad definition, the family of polyesters includes both linear or also saturated polyesters (PET: polyethylene terephthalate) and unsaturated polyesters (crosslinking resins) formed during the polymerization of saturated or saturated and unsaturated ester monomers.

Unsaturated polyester resins in the composite industry are synthetic resins which consist of unsaturated yarn molecules prepared by polycondensation and which can be cured to a crosslinked solid product by copolymerization with molecules of a reactive solvent (monomer). Although there are practically very few unsaturated bonds in the copolymerized solid state, so the term unsaturated polyester is incorrect, this term, "unsaturated polyester", has become commonplace.