Journal of the University of Chemical Technology and Metallurgy, XXXVII, Book 3, 2002
ZnO - SORBENT EXPLOITATION PROPERTIES MODELLING I . HYDROXICARBONIZATION OF ZnO - TECHNICAL GRADE AS A METHOD TO OBTAIN ZnO - ACTIVE SORBENT
Tz. Velinova, L. Angelov, D. ShishkovCOMPLEX INDUSTRIAL PROCESSING OF NONBAUXITE Al-CONTAINING RAW MATERIAL
D. BojinovaRHEOLOGICAL PROPERTIES OF WOOD-POLYVINYLCHLORIDE COMPOSITES
R. Mansur*, M. Natov**, St. Vassileva**A METHOD FOR CALCULATING THE AZEOTROPIC COMPOSITIONS OF MULTI-COMPONENT COPOLYMERS
L. ChristovMICROHARDNESS OF POLYMER BLENDS OF POLYETHYLENE AND ELASTOMERS
M.Filipova, St.Vassileva*OLIGOMER-POLYMER MODIFIER COMPLEX STUDY OF THE PHYSICO-MECHANICAL CHARACTERISTICS OF PVC COMPOSITIONS, CONTAINING IT IN A WIDE CONCENTRATION RANGE
R. BoshnakovaUTILIZATION OF WASTES FROM THE COKE-CHEMICAL PRODUCTION AND SEWAGE SLUDGE AS ADDITIVES IN THE BRICK - CLAY
J. Balgaranova, A. Petkov, L. Pavlova, E. AlexandrovaCONCENTRATION FLAMABILITY LIMITS II. ALKANONS
M. Hristova, Z. Zdravchev, S. Tchaoushev
ZnO - SORBENT EXPLOITATION PROPERTIES MODELLING
I . HYDROXICARBONIZATION OF ZnO - TECHNICAL GRADE AS A METHOD TO OBTAIN ZnO - ACTIVE SORBENT
Tz. Velinova, L. Angelov, D. Shishkov
University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
The general application of natural gas as a source of ammonia production predetermined the development of new and active catalytic compositions for the different stages of its processing. These compositions are inhibited by some impurities. For example, sulfur compounds can poison catalytic compositions based on metals from the transition group. That is why preliminary cleaning of the natural gas is necessary. Sorbents based on ZnO (active ZnO) are the most applied in practice.
Keywords: sorbent, structure, hydroxicarbonization, micronization, kinetic, optimization.
COMPLEX INDUSTRIAL PROCESSING OF NONBAUXITE Al-CONTAINING RAW MATERIAL
D. Bojinova
University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: bojinova@uctm.edu
The aim of this study was to establish the possible application of combined method for processing of low qualitative nonbauxite Al-containing raw material /Bulgarites/. The preliminary mechanical activation of the Bulgarites in combination with acid decomposition resulted in high extent extraction of the useful components.
The investigations were carried out through the method of design experiment using D - optimal plan for second order model. The influence of the time for mechanical activation, the temperature and the time of acid decomposition on the extraction extent of Al, K, Na, Ca, Mg, Cu, Zn, Mn and Si were studied. Based on the experimental data adequate regression equations were deduced. An optimisation for finding the compromise decision in studied objective parameters was done. The optimal conditions to obtain the following extraction extent of the main components in Bulgarites ( , %): Al-70; K-74; Na-82; Cu-100; Zn-65 and Mn-100, were determined. These investigations confirm the positive effect of the preliminary mechanical activation of Bulgarites on the next step of acid decomposition with sulphuric acid.
Keywords: aluminosilicates; acid extraction; Al-containing nonbauxite raw material; mechanical activation; decomposition of aluminosilicates.
RHEOLOGICAL PROPERTIES OF WOOD-POLYVINYLCHLORIDE COMPOSITES
R. Mansur*, M. Natov**, St. Vassileva**
* Teshreen University-Lattakia, Syria
E-mail: dayoubs@scs-net.org
**University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
Polyvinylchloride composites containing a new type of stabilizer (lead paste of PbSO4:PbO2:PbO = 4:2:1) and up to 30 % (by mass) of wood flour filler are studied.
On the basis of experimental rheological curves, the consistency coefficients and the flow indices of wood-polyvinylchloride are determined. It is established that all composites are characterized by a pseudoplastic flow of their melts, the filler influencing mainly the consistency coefficient. The activation energy of viscous flow is determined as a function of the wood flour content; it increases with the rise of wood flour content up to 15 % (by mass) and remains almost constant at higher concentrations.
The effect of the particle size on the rheological properties of the polymer melts is also studied. With finely ground wood flour an increase of the flowability is observed in the range from 1 % to 15 % (by mass) wood flour and this is explained by foaming of the melt as a result of intensive gas formation.
