SYNTHESIS AND PROPERTIES OF ALIPHATIC POLYURETHANES AND MODEL COMPOUNDS CONTAINING ALPHA,ALPHA,ALPHA',ALPHA'-TETRAMETHYL - PARA-XYLYLENE - DIISOCYANATE (HYSTERESIS, ELASTOMER, X-RAY CRYSTALLOGRAPHY)

New materials are needed to replace the rubber compounds which are in current use in certain high stress environments. The rubber materials usually fail due to the high internal temperature which results from compressive cycling under heavy loads. Rubber formulations, such as styrene-butadiene, also fail due to severe mechanical stresses, such as tearing forces.;The properties of p-TMXDI-based polyurethanes are comparable to other polyurethane classes. When 1,4-butanediol was the chain extender, the samples possessed good tensile and tear strength and low glass transition temperatures, with high-temperature softening above 150(DEGREES)C. Compressive fatigue tests on block samples demonstrated the resistance of these polyurethanes to the buildup of high internal temperatures which would cause failure of the polymer.;The model compounds of p-TMXDI provided information on the possible conformation of this unique structure in the polyurethane chains. Until recently, polyurethanes made from diphenylmethane-4,4'-diisocyanate were the only polyurethane class which had been characterized by X-ray scattering and X-ray crystallographic techniques.;Polyurethanes are being examined as possible replacements due to indications of better mechanical strength. However, hysteretic heat buildup in polyurethanes is a major problem. The compound (alpha),(alpha),(alpha)',(alpha)'-tetramethyl-p-xylylene-diisocyanate (p-TMXDI) was examined as a viable component in polyurethanes. Poly-(1,4-butanediol) of two high molecular weights was used as the soft segment, with 1,4-butanediol, resorcinol-1,3-bis((beta)-hydroxyethyl)ether, and 4,4'-isopropylidenediphenol-4,4'-bis ((beta)-hydroxyethyl)ether tested individually as chain extenders and 2-ethyl-2-(hydroxymethyl)-1,3-propanediol and triethanolamine used as crosslinkers. Mechanical and thermal measurements were made on polymers prepared with various ingredient types and ratios. Investigation of the molecular arrangement of the polyurethane samples was made using infrared and X-ray scattering techniques. Low molecular weight model compounds, simulating the polar regions of the polyurethanes, were prepared and characterized by single crystal X-ray diffraction by Dr. Jerry P. Jasinski. Compressive fatigue tests were conducted on some samples which showed good thermal resistance by other tests.