Implementing plant‐derived isosorbide and isomannide as comonomers for polyester synthesis: Effects of crystallization properties on optical properties

This article describes the implementation of plant‐derived isosorbide (IS) and isomannide (IM) in the copolymerization modification of poly(ethylene terephthalate). The effects of the two comonomers on the optical, crystallization, and thermal properties of the resulting copolyesters were studied using the following analytical methods: proton nuclear magnetic resonance; differential scanning calorimetry; X‐ray diffraction; thermogravimetry; and ultraviolet‐visible spectroscopy. As comonomers, IS and IM increased the transmittance and reduced the haze of the copolyesters. Moreover, while IM improved the optical properties more than did IS, both monomers improved the optical properties of the copolyesters by lowering its crystallization ability. After the copolymerization modification, the crystallization rate of the copolyesters was reduced, decreasing the crystallinity and crystal size and thereby reducing the light transmission interference. The comonomers also altered the light absorption properties of the copolyesters and conferred a substantial increase in the transmittance of near‐infrared (NIR) wavelengths. These changes in optical properties exhibit the potential of these comonomers for applications in optical materials and NIR detectors. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45444.     

Porosity reduction of polyethylene glycol phase change materials by using nanoscale thermal‐energy‐conducting medium during crystallization process

Poly(ethylene glycols) (PEGs) are phase change materials (PCMs) that exhibit undesirable heat transfer properties, which restrict their industrial utility. Apart from the intrinsic material properties, a large quantity of micropores in the crystalline PEG polymers cause poor heat transfer performance. In this work, the formation and growth of micropores are reported through in situ characterization. The addition of a nanoscale thermal‐energy‐conducting medium into PCMs has been proposed for reducing their porosity. The mechanism for reducing porosity is reported for prepared composite PCMs. The intrinsic causes are thought to be the following. Metal oxide nanoparticles can migrate with the liquid PEG flow, which can reduce the thermal stresses in the crystal growth process. In addition, the nanoscale medium promotes heterogeneous nucleation. The results of this study show that reducing the porosity of the polymer crystals is an important approach for improving the heat transfer properties of the PEG PCMs. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45446.     

Evolution of magnetic and bone mineral phases in heat-treated bioactive glass containing zinc and iron oxides

Melt-quenched 15(ZnO,Fe₂O₃) 50SiO₂·20(CaO,P₂O₅) 15Na₂O bioactive glass was heat treated at temperatures (T_A) ranging from 550°C to 850°C for different time periods (t_A=1, 2 and 3 hours) to understand its devitrification characteristics. Crystallization of calcium sodium phosphate, zinc ferrite, magnetite, and hematite phases depended on heat treatment conditions. Decrease in saturation magnetizations (M_s) with increase in t_A of glass heat treated at T_A≥750°C is attributed to the formation of hematite which is a weak magnetic material. Magnetic properties as functions of T_A and t_A are interpreted on the basis of clustering of Fe ions, super-exchange interaction between Fe²⁺ and Fe³⁺ ions and formation of ferrimagnetic and weakly magnetic iron oxide phases with different heat treatment conditions. Electron paramagnetic resonance parameters reveal the variations in site distortions and randomness in Fe ion environment in the matrix upon heat treatment. In vitro mineralization ability of the glass-ceramics was evaluated by immersion in simulated body fluid (SBF) and monitoring both the pH variation of SBF and formation of hydroxyapatite surface layer as a function of immersion time. These studies help in assessing these glass-ceramics for hyperthermia treatment and in optimizing the processing conditions for this application.     

A hundred times faster: Novel,rapid sol-gel synthesis of bio-glass nanopowders (Si-Na-Ca-P system,Ca:P = 1.67) without aging

Synthesis of sol-gel glass with incorporation of Na₂O is extremely difficult, as such glasses have a great tendency to crystallize. Slow drying and aging over several days or weeks is usually required in sol-gel preparation procedures. This work reports a fast, novel route for the synthesis of bioglass powders in a considerably shortened period of 1 h. A comparative study of sol-gel derived glasses made by this novel route using rotary evaporator drying, and a conventional route using oven drying and aging, revealed that the two methods produce stabilized (devitrified) bio-glasses with virtually identical behavior and properties. Indeed, the rapidly dried powder exhibited slightly enhanced properties that should result in improved bioactivity. Fourier-transform infrared spectroscopy was used to understand the structures of the synthesized powders, and MAS-NMR was used to look at the degree of polymerization. This innovative, rapid route was successfully demonstrated to produce glass and devitrified glass nanopowders more than one hundred times quicker than the quickest reported standard drying methods.     

工业结晶过程中结晶动力学模型探讨

针对工业结晶过程中的溶液结晶部分,探讨了晶体成核和成长的动力学模型,并对模型的应用情况进行了简单的阐述。     

还原炉电极外套强制冷却装置的研究

分析了常用的还原炉电极外套强制冷却装置在技术上的不足,提出了新的强制冷却装置的设计方案。新的冷却装置在实际应用中取得了很好的效果,从而保证了多晶硅的产量和质量。     

熔融结晶法提纯1-萘酚

从混合萘酚中分离提纯1-萘酚采用熔融结晶技术,通过对降温速率、结晶终温、升温速率及“发汗”终温等因素对粗晶体收率及纯度的影响的综合考虑,经多次反复实验,确定了结晶提纯1-萘酚较佳的工艺参数条件,经过单级结晶1-萘酚的含量由80％上升到了93％。     

石灰乳中和模拟酸性废水形成的二水硫酸钙的晶粒形貌与粒度分布

实验研究了各工艺参数及废水中Mg2+与Fe3+主要杂质离子对石灰乳中和模拟酸性废水形成的二水硫酸钙晶体形貌与大小的影响. 结果表明,反应温度是主要影响因素,当其从25℃提高至70℃时,硫酸钙晶体形貌从片状和针状向棒状转变;而搅拌转速、石灰乳浓度、石灰乳加入速度对结晶过程的影响较不明显. 废水中Mg2+和Fe3+离子对硫酸钙晶体生长有抑制作用,浓度越大,抑制作用越强,Mg2+浓度达1945 mg/L时晶体由片状转变为棒状. 石灰乳二段中和模拟工业酸性重金属废水,得到团聚的针状硫酸钙晶体,废水达标排放.     

聚乳酸结晶成核剂的研究进展

聚乳酸作为一种新型可生物降解高分子材料,具有优良的机械性能和生物降解性,但结晶速度缓慢也制约了其应用,添加结晶成核剂是一种改善聚合物结晶行为的有效手段,本文综述近年国内外对聚乳酸结晶成核剂的研究情况。