An Efficient Method for the Olefination of Aldehydes with Ethyl Diazoacetate Using Iron (II) Phthalocyanine as Catalyst

A variety of aliphatic and aromatic aldehydes were smoothly converted to the corresponding olefins in excellent yields with ethyldiazoacetate using iron (II) phthalocyanine as catalyst in the presence of triphenylphosphine as reducing agent.     

Effects of styrene–ethylene–butylene–styrene based additives on the mechanical properties of rice hull/polypropylene composites

The purpose of this study was to improve the mechanical properties (such as tensile, flexural, and impact strength) of rice hull/polypropylene composites, with the use of styrene–ethylene–butylene–styrene copolymer (SEBS) and maleated styrene–ethylene–butylene–styrene copolymer (SEBS-MA). The results suggested that both types of additives increased the impact strength of the composites significantly as their contents increased. However, only SEBS-MA improved the tensile and flexural strength of the composites. The results also indicated that the composites with SEBS-MA consistently showed better mechanical properties than the SEBS counterparts for all the contents. POLYM. ENG. SCI., 47:1148–1155, 2007. © 2007 Society of Plastics Engineers     

Bleach activation of thermomechanical pulp

Under mild alkaline condition the bleaching activator tetraacetyl ethylenediamine (TAED) forms peroxyacetic acid with sodium perborate and improves the brightness of thermomechanical pulp. The activator makes it possible to bleach the pulp efficiently even without addition of sodium hydroxide at any temperature in the range 40 to 70°C. A mathematical model has been proposed to allow estimation of the total peroxy acid consumption during activated bleaching process. Using this model it is possible to calculate the extent of peroxy acid decomposition by predetermining the rate constant and activation energy. The effect of bleach activation was found to be maximum at temperatures below 60°C. The influences of bleaching time, pH, consistency, temperature and TAED charge on the bleach activation has been evaluated. The activator is effective enough to improve the brightness of sodium perborate bleached pulp at an average charge of about 50 mass% of sodium perborate. Apparently, high consistency dispersive bleaching without free alkali is a technological and economic advantage of the process.     

The effect of dispersed elastomer particle size on heterogeneous nucleation of TPO with N2 foaming

Blending polypropylene (PP) with elastomeric modifiers provides a simple method of improving polymer's impact strength. Such PP/elastomer blends are commonly called thermoplastic polyolefin (TPO) blends. Developing TPO materials suitable for foaming is of great interest because they can be applied in high-volume markets such as the automotive industry. For immiscible polymer blends such as TPO, it has been often noted that the dispersed particles can act as cell nucleating agents, thereby enhancing heterogeneous nucleation. However, little work has been done to assess the effects of blend morphology on the nucleation behavior. Furthermore, the effects of elastomer dispersion on TPO foamability are still unknown. In this work, TPO blends with different blend morphologies were prepared by controlling the viscosity ratio between the blending components. Experimental results from both batch foaming and extrusion foaming processes with nitrogen (N₂) indicate that the foam structure is influenced by the size and the number density of the dispersed particles.     

Investigation of Structural Changes of Alkaline-extracted Wood Using X-ray Microtomography and X-ray Diffraction: A Comparison of Microwave versus Conventional Method of Extraction

Abstract

The effect of extraction of wood components on wood anatomy and cellulose crystallinity was studied using X-ray computed microtomography (micro CT) and X-ray crystallography. Micro CT of the xylem vessels of birch wood samples was used for the quantitative determination of the wood porosity after conventional and microwave extraction. The method was also used as an indirect means for the determination of temperature generated inside the fibers. Original porosity of birch wood was 18.5 ± 1.5%, and porosity increased with both extractions. The increase in wood porosity after 10 minutes of microwave extraction was double that of wood after conventional method of extraction at 90°C for two hours (42% vs. 26%), indicating a sudden rupture of the wood structure due to the volumetric heating effect produced by the microwave heating. Comparison of porosities of the conventionally extracted samples at different temperatures for the same duration indicated that the temperature generated inside the fibers during 10 minutes of microwave extraction is around 120°C. Crystallinity of cellulose did not change after both extractions, suggesting that the extraction did not affect the strength of the fibers.     

扭转挤出技术制备再生碳纤维增强聚苯乙烯化学发泡复合材料

采用再生碳纤维（RCF）作为增强体和成核剂及扭转挤出技术制备了聚苯乙烯（PS）/RCF为主体成分的硬质泡沫,利用三维（3D）层析成像技术、电子显微镜等对泡沫材料的微观结构、泡孔形态进行了研究。结果表明,在扭转挤出过程中,聚合物熔体产生了扭转螺旋流动,使纤维充分分散并沿流动方向取向;并且改善了整个体系的混合和温度性能,使得泡孔形态整体较为均匀;此外,泡沫质量受到机头温度的影响,且当机头温度高于180 ℃时,制品表面变得凹凸不平,气体发生逃逸现象;RCF的加入,会使气泡会沿着RCF取向方向生长,但是添加过多的RCF,会影响气泡成核。     

钢渣矿渣掺合料对水泥性能的影响

研究了钢渣的掺入量对水泥浆体性能的影响,以及钢渣单掺和钢渣与矿渣复掺对水泥胶砂强度的影响。结果表明:钢渣的掺入可以改善水泥浆体的流动性,凝结时间随钢渣掺量增加而延长。单掺钢渣时,水泥胶砂强度下降明显。钢渣与矿渣复掺会相互激发、相互促进水化,水泥胶砂强度变化不大,且钢渣在复合粉中的比例为20%,替代水泥量为50%时,28 d强度已超过基准样。     

Effect of Natural Fiber Network on Permeability and Tensile Strength of Composites through Vacuum Infusion Process

This investigation is primarily focused to study the effect of fiber network on the permeability in vacuum infusion molding process. The unsaturated permeability of several natural fiber mats with different networks is measured. The experimental permeabilities are fitted by the Kozeny model and contact angle model. The outcome highlighted that the contact angle model shows more precise results as compared to kozeny model. The obtained permeability for the random fiber mats shows higher values than directional fiber mat. Furthermore, the maximum increase in tensile strength is observed in the unidirectional composites and the flow along the fiber direction.