Antonella Castelli

Dyeing of Cotton in Supercritical Carbon Dioxide

Abstract The dyeing of cellulosic fibers with disperse and natural dyes was attempted using supercritical carbon dioxide (CO2SCF) as solvent system. The dye uptake was strongly increased if cotton was pretreated with polyethylene glycol (PEG), a known plasticizing agent of cellulose, while reasonable wet-washing and light fastness properties were achieved if PEG-treated cotton was dyed in CO2SCF with disperse dyes included in benzamide crystals. This might be a consequence of partial occlusion of cellulose pores by benzamide, forming hydrogen bonds with cotton and PEG.

Influence of interfacial agents on the physicochemical characteristics of binary polyethylene/polyamide 6 and ternary polyethylene/polypropylene/polyamide 6 blends

Binary low-density polythylene/polyamide 6 and ternary low-density polyethylene/polypropylene/polyamide 6 blends were prepared by melt mixing, without and with the addition of two different commercial products [poly(ethylere-co-buthylacrylate-co-maleic anhydride) and poly(ethylene-co-vinylacetate) grafted with maleic anhydride] used as interfacial modifiers. More precisely, the polypropylene was a propylene/ethylene random copolymer, containg 6% by weight of ethylene. The polyamide 6/interfacial agent and polyethylene/ interfacial agent systems were also considered. Differential scanning calorimetry, microscopic observations—together with chemical etchings—and mechanical tests supported the occurrence of strong interactions at the interface, especially when using the buthyl acrylate-based agent. The compatibilizing effect of the interfacial agents was also analyzed in the light of interfacial tension determinations. Eventually, low-density polyethylene modifications induced by compatibilization were studied carrying out WAXD analysis.

Morphological changes and dye uptake of poly(ethylene terephthalate) and 2,5-cellulose diacetate immersed in supercritical carbon dioxide

Abstract The dyeing process of poly(ethylene terephthalate) (PET) and 2,5-cellulose diacetate (CA) fibers at 40–100°C using supercritical carbon dioxide (CO2SCF) as solvent system has been kinetically investigated in relation to the morphological modifications induced by the CO2SCF treatment in these fibers, determined through DSC, X-ray diffraction, SEM analysis and shrinkage measurements. A comparison between the effects of annealing both polymer fibers in CO2SCF and in hot air evidenced that CO2SCF has a plastifying action towards PET by lowering its Tg value to 0–5°C and thus favoring the dyeing process at low temperature. Such effect was not observed with CA.

Hydrous pyrolysis of polystyrene

Abstract Thermal degradation of polystyrene has been investigated in the presence of water under subcritical conditions (hydrous pyrolysis). The experiments were carried out in closed systems under inert atmosphere, in the temperature range 300–350°C, at pressures up to 18 MPa, for 1–120 h. The products obtained, separated as gases, volatiles, and heavy compounds, were analyzed qualitatively and quantitatively by gas-chromatography, gas-chromatography/mass spectrometry and size exclusion chromatography. The results showed that the presence of water increases the yields of the volatile products, mainly in the first steps of the pyrolytic process, and leads to higher yields of monomer. This latter observation suggests a lowering of the secondary reactions extent.

Hydrous pyrolysis of silica-supported polystyrene

Thermal degradation of polystyrene has been studied in the presence of water under subcritical conditions (hydrous pyrolysis). The experiments were performed in closed systems under inert atmosphere, in the temperature range of 300-320°C, for 1-24 h. The results showed that the presence of water increases the yields of the volatile products, mainly in the first steps of the pyrolitic process, with a higher selectivity of monomer. In order to improve the effective phase contact between water and the polymer during the degradation, hydrous pyrolysis runs have been carried out on silica-supported polystyrene. Some of these experiments were performed using a stirred reactor. Under these conditions, the above effects appeared to be greatly emphasized. Qualitative and quantitative analyses of the degradation products have been reported for the series of runs investigated. The best recovery of styrene has been achieved at 320°C and 8 h, being close to 71%.

Formation of radicals in thermal degradation of kerogen. A kinetic study

Abstract Two source rocks containing type II kerogen, both from Italy, were studied to evaluate the formation of radicals during thermal treatment. Crushed and extracted rocks were pyrolysed in sealed tubes at different times and temperatures in the range 350–500°C. The pyrolysed samples were spectroscopically analyzed by ESR and the formed radicals were quantitatively determined. The experimental data were kinetically interpreted. The kinetic coefficients and the parameters obtained were compared with those of the reaction generating hydrocarbons. The maximum amount of radicals formed in the laboratory experiments was in a good agreement with the maximum concentration of radicals observed in kerogens of different natural maturation.

The cis-trans isomerization and lightfastness of azo dyes dispersed in thermoplastic fibers with different structural features

Abstract The cis-trans isomerization of 4-N,N-diethylaminoazobenzene dispersed in two polyamidic fibers has been studied. The fibers were obtained by blending polyamide 6 with appropriate amounts of an aromatic copolyamide, which allowed a controlled enhancement of the Tg value of the polyamide. The different fastness properties of the dyed materials could be explained in terms of the observed fifferent structural features of the blends.

Characterization of polypropylene-poly(1-butene)-hydrogenated olygo(cyclopentadiene) ternary blends

Ternary blends containing polypropylene (PP), poly(1-butene) (PB), and hydrogenated oligo(cyclopentadiene) (HOCP) have been studied using microscopic calorimetric and dynamic mechanical techniques, with no phase separation having been observed in the melt for all the considered compositions. The morphology of the crystallized blends and spherulite growth rate of the PP component appeared to be influenced by the blend composition. The presence of one or two Tgs revealed by dynamic mechanical thermal analysis (DMTA) on quenched or crystallized blends has suggested that demixing phenomena can occur during the crystallization of the components. The blend composition has been found to affect the overall crystallization rate and the equilibrium melting temperature of the PP component. A parameter describing the enthalpic interactions between the PP component and the diluent fraction evidenced that the addition of HOCP to PP and PB increases the stability of the ternary blend. The above results suggest that the three components can form a miscible blend in the melt.