Giovanni Testa

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.

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.

Inducing water bath dyeability in polypropylenic fibers by their blending with polyamide 6

Melted blends of polypropylene and polyamide 6 compatibilized with a poly(propylene)/maleic anhydride copolymer were extruded and stretched to give filaments. The polypropylenic fibers obtained by this method were found to be easily dyeable in an aqueous dyebath. The wet-washing at 40, 60, and 90°C and the light and dry-cleaning fastnesses of the new material appeared quite satisfactory.

Characterization of Native Cellulose/Poly(ethylene glycol) Films

Water molecules retained in native cellulose gels obtained from Acetobacter xylinym (AX) were displaced by poly(ethylene glycol)s (PEG) of different molecular weight. The so obtained native cellulose/PEG material, characterized in film form by differential scanning calorimetry, dynamic mechanical thermal analysis and wide angle X-ray scattering, revealed that strong interactions occur between PEG and cellulose and that the polymer mixture is in the rubbery state at ambient temperature. Moreover, it could be dyed in supercritical carbon dioxide by disperse dyes, thus exhibiting typically lipophilic properties and suitability to be employed as a bio-compatible support for lipophilic active species.

Kinetic studies on the accelerated aging of cellulosic materials

The natural aging of cellulosic materials (high purity paper, cotton, raw and bleached flax, viscose) was simulated by thermal oxidation in air at constant temperature (123-192°C). Also the synergetic effect of light was investigated at 50-85°C. The kinetics of polymer degradation was followed through intrinsic viscosity measurements and was correlated with the degree of crystallinity, determined by X-ray diffraction, and with the surface oxidation of the investigated samples, evaluated through XPS analysis. At least two constant rate stages were observed in kinetic runs. The acceleration factors and time necessary for simulating a 20-year thermal aging of the investigated cellulosic materials were obtained from the calculated activation parameters by extrapolation of the process rate coefficients to room temperature. Surface oxidation parallel to aging led to the formation of low-molecular-weight, easily removable products in pure cellulose materials, while in lignin-containing materials mainly lignin was involved.

Oxygen permeation through films of compatibilized polypropylene/polyamide 6 blends

Polypropylene/polyamide 6 blends were prepared by melt mixing, without or with the addition of a suitable commercial product, a polypropylene grafted with 1% maleic anhydride, used as an interfacial modifier. The oxygen permeation through their films was studied as a function of temperature and the effect of the presence of the compatibilizer on the barrier properties of the material was examined. In addition, the diffusion coefficients were measured. The relationships between transport parameters and blend morphology were investigated by microscopic observations, together with chemical etchings, and a simple model was applied for interpreting the experimental permeation data. Differential scanning calorimetry was used in the determination of the degree of crystallinity of the blends.

Oxygen permeation through films of polypropylene/hydrogenated oligocyclopentadiene blends

Abstract Oxygen permeation through films of isotactic polypropylene (iPP)/hydrogenated oligocyclopentadiene (HOCP) blends was studied as a function of the weight fraction of the two components and temperature. Increasing HOCP content lowers oxygen permeability and diffusivity through the films and increases the glass transition temperature of the polymer blends. Activation energies for permeation and diffusion processes were also measured. Annealing for 2 min at 100°C was shown to completely transform the smectic phase in the α-crystalline form and to induce a marked increase in oxygen permeability and diffusivity, especially in the blends, and a corresponding decrease in the activation parameters.

Effect of thermal accelerated ageing on the properties of model canvas paintings

Abstract The aim of this study is to develop a laboratory technique to simulate a natural ageing of canvas paintings adopting artificial ageing methods in air (thermal oxidation), in the absence of light. Four models of canvas paintings aged up to 315 years are considered. Paintings are constituted of oil film on oil ground layer, oil film on tempera ground layer, tempera film on tempera ground layer or by tempera film on oil ground layer. Surface strength and the colour of the paintings and the degree of polymerization (DP) of linen canvas were evaluated at different steps of ageing. The degradative result was estimated as the DP of linen canvas after prefixed times of microbial attack.

Preservation treatments of aged papers by supercritical carbon dioxide

Innovative neutralizing and strengthening treatments for aged acidic paper have been developed, based on the use of supercritical carbon dioxide (CO2SCF) as solvent system. After treatment with the non toxic neutralizing agent CaCO3 in CO2SCF, acidic papers exhibited a pH increase of water extracts, the creation of an alkaline reserve and a decrease in the rate of artificial aging, while mechanical tensile properties of aged acidic papers improved after treatment with catechol both simply dissolved in ethanol or in CO2SCF in the presence of ethanol as co-solvent.

Physico-chemical characterization of compatibilized poly(propylene)/aromatic polyamide blends

Poly(propylene)/aromatic polyamide blends were prepared by melt mixing, without or with the addition of an interfacial modifier, viz. a poly(propylene) polymer grafted with 1 wt.-% of maleic anhydride. The characteristics of these polymer blends were investigated by differential scanning calorimetry, dynamic mechanical thermal analysis, scanning electron microscopy and surface tension measurements. The transport parameters of oxygen through films of such polymer blends were also determined by the differential permeation method. The new compatibilized blend materials, being transparent, sterilizable, dimensionally stable, and having very high barrier properties towards oxygen, are particularly suitable for packaging applications. Blends aus Poly(propylen) und aromatischen Polyamiden wurden im Schmelzemischverfahren hergestellt, teilweise unter Zugabe eines mit 1 Gew.-% Maleinsaureanhydrid gepfropften Poly(propylen)s als Grenzflachenmodifikator. Die Eigenschaften dieser Blends wurden mittels Differentialkalorimetrie, dynamischer mechanisch-thermischer Analyse, Rasterelektronenmikroskopie sowie Messungen der Oberflachenspannung untersucht. Die Parameter fur den Sauerstofftransport durch aus diesen Polymerblends hergestellte Filme wurden mittels Differentialpermeation bestimmt. Da die neuen kompatibilisierten Blends durchsichtig, sterilisierbar und formbestandig sind und auserdem eine hohe Undurchlassigkeit gegenuber Sauerstoff aufweisen, sind sie besonders fur Verpackungszwecke geeignet.