Polyurethane/Polysiloxane Ceramer Coatings: Evaluation of Corrosion Protection

A series of polyurea and polyurethane ceramer coatings were formulated using hexamethylene diisocyanate (HDI) isocyanurate, alkoxysilane‐functionalized HDI isocyanurate, tetraethyl orthosilicate (TEOS) oligomers and cycloaliphatic polyesters. The coatings were prepared as a function of alkoxysilane‐functionalized HDI isocyanurate and TEOS oligomers concentration. Also, the effect of acid catalyst was investigated. The corrosion resistance of polyurea or polyurethane ceramer coating systems were evaluated using a prohesion chamber on aluminium alloy 2024‐T3 substrate. The polyurethane ceramer coatings were compared with the chromate pretreatment and the epoxy‐polyamide primer containing the chromate pigment. In addition to prohesion, the interface between the coating and substrate was characterized using X‐ray photoelectron spectroscopy (XPS). The prohesion data showed that the corrosion was inhibited by the TEOS oligomers. However, high concentrations of TEOS oligomers and acid catalyst produced blistering in the polyurea/polysiloxane ceramer coatings. The prohesion data also showed that the corrosion protection of ceramer coatings performed as well as the chromate pretreatment and competitively with the epoxy primer. From the XPS and prohesion data, a self assembling silicon oxide layer at the metal‐coating interface was proposed.     

UV固化低聚物及其涂料研究进展

综述了UV固化低聚物(主要是环氧丙烯酸酯和聚氨酯丙烯酸酯)的研究进展。环氧丙烯酸酯研究进展包括:降低黏度、改善柔韧性、光敏活性、耐热性、耐磨性和阻燃性能;聚氨酯丙烯酸酯的研究进展包括:紫外光固化的聚氨酯丙烯酸酯预聚物合成方法;聚氨酯丙烯酸酯/无机纳米复合材料;光固化无机/有机杂化材料;水性UV固化聚氨酯丙烯酸酯和UV固化超支化聚氨酯丙烯酸酯。较为详细地论述了氧阻聚的3种作用机理及解决方法(物理和化学2种方法),最后对光固化技术的5大发展趋势进行了展望。     

PTMG/TDI系聚氨酯低聚物流变特性

研究了聚四氢呋喃多元醇／甲苯二异氰酸酯系聚氨酯弹性体低聚物的流变特性及黏度～温度关系。结果表明：该聚氨酯低聚物具有剪切变稀的假塑性,其非牛顿性随相对分子质量及分子链中氨酯基含量的增加而增强;而低聚物的黏度与温度的关系符合Andrade方程。同时探讨了自动化浇注聚氨酯制品工艺的优化问题。     

废旧PET的化学回收方法研究进展

PET综合性能良好,应用广泛,但难以生物降解,随着排入自然界的废旧PET日益增多,对其进行回收利用已迫在眉睫。回收方法包括物理方法、化学方法、物理化学方法等,其中,化学回收方法将PET解聚成单体或低聚体,是实现废旧PET循环利用最有前途的途径之一,包括醇解法、水解法等。本文重点对废旧PET的化学回收方法研究现状及新进展进行了综述,旨在为PET的工业回收利用提供参考。     

有机硅改性聚氨酯的合成与性能

在无溶剂条件下利用烷氧基硅烷合成了有机硅低聚物,用聚酯多元醇对其进行了改性。采用了红 外光谱对低聚物进行了表征,同时测试了材料的粘接性能、力学性能、耐水性、耐热性。结果表明,改性后的聚 氨酯具有优良的耐水性、耐热性。     

New crosslinked polyurethane elastomers with various physical properties from natural rubber derivatives

