Mechanical and thermal properties of waterborne epoxy composites containing cellulose nanocrystals

Cellulose nanocrystals (CNCs) are reinforcing fillers of emerging interest for polymers due to their high modulus and potential for sustainable production. In this study, CNC-based composites with a waterborne epoxy resin matrix were prepared and characterized to determine morphology, water content, and thermal and mechanical properties. While some CNC aggregation was observed, the glass transition temperature (T_g) and modulus for the composites increased with increasing CNC content. Relative to neat epoxy, at 15 wt.% CNC the storage modulus increased by 100%, the T_g increased from 66.5 °C to 75.5 °C, and tensile strength increased from 40 MPa to 60 MPa, suggesting good adhesion between epoxy and CNC surfaces exposed to the matrix. Additionally, no additional water content resulting from CNC addition were observed. These results provide evidence that CNCs can improve thermomechanical performance of waterborne epoxy polymers and that they are promising as reinforcing fillers in structural materials and coatings.     

在我国经济“转型”发展中木器行业中涂料及涂装如何顺应

该文介绍了水性木器涂料在我国的发展及取得的成就,同时介绍水性涂料的涂装方式为手工和喷,辊、滚、浸印、帘幕等机械涂装;水性涂料的干燥,影响因素及涂膜弊病干燥设施等;指出涂装是涂料性能的体现而涂料配方的设计应满足涂装和施工要求。     

Long-term Emission of Volatile Organic Compounds from Waterborne Paints – Methods of Comparison

The emission of volatile organic compounds (VOCs) from five different waterborne paints was measured in small climatic chambers under standard conditions over a one-year period. The aims of the study were to evaluate the time emission profiles and to develop methods for comparison of different paints. The paints were applied to tin-plated steel sheets. VOCs were sampled on Tenax TA and analysed by thermal desorption and gas chromatography. The chamber concentrations increased rapidly during the first few hours and then decreased as the emission rates dropped. A model expression including an exponentially decreasing emission rate of the paint film, the air exchange rate, and a normalization of the film thickness was fitted to the concentration versus time data. The time required to reach a given emission rate was estimated and found suitable for comparison of the emission of VOCs from the paints. It was found that data sampled within three weeks or less may be sufficient to predict the emission of VOCs up to one year. Reduction of long-term emissions may be achieved most efficiently by (1) substituting a more -volatile VOC whose emission is controlled by evaporation for a less volatile VOC characterized by diffusion-controlled emission and (2) reducing the paint film thickness rather than reducing the initial VOC content of the paint.     

Corrosion protection of waterborne epoxy coatings containing mussel-inspired adhesive polymers based on polyaspartamide derivatives on carbon steel

A novel mussel-inspired adhesive polymer (PHEA-DOPA) containing the 3,4-dihydroxyphenylalanine (DOPA) functional group based on polyaspartamide derivatives was synthesized. The corrosion protection of the waterborne epoxy coatings containing the adhesive polymers was investigated by electrochemical impedance spectroscopy (EIS). The results indicated that the PHEA-DOPA could improve the corrosion resistance of the waterborne epoxy coating. The corrosion products were also analyzed by Raman microspectroscopy (RM), indicating the formation of the insoluble DOPA-Fe complexes on the carbon steel surface. These complexes simultaneously acting as a passivating layer, can inhibit the process of corrosion at the metal-solution interface. The differential scanning calorimeter (DSC) measurement indicated that PHEA-DOPA can increase the crosslinking density of coating. The effect of O₂ on the protective mechanism of the PHEA-DOPA coating in a 3.5% NaCl solution was also evaluated by EIS. The results indicated that the barrier effect was significantly improved under aerated conditions because DOPA was oxidized to DOPA–quinone (Dq) by O₂, which triggered the reaction with Fe ions that were released from the surface of the carbon steel. This led to more compact coatings.     

