István Csontos

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.

Influence of modified rheology on the efficiency of intumescent flame retardant systems

Optimal concentration of boroxo siloxane elastomer synergist was determined by LOI and cone calorimetric measurements on ammonium polyphosphate and pentaerythritol containing intumescent flame retardant for polypropylene. The increased viscosity of the melt and plasticity of intumescent char due to boroxo siloxane elastomer could be proved by a thermal scanning rheometric investigation. It is presumed, the increased melt viscosity is created by the product of boroxo siloxane-pentaerythritol, formed during the compound preparation, while the improved char plasticity is the result of product formed at high temperature from boroxo siloxane and ammonium polyphosphate.

Role of pigments in the stability of polyethylene systems

The photodegradation processes of high-density polyethylene (HDPE) films containing either a phthalocyanine-based pigment, or a rutil (TiO 2 )-based pigment, as well as of the unpigmented films stabilised differently were investigated during photo-ageing, applying mechanical, gel content and XPS measurements. The phthalocyanine pigment-containing film showed degradation characteristics (abrupt decrease of elongation at break after short irradiation period, no gel formation, high concentration of oxygen-containg functional groups on the surface) similar to those of the films containing a low amount of stabiliser. The behaviour of the TiO 2 -containing film and that of the unpigmented films containing a higher amount of stabiliser were also similar (slow decrease of elongation at break, increase of gel content, lower amount of oxygen-containing functional groups on the surface). The concentration of oxygen-containing functional groups in samples pigmented with phthalocyanine increased remarkably with increasing processing temperature. The results suggest that the phthalocyanine pigment influences the photostability indirectly, through reduction of the thermal stability of polymer due to the adsorption of the thermal stabiliser by the phthalocyanine pigment. Coating the surface of phthalocyanine with reactive surfactant improved the photostability of the HDPE film.

Role of interface modification in filled and flame-retarded polymer systems

New reactive surfactants (RS) and synergistic reactive surfactants (SRS), containing reactive groups and longer unsaturated apolar hydrocarbon chains have been synthesised and applied in filled and flame-retarded polymer systems, respectively. These additives are capable of reactions with the polymer matrix and the disperse phase as well. The reaction of these compounds with polyolefins was proven on model system by surface analysis, while their reaction with fillers was demonstrated by DSC. The interface modification in filled/reinforced polymer systems and polymer blends resulted in improved mechanical properties, while in pigmented PE it contributed to higher photostability. Furthermore, the efficiency of intumescent flame retardant additives in polyolefins could be enhanced.

Green chemical tools in organophosphorus chemistry-organophosphorus tools in green chemistry

Abstract A variety of reactions including esterifications, alkylations, additions, cycloadditions, fragmentations, and condensations were carried out under microwave MW-assisted and solventless conditions, occasionally in ionic liquids (ILs). In a few cases, MW was synergic with phase transfer catalysis or could substitute it. A variety of P(III) ligands were developed and converted to Pt(II) complexes that can be used as catalysts. Finally, phosphorylations and the Kabachnik–Fields reaction were monitored and optimized by an on-line method, in situ Fourier transform IR spectroscopy.

New reactive additives for interface modification in multicomponent polyolefin systems

New reactive additives were synthesised and used as interface modifiers in different multicomponent polyolefine systems. The synthesis was carried out in computer-controlled reactor by means of Diels-Alder reaction and condensation. These additives are capable of combining the benefits of dispersing and coupling agents. A part of the synthesised reactive surfactants have also synergistic effect in flame retardant systems. Their surface-active character facilitates the reactive compounding. The undesirable transport processes of stabilisers and components of flame-retardants in polyolefine systems could be effectively controlled by interface modification.

The synthesis of α-aryl-α-aminophosphonates and α-aryl-α-aminophosphine oxides by the microwave-assisted Pudovik reaction

A family of α-aryl-α-aminophosphonates and α-aryl-α-aminophosphine oxides was synthesized by the microwave-assisted solvent-free addition of dialkyl phosphites and diphenylphosphine oxide, respectively, to imines formed from benzaldehyde derivatives and primary amines. After optimization, the reactivity was mapped, and the fine mechanism was evaluated by DFT calculations. Two α-aminophosphonates were subjected to an X-ray study revealing a racemic dimer formation made through a N–H···O=P intermolecular hydrogen bridges pair.

Thermal and surface analytical study of flame retarded polyolefins. I. Interaction of additives and structure formation

Pentaerythritol may react with tetraethoxy-silane and ammonium-polyphosphate in flame retarded polyolefins and an interfacial layer can be formed around the ammonium-polyphosphate particles. It is advantageous to study such systems using methods of thermal and surface analysis together.

Monitoring the Phosphorylation of Phenol with Diethyl Chlorophosphate in Aqueous Medium in the Presence of Sodium Hydroxide by in Situ Fourier Transform Infrared Spectroscopy

In situ Fourier transform IR spectroscopy has been found to be an appropriate tool for monitoring the title reaction resulting in the formation of diethyl phenylphosphate.

Monitoring the phosphorylation of phenol derivatives with diethyl chlorophosphate in liquid-liquid and solid-liquid phase by in situ fourier transform infrared spectroscopy, part II

The reaction of 4-chlorophenol and 4-nitrophenol with diethyl chlorophosphate carried out in a liquid–liquid and solid–liquid two phase system, respectively, was monitored by in situ Fourier transform IR spectroscopy.