The influence of the hydroxyl coating on silica and alumina on their adsorption capacities has been studied in regard to sulfur-containing organic compounds in Diesel fuel. It has been established that after an appropriate thermal treatment the adsorbents under investigation could become promising supports to prepare active materials for purifying Diesel fuel from sulfur compounds.
Keywords: silica, alumina, sulfur content in Diesel fuel.

OLIGOMER-POLYMER MODIFIER COMPLEX. STUDY OF THE PHYSICO-MECHANICAL CHARACTERISTICS OF PVC COMPOSITES, CONTAINING ITS PURE COMPONENTS
R. Boshnakova, D. Nenov, B. Kostadinov

The independent action of the basic components of Oligomer-Polymer Modifier Complex (OPMK): oligomer of the epoxy-novolac resin (OENR) and polymer of the acetal type upon the physico-mechanical properties of the electro-isolation composition has been studied.
An analysis has been made of the limits of their usage.
The impact of the modifiers as “small additives” amounting up to 2 % in the composites is described.
A conclusion has been made that the independent usage of the two modifiers is possible within certain limits, reporting only their impact upon the physico-mechanical properties without taking into consideration technological problems.
Keywords: modification, composites, polyvynilchloride, oligomer-polymer modifier complex, oligomer of epoxy-novolac resin, polymer of the acetal type.

TESTING OF POLYMER BLENDS BY THE METHOD OF DIFFERENTIAL DEFORMATION CHARACTERISTICS
G. Boijadjiyski, M. Koleva

Technical University of Gabrovo
4, Hadji Dimitar str, 5300 Gabrovo, Bulgaria,
E-mail: miki@tugab.bgu

Received 21 May 2004
Accepted 19 July 2004

An improved technique for studying the mechanical properties of polymer blends from unsaturated polyester resin and two polymer additives – impact polystyrene and styrene-butadiene rubber (SBl) - as impact modifiers by graphic differentiation and determination of differential strain characteristics in real time has been developed and experimented. The technique enables the automatic determination of elasticity and yield physical limits, the tracing of elasticity modulus variations and the high accuracy determination of the critical state of materials. The tests are performed by means of a unique programmable device using standard specimens. Its advantages in comparison with available devices are the wide range of loading speed variation achieved by applying of two independent loading systems – thermal-mechanical and screw driven. That makes the device applicable to testing both brittle and plastic materials. A multiprocessor system provides numerous load modes (including cyclic) as well as monitoring the strain parameters in real time.
The experimental data provide information about the influence of the modifier on the mechanical behavior and deformation properties of the resin. Real strain limits of the materials have been determined. The results were used as a basis for polymer additives content optimization.
Keywords: mechanical behavior, polymer blends, differential strain characteristics.

STUDY ON THE ADSORPTION OF ACID AND DIRECT DYES ON THERMOTREATED MINERAL SORBENT
D. Pishev, S. Veleva, A. Georgieva

University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: pishev@uctm.edu

Received 26 May 2004
Accepted 10 June 2004

The adsorption of acid and direct dyes on thermotreated grus mineral sorbent with polymineral composition was studied. It is established that thermotreated grus material has higher adsorption ability than untreated one. By means of physicochemical approach it was found that the adsorption process can be described by the Freundlich isotherm. Some basic thermodynamic characteristics as the change of the enthalpy and the change of the entropy were determined. It is established that the adsorption process is exothermic and the bond between the adsorbent and acid dyes is stronger than with direct dyes. The conclusion is made that the mechanism of the adsorption of the acid and direct dyes on the investigated sorbent is similar, which is confirmed by the compensatory effect between the enthalpy change and the entropy change.
Keywords: adsorption, grus mineral sorbent, acid dyes, direct dyes.

ALGORITHM FOR DESIGNING OF SHOE LASTS TOE
S. Cheshmedjiev, K. Mutafchieva

University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: kalina@uctm.edu

Received 01 July 2004
Accepted 29 July 2004

There are some systems for lasts computer design, that are in practice of few companies and there are little publications about detailed data for the used methods and the algorithms.
Lasts with standard back part are used in shoe production. Last toe part is modeling on the model trends mainly. Well-established practice is to work on the base of constructed patterns of the bottom of the last and longitudinal section. It is a manual work and needs very long time. There is a need of mathematical model development, describing the complicated surface of shoe lasts for modeling and constructing them by computers.
In this work are compared different methods for approximation of cross section’s lines of toe shoe lasts with real data and was found that circle arcs for every cross section could be used as a base for approximation of last toe part surface. It was developed and experimented algorithm to receive data for 3D representation of last toe part surface. Programs were written in PASCAL 6.0. Additional experimentations are needed especially for 3D representation of last toe part, because of some deviations from real data, that the algorithm for triangle pieces gives in regions with large curvature of the top toe.
Keywords: design, shoe last, computer.

OPTIMIZATION OF THE COMPOSITION OF COMPLEX MIXTURES FOR RECULTIVATION AND FERTILIZATION
V. Ivanova, Y. Pelovski, St. Stoyanov

University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: vihris@yahoo.com

Received 07 July 2004
Accepted 23 July 2004

The available uptake form of certain nutrients and the soil humidity level are of great importance for soil productivity. The present paper proposes the input of the most important nutrition elements via complex mixtures utilizing two types of waste: phosphorus-containing sludge and ashes from a thermal power plant, characterized by sorption properties.
From an active experimental design, attractive ratios between the mixture components are determined. Important mixture characteristics are investigated and via regression analysis the interrelations between parameters are identified. The obtained results prove that parameters of the proposed mixtures exceed the standard values for fertilizers and successfully can be implemented for fertilization purposes and remediation of degraded soils. Through the optimization conducted, optimal compositions and ratios between individual components, which can serve as a basis for further investigations are suggested,.
Keywords: mixed fertilizers, sorbents, ashes, regression analysis, optimization.