Master Bond EP21TP-2 is a very strong two component polysulfide/epoxy based formulation developed by Master Bond Inc. for high performance bonding, sealing, potting and encapsulation. Interestingly it has unique optical characteristics as well, and transmits light over a wide wavelength range, including the infra-red spectrum. It has an index of refraction of 1.58. EP21TP-2 bonds exceptionally well to metals, glass, ceramics, wood, vulcanized rubbers and many plastics and readily develop a high bonding strength of more than 3000 psi at room temperature. It produces durable high strength and tough, flexible bonds which are remarkably resistant to thermal cycling and chemicals including water, oil, fuel and most organic solvents. EP21TP-2 is serviceable over the exceptionally wide temperature range of -62°C to 121°C (-80°F to 250°F) and has good low temperature flexibility.

Master Bond EP21TP-2 can be applied without sagging or dripping even on vertical surfaces. Unlike many other epoxy adhesives, it is relatively insensitive to mixing ratio or substrate cleaning procedures. The hardened adhesive/sealant is an electrical insulator and fully meets the requirements for polysulfide/epoxy type sealants. Typical optical applications range from bonding and potting fiber-optic cables, connectors and terminations, and upgrading the vibration and shock resistance of electro-optic assemblies. Other applications include cementing and coating optical parts, potting LED devices, optical replications, bonding ferrules and connectors, and coating or encapsulating a wide variety of aerospace, fuel tank and laser components.