reached and where it is released two types of super absorbent copolymers are considered as particularly useful the first is a copolymer of poly 2 propenamide co 2 propenoic acid sodium salt the second super absorbent copolymer is a sodium polyacrylate and presented as a comparison to demonstrate the particular properties of the first other sap such as polyacrylamide or modified crosslinked poly meth acrylate are also interested for self healing applications these types of copolymers are made up of cross linked polymers which swell into a gel when in contact with water the swelling is a consequence of electrostatic repulsion between charge sites on the copolymers in the presence of water the addition of highly concentrated salt solution will make the gel collapse instantly due to the screening of the charged site on the copolymer the sensitivity towards high salinity has at least one drawback but also advantages the major drawback is that in the presence of ions in the water the copolymer will swell less as well as lose some of its gel strength compared with fresh water this is the case when used in e g cement where high concentrations of calcium ions are present one advantages is that in the event that a cement copolymer system becomes solid like in.