Preparation And Properties Of Maleopimaric Acid Modified Two-component Waterborne Polyurethane

Two-component waterborne polyurethane(2K-WPU) with low-pollution, ease of construction, good weather resistance and low film forming temperature has become a research hotspot in the field of high-performance and environmentally friendly polyurethane. Rosin is an important forest resource in China, and its annual output is 700 000 ~ 800 000 tons. However, the level of deep processing and utilization of rosin is low.In this paper, maleopimaric acid modified polyester polyol(MPP) aqueous dispersion with hydrophenanthrene ring structure was prepared by introducing maleopimaric acid(MPA) into polyester polyol chain. The MPP aqueous dispersion was then crosslinked with polyisocyanate to prepare maleopimaric acid modified two-component waterborne polyurethane(MPP-2K-WPU). The MPP-2K-WPU was further mixed with nano materials(cellulose nanocrystals(CNCs) and nano-Ti O2) to prepare nano materials modified MPP-2K-WPU(MPP-2K-WPU/CNCs and MPP-2K-WPU/Ti O2). The preparation conditions of MPP aqueous dispersion and the kinetics of crosslinking reaction between MPP and polyisocyanate were studied. The properties of MPP-2K-WPU, MPP-2K-WPU/CNCs and MPP-2K-WPU/Ti O2 and the relationship between structure and properties of the product were also investigated. This study aims to provide a new way for the development of rosin to higher value and deeper processing.MPP aqueous dispersion was prepared by partly substituting MPA for isophthalic acid. Through the study of factors influencing the preparation of MPP aqueous dispersion, the optimized conditions were identified as 0.1% catalyst content, 1.4:1 molar ratio of alcohol to acid, 2.86% 5-SSIPA content, and 14.3% MPA content. Rheological analysis showed that MPP aqueous dispersions were pseudoplastic fluids.MPP-2K-WPU was prepared by the crosslinking reaction between MPP aqueous dispersion and polyisocyanate. The film formation process of MPP-2K-WPU composite system was investigated. The results validated that the particles aggregating, merging and chemical reaction processes were occurred during the film formation process. The influences of MPA content on the properties of MPP-2K-WPU were studied. The results showed that the introduction of MPA enhanced the crosslinking density and molecular chain rigidity of MPP-2K-WPU, thus the pencil hardness, tensile strength, thermal resistance, water resistance, antifouling and blocking resistance and ethanol resistance of MPP-2K-WPU were improved. Moreover, MPP-2K-WPU based on higher MPA content exhibited faster drying, higher gloss, but lower elongation at break. Considering the influences of MPA content on the stability of MPP aqueous dispersion and the properties of MPP-2K-WPU, the MPA content was chosen as 14.3%. The influences of —NCO:—OH molar ratio(n(—NCO):n(—OH)) on the properties of MPP-2K-WPU were also investigated. The results indicated that when n(—NCO):n(—OH) increased, the crosslinking density and hydrogen bonding interactions of MPP-2K-WPU were improved, leading to the enhancement of pencil hardness, thermal resistance and ethanol resistance of MPP-2K-WPU. The surface free energy(γS) and the dispersive component of surface free energy(γS d) of MPP-2K-WPU decreased firstly and then increased with increasing n(—NCO):n(—OH), and the γSd depending on the structure of macromolecules made major contribution to the surface free energy of MPP-2K-WPU film. The water resistance of MPP-2K-WPU was enhanced firstly and then weakened with increasing n(—NCO):n(—OH), and the MPP-2K-WPU exhibited the best water resistance at n(—NCO):n(—OH) of 1.5:1. In addition, the MPP-2K-WPU film showed almost no changes when the n(—NCO):n(—OH) was larger than 1.5:1. Hence, the optimum n(—NCO):n(—OH) was found to be 1.5 : 1.The kinetics of crosslinking reaction of MPP-2K-WPU composite system was evaluated by non-isothermal DSC method. The experimental data were analysed by Kissinger-Crane method and Málek’s mechanism function method, respectively. The results indicated that the reaction rate of MPP-2K-WPU composite system increased firstly and then decreased with increasing temperature. n-order reaction kinetic model deduced from Kissinger-Crane method had great distinction with the experimental data. However,JMA(n) and SB(m, n) kinetic models obtained from Málek’s method showed good agreement with the experimental data. The results revealed that the kinetic models from Málek’s method could well describe the crosslinking reaction process of MPP-2K-WPU composite system.MPP-2K-WPU/CNCs film was prepared from CNCs suspension and MPP-2K-WPU. Scanning electron microscope(SEM) was used to characterize micromorphology of MPP-2K-WPU/CNCs. The results demonstrated that CNCs were dispersed well in MPP-2K-WPU matrix. The effects of CNCs content on the properties of MPP-2K-WPU/CNCs were examined. The results indicated that MPP-2K-WPU/CNCs based on higher CNCs content exhibited higher pencil hardness, better thermal resistance, greater water resistance and tensile strength, but lower elongation at break.MPP-2K-WPU/Ti O2 film was prepared from nano-Ti O2 suspension and MPP-2K-WPU, and characterized by SEM. The results showed that nano-Ti O2 were distributed well in MPP-2K-WPU matrix. The effects of nano-Ti O2 content on the properties of MPP-2K-WPU/Ti O2 were studyed. The results showed that the introduction of nano-Ti O2 not only improved the pencil hardness, thermal resistance, water resistance and tensile strength of MPP-2K-WPU/Ti O2 with sacrifice of elongation at break, but also endowed MPP-2K-WPU/Ti O2 with anti-ultraviolet, photocatalytic degradation of organic contaminants and antibacterial properties.