Morris A. Mendelsohn

Characteristics of a Series of Energy-Absorbing Polyurethane Elastomers

Abstract Compositional effects were measured on a series of polyurethanes prepared by extending MDI-terminated PTMG prepolymers with dihydric alcohols and MCHDI-terminated prepolymers with diamines. The tensile and compressive stiffness and hysteretic loss increased while the resilience decreased with a decrease in the isocyanate equivalent weight of the prepolymer. Polyol chain extenders having an aromatic structure provided greater rigidity and increase in temperature on compressive cycling than did their aliphatic counterparts. Structural linearity and symmetry of both the aliphatic and aromatic extenders promoted greater rigidity and resiliency and less damping. Although direct replacement of MDI with MCHDI gives softer polyurethanes, use of the aromatic diamine extenders with the MCHDI-terminated prepolymers gave materials displaying the least resilience and greatest rigidity under static test conditions and the highest increase in temperature on compressive cycling. However, a significant increase i...

A Comparative Study Of The Degradation Of Elastomeric Sealants In The Environment Of The Solar Collector

Elastomers employed as gaskets and caulking compounds play an important role in maintaining the energy efficiency of solar collectors by reducing the accumulation of foreign material on the surfaces of the glazing and absorber. Collector efficiencies decrease considerably from the collection of dust and condensed pollutants, and from degradation products evolved from the polymeric components of the solar collector. The proper functioning of the sealants depends upon their resistance to environmental factors that include extremes of temperature, oxygen, ozone, water and ultraviolet radiation. This paper describes several of the methods of evaluation of the elastomeric polymers, and relates the degradation processes to the nature of the polymeric material. In addition to the outgassing studies, data are also presented on the effects on mechanical properties of the various sealants during exposure to thermal and hydrolytic aging conditions.