增韧尼龙66的结构分析

研究了改性三元乙丙橡胶增韧尼龙66时橡胶含量对冲击韧性的影响。用WAXD研究了增韧前后尼龙66的结构变化,计算了结晶度和微晶尺寸,结果表明超韧后尼龙66的结晶性下降。同时测定了冲击断口应力发白区的结构变化,说明在断裂过程中,由于基体屈服,韧性尼龙66晶型发生了转变(部分α型转化为准六方晶型)     

Organic-inorganic nanocomposite polymer electrolyte membranes for fuel cell applications

Organic-inorganic nanocomposite polymer electrolyte membrane (PEM) contains nano-sized inorganic building blocks in organic polymer by molecular level of hybridization. This architecture has opened the possibility to combine in a single solid both the attractive properties of a mechanically and thermally stable inorganic backbone and the specific chemical reactivity, dielectric, ductility, flexibility, and processability of the organic polymer. The state-of-the-art of polymer electrolyte membrane fuel cell technology is based on perfluoro sulfonic acid membranes, which have some key issues and shortcomings such as: water management, CO poisoning, hydrogen reformate and fuel crossover. Organic-inorganic nanocomposite PEM show excellent potential for solving these problems and have attracted a lot of attention during the last ten years. Disparate characteristics (e.g., solubility and thermal stability) of the two components, provide potential barriers towards convenient membrane preparation strategies, but recent research demonstrates relatively simple processes for developing highly efficient nanocomposite PEMs. Objectives for the development of organic-inorganic nanocomposite PEM reported in the literature include several modifications: (1) improving the self-humidification of the membrane; (2) reducing the electro-osmotic drag and fuel crossover; (3) improving the mechanical and thermal strengths without deteriorating proton conductivity; (4) enhancing the proton conductivity by introducing solid inorganic proton conductors; and (5) achieving slow drying PEMs with high water retention capability. Research carried out during the last decade on this topic can be divided into four categories: (i) doping inorganic proton conductors in PEMs; (ii) nanocomposites by sol-gel method; (iii) covalently bonded inorganic segments with organic polymer chains; and (iv) acid-base PEM nanocomposites. The purpose here is to summarize the state-of-the-art in the development of organic-inorganic nanocomposite PEMs for fuel cell applications.     

PAB/PET热致液晶共聚酯酰胺的WAXD研究

本文采用广角Ｘ 射线衍射仪,示差扫描热分析仪对ＰＡＢ（ 对氨基苯甲胺）／ＰＥＴ（ 聚对苯二甲酸乙二脂） 热致液晶共聚酯酰胺进行了研究,着重探讨了聚合物链组成对共聚物晶态结构和结晶性能的影响。结果表明,随着ＰＡＢ 含量的增加,ＰＡＢ各晶面间距ｄｈｋ１ 基本不变,但结晶晶体结构发生明显畸变,微晶尺寸显著增大,结晶度急剧降低。     

长碳链PA1212弹性体在热环境中的分子运动和氢键研究

热塑性聚酰胺弹性体因其优异的回弹性和二氧化碳选择透过性而受到广泛关注,而材料内氢键作用对弹性体相分离行为和力学性能有决定性影响。基于PA1212聚醚型弹性体,即PA1212为硬段,聚丙二醇-聚乙二醇-聚丙二醇三嵌段共聚醚为软段,通过原位红外光谱（FT-IR）、二维相关红外光谱（2D FT-IR）、原位广角X射线衍射（WAXD）分析,结合分子动力学模拟,研究了PA1212弹性体分子链运动行为和氢键解离方式。弹性体受热导致分子链运动能力增强,体系中氢键作用减弱,有序氢键（ordered hydrogen bond）向无序氢键（disordered hydrogen bond）转变,其中软段C—O—C和N—H形成的氢键优先解离,而硬段微区PA1212中C==O和N—H形成的氢键解离滞后;相比形成氢键的分子链间距d₁₀₀,氢键面间距d_010/110受热变化更敏感,最终分子链间距和氢键面间距近似相等,即发生Brill转变,WAXD结果表明,加热促进了氢键的解离。分子动力学模拟结果验证了红外分析结果,氢键键长增加,氢键作用减弱,PA1212微区的氢键密度...     

