Christopher P. Christenson

Modeling Mechanical Properties of Segmented Polyurethanes

We review recent developments in modeling mechanical properties of segmented polyurethanes. Polyurethanes, poly(urethaneureas), polyureas, and polyisocyanurate materials are widely used in a variety of industries due to the versatility of their properties. We concentrate on segmented polyurethane elastomers and discuss the relationship between formulation variables, polymer morphology, and polymer mechanical properties (Young’s modulus, tensile stress-strain curves, etc.). Specifically, we show how one can derive predictive structure—property relationships by combining thermodynamic block copolymer theory with micromechanical models. The resulting predictions for Young’s modulus and stress-strain curves compare favorably with

Real-Time Measurement Of Polyurethane Foam Reactions And Hydrogen-Bonding By FT-IR Spectroscopy

The reaction and hydrogen-bond formation kinetics which occur in polyurethane foams will have an ultimate effect on the properties of these materials. Measurement of several urethane and urea carbonyl absorptions (free and hydrogen-bonded) provides two important pieces of information: (1) the chemical reactions which occur and (2) the progression of hydrogen-bond formation after reaction has completed. An attenuated total reflectance (ATR) Fourier-transform infrared spectroscopic technique has been previously developed which allows real-time data to be obtained during the foaming reaction 1,2. The authors have adapted a similar system to studying foams in order to more quantitatively interpret the real-time data in terms of the complex hydrogen-bonding structure. The vibrational assignments used for the carbonyl region of polyurethane foam spectra are as follows: 1732 cm-1 free urethane 1712 free urea 1701 ordered hydrogen-bonded urethane 1699-1653 monodentate hydrogen-bonded urea (Fig. 1) 1641 bidentate/ordered hydrogen-bonded urea. (Fig. 1)