Influence of the geometrical and gasdynamic parameters of a mixer on the mixing of radial jets colliding with a crossflow

Results of investigation of the mixing of a system of axisymmetrical jets with a subsonic carrying flow in a cylindrical channel are presented. The main characteristics of the mixer were varied in wide ranges in the process of experiments. The regime of colliding jets was realized in the majority of experiments. The influence of individual factors on the quality of the mixing was considered. A combination of the mixer parameters within the ranges investigated, optimum for a high-quality mixing, has been determined. The experimental results obtained were compared with the corresponding data of other authors.     

Catalyst effect on the transesterification reactions between polycarbonate and polycaprolactone-B-polydimethylsiloxane triblock copolymers

Summary Transesterification reactions between bisphenol-A polycarbonate and polydimethylsiloxane-polycaprolactone block copolymers were studied in melt at 270°C. Influence of the composition of reaction mixture and the catalyst type on the formation and properties of the products obtained were investigated by spectroscopic, chromatographic and thermal methods. Both of the catalysts used, zinc acetate and lanthanum acetylacetonate are very efficient transesterification catalysts for the system studied. GPC and DSC results clearly show the formation of novel polymers displaying combined properties of the polycarbonate and the silicone-ester copolymer. Received: 22 June 1999/Accepted: 8 September 1999     

Effect of accelerated electrons on zeolite-containing rocks of the East Transbaikalia

It has been found that accelerated electrons have great influence on strength properties of zeolite-containing rocks, and on their post-grinding grain-size composition and the degree of unlocking, which intensifies further processing. The authors illustrate potentiality of reducing the content of ferruginous admixture in zeolite products: from 3.14 to 0.36% for zeolite-containing rocks from Shivyrtuiskoe deposit and from 11.2 to 0.12% for chabasite-containing basaltic andesite from Talan-Gozagorskoe deposit.     

Novel amine terminated elastomeric oligomers and their effects on properties of epoxy resins as a toughener

The objective of this study was to investigate the effects of amine terminated elastomeric epoxy tougheners on the mechanical and thermal properties of diglycidyl ether of bisphenol A based epoxy resin. The amine terminated polycaprolactone (PCL) (1) and PCL‐PDMS‐PCL (2) based oligomers were synthesized and characterized by FTIR spectroscopy. The stoichiometrical amount of the reactive oligomers as toughener, reactive epoxy resin and the curing agent, 4,4′‐diaminodiphenyl sulfone (DDS) were mixed and degassed. The homogenous mixtures were cured at 120°C into the preheated molds. The mechanical and thermal characterizations of toughened epoxy resin system were evaluated. It has been shown that the mechanical and thermal properties of toughened epoxy system vary as a function of the chemical structure and the concentration of rective oligomers. Higher mechanical properties were obtained for epoxy resin toughened by PCL‐PDMS‐PCL (2) based oligomer. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of the processing on the production of cordierite–mullite composite

In this study, effect of process on the production of cordierite–mullite composite was studied. For this reason two different processing methods were used in the production of cordierite–mullite composites. In first process, in situ cordierite–mullite composites were produced from cordierite and mullite layers which were formed by using aqueous tape casting method. In second one, composite was produced by addition of pre-produced mullite powders (in different weight percents, 0–30) into cordierite starting powders. The results show that the addition of pre-sintered mullite powders to the cordierite slip has more effect on densification behavior and mechanical properties of composites than layered production method.     

Genetic analysis of Turkish rice varieties (Oryza sativa L.) using seed storage proteins and RAPD markers

Due to an increasing demand for rice in Turkey, assessing and maintaining genetic variability in rice cultivars is essential for the success of rice breeding programs. Genetic polymorphisms in seed storage proteins (SSP) and RAPD markers were evaluated among different Turkish cultivars of Oryza sativa L. Twenty-one rice cultivars of Turkish origin and 11 rice cultivars from Bulgaria, France, Italy and Russia were analyzed. SDS-PAGE profiles from SSP of 20 cultivars showed similar expression patterns. Seven polymorphic and reproducible RAPD primers produced 42 bands ranging from 250 to 2,500 bp; 29 were polymorphic (69%) and 13 monomorphic (31%). Unweighted Pair-Group Method with Arithmetic Mean (UPGMA) was performed to generate a pairwise genetic distance (or similarity) matrix. A rooted dendrogram resulted in two main groups based on Jaccard’s coefficients. Sürek-95, Serhat-92, and Rocca were placed in one group, and all other cultivars in another group. Principle coordinate analysis was also conducted and the results supported UPGMA results, where Sürek-95, Serhat-92, and Rocca were distinct from all other cultivars. Our results suggest that the rice cultivars screened in this study exhibit narrow genetic diversity. In addition, RAPD-based genetic characterization can aid in both conservation and selection of desired rice cultivars in future breeding studies.     

Investigation the effects of obstacle geometries and injection molding parameters on weld line strength using experimental and finite element methods in plastic injection molding

In this study, effects of injection parameters and weld line on the mechanical properties of polypropylene (PP) moldings were studied. To produce weld line at PP specimens, the obstacles having edge angle of 0°, 15° and 45° were designed. These obstacles were located at the center of the mold. The effects of both obstacles angles and the injection molding parameters such as melt temperature and packing pressure on the mechanical strength were investigated. Mechanical properties such as tensile strength and izod impact strength (notched) of the specimens were measured by test methods. The effect of molecular orientation on the mechanical properties of the specimens was discussed by Finite Element Analysis. Weld line tensile strength of injection molded specimens having obstacle edge angle (OEA) of 15° was obtained higher than the other obstacle edge angles.     

Thermal stabilities of end groups in hydroxyalkyl terminated polydimethylsiloxane oligomers

Summary Thermal stabilities of α,ω-hydroxypropyl, α,ω-hydroxybutyl, α,ω-2-hydroxypentyl and α,ω-hydroxyhexyl terminated polydimethylsiloxane (PDMS) oligomers were studied. Hydroxypropyl and hydroxybutyl terminated polydimethylsiloxane oligomers showed degradation upon heating, through the loss of functional end groups as determined by FT-IR spectroscopy and gel permeation chromatography. α,ω-Hydroxyhexyl and α,ω-2-hydroxypentyl terminated polydimethylsiloxane oligomers were stable under similar conditions. Instability of the end groups is due to the back biting of the terminal silicon in the PDMS by the primary hydroxyl oxygen, leading to the formation of 5 and 6 membered, stable, heterocylic compounds. Loss of end groups also resulted in a dramatic increase in the molecular weights of the oligomers produced, as determined by gel permeation chromatography. Received: 19 January 1998/Revised version: 27 February 1998/Accepted: 5 March 1998