Coatings prepared from waterborne polyurethane dispersions obtained with polycarbonates of 1,6-hexanediol of different molecular weights

Waterborne polyurethane dispersions (PUDs) were synthesized with polycarbonates of 1,6-hexanediol of different molecular weight (500–3000 Da) and their properties, adhesion (Hatch adhesion) and coatings on stainless steel properties (Pencil hardness, Persoz hardness, gloss at 60°, chemical resistance, yellowness index) were characterized. The hatch adhesion of the polyurethane coatings to stainless steel was very good and decreased slightly by increasing the molecular weight of the polycarbonate of 1,6-hexanediol. Both the Pencil and Persoz hardness values of the coatings increased by increasing the hard segments content in the polyurethane, i.e. by decreasing the molecular weight of the polycarbonate of 1,6-hexanediol, whereas the gloss and the yellowness index were lower for the coatings obtained with the polycarbonate of 1,6-hexanediol of molecular weight of 500 Da. Very good chemical resistance against ethanol for all polyurethane coatings on stainless steel plates was obtained but for long time of ethanol in contact with the coating surface the chemical resistance decreased, more markedly for the polyurethane coating obtained with the polycarbonate of 1,6-hexanediol of higher molecular weight. In summary, the segmented structure of the waterborne polyurethane dispersion determined the properties of the polyurethane coatings obtained from them.     

国内超支化水性聚氨酯研究进展

简述超支化聚合物特性、制法和应用。重点介绍国内超支化水性聚氨酯合成方法和相应性能表征,为进一步深化研究提供参考。     

泡沫塑料保温材料的研究进展

简述了国内外泡沫塑料保温材料的发展现状;介绍了聚氨酯泡沫塑料、聚苯乙烯泡沫塑料和酚醛泡沫塑料的研究进展;展望了泡沫塑料保温材料的应用前景和发展趋势。     

4D printing of polyurethane paint-based composites

ABSTRACT

In recent studies, polyurethane has shown multiple properties that make it an excellent candidate material in 4D printing. In this study, we present a simple and inexpensive additive method to print waterborne polyurethane paint-based composites by adding carboxymethyl cellulose (CMC) and silicon oxide (SiO₂) nanoparticles to the paint. The first function of CMC and SiO₂ is to improve rheological properties of the polyurethane paint for making a printable precursor, which improves the printing resolution and enhances additive manufacturability. Second, the composite precursors improve the curing rate of the polyurethane paint without changing its inherited shape memory properties. Third, the printed composite parts shown enhanced mechanical strength compared with that of the parts printed with pure polyurethane. Finally, the 3D printed polyurethane-CMC and SiO₂ parts exhibit time-resolved shape transformation upon heat stimulation. To the best of our knowledge, this is the first study of using the polyurethane paint as the precursor for 4D printing, which would open new possibilities in future applications in biomedical engineering, soft robotics and so on.     

Synthesis and characterisation of polyurethanes derived from waste black liquor lignin

Waste black liquor lignin, obtained from bagasse from the small-scale paper industry, can be utilized for the synthesis of polyurethanes (PUs). Several polyurethane samples were prepared from laboratory black liquor (LBL) by reacting varying amounts of lignin ranging from 5 to 70% (w/v) in poly(ethylene glycol) (PEG) (having molecular weights of 200, 600, 1000, 1500 and 4000) with tolylene 2,4-diisocyanate (TDI). The effects of lignin concentration and molecular weight of PEG on mechanical and thermal properties of PUs obtained were investigated. The polyurethanes synthesised were characterized for different properties such as shear strength, adhesion and thermal stability. The shear strength of PU joints with aluminum was found to decrease with increase in both lignin concentration and molecular weight of PEG. Maximum shear strength, i.e. 3.6 N/mm², was shown by 50% (w/v) lignin in PEG of molecular weight 200.     

Modification of waste silicas by silanes and titanates and their use as reinforcing fillers in elastomer composites

Results on the use of waste silica, a by-product in the production of aluminum fluoride, as an elastomer filler are presented. Modification of the purified silica surface with silane and titanate coupling agents has been carried out. The effect of the type and amount of modifying agent on the physico-mechanical properties in vulcanizates of butadiene-styrene rubber and in polyurethane elastomers has been tested. The mechanical properties of butadiene-styrene rubber vulcanizates filled with waste silica show that the most favorable modifying effect is shown by mercaptosilanes A-189 and A-1893, polysulfide Si-69, and titanate KRTTS, as indicated by increased strength parameters. However, testing of the mechanical properties in polyurethane elastomers filled with waste silica has demonstrated that silica modification with aminosilanes A-1100 and A-1120 yield polyurethane compositions of optimum strength parameters.     

Self adhesion of short Kevlar fibre-thermoplastic polyurethane composite

The self adhesion behaviour of thermoplastic polyurethane (TPU) in itself and its composite with short Kevlar fibre with respect to contact time, temperature, pressure, and fibre loading has been studied. The adhesion strength showed two linear increments of different slopes with respect to the square root of time: with temperature and pressure of contact, the adhesion strength was improved. The maximum strength was obtained with 20 phr of short fibre in only one of the mating substrates in the peel test sample. The duration for wetting and diffusion was shifted to longer time intervals with fibres loaded in both the substrates.     

聚氨酯丙烯酸酯齐聚物的合成及其反应动力学

以异佛尔酮二异氟酸酯、丙烯酸羟丙酯和聚乙二醇为原料。采用本体法两步合成聚氨酯丙烯酸酯齐聚物,经光热引发交联成型后可用作聚氨酯弹性体。通过温度、原料、催化剂类型及其用量对反应速率常数影响的实验,研究结果表明;齐聚物的合成是二级反应;温度对反应速率常数影响大;不同反应物的反应速率常数明是不同。由于催化机理的不同。有机锡和叔胺催化剂造成反应速率常数差异较大．并且发现使用三乙胺催化时,催化剂用量对反应速率常数影响明显。     

聚氨酯(脲)有机-无机纳米复合材料的研究进展

对国内外聚氨酯(脲)有机-无机纳米复合材料的研究进展进行了综述,主要介绍聚氨酯(脲)/层状硅酸盐和聚氨酯(脲)/无机刚性粒子2类有机-无机纳米复合材料的制备原理、结构与性能表征及其在弹性体、胶黏剂、涂料、膜分离和生物医学等方面的应用。     

异氰酸酯三聚研究进展

异氰酸酯三聚体具有热稳定性好、黏度和挥发性低等特点,在聚氨酯材料制备中得到广泛应用。异氰酸酯三聚体制备工艺中,最主要的是催化剂的选用。主要介绍国内外异氰酸酯三聚体的制备状况。