Study On The Forest Resource-based Waterborne Polyurethane Dispersion And Their Varnish Properties

Polyurethane was used as coatings in abundance. Solvent-based polyurethane coating caused damage to the environment. Waterborne coating had many excellent properties such as easily available, easily purify, low viscosity, good coating adaptability, non-toxic, and non-irritating. Waterborne coating showed growth in commercial application. Rosin was an abundant forest resource and rosin-based chemicals were biodegradable. Rosin-based waterborne PU with high performances was the significant topic recently and finded extensive application in coating and adhesive, etc.In this paper, the maleopimaric rosin was synthesized from rosin and maleic acid by Diels-Alder reaction with yield 86%, and acid value 390mgKOH/g(theoretical value 402mgKOH/g). Then the maleopimaric rosin glycol ester(MRE) was prepared from maleopimaric rosin and glycol with yield 88%, and the acid value 105mgKOH/g(theoretical value 110mgKOH/g). The chemical structures of maleopimaric rosin and MRE were characterized by FT-IR and 1H-NMR.Waterborne polyurethane was prepared from maleopimaric rosin glycol ester(MRE),TDI,polyethylene and glycol. MRE was the hydrophilic chain extender. The influence of reaction time, reaction temperature and the recipe in the prepolymerization step were investigated. Mechanical performances were measured. Infrared spectroscopy(IR) and 1H Nuclear Magnetic Resonance(1H-NMR) were used to characterize the curing varnishes. The results showed the rationality of molecular structure. The thermal property was studied by TGA and the particle size and its distribution of the dispersion were measured. The uncrosslinked polymer was well soluble in several organic solvents. At the same time, water resistance and physical properties such as hardness, impact strength, flexibility, gloss and adhesion were investigated systematically.Since the water resistance and hardness properties were still non-optimal, we used cross-linking agents, crylic acid, crylic acid and epoxy resins to modify the WPU, respectively. Some hardness of films reached 6H, contact angle reached 90°, flexibility reached 0.5mm and adhesion forces reached grade 2. The gloss and impact strength of all the modified varnish were very well. The results showed that environmentally friendly waterborne polyurethane which possesse good mechanical properties prepared successfully. It could be candidate for coating and adhesive industries, etc.