In a study, a series of novel diol chain-extender trimethylol propane monoesters were synthesised to prepare novel aqueous polyurethane dispersions.
Preparation and assistant-film-forming performance of aqueous polyurethane dispersions. Source: pixabay.com/CCO colorless acetonitrile liquid
They were used as a polymer coalescent to assist the film forming of high Tg polyacrylate latexes.
The results showed that the aqueous polyurethane dispersion (PUD) prepared from trimethylol propane monolaurare (TMPLA) with long-chain alkyl groups displayed excellent assistant-film-forming ability. The assistant-film-forming ability of PUD was increased with decreasing of NCO/OH molar ratios and hard segment proportions. The optimum preparation process of better assistant-film-forming PUD was that isophorone diisocyanate, polyether 220 (N220), TMPLA and adipic acid dihydrazide as reactants, 1.5 of the NCO/OH molar ratios, 55/45 of the soft/hard segment mass ratio and 5% of ω (DMPA).
The high Tg polyacrylate latexes with PUD could form a continuous transparent film at 5°C with 30 g L−1 of the VOC contents and display good film performance. The novel aqueous polyurethane disepersions are a promising approach for the formulation of waterborne wood coatings with ultralow VOCs contents.
The study is published in: Progress in Organic Coatings, Volume 105, April 2017, Pages 9–17
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