Molecular structure of metallocene catalyst Cptt2ZrCl2 and structural analysis of PE catalyzed by Cptt2ZrCl2

Cp^tt₂ZrCl₂ (Cp^tt = η⁵?^tBu₂C₅H₃) was synthesized by the reaction of LiCp^tt with ZrCl₄ and characterized by X‐ray crystallographic studies. It was used as catalyst for ethylene polymerization. Structural analysis was carried out on the polyethylene (PE) catalyzed by Cp^tt₂ZrCl₂ via wide‐angle X‐ray diffraction (WAXD) and small‐angle X‐ray scattering (SAXS). The degree of crystallinity (W_c,x) was calculated by WAXD. The semiaxises of the particles (a, a, b) of PE were determined by SAXS and it could be found that the crystalline particles of PE are mainly rod shaped determined by the characteristic function v₀ (r). The radius of gyration R_g, crystalline thickness L_c, the thickness of noncrystalline region L_a, long period L, electron‐density difference between the crystalline and noncrystalline regions η_c ? η_a, and the invariant Q are determined by SAXS. The results also indicate that a transition zone exists between the traditional “two phases” with a clear dimension of 1.3 nm. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 169–175, 2005     

聚丙烯/尼龙6共混物的X射线衍射研究EI

用广角 X射线衍射 (WAXD)方法研究了不同接枝聚丙烯对聚丙烯 /尼龙 6 (PP/PA6 )共混物结晶行为的影响。结果表明 ,与简单机械共混物相比 ,由于增容剂的加入 ,PP的结晶行为发生变化——不同晶面的生长速率不同 ,且在所研究的范围内有随增容剂含量的增加 。     

Green Nanocomposites from Renewable Resources: Effect of Plasticizer on the Structure and Material Properties of Clay‐filled Starch

Nanocomposites of starch were prepared via different addition sequences of plasticizer and clay by the solution method. The extent of dispersion of the filler was evaluated by wide angle X‐ray diffractometry (WAXD) in the resulting composites. Thermal stability, mechanical properties and water absorption studies were conducted to measure the material properties whereas FT‐IR spectroscopy was used to study the microdomain structure of composites. The sequence of addition of components (starch /plasticizer (glycerol) / clay) had a significant effect on the nature of composites formed and accordingly properties were altered. Glycerol and starch both have the tendency to penetrate into the silicate layers but penetration of glycerol is favored owing to its smaller molecule size. The filler dispersion becomes highly heterogeneous and the product becomes more brittle when starch was plasticized before filling with clay due to the formation of a bulky structure resulting from electrostatic attractions between starch and plasticizer. It was concluded that best mechanical properties can be obtained if plasticizer is added after mixing of clay in the starch matrix.     

Crystal structure changes during isothermal crystallization, cooling and heating of linear polyethylene

The dynamic process of crystal structure change during isothermal crystallization, cooling and heating of linear polyethylene with different molecular weight and polydispersity was followed by wide-angle X-ray diffraction (WARD) measurement. From the WARD data, variations of unit cell parameters a and b and changes in crystallinity were estimated. During isothermal crystallization, both cell parameters were found to decrease with time, suggesting that the crystal structure was becoming more perfect. With an increase in molecular weight or crystallization temperature, the rate of crystal perfection and the attainable crystallinity were found to decrease. This behavior can be explained by the formation of thicker lamellae, which probably have a lower degree of defects and a reduced surface-to-volume ratio in the crystals. Upon cooling and heating, the cell parameters appeared to contract and expand accordingly. The thermal contraction and expansion of parameter a is considerably larger than that of b, which probably results from the weaker intra-chain interactions along the a-axis, which is perpendicular to the spherulite growth direction.     

涤棉混纺物的X射线衍射分析

以计算机分峰法对ＷＡＸＤ测得的涤棉混纺物的Ｘ射线衍射图谱进行分峰,并依此绘制涤棉混纺物的Ｘ射线衍射组分定标工作曲线,求得定标曲线方程,建立了一种新的涤棉混纺物混纺比的Ｘ射线分析方法     

The conformational changes,crystal structure and melting behavior of poly(ethylene/ trimethylene terephthalate) copolyesters

The conformational changes, crystal structure and melting behavior of poly(ethylene/trimethylene terephthalate) (ET) copolyesters were investigated using in situ Fourier transform infrared (FTIR) spectroscopy, wide‐angle X‐ray diffraction (WAXD), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC) under isothermal crystallization conditions. The results show that the minimum melting temperature was observed in ET53, in which the relative amount of ethylene glycol (EG) to 1,3‐propanediol (PDO) was 52.68/47.32 and the PDO‐dimethyl terephthalate (DMT)‐PDO segments in the molecular chain dominated the crystal formation. The minimum crystallinity of ET copolyesters was found in ET66, in which the relative amount of EG/PDO was 65.91/34.09 and the EG‐DMT‐EG segments in the molecular chain dominated the crystal formation. A rapid and continuous conformational transition in ET copolyesters was observed using in situ FTIR in the first 10 min under isothermal crystallization conditions. The continuously adjusting conformation in the molecules reflects the crystallization of ET copolyesters. Based on the DSC and the X‐ray analyses of the crystallization behavior in the ET copolyesters, crystalline conformation transitions of molecules in ET copolyesters take place rapidly and early. Copyright © 2012 Society of Chemical Industry