In Situ Monitoring of Selective Catalysts on Urethane Formation by FT-IR Spectroscopy

A number of tertiary amines and organotin catalysts for the phenyl isocyanate- 1,2-propylene glycol reaction were investigated by using in situ FT-IR. The reaction rate of each hydroxyl group, which is defined as the ratio between the rate constant of the secondary hydroxyl group and the rate constant of the primary hydroxyl group, is described with a second-order equation. The influence of different catalyst concentrations as well as the reaction temperature is discussed. It is observed that the selectivity depends on temperature but not on concentration, and stannous octoate is the most effective catalyst. The thermodynamic parameters were determined for the catalyzed reactions, primary and secondary hydroxyl groups being differentiated.     

Effect of MWCNTs and graphene on the crystallization of polyurethane based nanocomposites,analyzed via calorimetry,rheology and AFM microscopy

Isothermal crystallization of two nanocomposites composed of multiwalled carbon nanotubes (MWCNT) and graphene dispersed in a hot melt adhesive polyurethane (PUR) is investigated. Rheological percolation is reached for PUR/MWCNT, but not for PUR/Graphene nanocomposites. Analysis of the elastic modulus versus time indicates that the crystallization process is more hastened by MWCNTs than by graphene, favouring the welding process of the corresponding adhesives. Correlative AFM images show that the crystal size follows the order: Crystals in neat PUR > Crystals in PUR/Graphene > Crystals in PUR/MWCNT. The nucleation density is higher in the case of MWCNTs due to the poorer dispersion of graphene in the PUR matrix. Analysis of DSC results by the Avrami equation and the fitting of G′-time results to a rheological equation adapted from the Avrami equation, show that the parameter n decreases from n = 3 for neat PUR to n = 2 for both nanocomposites. The coherence between the value n = 2 and AFM images is demonstrated: The lamellae organization in two dimensional growth, that brings about nucleated axialites, as expected for n = 2, is confirmed by AFM microscopy.     

聚氨酯制备的多尺度模拟方案

针对聚氨酯材料特性设计了多尺度计算机模拟方案,并研究了不同原料及相同原料但不同官能度对所制备的聚氨酯材料力学性能和玻璃化转变温度的影响.基于原子级别的结构,建立了耦合聚合反应的粗粒化耗散粒子动力学模型来描述组分扩散及交联网络结构的形成过程.并反映射这个粗粒化结构到全原子级别来分析材料的力学性能和热力学性能.这个多尺度研究方案也可推广到研究多个竞争性因素同时主导的复杂体系中.     

The thermal stability of fully charged and discharged LiCoO2 cathode and graphite anode in nitrogen and air atmospheres

Polyethylene glycol (PEG) compounds and mixtures have many properties that make them suitable for thermal applications in buildings, such as having high heat of fusion, phase change repeatability, chemical stability, non-corrosive behavior, and low-cost. In this study, we developed a number of PU rigid foams incorporated with three types of PEGs, as new insulation materials provided with an enhanced thermal capacity, and sought their suitability for various applications such as layer of floor and ceiling coverings in constructions, insulations in controlled temperature transportation packaging, inner coverings of automobile seats, etc. In order to investigate the thermal properties of PEG-containing PU foams, differential scanning calorimeter (DSC) tests were conducted first. Then, a two-layer concrete–PU foam system was designed in the laboratory conditions to examine the insulation performances via using a computer-aided thermal measurement setup which was sensitive to the simulated environmental temperature changes. The PU-PEG composites produced here can be helpful for the design of thermal insulators. PUI, including 44% PEG 600, exhibited fairly efficient thermal regulation under moderate ambient temperature conditions, whereas PUII (49% PEG 1000) is suitable for temperature control in both mild and hot surroundings. PUIII, containing 53% PEG 1500, showed suitable heat storage and thermal stability characteristics. PUIV, containing 38% PEG 600/PEG 1000/PEG 1500, also confirmed good thermal and durability characteristics. The blend of three PEGs is suitable for preventing discontinuous thermal regulation when the external temperature increases or decreases. PU foams containing PEGs can be assumed to be leak-resistant, which is promising for their industrial applications.     

X射线不透性体温固化聚氨酯髓核假体材料的研究

为了制备X光可显影且可以体温固化的聚氨酯,合成了N,N'-双(1,3-二羟基丙基)-2,3,5,6-四碘对苯二甲酰胺(BDTIP)含碘四元醇,将其作为聚氨酯固化的交联剂和X光显影剂,与聚氨酯预聚物混合反应得到一种新的可用于人工髓核假体的材料.利用红外光谱监测BDTIP的反应程度;利用X射线对不同BDTIP含量的聚氨酯材料的显影效果进行评定;利用噻唑蓝(MTT)比色法测试材料细胞毒性,并对具有不同碘含量聚氨酯材料的力学性能进行了对比研究.结果表明,碘的加入对聚氨酯的显影效果有很好的促进作用,较低碘含量(0.2 wt%)的聚氨酯材料即有较好的X光显影效果,而且此时聚氨酯依然保持较好的力学性能;MTT法测试表明含BDTIP的聚氨酯材料不具有细胞毒性.     

Synthesis and fluorescence enhancement behavior of a novel fluorescent aqueous polyurethane emulsion DDAQ-TDI-PU

A novel fluorescent aqueous polyurethane emulsion DDAQ-TDI-PU was synthesized by blocking the anthraquinone moiety of 1,4-diamino-2,3-diphenoxyanthraquinone(DDAQ) into polyurethane chain using 2,4-tolylene diisocyanate(TDI),poly(propylene glycol) and 2,2-dimethylol propionic acid.The chain structure of DDAQ-TDI-PU was confirmed by means of Fourier transform infrared spectroscopy and UV-vis analysis.Comparing to the UV-vis spectrum of DDAQ,DDAQ-TDI-PU showed a hypsochromic shift from the absorption maxima of 518,558,609 nm to 510,548,586 nm,respectively.It was found that the fluorescence intensity of DDAQ-TDI-PU emulsion was enhanced greatly comparing with that of DDAQ.The fluorescence of DDAQ-TDI-PU was very stable not only for the long term storage but also for the fluorescence quencher.     

一种X-射线不透性聚氨酯显影材料的制备及性能研究

利用对碘苯胺对含有过量异氰酸根的聚氨酯分子进行封端,合成了一种新型的X-射线不透性聚氨酯显影材料.利用X-射线映射对不同封端量聚氨酯的显影效果进行评定;利用DSC和TGA对其热性能进行表征,并评估封端反应对聚氨酯热稳定性的影响;利用噻唑蓝(MTT)比色法测试了材料的细胞毒性;并对具有不同碘含量聚氨酯材料的显影效果、相对分子量及其分布、力学性能进行了对比研究.研究结果表明,当碘含量达到3.5wt%左右时聚氨酯材料即可达到同等厚度铝板相同的显影效果,而且在此条件下,聚氨酯材料依然保持较好的力学性能和热稳定性.MTT法测试表明对碘苯胺封端的聚氨酯材料不具有细胞毒性.