Novel Small Scale Procedures for Initial Formulation Selection in the Development of Polyurethane Foams

The small scale mixing methods and assessment techniques described have proved their worth over the past ten years. The methods are simple, quick, reliable, reproducible, economic and have been used successfully to predict behaviour in larger scale mixings in a wide range of development projects. An electric hand drill using a special stirrer is used to mix a basic resin blend with the other formulation ingredients and the foaming proceeds in the mixing cup and has been found to have advantages over the usual method of pouring a larger foam mix into a mould box. The use of a corer which gives quick and accurate density and strength comparisons is described. A stratagraphic method of measuring foam strengths relative to the position from where the core is taken provides useful additional data on relative flow and anisotropy. Also a portable apparatus for the rapid measurement of closed/open cell content is described. All the properties are determined using the same foam cores.