New hydroxytelechelic cis‐1,4‐oligoisoprenes exhibiting variable values and distributions of the hydroxyl functionality were successfully prepared. The synthesis reactions involved chemical modifications of carbonyl telechelic cis‐1,4‐polyisoprene, which was obtained by controlled degradation of synthetic or natural rubber. These new oligomers were reacted with toluene diisocyanate to elaborate crosslinked polyurethane elastomers. The thermomechanical properties of the prepared polyurethanes were investigated. The results show a strong relationship between the chemical structures and properties. This work mainly shows the potentiality of making new crosslinking polyurethane materials with controlled and various properties from natural rubber, a renewable resource. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Mechanical properties of crosslinked polyurethane elastomers based on well‐defined prepolymers

This article presents research findings for selected mechanical properties of polyurethane elastomers. The studied elastomers were synthesized with the prepolymer‐based method with the use of controlled molecular weight distribution (MWD) urethane oligomers and with the classical single‐stage method. Prepolymers with defined MWDs were obtained with the use of a multistage method, that is, step‐by‐step polyaddition. To produce elastomers, isocyanate oligomers were then crosslinked with triethanolamine, whereas hydroxyl oligomers were crosslinked with 4,4′,4′′‐triphenylmethane triisocyanate (Desmodur RE). The tensile strength of the obtained elastomers ranged from 1.0 to 7.0 MPa, the ultimate elongation approached 1700%, the Shore A hardness varied from 40 to 93°, and the abrasion resistance index fell within 15–140. The effects of the types of raw materials used, the chemical structures, the production methods, and the supermolecular structures on the mechanical properties of the obtained polyurethane elastomers were examined. When the obtained findings were generalized, it was concluded that the structural changes in the polyurethanes, which were favorable for intermolecular interactions, improved the tensile strength, hardness, and abrasion resistance of the materials and impaired their ultimate elongation at the same time. More orderly supermolecular structures and, therefore, superior mechanical properties were found for polyurethane elastomers produced with the prepolymer method. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Dual‐curable unsaturated polyester inorganic/organic hybrid films

An unsaturated polyester, based on maleic anhydride, 1,6‐hexanediol, and trimethylol propane, was formulated with tetraethylorthosilicate (TEOS) oligomers and a coupling agent to prepare inorganic/organic hybrid films. TEOS oligomers were prepared through the hydrolysis and condensation of TEOS with water, and 3‐(triethoxysilyl)propylisocyanate was used as the coupling agent between the organic and inorganic phases. The hybrid materials were cured by moisture via sol–gel chemistry and by the UV curing of unsaturated polyesters. To compare the properties of the moisture‐cured inorganic/organic hybrid films, a conventional 2K polyurethane system was also prepared. The tensile, adhesion, abrasion, and fracture toughness properties were investigated as functions of the coupling agent and relative amount of UV cure versus thermal cure. Although no difference could be observed in the tensile properties, the abrasion resistance, fracture toughness, and adhesion were enhanced by the incorporation of TEOS oligomers into polyurethane films. Also, the abrasion resistance, fracture toughness, and tensile properties were increased with both moisture and UV exposure. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 115–126, 2006     

Natural rubber–polyurethane block copolymers: Nonlinear structural variations with NCO/OH ratio

A series of segmented block copolymers was prepared by the chain extension of hydroxyl terminated liquid natural rubber (HTNR) with polyurethane oligomers derived from toluene diisocyanate (TDI) and 1,3‐butane diol at varying NCO/OH ratio. The previously reported two‐step method of synthesis was modified to get improved products. This was done by optimizing the formation of polyurethane oligomers in the first step of the synthesis. All the samples were characterized by solubility testing, DSC, tensile testing, etching studies, and SEM. The data obtained were correlated to the structural features of the block copolymers. It was found that NCO/OH ratio played an important role in determining the structural variations in the block copolymers. POLYM. ENG. SCI. 46:1812–1821, 2006. © 2006 Society of Plastics Engineers     

Design and Preparation of Tertiary Amine Modified Polyurethane Acrylate Oligomer with Co‐Initiation/Polymerization Bifunctions for Photo‐Curable Inkjet Printing of Textiles

