An epoxy resin is a linear molecule of long length terminated at each end by an epoxide group. The name epoxy is derived from the Greek epi meaning "outside" and oxide (oxygen) because this oxygen is outside the group. Epoxy resins are manufactured from chemicals obtained from the natural gas or coke by-product industry. These systems have four outstanding characteristics: (1) exceptionally high adhesion; (2) high chemical resistance; (3) cured expoxy systems are good for resisting temperatures up to 250 degrees F.; (4) no toxicity after curing. While epoxy resin systems can be formulated from very flexible to very hard and brittle compounds, the flexible ones will not stretch much and therefore are not generally suitable for filing joints. However, the polysulfide polymer can be incorporated into a system and cured with a curing agent to provide a rubber-like material. This means that joint sealers can be manufactured in the laboratory with extension characteristics up to 800 percent of their original length. Four basic types of systems can be formed with polysulfides. One, adhesives capable of bonding plastic concrete to hardened concrete or rigid materials to each other. Two, mortars and concretes with a resin instead of cement base that can be used for patching, feather-edging and repair work. Three, sealants which provide flexibility for caulking, sealing joints, and for moving parts of buildings. And four, coatings which give chemical resistance and abrasion resistance as well as protection to concrete.