Molecular orientation and relaxation in poly(butylene terephthalate)/polycarbonate blends

Rheo-optical Fourier-transform infrared (FTIR) spectroscopy is based on the simultaneous acquisition of stress-strain data and FTIR spectra on-line to the mechanical treatment of polymers and is frequently applied for the characterization of transient structural changes during deformation and stress-relaxation. In the present communication, this technique has been employed in order to investigate the distribution of molecular orientation and its relaxation in uniaxially drawn solution-cast films of semicrystalline partial miscible blends of poly(butylene terephthalate) (PBT) with polycarbonate (PC) containing 10, 30 and 50 wt% PC. The uniaxial deformation of these blend films having a PBT-crystallinity degree ranging from 31 to 12%, in unstretched blends, leads to a appreciable high segmental orientation for the crystalline PBT due to a structural transformation from lamellae to microfibrils. The formation of this fibrillar structure is attributed to non-reversibility of an extended phase with all-trans conformational sequence of the aliphatic segments of PBT, occurring during elongation. The rate of relaxation of this conformational transition, however, increases with increasing amorphous content in the blends. Also it is observed that even with increasing amorphous content in the PBT/PC blends the crystalline PBT shows significant orientation. In such cases, apart from the few lamellae which transform to microfibrils, it is suggested that a stress induced transformation of PBT chains in amorphous PBT-component to irreversible all-trans extended crystalline form also contributes to PBT crystalline orientation. In contrast with this high crystalline orientation, the amorphous PBT located in the interlamellar regions inside the PBT-spherulites show a lower orientation in blends as compared in pure PBT.On the other hand, an overall segmental orientation of PC chains in blends is of lower order which is attributed mainly to low stretching temperature compared to T_g of pure PC. The results are discussed in terms of the resulting spherulitic morphology and the temporary network formed by the elongated PBT and PC chains inside the interlamellar regions, in blends.     

Diffuse reflectance fourier transform infrared spectroscopy of phospholipid adsorption onto silicic acid

Diffuse reflectance Fourier transform infrared spectroscopy was used to study the mode of adsorption of phosphatidylcholine (PC) in hexane onto silicic acid (SA). PC adsorption was mainly through the charged phosphate group with minimal binding through the ester carbonyl. When the SA surface with adsorbed PC is washed with hexane, containing a small concentration of isopropanol, the desorbed PC is recovered without structural change, i.e., there is no evidence of PC hydrolysis in the adsorption process. Adsorbent misture probably promotes PC adsorption due to the increased availability of surface water hydroxyl groups for interaction with the PC phosphate groups. Isopropanol promoted PC binding by destabilizing PC reverse miscelles in solution, thus promoting its adsorption.     

Mullite for Structural, Electronic, and Optical Applications

Mullite (3Al₂O₃·2SiO₂) is becoming increasingly important in electronic, optical, and high-temperature structural applications. This paper reviews the current state of mullite-related research at a fundamental level, within the framework of phase equilibria, crystal structure, synthesis, processing, and properties. Phase equilibria are discussed in terms of the problems associated with the nucleation kinetics of mullite and the large variations observed in the solid-solution range. The incongruent melting behavior of mullite is now widely accepted. Large variations in the solid solubility from 58 to 76 mol% alumina are related to the ordering/disordering of oxygen vacancies and are strongly coupled with the method of synthesis used to form mullite. Similarly, reaction sequences which lead to the formation of mullite upon heating depend on the spatial scale at which the components are mixed. Mixing at the atomic level is useful for low-temperature (<1000°C) synthesis of mullite but not for low-temperature sintering. In contrast, precursors that are segregated are better suited for low-temperature (1250° to 1500°C) densification through viscous deformation. Flexural strength and creep resistance at elevated temperatures are significantly affected by the presence of glassy boundary inclusions; in the absence of glassy inclusions, polycrystalline mullite retains >90% of its room-temperature strength to 1500°C and displays very high creep resistance. Because of its low dielectric constant, mullite has now emerged as a substrate material in high-performance packaging applications. Interest in optical applications mainly centers on its applicability as a window material within the mid-infrared range.     