In order to resolve the conflict issues existing in currently available polyurethane acrylate (PUA) oligomers for photo‐curable inkjet printing of textile, and to avoid the safety problems caused by the immigration of small molecule amine co‐initiator, a series of tertiary amine modified PUA oligomers are delicately designed and synthesized. The chemical structures of the synthesized PUA oligomers are confirmed by FTIR and ¹H‐NMR analyses. The optimized PUA oligomer/hydroxyethyl acrylate based polymerization system show a low viscosity, high storage stability and good compatibility with various functional segments. Furthermore, the modified PUA oligomer acts as both the photopolymerization constituent and the macromolecular co‐initiator assisting to achieve high photopolymerization rate and conversion rate, and avoiding the disadvantages caused by the migration of small amine co‐initiators. Benefitting from the semi‐IPN formed by this polymerization system with suitable crosslinking density and phase separation degree, a soft, strong and flexible cured film is obtained. The high photo‐reactivity with low viscosity of the polymerization system and the good flexibility with high strength of the resultant photo‐cured film ensures the applications of the modified PUA oligomer, and the printed fabrics achieve 4 grade of colorfastness with improved handle properties, as well as brilliant color and fine patterns.     

Novel quinoline-based polyurethane elastomers. The effect of the hard segment structure in properties enhancement

Polyurethane elastomers incorporating a quinoline moiety along their polymeric backbones and aliphatic, aromatic or heterocyclic crosslinkers have been synthesized and characterized. For this, NCO-terminated urethane oligomers were prepared from poly(butylene adipate) diol and methylene diphenyl diisocyanate and were subsequently chain extended with 2,4-quinolinediol and different crosslinkers. This study reports the influence of the different crosslinker chemical structures and the hard segment molar ratio on the thermal and dynamic mechanical thermal properties, as well as on the mechanical properties of these elastomers. The fluorescence spectra of polyurethane elastomers were determined at an excitation wavelength of 290 nm. The different chemical structures of the crosslinkers determine the hard segment cohesion and reduce the mobility of the soft phase, having an important effect on thermal stability and on the mechanical properties of the polyurethane films. Thus the incorporation of aromatic crosslinkers results in polyurethanes with lower elongation and stress at break. The highest mechanical properties were obtained for polyurethanes crosslinked with aliphatic crosslinkers.     

Preparation and characterization of UV-curable urethane acrylate oligomers modified with cycloaliphatic epoxide resin

The UV-curable urethane acrylate oligomers modified with cycloaliphatic epoxide resin, including polyether-modified cycloaliphatic polyurethane acrylate (CE-MP-UA) and oleic acid-modified cycloaliphatic polyurethane acrylate (CE-OA-UA), have successfully been synthesized and characterized by ¹HNMR and FTIR. The kinetics of the synthesis processes are studied in this paper. The effects of the molecular structure of the oligomers on the properties of cured film, including pencil hardness, impact resistance, adhesion and boiling water resistance, are discussed in detail. The experimental results indicate that the films formed by CE-OA-MP oligomers show good comprehensive performance, especially good adhesion and boiling water resistance due to the numerous hydroxyl groups, flexible segment and alicyclic structure of the oligomers. The results reveal that the alicyclic structure in the oligomer molecular make-up can effectively improve the adhesion of UV-curable coatings.     

聚氨酯丙烯酸酯紫外光固化三聚氰胺板材底漆的研制

合成了一种聚氨酯丙烯酸酯和一种附着力促进剂,通过与其它树脂、单体、引发剂的配合,配制三聚氰胺板材UV固化底漆,测试了涂膜的附着力、耐温性、耐水性,掌握了配方中树脂与单体的最佳比例、底漆的最佳光照时间、附着力促进剂的最佳用量、选出了较好的复配树脂,最终得到了性能优异的三聚氰胺板材底漆配方。     

Star oligomers with different reactivity in low VOC polyurethane coatings: Part II