Unique waterborne systems based on TMXDI (meta) aliphatic isocyanate and TMI (meta) unsaturated isocyanate

TMXDI (meta) aliphatic isocyanate and TMI (meta) unsaturated isocyanate have been formulated into unique waterborne polymer systems. Poly(urethane) dispersions based on TMXDI (meta) aliphatic isocyanate are characterized by very low volatile organic component (VOC) levels as no solvents are required, excellent toughness and flexibility, high solids capability and low viscosity. Acrylic latexes modified with TMI (meta) unsaturated isocyanate are characterized by higher hardness levels with little loss of flexibility, and improved chemical and solvent resistance when compared to non-modified systems. Application areas for these coatings include automotive isocyanatoethylmetacrylate (OEM) and refinish, as well as trade sale paints.     

亲水扩链剂对水性聚氨酯性能的影响

本文以1,2-二羟基-3-丙磺酸钠（DHPA）为亲水扩链剂,探讨了DHPA含量的改变对水性聚氨酯乳液及其涂膜性能的影响,实验结果表明：DHPA含量在5％～7％之间可获得比较稳定的乳液;随着DHPA含量的增加,乳液的粒度变小,粒径的分散性变窄;涂膜拉伸强度增强,伸长率下降。     

Preparation and properties of waterborne polyurethane/epoxy resin composite coating from anionic terpene-based polyol dispersion

An anionic polyol (T-PABA) dispersion was prepared by modifying terpene-based epoxy resin with para-aminobenzoic acid. Then T-PABA dispersion was crosslinked with a hexamethylene diisocyanate (HDI) tripolymer to prepare waterborne polyurethane/epoxy resin composite coating. The rheological properties and particle size distribution of the composite system were characterized by rotary rheometer and laser particle size analyzer. The crosslinked composite product has good thermal resistant properties, with glass-transition temperatures (T_g) about 40% and 50% weight loss temperatures (T_d) in the range of 400–420. The smooth and transparent film obtained from the composite product has good flexibility, adhesion, impact strength, antifouling and blocking resistance properties. The impact strength, pencil hardness, water-resistant and thermal-resistant properties of the composite products increased with the molar ratio of isocyanate group to active hydrogen of T-PABA.     

Chemical resistance of waterborne epoxy/amine coatings

Waterborne epoxy/amine coatings, compared to solvent-based, show considerably lower chemical resistance. This fact is often blamed on hydrophilic emulsifiers or crosslinking agents remaining inside the coating after curing. To judge this assertion, the influence of surfactants and hardeners, as well as various other parameters were investigated. Surfactants appear just to influence the solvent resistance slightly. The main responsibility for the poor resistance to other chemicals – especially acids – lies with unreacted amine curing agents and/or water trapped inside the coating, and, most important, an inhomogeneous film structure due to insufficient coalescence during the curing process. Incremental improvements are possible by using excess epoxy, increasing the film thickness, or curing at elevated temperatures. The latter forces water out of the coating, drives the epoxy/amine reaction to completion, and also somewhat improves the coalescence. However, the resistance can still not be enhanced to the level of a solvent-based system. But although there seem to be inherent limitations to the chemical resistance of waterborne epoxy systems, for many practical applications it is adequate.     

紫外光固化水性涂料的发展概况

综述了一类具有环境友好和快固化特点的光固化水性涂料,对其优缺点、国外发展状况、分类、典型树脂体系基本性能、适用光引发剂、当前存在的技术困难与问题分别进行了阐述。并简要介绍了作者在此方面的一些研究工作。     

环氧树脂改性水性聚氨酯的制备与性能研究

以异氟尔酮二异氰酸酯(IPDI)、聚四氢呋喃醚二醇(PTMG)以及二羟基甲基丙酸(DMPA)为主要原料合成水性聚氨酯(WPU)预聚体,在此基础上加入环氧树脂(EP,E-44)制备了环氧树脂改性水性聚氨酯(PUE)复合乳液。探讨了不同环氧树脂含量对复合乳液性能的影响,并对胶膜的力学性能、吸水率、接触角和热性能等进行了表征。结果表明,适量的环氧树脂改性过后的复合乳液比较稳定;随着环氧树脂含量的增加,乳液粒径和黏度增大,同时胶膜的拉伸强度增大,水的接触角增大,胶膜的热稳定性增加。E-44质量分数为7%~9%时,复合乳液及其胶膜的综合性能较好。