MODIFICATION OF POLYMERS

MECHANICAL PROPERTIES OF IMPACT MODIFIED POLYPROPYLENE COMPOSITES
V. Hristov, S. Vassileva, M. Natov

The mechanical properties of polypropylene/polyisoprene (PP/SKI) and polypropylene/wood flour (PP/WF) composites with maleated polyprpylene (MAPP) as a compatibilizer have been studied. It has been established considerably increasing of impact notched strength of the composites containing MAPP as a compatibilizer. Morphological observations showed that the wood and elastomer particles were uniformly distributed in the PP matrix when MAPP was used as a compatibilizer. The fracture mechanisms of the composites have been also discussed.
Keywords: polypropylene composites, maleated polypropylene, mechanical properties.

ELASTIFICATION OF POLYOLEFINS WITH BUTADIENSTYRENE AND POLYISOPRENE ELASTOMER
M. Filipova

Polyethylene and polypropylene are elastificated by mixing with butadienstyrene rubber and poly cis-1,4-isoprene rubber. The influence of the elastification additives upon the melting point of the matrix polymer was discovered and it is explained with their influence upon the overmolecular structural formation in polymers. It was studied the influence of the steric netting of the polymers, containing 12,5 wt % elastomer and vulcanization groups. It is established that steric netting does not influance their strength characteristics considerably.
Keywords: polyethylene, polypropylene, netting, impact strenght.

THERMAL CONDUCTIVITY TENSOR OF FIBER REINFORCED PIPE VISCOUS ELEMENT
A. Alexandrov, Tz.Tzolov

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

Received 2 March 2002
Accepted 5 March 2002

This work employ a homogenization technique to obtain the effective thermal conductivity tensor of fiber reinforced pipe viscous element. The viscous element represent a composite material containing inclusions (polyester fibers) with unidirectional repartition in a vulcanized rubber matrix. From thermal point of view the composite thus formed possesses a transversal isotropy. The work concerns composite with good contact between matrix and inclusions so that there is no temperature discontinuity across interfaces. Simple expressions between the effective tensor components of the thermal conductivity and the respective components of the composite phases have been obtained . One consider the inclusions repartition with the help of texture tensors.
Keywords: Thermal conductivity, anisotropy, texture tensors, polyester fibers, vulcanized rubber.

WOOD-POLYVINYLCHLORIDE COMPOSITES AS WOOD SUBSTITUTES
R. Mansur, M. Natov, S. Vassileva

*Syria, Teshreen University-Lattakia, Faculty of Engeneering, Mechanical and Electrical Departement, Fax: 0096341-418504
**University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail natov@uctm.edu

Received 2 March 2002
Accepted 5 March 2002

Investigations are carried out on composites of polyvinylchloride, stabilized with lead stabilizers, filling by white pine wood flour with particle sizes of 100-140 m. It was found that all composites in melted state are pseudoplastic fluids. Because of easy expanding, all melts have elevated flowability at wood flour contents of 4-7% These composites are especially suitable for extrusion of profile articles. High-filled composites do not expand even if special blowing agents are employed.
The rheologic and mechanical properties are investigated as a function of the size of the wood flour particles. It was found that especially good results are achieved at particle size below 60 m. Using a capillary viscosimeter, the profiles of the flow rates of the melts in the viscosimeter capillary are outlined for four lubricants of the Loxiol type. The profiles of the flow rates in the viscosimeter capillaries can be used for characterization of the lubricity. The behaviour of the internal and external (near-wall) lubricants for composites melts is snown.
Keywords: polyvinylchloride-wood flour, composites, rheology, lubricants, mechanical properties.

MODIFICATION OF CYCLIC p-ISOPROPENYLCALIX[n]ARENES WITH POLY(ETHYLENEGLYCOLE) IN THE PRESENCE OF VARIOUS ACIDIC CATALYSTS
St. Miloshev, P. Petrova, P. Novakov, P. Tuleshkov

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

Received 2 March 2002
Accepted 5 March 2002

Calixarenes belong to the class of cyclic oligomers and are prepared via polycondensation of p-substituted phenols with formaldehyde and further condensation. The p-isopropenyl substituent in the novel p-isopropenylcalix[n]arenes we have synthesized comprises a reactive double bond which unequivocally raises the interest in the open opportunities to modify the structure of the compounds. The present study deals with the possible association of poly(ethyleneglycol) to the p-isopropenyl substituent in a real mixture of p-isopropenylcalix[4]arene and p-iso-propenylcalix[6]arenes in the presence of various acid catalysts. It has been established that the effectiveness of the addition reaction depends on the activity of the electrophilic agent. Side reactions yielding large calixarenes like p-isopropenylcalix[8]arenes etc., have been also observed when using trifluoracetic acid as a catalysts .
Keywords: calixarenes, p-isopropenylcalixarenes, modifi-cation, poly(ethyleneglycol)

RELATION BETWEEN PERMAHOR AND DEGRADABILITY OF POLYMERS
Iv. Glavchev*, B. Purevsuren**, R. Ganev***, P. Novakov*

*University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail ivglav@uctm.edu
**Academy of Science, Ulan Bator, Mongolia
***Ministry of Defence, Armaments Policy Directorate,
8 Kapitan Andreev St, Lozenets, 1421 Sofia, Bulgaria

Received 2 March 2002
Accepted 5 March 2002

The values of permahor for three nitrogen-containing cycloaliphatic and two aromatic epoxy resins cured with maleic anhydride were compared with loss of weight and activation energy of thermal degradation of the samples. The dependence obtained is the same both for loss of weight of the two mixtures nitrocellulose-epoxy resins and three mixtures nitrocellulose-vinyl polymers after accelerated ageing by 240 h irradiation and 672 h treatment of coatings with different temperatures and humidity.
Keywords: permahor, epoxy resin, vinyl polymer coating, accelerated ageing

SOIL STRUCTURE-FORMING ABILITY OF LOW-MOLECULAR POLYAMIDES
N. Todorova, M. Georgieva, M. Natov

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

Received 2 March 2002
Accepted 5 March 2002

The soil medium provides everything necessary for the development of plants to the highest degree. Two opposing processes occur in the soil continuously - of regenerating and destroying its structure. Modern methods have been developed for improving the soil structure by increasing the water resistance of the structural aggregates through the use of synthetic polymer substances - polyacryamide, acrylamids, co-polymers with other monomers hydrolysis products of polyacrylonitrile, etc. Investigating the reaction of polycaproamide with orthophosphorous acid it was established that crystalline products - oligoamidephosphates are produced. Their molecular mass is in the range of M 500 - 2000, while those with M 800 predominate. For the aims of our work these are low values, which cannot guarantee the continued action of the substances. Therefore, we stopped the heating immediately after the clarification of the solution. Mv - determined by using the viscometer of Oswald - remains almost constant. The small deviations are within the boundaries of the method precision. We determined the structure-forming ability of the obtained product by the method of aggregate analysis of Savinov. The percentage content of the water resistance fractions of the soil, treated with our product, is higher than that of treated with water. Consequently, the obtained solutions of polyamide in phosphoric acid have good soil structure-forming ability.
Keywords: polyamide, oligoamidephosphates, soil, phosphoric acid, structure-forming ability