EFFECT OF BLOCKING-AGENTS ON THE SHOCK ABSORBING PROPERTIES OF THE FILMS OF POLYURETHANE ADHESIVES

Various 4,4-diphenylmethane diisocyanate (MDI) based polyurethane adhesives have been developed using polyethylene glycols (PEG) of different molecular weights. The formulations were modified using different-blocking agents to inhibit the isocyanate-moisture reaction. Composites of poly(methyl methacrylate) sheets were developed in which these adhesives gave transparent films and their shattering characteristics were tested in a bullet firing machine developed here. The damaged area was measured and used to characterize the adhesive strength. The molecular weight of the soft segment(diol) and the nature of the blocking agent both were found to affect drastically the urethane film properties.