Keywords: Polyvinylchloride composites, wood flour filler, rheology, stabilizers for PVC, filler dispersity
A METHOD FOR CALCULATING THE AZEOTROPIC COMPOSITIONS OF MULTI-COMPONENT COPOLYMERS
L. Christov
University of Sofia, Department of Chemistry
1 James Bourchier Blvd., Sofia 1164, Bulgaria
e-mail: lchristov@chem.uni-sofia.bg
Using regular Markov chains, a numerical algorithm has been developed for calculating the azeotropic compositions of copolymers prepared from any number (n) of monomers copolymerizing according to the terminal model of chain propagation given the monomer reactivity ratios. The algorithm is universal and at the same time very simple that puts it ahead of the currently known methods. By solving no more than two systems of n linear equations it is possible to determine whether there is an azeotropic composition for the given monomer reactivity ratios and if so - to calculate it. Application examples for binary and ternary copolymerization are given.
Keywords: azeotropic copolymerization, Markov chains
MICROHARDNESS OF POLYMER BLENDS OF POLYETHYLENE AND ELASTOMERS
M.Filipova, St.Vassileva*
Vassil Levski Land Forces Academy, V.Tirnovo 5000
E-mail: mfilipova.vt@mail.bg
University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: vasileva@uctm.edu
It has been a well-known fact that microhardness (MH) depends to a considerable extent on the intermolecular structure of the material and that, on the other hand, it reflects to a varying degree it,s mechanical properties. The study on MH of elastified composite blends presents an interesting subject since there have been no reports on it. The blends' samples were irradiated to absorbed doses ranging from 1.104 Gy to 25.104 Gy in air at room temperature (250C) and a dose rate of 150 Gy/h and 2 kGy/h. Blends were prepared in a granulating extruder equipped with a special mixing screw. The MH of the elastified and irradiated polyethylene (PE) was compared to the degree of crystallinity and the impact strength of the composite blends. Determined were the optimal values for the exponent in the Mayer equation, as well as those values of the degree of crystallinity which result in a higher impact strength of the composite. The elastification of PE with various rubber was found to affect the behavior of the latter, which could be anticipated when comparing the (MHT) and the (MHV) of the composites.
Keywords: Microhardness, polymer blends, polyethylene, elastomers
OLIGOMER-POLYMER MODIFIER COMPLEX STUDY OF THE PHYSICO-MECHANICAL CHARACTERISTICS OF PVC COMPOSITIONS, CONTAINING IT IN A WIDE CONCENTRATION RANGE
R. Boshnakova
Technical University - Sofia
8 Kl. Ohridsky, 1756 Sofia, Bulgaria
E-mail: boschnakova@tu-sofia.acad.bg
The introduction of oligomer of epoxy-novolac resin (OENR) as a modifier in soft polyvynilchloride compositions used for cable isolation proved effective with respect to their electro-isolation properties. The process difficulties, that go along with its mixing with the rest of the components are overcomed by using a composition called Oligomer-polymer modifier complex (OPMC), in which the OENR is combined in different proportions with an acetal type polymer.
The impact of these two substances upon the physico-mechanical properties of PVC compositions has been studied by differentiation of two major factors of impact: the quantity of OPMC in the PVC composition from 1 to 10% by mass and the proportion of both modifiers in it,in a range from 0 to 100%.
The utilization of a design of the experiment provides an opportunity for mathematical estimation of the modification results in a wide concentration range. The impact of each of the two independent factors as well as their mixed interaction upon the tensile strength and relative deformation of OPMC containing compositions is given by a two factor analysis of variance.
The conclusion has been made that OPMC influences strongly the physico-mechanical properties of PVC compositions and can be utilized for modification in a certain direction.
Keywords: compositions, polyvynilchloride, oligomer-polymer modifier complex, oligomer of epoxy-novolac resin, statistical methods of estimation, analysis of variance.
UTILIZATION OF WASTES FROM THE COKE-CHEMICAL PRODUCTION AND SEWAGE SLUDGE AS ADDITIVES IN THE BRICK - CLAY
J. Balgaranova, A. Petkov, L. Pavlova, E. Alexandrova
University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: petkov@uctm.edu
Current modern building technologies use a greater variety of building materials and elements. Lately, intensive work has been done on investigating possibilities for using different wastes as additives in the production of new ceramic building products. This demonstrates that the raw material base can be enlarged and some environmental problems solved.
The present work investigates the possibility of combined utilization of sludge from the Sofia wastewater treatment plant and waste products from coke-chemical production as additives to brick clay. The most appropriate combinations and concentrations of the materials used, and the means of preparing and firing the brick masses are determined. The strength characteristics of the resulting products are studied. The results obtained are useful in showing possibilities for the solution of environmental problems.
Keywords: brick clay additives, coke-chemical wastes, sewage sludge, utilization.
CONCENTRATION FLAMABILITY LIMITS
II. ALKANONS
M. Hristova, Z. Zdravchev, S. Tchaoushev
University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: mariana_hristova@hotmail.com
New methods are proposed for the estimation of the concentration flammability limits of alkanons as a function of their molecular mass and boiling point temperature. These alkanons are of interest as components of mixed solvents used in the lacquer and varnish process industries. Corresponding expressions are obtained on the basis of standard statistical methods. The derived expressions permit the estimation of the concentration flammability limits with a satisfactory accuracy for practical purposes.
Keywords: concentration flammability limits, estimation, alkanons, flammability characteristics
