Synthesis, structure and reactive mechanism of intermetallic W4Mg

Assisted by a mechanical alloying and high-pressure technique, a new W4Mg intermetallic was formed. W4Mg amorphous mixture was obtained by mechanically alloying the pure metal powder mixtures at designated composition for 20 h. A new compound was found after the subsequent high-pressure and high-temperature treatment. W4Mg intermetallic was identified as a cubic structure and the lattice parameter was a=0.4150 nm. The synthesis mechanism is also discussed in this paper.

Reactive compatibilization of polyamide 6 with isocyanate functionalized ethylene-propylene copolymer

Reactive compatibilization of ethylene-propylene copolymer functionalized with allyl (3-isocyanato-4-tolyl) carbamate (TAI) isocyanate (EPM-g-TAI) and polyamide 6 (PA6) was investigated in this paper, FTIR analysis revealed the evidence of a chemical reaction between the end groups of PA6 and EPM-g-TAI. Thermal, rheological, morphological, and mechanical properties of the resultant system were examined, DSC analysis indicated that the crystallization of PA6 in Pa6/EPM-g-TAI blends was inhibited, due to the chemical reaction that occurs at the interface of PA6 and EPM-g-TAI. Rheological measurement showed that complex viscosity and storage modulus of PA6/EPM-g-TAI were both dramatically enhanced compared to those of PA6/EPM at the same blending composition. After examining the morphology of both blending systems, smaller particile sizes, more homogeneous distribution of domains and improved interfacial adhesion between matrix and domains were observed in the compatibilized system. Mechanical properties such as tensile strength. Young's modulus, flexural strength and modulus, as well as notched and un-notched impact strength of PA6/EPM-g-TAI blends were also found to improve gradually with increasing the content of grafted TAI.

Reactive reinforcement of the interface of poly(ether sulfone)/poly(phenylene sulfide) polymer blend by PMR-POI

The effect of polymerization of monomer reactant-polyimide (POI) as the interfacial agent on the interface characteristics, morphology features, and crystallization of poly(ether sulfone)/poly(phenylene sulfide) (PES/PPS) blends were investigated using a scanning electron microscope, FTIR, WAXD, and XPS surface analysis. It was found that the interfacial adhesion was enhanced, the particle size of the dispersed phase was reduced, and the miscibility between PES and PPS was improved by the addition of POI. It was also found that POI was an effective nucleation agent of the crystallization for PPS.

Reactive reinforcement of the interface of high performance polymer blends by PMR-POI

The effect of PMR-polyimide(POI) as the interfacial agent on the interface characteristics, morphology features and crystallization of poly (ether sulfone) /poly (phenylene sulfide) (PES/PPS) and poly(ether ether ketone)/poly (ether sulfone) (PEEK/PES) partly miscible blends were investigated by means of the scanning electron microscopy, WAXD and XPS surface analysis. It is found that the interfacial adhesion was enhanced remarkably, the size of the dispersed phase particles was reduced significantly and the miscibility was improved by the addition of POI. During melt blending cross-link and/or grafting reaction of POI with PES, PEEK and PPS homopolymers was detected, however the reaction activity of POI with PPS was much higher than that of PES and PEEK. It was also found that POI was an effective nucleation agent of the crystallization of PPS.

Reactive blending of polyamide 6,6 and Vectra A

In this paper, blends of Nylon 6,6 with the liquid crystal polymer Vectra A950 are considered; specifically we focused our attention on Nylon 6,6 modifications by interchange reactions that can occur in the melt, as a function of mixing conditions and blend compositions. Two matrix samples have been used, characterised by a slightly different relative amount of amine and carboxylic end groups, being the latter predominant in both cases. The dried polymers Nylon 6,6/Vectra, combined in weight ratios between 95/5 and 50/50, were subjected to reactive blending with different methods (single-screw extruder, Brabender, pyrex reactor). Pure Nylon samples have been also investigated as reference materials. The soluble Nylon 6,6-rich fraction of each blend was separated from the insoluble Vectra-rich one and used for molecular and spectroscopic characterisations. Thermal and morphological analyses, as well as testing of tensile properties, were carried out on the blends. Evidences of the occurrence of interchange reactions are given and the most probable ones are suggested. (C) 2001 Elsevier Science Ltd. All rights reserved.

Functionalization of isotactic polypropylene with maleic anhydride by reactive extrusion: mechanism of melt grafting

In this work, chemical structures and molecular parameters of grafted materials of PP-g-MAH prepared by melt reactive extrusion were studied by using electrospray ionization-mass spectrometer and gel permeation chromatography. It was found that the initial radicals, due to homolitic scission of dicumyl peroxide could be combined with maleic anhydride (MAH) monomers as well as polypropylene (PP) molecular chains. The homopolymerization of MAH cannot occur and the MAH radicals undergo a dismutational reaction under the processing condition (180-190 degreesC). A modified mechanism of melt grafting MAH onto PP has been proposed tentatively on the basis of our experimental results and other experimental findings published in the literature. (C) 2001 Elsevier Science Ltd. All rights reserved.

