Synthesis and characterization of terpolymer of N‐cyclohexylmaleimide,methyl methacrylate,and acrylonitrile

Terpolymers of N‐cyclohexylmaleimide, methylmethacrylate, and acrylonitrile (AN) at different AN feed content were synthesized by suspension polymerization. The thermal properties of the terpolymers such as glass transition temperature (T_g) and Vicat softening temperature (T_Vicat) were determined by torsion braid analysis and Vicat softening temperature tester, respectively. The value of T_g and T_Vicat decreased with increasing AN feed content. Thermogravimetric analyses were carried out with the results that the incorporated AN units enhanced the thermal stability of the resulting polymers and a second degradation step appeared with the addition of AN. The mechanical properties (tensile strength and impact strength) of the terpolymers were also detected and the results show that the tensile strength and impact strength of terpolymers increase with increasing AN feed content. The rheological results illustrated that the terpolymers showed rheological behavior similar to that of pseudoplastic liquid. The apparent shear viscosity decreased with the increasing of AN feed content. The flow power index n increased with increasing AN feed content. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 792–796, 2007     

Isothermal crystallization kinetics and melting behaviors of nanocomposites of poly(trimethylene terephthalate) filled with nano‐CaCO3

The isothermal crystallization and subsequent melting behavior of poly(trimethylene terephthalate) (PTT) composites filled with nano‐CaCO₃ were investigated at designated temperatures with differential scanning calorimetry. The Avrami equation was used to fit the isothermal crystallization. The Avrami exponents were determined to be 2–3 for the neat PTT and PTT/CaCO₃ composites. The particles of nano‐CaCO₃, acting as nucleating agents in the composites, accelerated the crystallization rate, with the half‐time of crystallization decreasing or the growth rate constant (involving both nucleation and growth rate parameters) increasing. The crystallization activation energy calculated from the Arrhenius formula was reduced as the nano‐CaCO₃ content increased from 0 to 2%, and this suggested that nano‐CaCO₃ made the molecular chains of PTT easier to crystallize during the isothermal crystallization process. Subsequent melting scans of the isothermally crystallized composites exhibited triple or double melting endotherms: the greater the content was of nano‐CaCO₃, the lower the temperature was of the melting peak. The degree of crystallization deduced from the melt enthalpy of composites with the proper concentration of nano‐CaCO₃ was higher than that of pure PTT, but it was lower when the nano‐CaCO₃ concentration was more than 2%. The transmission electron microscopy pictures suggested that the dispersion state of nano‐CaCO₃ particles in the polymer matrix was even when its concentration was no more than 2%, whereas some agglomeration occurred when its concentration was 4%. Polarized microscopy pictures showed that much smaller or less perfect crystals formed in the composites because of the interaction between the molecular chains and nano‐CaCO₃ particles. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

The role of SO2 in the reduction of NO by CO on La2O2S

The decomposition of NO and the reduction of NO by CO on La₂O₂S were studied using temperature-programmed reaction technique coupled with fast mass spectrometry, powder X-ray diffraction and X-ray photoelectron spectroscopy. The role of SO₂ plays in the reduction is explored. It is found that the decomposition of NO is a favorable reaction step for the reduction of NO by CO achieved through a sulfur-assisted path. The oxygen produced in the decomposition is removed by the sulfur in the oxysulfide as SO₂, which in turn is reduced back to sulfur by CO on La₂O₂S. An external supply of sulfur, such as SO₂, in the feed is needed to maintain the population of sulfur in the oxysulfide and thus make the reduction sustainable.     

蚕丝蛋白开发利用的研究进展

较为全面地综述了最近几十年国内外关于蚕丝蛋白的组成、性能,介绍了蚕丝新用途和利用原理,蚕丝脱胶精炼方法,以及蚕丝在化妆品、医药、固定化酶载体材料、食品、再生丝和涂膜化纤表面等方面的应用和研究进展。     

燃烧法制备白光发光二级管用Ca1-xSrxS:Eu2+红色荧光粉

利用硝酸盐和含硫燃烧剂硫脲的氧化还原反应,通过燃烧法在较低的起始温度(500～550℃)合成了白光发光二级管用红色荧光粉Ca1-xSrxS:Eu2 ,研究了其发光性质.X射线衍射分析表明合成物为纯相的Ca1-xSrxS:Eu2 .激发谱和发射谱的研究表明:(Ca1-xSrx)S:Eu2 能被430～500 nm的可见光有效地激发而发出600～650 nm的红光.与高温固相法相比,燃烧法制备的荧光粉的激发光谱没有明显变化,燃烧法生成物分散性好,制备过程中反应初始温度比较低(500℃左右),反应时间短(10min左右),无污染.反应所用的硫脲价格低廉,反应速度快,是一种实用的燃烧剂.     

离子色谱法测定精胺沉淀物中的无机离子

采用非抑制型电导检测离子色谱法分离测定甲胺磷中间体精胺沉淀物中的无机离子。以2.5mmol/L邻苯二甲酸+2.4mmol/L三羟甲基氨基甲烷水溶液为淋洗液,沉淀中检出Cl-和SO42-;以6mmol/LHNO3水溶液为淋洗液在沉淀中检出NH4+。用该法分析精胺沉淀物中的无机离子经济、简便、快速。     

水中合成2-苯甲酰基-1,3,5-三苯基-4,4-二腈基环己醇的洁净方法

在水中以苯亚甲基苯乙酮和丙二腈为原料,十六烷基三甲基溴化铵(HTMAB)催化下,合成了标题化合物。考察了不同催化剂、催化剂用量及不同溶剂对反应的影响。产物的结构经IR和1HNMR进行了表征确证。该方法具有反应条件温和、操作简便、环境友好的优点。     

液晶p-PAEB原位改性不饱和聚酯树脂的结构形态和性能研究

合成了双4-烯丙基乙氧基苯甲酸对苯二酚酯液晶化合物（p-PAEB），并与甲基四氢苯酐型不饱和聚酯（UP）进行共聚合反应。研究了液晶化合物的用量对共聚合固化产物的微观形态和性能的影响。结果表明：一方面含有不饱和双键的液晶化合物可参与不饱和聚酯共聚合形成交联网络，使树脂的玻璃化转变温度提高9℃；另一方面由于液晶分子的自聚集能力，产生海岛式微相分离使纯树脂的冲击强度由0．139kJ／m^2提高到0．305kJ／m^2，但p-PAEB加入量超过8％会因产生明显的相分离而使性能降低。     

Preparation of Y2O3 Buffer Layer on LaAlO3 Substrate by TFA-MOD Method

Chemical solution deposition is a promising technique for fabrication of high-temperature superconducting films and oxide buffer layers due to its reproducibility and low cost. In this work, Y₂O₃ buffer layers were prepared on (100) LaAlO₃ substrates by mental organic deposition method using trifluoroacetate. The resulting Y₂O₃ films crystallized as a single phase at 900°C and showed a low degree of c-axis orientation. The scanning electron micrography showed that the surface of the films was smooth with a uniform grain size of approximately 10 nm.     

拟阵贪婪算法在景区装饰灯中的应用

该文立足于实际,就如何在景区设置装饰灯问题给出了数学模型及求解步骤。在解决过程中采用了拟阵的贪婪算法,此算法简洁、易行。