HDPE耐环境应力开裂性能的研究及改进

对HDPE的耐环境应力开裂性能进行了研究。试验表明:采用共混及化学改性的方法,HDPE的耐环境应力开裂性能有了很大提高,为解决HDPE树脂在制作管材时出现的短时间内应力开裂问题提供了依据。     

EMD-IT去噪算法的阈值估计方法

为解决EMD-IT去噪算法中阈值难以确定的问题,提出一种基于高斯白噪声能量分布的阈值估计方法。将含噪信号进行经验模态分解并估计各固有模态函数(IMF)中噪声的能量;根据模态单元阈值的含义,在各IMF中利用去除掉的模态单元包含的总能量等于噪声能量这一准则估计阈值。合成数据和实际心电信号的去噪仿真实验验证了该方法的有效性,其是自适应的且避免了阈值选择的主观性。     

THE EFFECT OF PRECIPITATION PARAMETERS ON PREPARATION OF LITHIUM FLUORIDE (LIF) NANO-POWDER

Lithium fluoride powder (LiF) is a white powder with a density of 2.64 gr/cm³ and a melting point of 848°C. This powder has several applications such as flux, glaze, soldering, and aluminum melting process, but one of the most important uses of this powder is its application in dosimetry. The commercial powders currently used for this purpose have average sizes of 5 to 10 micrometers; the objective of this research is to produce LiF powder with nano-metric particle size. In this study, the reaction of LiOH + HF → LiF + H₂O has been selected from among several reactions that were able to produce LiF powder, and some precipitation parameters such as temperature, time, agitation type, and supersaturation degree have been controlled. The morphology, phase analysis, and particle size distribution of the resulting powders were analyzed by SEM, XRD, and LPSA. Finally, lithium fluoride nano-powder was synthesized at a temperature of 25°C, pH about 2-3, reaction time less than 1 s, and agitation by ultrasonic bath.     

Miscibility behavior of blend of polyesteramides of linseed oil and dehydrated castor oil with poly(methacrylic acid)

Blending of two polymers in solution is a simple and cost‐effective technique to improve upon the physical and mechanical properties of the component polymers through synergism. To obtain maximum synergy in their properties, the component polymers should be miscible with each other on molecular scale. Polymer blends of complex physicomechanical properties are being actively investigated. Poly(methacrylic acid) (PMAA), a commercial polymer, yields transparent, hard, brittle, and water‐sensitive films. It has been blended with natural polymers like dextran, collagen, and gelatin to obtain films with improved physical and mechanical characteristics. Polyesteramides, which are easily synthesized from vegetable seeds oil, a sustainable resource, have found application in surface coatings. These oligomeric products do not make free standing films in the ambient condition. The polyesteramides from vegetable seeds oil can be used to obtain blend with PMMA of improved mechanical and water absorption properties. In this study, linseed oil polyesteramide (LOPEA) and dehydrated castor oil polyesteramide (DCPEA), the source oils with different unsaturation in their fatty acid chains, were blended with PMAA through mixing in solution in the ratio DCPEA/LOPEA: PMAA as 80/20, 70/30, 60/40, 50/50, 40/60, 30/70, and 20/80. In the first instance, the miscibility of the two components was investigated in solution by viscosity and ultrasonic measurements and in solid phase through differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). Moisture absorption by the blend was also studied. DCPEA and LOPEA show immiscibility with PMAA in solution phase while LOPEA with more unsaturation in the fatty acid chain of the oil was found more immiscible than DCPEA. DCPEA shows a narrow miscibility window in the solid phase while LOPEA was found immiscible with PMAA in the solid phase too. Uptake of moisture was found to be markedly reduced in the blends of DCPEA/LOPEA with PMAA. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1367–1374, 2007:     

