Waterborne polyester is a common eco-friendly material in which ester bonds are easy to hydrolyze. Therefore, we synthesized a series of waterborne comb-like polyesters (WCPEs) with hydrophilic side chains through aza-Michael addition under green and mild conditions. The physicochemical structure of the polyesters was verified by 1 H NMR, FTIR, and GPC characterizations. The pH value of dispersions dropped by less than 0.7 after storage for 2 months. The dispersions remained stable after 6 months at room temperature. In addition, the WCPEs exhibited good wetting and dispersing ability for pigment particles as Tego 740 W, which is a mature pigment dispersant product for waterborne coatings. Moreover, the cross-linked WCPEs exhibited excellent chemical resistance, there was only 1.2% weight loss, and almost no mechanism properties decline for cross-linked transparent films even after treatment under an alkaline environment for 20 days. Thus, the synthesized WCPE has potential application as an alkali resistance eco-friendly material, and possesses excellent performance as pigment-dispersion resin.
Waterborne polyurethanes (WPUs) with high solid contents were synthesized 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. For comparison, 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 particle size and distribution of the emulsions were measured and analyzed by submicron particle size Zeta-potential analyzer and transmission electron microscopy (TEM). The storage stability, contact angle and viscosity of the emulsions were also tested. The structure, mechanical properties, acid and alkali resistance, water absorption and thermogravimetric analyses (TGA) of WPU films were also characterized. The results showed that the WPU emulsions exhibited narrow particle distributions, small particle dimensions, good appearance and excellent storage stability. The emulsion viscosity increased slowly at low solid contents and then showed an abrupt change when the solid content exceeded 52%. PPC-WPU films showed superior overall properties in terms of tensile properties, rubber hardness and T-peel strength relative to the PPG-WPU films or PTMG-WPU films. 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. The hydrogen atom on the α-C atom and the special structure of bonds in the poly(propylene carbonate) glycol molecular chain resulted in excellent acid and alkali resistance but poor thermal stability at high temperature. 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.
Zonglin He,Zhenhong Huang,Jiahui Chen,Ansheng Chen,Jiaoyan Ai,Lina Song,Baohua Liu
Poly (propylene carbonate) diol (PPCD) is one of the most attractive CO 2 copolymers. PPCD-based polyurethane has excellent mechanical properties and hydrophilicity, and is widely used in various fields. However, poor alkali resistance limits the application of PPCD-based polyurethane in wet-type artificial leather (WPL). In order to solve this problem, polyurethane solution (PUS) for wet-type artificial leather was prepared by using PPCD and polytetramethylene ether glycol (PTMG) as soft segments. The chemical structure, viscosity, molecular weight and distribution, physical and mechanical properties, thermal properties and dynamic mechanical thermal properties of PUS were characterized. The changes of the physical and mechanical properties of PUS films and surface morphology of WPLs after soaking in 10 wt% NaOH solution at room temperature for 24 h were studied, so as to evaluate the alkali resistance of polyurethane. The retention of tensile strength and tearing strength of PUS films modified by PTMG increased from 80% to 96% and from 89% to 100%, respectively. The scanning electron microscopy results showed that appropriate PTMG was beneficial to the formation of microporous structure for CO 2 -based polyurethane leather. The leather without PTMG showed agglomeration phenomenon, the micropores were not obvious, and the changes were obvious after soaking in alkali solution. After being modified by PTMG, the morphology of leather after soaking in alkali solution was basically unchanged. Polyurethane leather prepared with PTMG and PPCD as soft segments has excellent alkali resistance. These results suggest that PPCD could be a potential artificial leather material.
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