Polyester based polyurethanes were synthesized from low molecular weight polyester (Mn 2000) and 4,4′‐methylene bis(phenyl isocyanate) (MDI) with butanediol as a chain extender and glycerol as a crosslinker. The polyester was synthesized from adipic acid and glycol which was a mixture of 1,6‐hexanediol and 1,2‐propanediol. The effect of the crosslinker content on the degree of H‐bond formation in the hard segments and the physical properties of polyurethanes were studied by differential scanning calorimetry (DSC), thermal mechanical analysis (TMA), Fourier transform infrared spectroscopy (FTIR) and mechanical testing. The experimental results revealed that incorporation of a triol crosslinker into the hard segments of polyurethane results in a decrease of hard segment H‐bond formation. The mechanical data indicate that the mechanical properties of polyurethanes depend on the concentrations of physical and chemical crosslinks and that there is an optimum concentration of triol crosslinker for the tensile stress and elongation properties. © 1998 Society of Chemical Industry

One thick filament-wound composite in the form of a large thick-walled cylinder with locally orthorhombic symmetry has been measured by ultrasonic velocity to calculate its elastic moduli. The basic assumption was that small sections of the composite could be treated as a homogeneous body analogous to a crystal for ultrasonic propagation. The experimental work and the results as best expressing homogeneous body theory are presented. Because of the high anisotropy with the normal to the layers (the three-direction) much different from the axial and hoop directions, it was necessary to calculate slowness surfaces with approximate values of c 13 and c 23 in order to find the directions of the Poynting vectors to use in making actual measurements on c 12 and c 13 . The elastic moduli of a thick composite as measured by ultrasonic bulk wave pulse velocity

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