Urea Domain Structure in Polyurethane Foams

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Abstract
Small angle X-ray scattering (SAXS) was used to study the size, spacing, and phase mixing of polyurea domains formed in water-blown slabstock and molded foams. These domains are important in the loadbearing and other mechanical properties of foams since they act as both reinforcing fillers and as physical crosslinkers of the polymer. For polyether polyols, ethy lene oxide (EO) content and distribution, molecular weight, and water level were shown to have effects on domain structure. Foams made from a polyol which contain randomly distributed EO tend to have larger domain sizes and spacings than those from a similar polyol composed completely of propylene ox ide. A polyol which is composed mainly of propylene oxide and capped with a poly(ethylene oxide) block gives foams with somewhat smaller domain spac ings than the polyols with randomly distributed EO units. It was also found that higher polyol molecular weight gives larger domain spacings. The thick ness of the interface between the hard domain and soft domain regions was in creased significantly by EO capping. Comparison of domain spacing with theo retical values of hard and soft segment lengths showed good agreement.