镁铝水滑石及其复合体系对PVC热稳定性能的调控

采用比色法、热失重法等研究了不同镁铝摩尔比的水滑石(LDHs)对PVC糊热稳定性能的影响。结果表明,在镁铝比分别为2、3、4的样品中,镁铝比为2的LDHs对PVC的热稳定效果最佳;将其与传统的铅盐、有机锡稳定剂复配,均具有良好的协同效应,可以实现对PVC糊热稳定性能的控制。其中,PVC/Mg-AlLDHs/Sn以100∶1.5∶1.5(质量份数,下同)比例复合后的体系,不仅热稳定性能优于传统的的铅盐体系,而且具有较低的糊黏度及较好加工流变性能。     

熔融缩聚法制备聚乳酸

通过熔融缩聚法制备了聚乳酸。探讨了反应温度、催化剂类型及用量、反应时间对聚乳酸的影响，并用红外光谱和1↑H NMR对聚合物进行了表征。结果表明，最佳的反应条件为：聚合时间30h左右、聚合温度160℃、以O．2％的对甲苯磺酸作为酸催化剂、O．5％的氯化亚锡为催化剂、真空度为O—1333Pa；而提高乳酸纯度是制备高摩尔质量聚乳酸的关键条件之一。     

一种单面涂铝PVC塑料吊顶材料燃烧性能的实验研究

采用锥形量热仪对市场上常见的一种内装修单面涂铝PVC吊顶材料的燃烧性能进行了实验研究。实验结果表明，在不同的辐射功率和不同暴露面下，该材料表现出不同的燃烧性能。当涂铝面(正面)暴露燃烧时，其质量损失速率(即燃烧速率)比未涂铝面(背面)小，正面的引燃时间比背面引燃时间长，这些特性对减小燃烧时的火焰蔓延速度有利；而正面暴露燃烧时的发烟量和一氧化碳的产率则比背面暴露燃烧时大，这一特性将增大材料燃烧时的烟气危害性。     

基于CPLD的光电编码器角位移拟合测速法

针对常用的M法和T法无法满足增量式光电编码器整个测速范围内误差要求的问题,提出了对码盘信号进行角位移拟合求采样时刻即时速度的新方法,在匀加速条件下对这3种方法进行了仿真实验,比较了测速误差。实验结果表明,角位移拟合法在整个速度范围内都能获得很高的测速精度和误差一致性。最后用CPLD对该方法加以实现,给出了Verilog硬件描述语言的设计程序和3种方法的实验结果比较。基于CPLD的实现方法电路简单,运行稳定可靠,处理速度快,为角位移拟合法提供了一种非常好的实现方法。     

Cr^3＋=Al2（WO4）3晶体生长助熔剂体系的研究

本文用DTA和XRD法研究了Na_2O-Al_2O_3-WO_3三元系中的Al_2(WO_4)_3-Na_2WO_4截面的相平衡关系。在这截面中发现一新化合物AlNa_3(WO_4)_2。以45mol％Na_2WO_4为助熔剂生长了Cr~(3+):Al_2(WO_4)_3晶体。     

Structural significance of the alkyl substituent at the C-4 of (+)-trans-verbenyl acetate in sex pheromonal activity of the American cockroach

The significance of the alkyl group at the C-4 of (+)-trans-verbenyl acetate, which is the sex pheromone mimic of the American cockroach, was investigated. Seven alcohols possessing an ethyl, propyl, or dimethyl group at this position of the 6,6-dimethylbicyclo[3.1.1]heptane skeleton were synthesized and evaluated by behavioral assay. All of the alcohols were inactive, while three of four acetates of the 2-alcohols induced sexual behavior in male cockroaches at the 0.02 or 0.5 mg dosage level, either of which is many orders of magnitude higher than the threshold level of the natural sex pheromones (10^–8 mg). Among the acetates, the compounds with a methyl group or an -oriented ethyl group at C-4 showed the highest activity. The results are discussed in terms of spatial requirements of the molecules for interactions with the receptor.Studies on the sex pheromone mimic of the American cockroach, (+)-trans-verbenyl acetate. Part VIII. For Part VII, seeComp. Biochem. Physiol.,70A: 229–234 (1981).