Epoxy putties use two components to create a hard, steel-like, material when mixed in the correct ratio. Embedded in one part of the putty is fiber, steel or plastic particles, which increase the strength of the hardened product. This allows certain types of epoxy to be machined and milled to create small replacement parts for damaged equipment. Selecting the correct epoxy putty for a certain application requires knowing the type of material being repaired or sealed with the epoxy, the use of the repaired part and the environment in which the repaired product will be used or stored.
Chemicals contained in the resin of epoxy determine the compatibility between the putty and the material being repaired. Certain types of epoxy resin are designed to adhere to plastics, others to wood and other to metals. Matching epoxy putty to the base material ensures a bond equal to or greater than the strength of the base material. A compatibility chart printed on the epoxy putty label will often state materials compatible with the epoxy putty. Beyond compatibility, other factors determine the ability of applied epoxy putty to remain bonded to the material without breaking down or losing strength.
Water-resistant epoxy putty allows for a repair on damaged parts used in and around water or other non-caustic fluids. Some types of epoxy putty can be applied and will cure under water, while others can be applied to damp surfaces. Some require a dry surface until it bonds to the base material. Certain types of putty break down when subjected to moderate exposure to fluids and should not be used for repairs subject to exposure to fluids unless specified by the manufacturer. The hardness of a cured epoxy putty will be an indicator of whether or not it will contain enough strength for machining to form structural connections.
Metal-based epoxies contain particles matching the composition of the base material. The added metal particles work through mixed epoxy to create a strong bond capable of holding machined threads and supporting threaded fasteners. Selecting a strong epoxy is also a factor when using epoxy putty to fill voids in products made of wood. Wood-based epoxy putties create a strong bond with the base material and allow the cured repair to be sanded, blending it in with the area surrounding the cured epoxy. Studying each factor before using epoxy putty will ensure a long-lasting, durable repair.