Crosslinked polymers are polymers in which long polymer chains are crosslinked together to form a 3D matrix of interconnect polymer chains. More specifically, a polymer has been crosslinked when the entire portion of polymer has been exposed to the cross-linking method. Its mechanical properties depend strongly on the crosslink density. Low crosslink densities increase viscosities of polymer melts. Medium level crosslink densities turn gummy polymers into elastomeric, high strength materials. High level crosslink densities cause materials to become rigid. Examples of crosslinked polymers include polyester fiberglass, adhesives, vulcanized rubber, epoxy resins.