梯度折射率聚合物细棒的制备和数学模拟

在聚甲基丙烯酸甲酯 (Poly(methylmethacrylate) ,PMMA)管中 ,加入单体甲基丙烯酸甲酯 (Methylmethacrylate ,MMA)和另一种高折射率的掺杂剂溴苯 (Bromobenzene ,BB) ,用界面凝胶均聚合方法制备了梯度折射率聚合物光纤预制棒 .这种光纤预制棒的梯度折射率是通过具有不同折射率的分子扩散而形成的 .通过对界面凝胶聚合过程的描述 ,该工作讨论了预制棒中聚合物的浓度分布及边界条件的假设 .并根据自由体积理论对其折射率分布进行理论模拟 .将得到的折射率抛物线分布与实验结果进行对比 ,结果表明聚合浓度的分布为ω =a(r/R) 2 +b时 ,理论预计的光纤预制棒的折射率分布与实验结果有着较好的符合 .同时 ,对聚合体系中BB对聚合物浓度分布的影响进行了讨论     

紫外/可见光谱在有机光纤研制中的应用

有机光导纤维是近十几年来在新型光功能性高分子材料领域中的一支独秀.相对于玻璃光导纤维,有机光导纤维加工容易、口径大、轻而柔软、抗挠曲、抗冲击、耦合容易,更重要的因素是制作成本低和用途广泛.通常光导纤维是一种带包层的透明圆柱型的细丝.芯子的折射率高于包层并且是不变的,这种纤维称为突变型(SI)光纤.由于SI型光纤的带宽小,不能满足高信息量传输的需要,因而渐变型(GI)有机光纤得以发展.在这种光导纤维中,纤芯的折射率是呈抛物线型分布的,其轴心的折射率最大,折射率由纤维轴心沿径向到包层逐渐变小,在芯/包层界面处折射率无突变,光线在这种光纤的传播路径近似正弦波.沿正弦波处的折射率均小于轴心区的折射率.由于光速是反比于折射率的,因此当光沿着正弦途径传输时,其速度大于光沿着轴心传输的速度.于是,较长的光路被较大的光速所补偿,结果是光在正弦波处的传输时间与在轴心处的传输时间上没有大的区别,而脉冲加宽是正比于传输时间的差值,因此有望在GI型有机光纤中得到较小的脉冲加宽.GI型有机光纤的制备一般可在GI型有机预制棒的基础上通过熔融热拉技术拉制而成.因此,制备GI型有机预制棒及其折射率分布的检测成为关键步骤.折射率分布的测量方法有很多,如近场扫描法、折射近场法、切片干涉法等.本文首次介绍了将紫外/可见吸收光谱应用于预制棒折射率分布的定性测试上,得到了在预制棒芯区沿径向掺杂剂分子溴苯的吸收强度呈抛物线型分布.因测试折射率分布的其他方法较为繁杂以及受仪器的限制,所以利用紫外/可见吸收光谱这一非常普通的仪器来估计折射率分布的情况不失为一种简单易行的方法.     

梯度型聚合物光纤中折射率分布的洛仑兹函数模型应用

利用洛仑兹函数对梯度型聚合物光纤(棒)中折射率分布曲线进行模拟,建立折射率分布的洛仑兹函数模型.该模型只需掺杂物的初始浓度、分子体积和聚合温度3个基本参数.利用该模型对各种高折射率的掺杂物掺杂聚甲基丙烯酸甲酯(PMMA)制备的梯度型聚合物光纤中的折射率分布进行了预测,发现掺杂物的折射率比分子体积对折射率梯度的影响更大;惰性掺杂物中二苯硫(DPS)掺杂效率最高;共聚掺杂物中苯甲酸乙烯酯(VB)掺杂效率最高.     

聚合反应条件对渐变型塑料光纤预制棒的折射率分布的影响

用甲基丙烯酸甲酯 (MMA)作为基质 ,采用界面 凝胶聚合技术成功地制备了渐变型塑料光纤预制棒 ,并探讨了掺杂剂浓度及其分子体积以及聚合温度对折射率分布的影响 .观察到聚合温度对折射率分布的影响以及掺杂剂分子的分子体积在极端情况下 (如溴苯与MMA分子的分子体积相似 ,联苯分子体积比MMA则要大的多 )对折射率分布的影响 ,清楚地显示出分子体积在界面 凝胶聚合过程中所起的重要作用 .实验结果表明了高温聚合有利于轴心Δn值的升高 ,可得数值孔径NA较大的预制棒 .低温聚合使得折射率分布趋于平缓化 .     

