Several aliphatic waterborne polyurethane prepolymers are prepared from isophorone diisocyanate,dimethylolpropanic acid, poly(butylene adipate) (PBA) and polypropylene glyco (PPG).The prepolymers are blocked with 2 methoxyethanol,followed by neutralization pendant carboxyl by triethylamine,then diluted to 50?wt% with methyl ethyl ketone,emulsified by adding deionized water under constant agitation.The principle of emulsification is explained.The aggregated structure of prepolymers in organic solvent is ...