Novel polyurethane dispersions based on renewable raw materials: Stability studies by variations of DMPA content and degree of neutralisation

Renewable resources, especially natural oils, have received increasing attention as raw materials for polymers. The synthesis and characterisation of novel aqueous polyurethane dispersions derived from rapeseed oil are investigated. The applied renewable polyol is high-hydrophobic due to the triglyceride backbone. Dimethylolpropionic acid (DMPA) as internal emulsifier was used to incorporate hydrophilic groups into the polymer chain to achieve stable self-emulsifying dispersions. By neutralisation of the carboxyl groups with triethylamine a predominately electrostatic stabilisation was generated. A weak steric stabilisation by pending chain ends exists beside the predominant electrostatic stabilisation. Outgoing from a DMPA content of 5.6 wt% related to the polymer, the content was decreased successively with the objective being to analyse the influence of ionic concentration and stability. Furthermore, the influence of the degree of neutralisation with respect to the stabilisation of these novel dispersions was investigated