邻苯二甲酸二烯丙酯和甲基丙烯酸甲酯共聚物梯度折射率棒制备过程的研究

<正> 梯度折射率棒是折射率沿径向或轴向连续变化的透明圆棒,具有光自聚焦性能。可用于制作自聚焦型光纤维和自焦聚透镜。用玻璃制得的梯度棒直径和折射率差都很小。近年来,开始研究高分子梯度棒,据估计其直径可望达到100mm,折射率差也可达0.1。本文采用二元掖体扩散共聚法,制得梯度棒,其径向折射率分布接近于抛物线型。     

N-异丙基马来酰亚胺在渐变型耐温塑料光纤中的应用

研究了以N－异丙基马来酰亚胺（IPMI）与甲基丙烯酸甲酯共聚物为基材,制备渐变形耐温塑料光纤的可行性。实验确定了链转移剂和N－烷基马来酰亚胺对体系玻璃化温度的影响。通过Lorentz-Lorenz公式,估算出IPMI在共聚物中的折光率值。用元素分析法证明IPMI在塑料光纤预制棒中呈渐变分布,测定了以此材料制备的塑料光纤预制棒的折光率分别布线,说明IPMI在提高塑料光纤耐温性的同时,可作为参杂剂使用。结果表明：IPM／MMA共聚物是制备渐变型耐温塑料光纤的良好材料。     

用聚焦法测试光纤预制棒折射率剖面的计算程序

聚焦法是一种最新的非破坏性的测量光纤预制棒或光纤折射率剖面的方法。它是由D.Marcuse于1979年提出的。本文用BASIC语言编制了一套该方法的计算程序,所得结果与D.Marcuse的结果很好地相吻合。测量的再现性优于1%。一、聚焦法的基本原理     

折射率梯度型塑料光纤棒的制备与模拟

采用溴苯作为高折射率掺杂剂，通过界面凝胶聚合法制备了折射率呈梯度型分布的塑料光纤棒，研究发现，在聚合反应前期，混合物在真空与60－70℃的条件下聚合，而后期反应在高压气氛中进行，可以消除光纤棒中的气泡或真空泡，利用Vrentas-Duda自由体积理论，对梯度型折射率分布的形成进行了分析，建立了物理模型，并进行了模拟分析。     

含双酚芴聚碳酸酯的合成与光学性能

将具有负双折射系数的双酚芴{9,9-二[4-(2-羟乙氧基)苯基]芴, BPEF}与双酚A(BPA)共聚, 制备本征双折射率接近零的含双酚芴聚碳酸酯(共聚PC). 研究发现, 碱性强、 pK_a值大的催化剂可以缩小BPA和BPEF的活性差异, 有利于制备高分子量含双酚芴聚碳酸酯, 缩聚温度为265 ℃、 缩聚时间为40 min时产物具有较高的分子量和较低的黄变指数. BPEF和BPA投料比(摩尔比)为40/60时共聚体系的重均分子量可达39800, ¹H NMR和¹³C NMR测试证明分子链呈无规共聚结构. 随着BPEF含量的上升, 共聚PC的折射率从1.586提高到1.639, 本征双折射率从0.1948下降到-0.0102. 当BPEF摩尔分数为87%时, 共聚PC的本征双折射率低至0.0028, 非常接近零双折射.     

LSJ-Ⅱ型拉丝系统

LSJ-Ⅱ型拉丝系统主要用于将预制光纤石英玻璃棒进行加热后拉制成光导纤维。送棒机构可夹8-12mm的光纤预制棒,送棒速度10mm/min,连续可调,误差不大于±0.015mm/min,送棒行程600mm。拉丝速度5-60m/min,连续可调,误差不大于±0.024m/min。收线长度大于1.5km。     

Cold fiber solid-phase microextraction device based on thermoelectric cooling of metal fiber

A new cold fiber solid-phase microextraction device was designed and constructed based on thermoelectric cooling. A three-stage thermoelectric cooler (TEC) was used for cooling a copper rod coated with a poly(dimethylsiloxane) (PDMS) hollow fiber, which served as the solid-phase microextraction (SPME) fiber. The copper rod was mounted on a commercial SPME plunger and exposed to the cold surface of the TEC, which was enclosed in a small aluminum box. A heat sink and a fan were used to dissipate the generated heat at the hot side of the TEC. By applying an appropriate dc voltage to the TEC, the upper part of the copper rod, which was in contact to the cold side of the TEC, was cooled and the hollow fiber reached a lower temperature through heat transfer. A thermocouple was embedded in the cold side of the TEC for indirect measurement of the fiber temperature. The device was applied in quantitative analysis of off-flavors in a rice sample. Hexanal, nonanal, and undecanal were chosen as three off-flavors in rice. They were identified according to their retention times and analyzed by GC-flame ionization detection instrument. Headspace extraction conditions (i.e., temperature and time) were optimized. Standard addition calibration graphs were obtained at the optimized conditions and the concentrations of the three analytes were calculated. The concentration of hexanal was also measured using a conventional solvent extraction method (697+/-143ng/g) which was comparable to that obtained from the cold fiber SPME method (644+/-8). Moreover, the cold fiber SPME resulted in better reproducibility and shorter analysis time. Cold fiber SPME with TEC device can also be used as a portable device for field sampling.     

