A new research deals with synthesizing high solid content waterborne polyurethanes (WPUs) by using poly(propylene carbonate) glycol (PPC) as the soft segment, methylene-bis(4-cyclohexylisocyanate) (HMDI) and 1,4-butanediol (BDO) as the hard segments, 2,2-bis(hydroxymethyl)butyric acid (DMBA) and 2-[(2-aminoethyl) amino]-ethanesulfonic acid monosodium salt (AAS) as the donors of hydrophilic groups. Except for PPC, , polypropylene glycol (PPG) and polytetramethylene ether glycol (PTMG) were also used as soft segments in the synthesis of WPUs (PPG-WPU and PTMG-WPU, respectively). The characterization of WPUs emulsions was performed by particle size and distribution, storage stability and viscosity. The structure, mechanical properties, acid and alkali resistance, water absorption and thermogravimetric analyses (TGA) of WPU films were also characterized.
It was revealed that the emulsion viscosity increased slowly at low solid contents and then showed an abrupt change when the solid content exceeded 52%.
The water absorption rate of the PPC-WPU film was slightly lower than that of the PPG-WPU film but higher than that of the PTMG-WPU film. Moreover, the crystallinity of the PPC-WPU film was lower than that of the PTMG-WPU film due to the irregular structure of poly(propylene carbonate) glycol.
This article is published in Progress in Organic Coatings, Volume 122, September 2018, Pages 38-44.