Sándor Keszei

Effect of fillers on the fire retardancy of intumescent polypropylene compounds

Abstract The effects of fillers (talc and calcium carbonate) were investigated on polypropylene /ammonium polyphosphate/polyamide-6 (PP/APP/PA-6) intumescent system by using mechanical testing, LOI method, cone calorimetry and thermoanalytical techniques. Calcium carbonate and talc affect the fire protective properties of PP/APP/PA-6 system in different ways. It is shown that talc induces an increase in the Youngs modulus and a decrease in the elongation at break. Calcium carbonate leads to a decrease in the elongation at break, but there is no improvement in the Youngs modulus. Talc increases fire protective performance due to forming a ceramic like protective shield at the surface, whereas calcium carbonate decreases it because of a reaction with APP. Effects of talc and calcium carbonate were furthermore investigated on PP/APP/PA-6 system by measuring Rate of Heat Release (RHR), Total Heat Emitted (THE), CO/CO 2 evolution and residual mass. Results are interpreted by means of decomposition, chemical reaction between components and formation of a protective shield at the surface at ignition.

Fire retardancy effect of migration in polypropylene nanocomposites induced by modified interlayer

Montmorillonite nanoparticles were found to be inefficient in polypropylene because of the lack of a heat insulating char layer and the decomposition of the compatibilising surfactant layer on their surface. Combination with an ammonium polyphosphate-based intumescent system showed some synergism due to modified rheology. The effect of surface and interface modification was analysed using Raman microscopy and X-ray photoelectron spectroscopy. Forming a heat resistant coating layer of low surface energy around the nanoparticles promotes their migration to the surface and formation of a flexible barrier layer, and thus leads to better performance.

Supercritical fluid extraction: A novel method for the resolution of tetramisole

Abstract A new resolution method, based on the selective distribution of enantiomers between a chiral solid and an achiral supercritical fluid phase, is reported. The chiral solid phase is formed from the optically active dicarboxylic acid derivative, (2 R ,3 R )- O , O ′-dibenzoyltartaric acid, and the racemic base (tetramisole). A new method is also described for the enrichment of enantiomeric mixtures which have an enantiomeric ratio other than 1:1. This is based on the partial salt formation of the enantiomeric mixture with an achiral substance, which is then followed by supercritical fluid extraction of the free enantiomer. The extract has an enantiomeric composition which is different from the starting mixture. The method is applied to an enantiomeric mixture of tetramisole with hydrochloric acid.

New route to enantiomers of cyclic β-hydroxyethers. The crystal structure of (S)-(+)-tetrahydrofurfuryl-O,O'-diacetyl-(2R,3R)-hydrogentartrate

Abstract Title compounds 1–2 were readily resolved into their enantiomers by crystallizing their half esters formed with O,O′-diacetyl-(2R,3R)-tartaric acid. An intermolecular H-bond between the free carboxyl group and the ring oxygen, determined by single crstal X-ray study of (S)-(+)-tetrahydrofurfuryl-O,O′-diacetyl-(2R,3R)-hydrogentartrate, enhances the selectivity and the crystallizing ability itself.