Applied Research and Development of Adhesives for Bonding Filled Carboxyl Terminated Polybutadienes to Various Substrates

A one-year applied research and development program was conducted on the bonding of carboxy-terminated polybutadiene (CTPB) propellant to various substrate materials encountered in solid propellant rocket motors. Under this program, in addition to CTPB liners, liners were also prepared from polyesters, polyethers, polyurethanes, polyacetal polymers, and epoxy resins. The use of various crosslinkers, emulsifiers, wetting agents, fillers, and stabilizers was also evaluated. Four optimized liner formuations with the best all-round properties were fully characterized. The optimized formulations represented an HC liner formulation with two Ievels of glycerol additive, an HC formulation with a sorbitol additive, and a Butvar polyacetal-type liner. A standard HC-polymer liner formulation, designated as TL-H-304, was used as a control. Unaged liner peel and shear properties were measured at -65°F, 77°F, and 160°F. Samples, aged for 30 days at 160°F, were tested at 77°F only. The liners were tested against propellant, steel, aluminum, magnesium, titanium, epoxy-fiberglass, phenolics, polyisoprene, and butadiene-acrylonitrile as substrate materials. The steel, titanium, and polyisoprene rubber substrates gave the best adhesive results. The substitution of asbestos and Cab-O-Sil for the Thermax filler in the liner gave comparable adhesive results while the substitution of clay fillers gave poor results. This program was performed while at the Elkton Division of the Thiokol Chemical Corporation in fulfillment of the requirement of Contract N123 (60530–53329A) U.S. NAVAL ORDNANCE TEST STATION, China Lake, California, reported previously in U.S. Naval Report NOTS-TP4283.