Efforts to decrease crosslinking extent of polyethylene in a reactive extrusion grafting process

Grafting of acrylic acid and glycidyl methacrylate onto low density polyethylene (LDPE) was performed by using a corotating twin-screw extruder. The effects of residence time and concentration of initiator and monomers on degree of grafting and gel content of grafting LDPE were studied systematically. Paraffin, styrene, p-benzoquinone, triphenyl phosphite, tetrachloromethane, and oleic acid were added to try to decrease the extent of crosslinking of LDPE. 4-hydroxyl-2,2,6,6-tetramethyl-1-piperidinyloxy (4-hydroxyl-TEMPO) and dipentamethylenethiuram tetrasulfide were also tried to inhibit crosslinking reaction of LDPE during its extruding grafting process. It was found that p-benzoquinone, triphenyl phosphite and tetrachloromethane were good inhibitors for crosslinking of LDPE. (C) 2000 John Wiley & Sons, Inc.

Synthesis and crystal structure of aluminium complex with 3-hydroxyflavone

[Al(C15H9O3)(3)](2) . 2CHCl(3) . 8H(2)O was synthesized, and its crystal structure was determined. It belongs to trigonal system, R3, a=b=1. 655 8(3) nm, c=3. 646 5(20) nm, alpha = beta = 90 degrees, gamma = 120 degrees, V = 8. 656 08(0. 005 86) nm(3). D-c = 1.45 g/cm(3), mu(Mo K alpha) = 3. 20 cm(-1), F (000) = 3 924. The crystal structure was solved by Patterson and Fourier techniques, and refined by a block-diagonal least-squares method. A total of 3 737 independent intensity data were collected, of which 1 033 with I greater than or equal to 3 sigma(I-0) were observed, R = 0. 091 8, Rw=0. 091 8. Al3+ ion was 6-coordinated, bound to six oxygen atoms from three 3-hydroxyflavones to form a distortional coordination octahedron.

A study of catalysis of copper-aluminium hydrotalcite-like compounds in the phenol hydroxylation

Copper-Aluminium Hydrotalcite-like compounds are synthesized by coprecipitation and characterized with XRD and IR. Catalysis of the above mentioned HTLcs are investigated in the phenol hydroxylation, good results are obtained. Meanwhile, the effects of the ratio of Cu/Al, reaction temperature, reaction medium and pH of reaction system are discussed, The reaction mechanism is also proposed.

Corrosion behaviour of hot dip zinc and zinc-aluminium coatings on steel in seawater

A comparative investigation of hot dip Zn-25Al alloy, Zn-55Al-Si and Zn coatings on steel was performed with attention to their corrosion performance in seawater. The results of 2-year exposure testing of these at Zhoushan test site are reported here. In tidal and immersion environments, Zn-25Al alloy coating is several times more durable than zinc coating of double thickness. At long exposure times, corrosion rate for the Zn-25Al alloy coating remains indistinguishable from that for the Zn-55Al-Si coating of similar thickness in tidal zone, and is two to three times lower than the latter in immersion zone. The decrease in tensile strength suggested that galvanized and Zn-55Al-Si coated steel suffer intense pitting corrosion in immersion zone. The electrochemical tests showed that all these coatings provide cathodic protection to the substrate metal; the galvanic potentials are equal to - 1,050, - 1,025 and - 880 mV (SCE) for zinc, Zn-25Al alloy and Zn-55Al-Si coating, respectively, which are adequate to keep the steel inside the immunity region. It is believed that the superior performance of the Zn-25Al alloy coating is due to its optimal combination of the uniform corrosion resistance and pitting corrosion resistance. The inferior corrosion performance by comparison of the Zn coating mainly results from its larger dissolution rate, while the failure of the Zn-55Al-Si coating is probably related to its higher susceptibility to pitting corrosion in seawater.

Ozonation of the purified hydrolyzed azo dye Reactive Red 120 (CI)

The combination of chemical and biological water treatment processes is a promising technique to reduce recalcitrant wastewater loads. The key to the efficiency of such a system is a better understanding of the mechanisms involved during the degradation processes. Ozonation has been applied to many fields in water and wastewater treatment. Especially for effluents of textile finishing industry ozonation can achieve high color removal, enhance biodegradability, destroy phenols and reduce the COD. However, little is known about the reaction intermediates and products formed during ozonation. This work focuses on the oxidative degradation of purified (>90%), hydrolyzed Reactive Red 120 (Color Index), a widely used azo dye in the textile finishing processes with two monochlorotriazine anchor groups. Ozonation of the dye in ultra pure water was performed in a laboratory scale cylindrical batch reactor. Decolorization, determined by measuring the light absorbance at the maximum wavelength in the visible range (53 5 nm), was almost complete after 150 min with an ozone concentration of 12.8 mg/l. The TOC/TOC0 ratio was about 74% and the COD was diminished to 46% of the initial value. The BOD5/COD ratio increased from 0.01 to 0.14. To obtain detailed information on the reaction processes during ozonation and the resulting oxidation products organic and inorganic anions were analyzed. Oxidation and cleavage of the azo group yielded nitrate. Cleavage of the sulfonic acid groups of aromatic rings caused an increase in the amount of sulfate. Formic acid and oxalic acid were identified as main oxidation products by high performance ion chromatography (HPIC). The concentrations of these major products were monitored at defined time intervals during ozonation.