Zs. Czégény

Pyrolysis and debromination of flame retarded polymers of electronic scrap studied by analytical pyrolysis

Abstract Two typical components of electronic scrap have been investigated by analytical pyrolysis: an electronic junction (phthalic polyester filled with ceramic fibres, flame retarded with brominated polystyrene) and a printed circuit board (epoxy resin on woven glass fibre support, flame retarded with brominated epoxy resin). Copyrolysis of these plastic materials has been carried out with inorganic solids of basic character. The volatile thermal decomposition products were analysed on line using pyrolysis-gas chromatography-mass spectrometry. The product analysis revealed that the decomposition reactions of the polymer constituents are significantly altered in the presence of the strong inorganic bases. Due to debromination of the dibromo- and tribromophenyl groups of brominated polystyrene, copyrolysis with sodium hydroxide and with basic zeolites resulted in a considerably reduced yield of dibromo- and tribromostyrenes. From brominated epoxy resins pyrolysed with sodium hydroxide an enhanced bromomethane evolution, while a depressed brominated phenol formation was observed. A diminished production of bromophenols takes place in pyrolysis with sodium-containing silicates as well.

Thermal decomposition of polyamides in the presence of poly(vinyl chloride)

Abstract Thermal decomposition of aliphatic and aromatic polyamides (polyamide-12, polyamide-6,6 and poly(1,4-phenylene terephthalamide) (Kevlar)) with poly(vinyl chloride) (PVC) was examined by pyrolysis-gas chromatography/mass spectrometry. Polyamide-PVC mixtures (typical mass ratio 1:1) were pyrolysed at 700 and 900°C. It was found that the presence of PVC promoted the hydrolytic decomposition routes of amide groups and volatile nitrile formation from all examined polyamides due to the hydrogen chloride eliminated from PVC under pyrolysis. In the presence of PVC an elevated yield of alkenenitriles was observed from polyamide-12. Benzeneamine is produced from Kevlar instead of benzenediamine in the presence of PVC, and the evolution of benzoic acid, benzenenitrile and benzeneisocyanate is promoted. At 900°C pyrolysis temperature enhanced hydrogen cyanide evolution was observed from polyamide-12 and polyamide-6,6 in the presence of PVC. Mechanisms are proposed for the hydrogen chloride assisted formation of nitriles.

Thermal decomposition of photooxidized isotactic polypropylene

Abstract Thermal decomposition of photooxidized isotactic polypropylene (iPP) samples were studied using analytical pyrolysis and thermal analysis techniques. It was found by thermogravimetry/mass spectrometry that the photooxidation decreases the thermal stability of the iPP. Oxygen-containing compounds are released over the range 100–300°C from the photooxidized iPP matrix. The beginning and the maximal rate of the decomposition are shifted to lower temperatures with the advancement of the oxidation of the iPP, however, the composition of the oligomer mixture formed did not change significantly. Detailed analysis of the volatile products was performed by pyrolysis-mass spectrometry and pyrolysis-gas chromatography/mass spectrometry. Volatile photo- and thermal decomposition products have been identified, some of them not yet reported. Mechanisms for their formation are proposed.

Inherently fluorescent and porous zirconia colloids: preparation, characterization and drug adsorption studies

Porous, fluorescent zirconia particles of nearly 380 nm diameter were prepared without template molecules or labeling dyes. The porous structure is the result of aggregation-induced particle formation. The inherent fluorescence is assigned to coordinatively unsaturated Zr4+ ions at the sol-gel derived ZrO2 surface. After physico-chemical characterization of the native zirconia particles carboxyl and/or amine bearing drug molecules (d,l-α-difluoromethylornithine - DFMO, ursolic acid - UA and doxorubicin - DOX) were adsorbed onto their surface, and the products were analyzed with Fourier-transform infrared spectroscopy (FTIR), thermogravimetry (TG), small-angle X-ray scattering (SAXS), fluorimetry and zeta potential vs. pH measurements. We have found that DOX complexes coordinatively unsaturated Zr4+ ions without dislocating them, while carboxyl-bearing drugs interact with basic surface Zr-OH sites eliminating some of the carbonate species. The adsorption of UA at the zirconia surface shifts considerably the isoelectric point of the surface and thus provides kinetic stability to the particles at physiological pH. An in vivo biodistribution study in two healthy dogs performed by SPECT/CT detection after 99mTc labeling of the nanocarriers has shown the possibility of drug delivery application.

Silica@zirconia@poly(malic acid) nanoparticles: promising nanocarriers for theranostic applications

Silica@zirconia@poly(malic acid) nanocarriers of 110 nm mean diameter were designed, synthesized and characterized for the targeted delivery of diagnostic and therapeutic 99mTc to folate-overexpressing tumors. An important achievement was that a multifunctional l-(-)-malic-acid-based copolymer was formed in situ at the surface of the inorganic cores in a single synthetic step incorporating l-(-)-malic acid, β-cyclodextrin rings, folic acid moieties, and polyethylene glycol chains. Morphological and in-depth structural analysis of the particles proved their core@shell structure. Stability experiments in aqueous media evidenced that stable suspensions can be obtained from the lyophilized powder in 10 mM phosphate buffer at pH 7.4. During 14-day degradation experiments, the nanoparticles were found to be slowly dissolving (including inorganic core) in saline and also in total cell medium. An in vitro toxicity assay on hepatocytes showed a concentration-dependent decrease of cell viability down to 63 ± 1% at the highest applied concentration (0.5 mg ml-1). Proof of concept experiments of technetium-99m radiolabelling and in vivo labelling stability are presented.