松花粉干预卵巢早衰大鼠肝脏的广泛靶向代谢组学分析

卵巢早衰是妇科领域的常见病,中医认为卵巢早衰与肝肾的正常与否息息相关,通过药食两用物质对肝脏代谢的调理是治疗卵巢早衰的一种重要手段。该研究基于超高效液相色谱-三重四极杆质谱(UHPLC-MS/MS)建立的广泛靶向代谢组学技术,探讨破壁松花粉对环磷酰胺诱导的卵巢早衰模型大鼠肝脏代谢的影响,旨在通过测定对照组、模型组、雌激素阳性对照组及施以不同剂量的松花粉干预组的SD大鼠肝脏组织中代谢物的含量变化,结合主成分分析(PCA)、正交偏最小二乘判别分析(OPLS-DA)等多元统计方法揭示松花粉干预卵巢早衰大鼠肝脏代谢的作用机制。通过正、负离子模式共检测出687种肝脏代谢物,PCA与OPLS-DA显示环磷酰胺诱导的模型组能够与对照组、阳性对照组、松花粉干预组等组别之间的代谢物较好的分离。通过单变量分析中的t检验(p<0.05)、变异倍数(FC>2或<0.5)与多变量分析中变量投影重要性(VIP值)>1相结合对差异代谢物进行筛选。与对照组相比,模型组SD大鼠肝脏中的32个生物标志物含量显著升高,28个生物标志物含量显著降低,主要涉及α-亚麻酸代谢、维生素B6代谢、嘌呤代谢、赖...     

Design,synthesis, and characterization of a partially chlorinated acrylic copolymer for low‐loss and thermally stable graded index plastic optical fibers

As a novel material of low loss and high thermal stability, a graded index plastic optical fiber (GI POF) comprised of a copolymer of methyl α‐chloro acrylate (MCA) and 2,2,2‐trichloroethyl methacrylate (TCEMA) was prepared and the thermal, mechanical, and optical characteristics were investigated. Although each homopolymer had low loss and desirable high thermal stability, they had crucial disadvantages for the fiber fabrication process. To draw a MCA polymer (PMCA) fiber, it has to be heated above 270 °C. However, the polymer started to decompose at a lower temperature and produced numerous bubbles. In contrast, TCEMA polymer (PTCEMA) is too brittle to roll up during heat drawing. In this study, we succeeded to improve the strong viscoelasticity and the low decomposition temperature of PMCA and the brittleness of PTCEMA by copolymerizing MCA and TCEMA. In addition, the glass transition temperatures (T_g) of the copolymers were in the range of 133–147 °C and the transmittances of the copolymers were much higher than that of PMMA which has been commonly used as a base material of POF. A suitable GI POF was obtained using the MCA and TCEMA copolymer. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3352–3361, 2009     

PDMS Rod-SBSE System Coupled with Gas Chromatography for Determination of PAHs in Aqueous Samples

A method for the analysis of trace polycyclic aromatic hydrocarbons(PAHs) in aqueous samples has been established by polydimethylsiloxane(PDMS) rod aided stir bar sorptive extraction(SBSE). The homemade PDMS rod has a size of 30 mm?3 mm o.d. with a volume of ca. 200 ?L, stable in thermal desorption process. The enriched PAHs by the PDMS rod were released in a homemade thermal desorption system coupled with gas chromatography. Experimental parameters for extraction of six PAHs were optimized including extraction time, pH, ionic strength and temperature of solution. The procedure has good recoveries of 80.0%―100.3% and very low limits of detection of 4.0―33 ng/L. PAHs in rain and river water were analyzed by this method.     

Poly (vinyl chloride)/poly (α‐methylstyrene–acrylonitrile)/acrylic resin ternary blends with enhanced toughness and heat resistance

In this study, tough and high heat‐resistant poly (vinyl chloride) (PVC)/poly (α‐methylstyrene–acrylonitrile) (α‐MSAN) blends (70/30) containing acrylic resin (ACR) as a toughening modifier was prepared. With the addition of ACR, heat distortion temperature increased slightly, which corresponded with the increase in glass transition temperature measured by differential scanning calorimetry and dynamic mechanical thermal analysis. Thermogravimetric analysis showed that addition of ACR improved the thermal stability. With regard to mechanical properties, tough behavior was observed combined with the decrease in tensile strength and flexural strength. A brittle‐ductile transition (BDT) in impact strength was found when ACR content increased from 8 to 10 phr. The impact strength was increased by 34.8 times with the addition of 15 phr ACR. The morphology correlated well with BDT in impact strength. It was also suggested from the morphology that microvoids and shear yielding were the major toughening mechanisms for the ternary blends. Our present study offers insight on the modification of PVC, since combination of α‐MSAN and ACR improves the toughness and heat resistance of pure PVC simultaneously. Copyright © 2011 John Wiley & Sons, Ltd.     