Conclusions  In this paper the effects of the reactivity of hydroxyl functional oligomers with a polyisocyanate crosslinking agent have been demonstrated by comparing the potlife/hardness of a 3.5 VOC two-component polyurethane clear coat based on a low TG, high reactive against a high TG, low reactive oligomer. The reaction rate of two polymers forming a crosslinked network becomes diffusion controlled when, during the reaction, the increasing TG comes close to the reaction temperature.⁴ If this reaction takes place in the presence of a solvent which evaporates during film formation and crosslinking, the speed of evaporation will affect both the reaction rate and the film TG. The results of this study have shown that the reactivity determines the potlife whilst the TG controls the hardness. The reactivity of blends of such oligomers against pure oligomers is different as can be calculated using the theory of branching processes and as shown from practical measurements. Blends of oligomers or a pure oligomer with up to 75% of the properties of the high TG, low reactive oligomer do show a hardness close to the properties of the low TG, high reactive oligomer which further proves that the chemical reactivity controls the overall drying performance. A fast chemical reactivity shortens the potlife with a risk of solvent entrapment near to and at the gel point which results in low hardness.     

聚氨酯/蒙脱土纳米复合材料制备及其性能研究

本文采用蒙脱土纳米材料改性聚氨酯，得到了理想的预期效果。通过单体插层，聚氨酯的单体可插层于蒙脱土中，经过多元醇与异氰酸酯的聚合反应制备了聚氨酯／蒙脱土纳米复合材料。用蒙脱土纳米材料改性聚氨酯，研究结果表明：蒙脱土纳米材料不仅提高了聚氨酯的模量，同时又使其强度不下降，密度不增大，这是加入其他刚性粒子所达不到的。同时探讨了聚氨酯／蒙脱土纳米复合材料之所以具有这些优良的力学性能的理论依据。     

基于表面改性技术的聚氨酯/脲涂层附着性能研究进展

简单介绍了聚氨酯/脲涂层的附着机理研究,从机械表面处理、化学表面改性两个方面综述了表面改性技术在聚氨酯/脲涂料附着性能研究中的应用,并对聚氨酯/脲涂料未来的研究方向提出展望。     

有机硅改性热反应型水基聚氨酯

用氨丙基聚硅氧烷与PU预聚体反应生成合硅氧烷的PU预聚体,通过NaHSO3封闭NCO基,并在水中分散制得有机硅改性热反应型水基聚氨酯乳液。考察了有机硅含量对封闭率和解封速率以及乳液粒径的影响。     

Effects of NCO/OH Ratio and Reactive Diluent Type on the Adhesion Strength of Polyurethane Methacrylates for Cord/Rubber Composites

A series of dual curable polyurethane methacrylate-based oligomers were synthesized by changing the NCO:OH ratio and then were included in adhesive formulations using trimethylolpropane trimethacrylate and tricyclodecane dimethanol diacrylate (TCDDA) as reactive diluents. The effects of NCO:OH ratio and reactive diluent type on the structural properties of UV-cured free films and adhesion properties between polyester cord/rubber surfaces were studied. The highest adhesion strength of the 103?N?cm^?1 was obtained when the NCO:OH ratio was set as 4 and the TCDDA was used as a reactive diluent.     

Star oligomers for low VOC polyurethane coatings

Conclusion  Hydroxyl functional star oligomers prepared by ring-opening polycondensation have a narrow molecular weight and composition distribution. Such oligomers give a solids/viscosity advantage over linear structures at the same molecular weight and can be used in low VOC two component polyurethane coatings. The solids/viscosity advantage is a combination of the highly branched structure and the narrow molecular weight distribution. Acrylic polyols formulated at the same molecular weight/polarity/average functionality and hydroxyl value give poorer drying properties. This difference can be explained by the fact that the free radical polymerisation technique leads to polymer compositions having a broad molecular weight and functionality distribution and high fractions of polymer with a low functionality. The potlife of acrylic polyols based formulations is adversely affected by the higher fractions of high molecular weight material and with a high average functionality. In low VOC polyurethane formulations star oligomers need to be formulated within a narrow range of compositions (TG, polarity), functionality and molecular weight to get an optimum balance of drying properties and potlife.