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This book reports on studies of the synthesis, morphology and the thermal and mechanical characterisation of a range of urethane-acrylic hybrid dispersions. N-methyl pyrrolidone (NMP) was used as a co-solvent in the preparation of some of these polyurethane dispersions (PUDs). NMP is commonly used as a co-solvent in PU coatings as it acts as both a processing and also as a coalescing aid. Environmental legislation will eventually demand its replacement. To this end, NMP was replaced in the synthesis by methyl methacrylate, or styrene. These monomers lead to the formation of urethane-acrylic hybrids. The monomer type and the composition, the glass transition temperature, controlled by copolymerising with n-butyl acrylate, the mode of monomer addition and the synthesis techniques were the main variables studied in this programme. The advantages of these hybrids with respect to latex blend systems were also studied.