Study On Waterborne Polyurethane Cladding Of RDX

Waterborne polyurethane (WPU) had characteristics of small odour, environment friendliness, being easy operation and Processing. WPU was used to coat RDX to decrease sensitivity of RDX, also meet the demands of green chemistry. Compared with solvent-borne polyurethane, WPU had disadvantages of low adhesion intensity, poor water-resistance and surface wettability for it used water as dispersion medium, then was unfit to coat the RDX. So the aim of this paper was increasing the adhesion intensity, water-resistance and surface wettability of WPU to coat RDX completely and uniformly.A waterborne polyurethane modified by epoxy resin and Siloxane coupling agent was synthesized, in which diisocyanate (TDI) and polyether(PTMG) were main materials, and the dimethylol propane acid(DMPA) as hydrophilic chain extender agent, the epoxy resin (E-44) and Siloxane coupling agent as cross-linking agent. The structure of waterborne polyurethanes was analyzed by FTIR. The influence of many factors to the properties of emulsion, Mechanical properties, water resistance of the film and the properties of coated RDX were discussed in details, such as R (the radio of NCO and OH), the content of DMPA, the content of E-44 and Siloxane coupling agent. The optimum technology condition was:R (the radio of NCO and OH) is 2.6, the content of DMPA is 7%, the content of epoxy resin (E-44) is 7%, the content of siloxane coupling agent is 2%.Waterborne polyurethanes (WPU) modified with epoxy resin (E-44) and Siloxane coupling agent were used as RDX coating agent. The effect of the coating method, coating time, coating temperature, the amount of WPU, the size of the RDX particles and the amount and kinds of surfactant on the mechanical sensitivity, thermal sensitivity and dispersion of the coated RDX were researched. The optimum coating process conditions have been gotten by the orthogonal test. The experimental results showed Monophasic coagulation method was superior to in-situ polymerization. When RDX was coated by Monophasic coagulation method, coating time is 30 to 40min, coated temperature is 40℃, the amount of WPU is 2%, RDX is 200-300 mesh size and the amount of surfactant is 0.9%,H50 is 48.5cm,and the 5s exploding point is 280.5℃, and the surface of the coated RDX particles is smooth, as well the residues between particles is little and the dispersivity is better.