Chemical cross linking is the intermolecular or intramolecular joining of two or more molecules through covalent bonding. These covalent bonds have high durability, and thus are stable thermally and mechanically. Chemical crosslinks are created by chemical reactions that are initiated through pressure, heat, change in PH, or irradiation. An example of chemical crosslinking is when an unpolymerized or partially polymerized resin is mixed with crosslinking reagents; in turn results in a chemical reaction that forms crosslinks. Another example is using electron beam processing for the crosslinking of the C type of crosslinked polyethylene.