Fatty acid composition of spanish shortenings with special emphasis on <Emphasis Type="Italic">trans</Emphasis> unsaturation content as determined by fourier transform infrared spectroscopy and gas chromatography

A Fourier transform infrared spectroscopic procedure was used to analyze 34 edible fats (22 shortenings and 12 vegetable margarines) as neat fats (IR_NF) to determine their total trans fatty acid (TFA) content. The sloping baseline was corrected with a reference spectrum based on a nonprocessed olive oil. The calibration was done using seven partially hydrogenated fats with an individual TFA content previously determined by the combination of gas chromatography (GC) with argentation thin-layer chromatography. Taking into account the different absorptivities of various trans isomers, different correction factors were calculated using the calibration standards (0.83 and 1.71 for single trans bonds in both diethylene and triethylene and for trans, trans-diethylene fatty acids, respectively) and applied to calculate the total TFA of samples. Moreover, the samples were converted to their methyl esters and reanalyzed following the same procedure (IR_FAME). Differences in TFA content of fats were not found when a t-test was used to compare the results obtained by IR_NF vs. either IR_FAME or GC, suggesting that IR of neat fats could be used, thus avoiding the need to prepare sample solutions in organic solvents and to prepare fatty acid methyl esters. The mean TFA content (determined by IR_NF) of a representative group of Spanish shortenings (22 samples) that varied widely in terms of fat sources, processes, and purposes (bakery, sandwiches, ice cream, coatings, chocolate coverings) was 6.55±11.40%, although more than 54% contained <3% of TFA. Fatty acid composition of shortenings by direct GC using a 100-m polar cyanopolysiloxane capillary column indicated that the mean trans-18∶2 isomer content was 0.58%, ranging from 0.9 to 3.4%. Small amounts of trans-18∶3 isomers (<0.3%) were observed in 18 of the 22 shortenings studied; the maximal value was <2%. The mean value of the fraction saturated+TFA of shortenings was high (59.95±12.73%), including two values higher than 83%.     

基于红外偏振的入射角确定

提出基于红外光的偏振度来确定透明物体形状检测中的入射角的方法。在可见光域,偏振度是入射角的二阶函数,即在布儒斯特角两侧各有一个入射角,不能唯一确定入射角。而在红外域,偏振度与入射角之间是一一对应关系,可以对可见光域的两个入射角做出区分,得到正确的入射角。这种方法提高了透明物体形状检测的精度,还可用于复杂形状的物体检测。     

红外测速光幕靶改进及测量精度分析

为提高XGK-2002型红外测速光幕靶的测量精度及安装调试速度,提出采用双辅助激光器实现光源和接收精确对准的光幕靶改进方案.在现有红外测速光幕靶工作原理及结构基础上,对光源和接收对准中存在的问题进行了探讨,分析了其影响.提出了在光幕靶两端分别设置一激光器实现对准的光幕靶改进方案,并从测时误差及靶距误差两方面对改进后测量精度进行了分析.结果表明,改进后的光幕靶可快速、直观的实现光源和接收的对准,测试精度及安装可靠性提高,改进后测速精度可达到1‰.     

改性聚氨酯固相微萃取吸附材料的合成及光谱分析

以羟基硅油、甲苯-2,4-二异氰酸酯（TDI）、聚己二酸乙二醇酯和1,6-己二醇为原料,以辛酸亚锡为催化剂,环己酮为溶剂,合成了有机硅-聚氨酯聚合物固相微萃取吸附材料。采用红外光谱法对聚合产物进行了结构表征。建立了分光光度法测定有机硅-聚氨酯共聚物中游离异氰酸酯基（NCO）含量的定量分析方法,吸光度与异氰酸基含量呈线性关系,相关系数为R2=0.9996。该方法相对标准偏差小于5%,回收率为99.4%～105%。考察了显色剂用量、体系的酸度、显色时间等因素对NCO测定结果的影响。     

无线远程控制LED显示系统设计

设计采用无线方式控制LED系统字模显示,依托PC机串口通信,并通过无线发射模块远程无线控制点阵显示屏系统,实现对显示信息进行更新和显示速度控制等操作,完成远程无线控制LED显示系统要求。     

基于新模糊准则与 DE算法的红外人体图像分割 *

人体目标的抽取是红外人体图像处理的基础 ,为了有效获取红外图像中的人体目标 ,提出了一种新的图像阈值化方法。首先在对模糊熵方法本质分析的基础上 ,通过参数变换定义了一种新的最小化模糊准则 ,然后将差分演化 ( differential evolution, DE)算法与新模糊准则相结合用于快速、有效地获取最佳阈值 ,最后在真实红外人体图像上与其他方法进行了对比实验。实验结果表明 ,所提出的方法不仅能得到理想的分割结果 ,而且 CPU耗时也较少 ,满足实时性处理要求。     

基于FPGA和PC机的客流统计系统设计

提出了一种基于FPGA和PC机的客流统计系统的设计方法。其中基于FPGA的下位机数据采集与处理电路模块采用Verilog HDL语言和原理图相结合的方式设计,上位机的人机交互界面及串口通信采用Visual C＋＋6．0设计完成。经模拟仿真和实际电路验证,结果表明该系统具有结构简单,成本低廉,计数准确率高的特点,能够很好地实现客流统计的功能,并可在不改变硬件平台的情况下对系统随时进行升级与重构,具有良好的适用性。