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A novel physical mechanism is proposed for microwave catalysis based on rotationally excited reactive species. The studies have shown that the microwave catalytic effect is less pronounced at higher temperatures, which have serious implications for the interaction of microwaves with living organisms in the context of mobile telephony.

The MoS2 nanotubes (NTs) were added to polyvinylidene fluoride (PVDF) with the aim to adjust its friction properties. Thin films and thin nanocomposite coatings were prepared with different MoS2 NT concentrations. Morphology and distribution of the NTs inside the nanocomposites were studied by optical and electron microscopy. Raman spectroscopy performed before and after friction tests was used to evidence partial transformation of PVDF into piezoelectric phase due to friction caused drawing. Friction tests in flat-on-flat and ball-on-disk configuration with AISI 316 stainless steel as counterpart revealed a strong reduction of coefficient of friction. [ABSTRACT FROM AUTHOR]

Wood liquefaction with glycols using p-toluenesulfonic acid as the catalyst was carried out under microwave heating. With rapid heating and temperatures in the 190-210 degrees C range complete liquefaction was achieved in 7 min. Liquefaction efficiency was dependent on the choice of glycol. Simple glycols such as ethylene glycol and propylene glycol were more effective than higher analogues. The use of glycerol in mixtures with glycols showed a synergistic effect. Size exclusion chromatography was used to follow the gradual emergence of liquefaction products in solution as well as the recondensation products that start forming early in the reaction and precipitate from solution when molar masses of approx. 1x10(4) g/mol are reached.

Fifty-eight fungi have been tested for their ability to degrade a recalcitrant synthetic polymer polyamide-6, generally known as nylon-6. Most of them were isolated from a factory producing nylon-6. After preliminary screening, 12 strains were selected for submerged culture in a medium with nylon fibres as the only N-source. No degradation was observed with the isolates from the factory. Wood degrading fungi from a culture collection, however, degraded nylon after incubation for several weeks. Bjerkandera adusta disintegrated the fibres most efficiently, starting with the small transverse grooves, which deepened into cracks. The superficial layers crumbled to leave a thin inner core of the fibre, which finally broke down into fragments. The remaining insoluble part of the nylon showed a decrease in number average molecular mass from 16900 to 5600 during a 60-day incubation. Its thermal properties, such as shifts in melting points and broadening of the melting endotherms, were altered. The reduction of the amount of nylon and the composition of the liquid phase indicated that part of the polymer was degraded into soluble products. After 50 days, the total nitrogen content of the soluble fraction was 10-fold higher than in the control sample. Manganese peroxidase, presumably responsible for the degradation, was detected in the liquid phase. The study shows that only white rot fungi are able to break down nylon-6. For the first time this polymer was shown to be disrupted by B. adusta. The extent of the biodegradation indicates its potential for application in nylon waste reduction.

The microstructure of bacterial poly(3-hydroxybutyrate-co-3-hydroxyvalerate) copolyesters (PHBV) as well as a mixture of two PHBV copolyesters of different comonomer composition and sequence distribution was studied by 13C NMR based on dyad and triad analysis and multistage electrospray ionization mass spectrometry (ESI-MSn). Both techniques gave results that were in good agreement for all investigated samples. The effect of microstructure on PHBV thermal properties was investigated from the melting behavior of samples. A PHBV copolyester with randomly distributed hydroxyvalerate units (12.0 mol % HV) showed a single melting peak, whereas samples with nonrandom composition distribution showed multiple melting peaks in their thermograms. Such complex melting behavior suggested that the 12.9 and 27.1 mol % PHBV copolyesters were actually blends of several copolymers with widely different comonomer-unit composition.

Characterization of poly-3-hydroxybutyric acid (PHB) and poly-3-hydroxybutyric-co-valeric acid (PHBV, 13% valerate) in chloroform was performed using size exclusion chromatography coupled to a multi-angle light scattering detector (SEC-MALS). Absolute molar mass averages, molar mass distribution, and the radius of gyration were determined. Three sample preparation methods were examined: dissolution in chloroform (1) at room temperature, (2) at 60 degrees C, and (3) after thermal pretreatment of samples (annealing at 180 degrees C with subsequent quenching in liquid nitrogen). Dissolution at 60 degrees C and dissolution of thermally pretreated samples gave molecularly dissolved PHB and PHBV. At 60 degrees C using acid free chloroform, there was no indication of degradation for up to 120 min dissolution time, whereas thermal degradation of polymers did take place during annealing at 180 degrees C. The degradation rate constants for number and weight average degree of polymerization at 180 degrees C were slightly higher for PHB (5.19 x 10(-5) min(-1), 4.95 x 10(-5) min(-1)) than for PHBV (4.99 x 10(-5) min(-1), 4.54 x 10(-5) min(-1)). The dependence of the radii of gyration on molar mass showed that both polymers form random coils in chloroform. The relationship between the absolute molar masses and relative SEC results was determined. DSC and NMR characterization also gave evidence of the progress of degradation.