The effects of L-shaped heat source in a quarter-tube enclosure filled with MHD nanofluid on heat transfer and irreversibilities,using LBM: numerical data,optimization using neural network algorithm (ANN)

Journal of Thermal Analysis and Calorimetry - In this paper, the process of natural convection heat transfer (NCHT) and production of entropy (POF) in a portion of a tube has been modeled...     

Synthesis of hexadecylamine capped CdS nanoparticles using heterocyclic cadmium dithiocarbamates as single source precursors

Heterocyclic cadmium dithiocarbamates, [Cd(S₂CNC₅H₁₀)₂] and [Cd(S₂CNC₉H₁₀)₂] were synthesized. The complexes were thermolysed in hexadecylamine (HDA) to give HDA capped CdS nanoparticles. A combination of close to spherical, rod, bipods and tripods was obtained by varying the reaction parameters such as precursor concentration and temperature. The optical properties and X-ray diffraction studies of the particles are also reported.     

Optimisation of mould surface temperature and bottle residence time in mould for the carbonated soft drink PET containers

Polyethylene terephthalate (PET) bottles, which are usually produced by injection stretch blow moulding (ISBM) are widely used for carbonated soft drinks (CSD) storage and transportation. Stretch rod movement, blow pressure, preform temperature profile, mould surface temperature and material properties are among the most important factors affecting the final product's quality in terms of the thickness distribution, burst pressure and top-load resistance of the bottles. However, the residence time of the blown bottle inside the mould is also an important factor affecting its final properties. Especially in PET bottle production for hot fillings, the residence time is a very important factor because the longer the residence time the better the crystalline structure of the PET. In this production, the lid section is desired to have a fully crystalline form so that it can withstand hot fluids. In this study, the aim was to optimise the mould surface temperature and the blown bottle's residence time inside the mould for 1 L soft drink PET bottle production based on the final properties using the ECHIP 7 design of experiment (DOE) program. The method employed through this program was a quadratic one. Optimum process parameters were determined by the response surface method (RSM) and the process settings ensuring maximum top-load, burst pressure, Tg and degree of crystallinity were regarded to be optimum. It was found that the optimum mould surface temperature and blown bottle residence time inside the mould were 10 °C and 20 s, respectively.     

Reversible and irreversible heat capacity of poly(trimethylene terephthalate) analyzed by temperature‐modulated differential scanning calorimetry

The heat capacity of poly(trimethylene terephthalate) (PTT) has been analyzed using temperature‐modulated differential scanning calorimetry (TMDSC) and compared with results obtained earlier from adiabatic calorimetry and standard differential scanning calorimetry (DSC). Using quasi‐isothermal TMDSC, the apparent reversing and nonreversing heat capacities were determined from 220 to 540 K, including glass and melting transitions. Truly reversible and time‐dependent irreversible heat effects were separated. The extrapolated vibrational heat capacity of the solid and the total heat capacity of the liquid served as baselines for the analysis. As one approaches the melting region from lower temperature, semicrystalline PTT shows a reversing heat capacity, which is larger than that of the liquid, an observation that is common also for other polymers. This higher heat capacity is interpreted as a reversible surface or bulk melting and crystallization, which does not need to undergo molecular nucleation. Additional time‐dependent, reversing contributions, dominating at temperatures even closer to the melting peak, are linked to reorganization and recrystallization (annealing), while the major melting is fully irreversible (nonreversing contribution). © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 622–631, 2000     

几种热塑性特种工程塑料的热分析研究

聚芳醚和聚芳硫醚两类聚合物都为热塑性的耐高温特种高分子材料 ,由于它们的加工性好、加工成型效率高 ,受到了世界各国的高度重视。这两类聚合物在结构上有许多相似之处 ,如它们的主链都含苯环、酮基或砜基 ,而聚芳醚类聚合物的柔性基团为醚键 ,聚芳硫醚类聚合物的柔性基团为硫醚键 ,但由于氧和硫在元素周期表中属于同一族元素 ,原子结构仍然相似 ,因而在某些方面具有一定的可比性。研究它们的性能差异对于改进聚合物性能以及进行进一步的结构设计将有一定的帮助。在这两类聚合物中 ,国内已商品化生产的品种有ＰＥＥＫ、ＰＥＳ和ＰＰＳ ,有…