P. Erra

Wettability, ageing and recovery process of plasma-treated polyamide 6

The wetting properties of polyamide 6 rods treated with radiofrequency (RF) low-temperature plasma (LTP) using three different non-polymerizing gases (air, nitrogen and water vapour) were determined using the Wilhelmy contact-angle technique. Information on the acidic or basic nature of the ionizable groups generated on the rod surface was obtained using contact-angle titration. The wettability obtained depends on the plasma gas used, and it tends to decrease with time elapsed after the treatment when the samples are kept in an air environment. However, the wettability can be recovered by immersion of the aged samples in water. The degree of recovery depends on the plasma gas used and the highest recovery was obtained with water vapour plasma treated samples. Both ageing and recovery behaviour can be attributed to the reorganisation of hydrophilic groups which tend to reversibly migrate or orient towards the bulk phase depending on the storage conditions, although other factors can also have influence.

Shrinkage Properties of Wool Treated with Low Temperature Plasma and Chitosan Biopolymer

Low temperature plasma treatments of wool modify only the cuticle surface of the fibers, improving their surface wettability, dyeability, fiber cohesion, and shrink resistance. The shrink-resist properties obtained with plasma treatment do not impart a machine-washable finish, which is an important end-user demand. However, the shrink resistance of air plasma. treated wool is suitably enhanced by a subsequent biopolymer chitosan application. Using a qualitative colorimetric method, chitosan adsorption is shown to increase after treatment with air plasma. SEM observations yield information about the etching effect and chitosan adsorp tion. Given that both kinds of treatments, air plasma and chitosan, are environmentally acceptable, a new ecological shrink-proofing process is proposed.

Surface active molecules: preparation and properties of long chain nα‐acyl‐l‐α‐amino‐ω‐guanidine alkyl acid derivatives

A new route for the synthesis of long chain Nα‐acyl‐l‐α‐amino‐ω‐guamdine alkyl acid derivatives, with cationic or amphoteric character has been established. The general formula of these compounds is shown below.

Shrink-resistance and wetting properties of keratin fibres treated by glow discharge

The influence of the gas type, air or nitrogen, and the treatment time in an RF glow discharge treatment on the shrink resistance properties of knitted wool fabric and wetting properties of keratin fibres were studied. Wetting properties were determined by means of contact angle measurements on single keratin fibres. This method allows measuring accurately the influence of the plasma gas type and treatment time on fibre hydrophilicity, and its modification with the time elapsed after plasma treatment. The modification of the surface properties should be taken into account, especially, when a biopolymer after-treatment is applied to achieve wool shrink resistance. Surface chemical changes were studied by means of XPS. Topographical changes in the wool fibre surface were observed by scanning electron microscopy (SEM) and surface damage was evaluated by means of the Herbig sac formation. Both air and nitrogen plasma treatments impart shrink resistance to wool fabric and hydrophilic properties to the keratin fibres. Even short exposure times are found to be enough to decrease drastically the advancing water contact angle and, therefore, to increase the shrink resistance effect. Slight differences were observed between the air and nitrogen plasma treatments. The time elapsed after the plasma treatment promotes an increase of the advancing contact angle and a decrease of chitosan adsorption. The plasma treatments studied here modify chemically the epicuticle but it is not removed.

Chromatographic characterization of internal polar lipids from wool

Wool internal polar lipids were isolated and separated into different fractions based on polarity. Qualitative and quantitative analyses of the different fractions were performed by thin-layer chromatography and thin-layer chromatography coupled to flame-ionization detection, respectively. Cholesterol esters, free fatty acids, sterols, ceramides, glycosylceramides, and cholesterol sulfate were the main components, with ceramides being in the highest proportion. The fatty acid composition of ceramides and glycosylceramides was determined by gas chromatography/mass spectrometry. As for other keratinized tissues, long-chain fatty acids predominated in comparison to either free fatty acids or phospholipid-linked fatty acids; in both cases, stearic and lignoceric acids were the most abundant fatty acids, and a low amount of 18-methyleicosanoic acid was found. This work opens new avenues in the study of lipid rearrangement in more complex and realistic vesicle structures than conventional liposomes.

Novel preparation methods for highly concentrated water-in-oil emulsions

Abstract Kinetically stable water-in-oil (W/O) high-internal-phase-volume-ratio emulsions with gel-like appearance have been formed in water/hydrogenated non-ionic surfactant/oil systems. Their visual aspect varies from transparent to translucent or white depending on composition variables and temperature. Systematic studies undertaken to characterize these emulsions, referred to as gel emulsions, have revealed that they form above the hydrophilic-lipophilic balance (HLB) temperature of the corresponding ternary system. They consist of two isotropic liquid phases; the dispersed phase is composed of aqueous droplets and the continuous phase is a W/O microemulsion. These emulsions can be prepared by gradual addition of the internal phase to the external phase while stirring, the most common method for preparing highly concentrated emulsions. In the ternary systems water/non-ionic surfactant/hydrocarbon we found two new procedures for preparing gel emulsions. (a) Mixing of the three components, at their final composition, with vigorous stirring, can lead, at the appropriate temperature, to gel emulsion formation. (b) Increasing the temperature of an isotropic phase, the composition of which is that of the final emulsion. These methods of preparation have been rationalized in terms of the evolution of system properties during the process.

Shrinkage Properties of Peroxide-Enzyme-Biopolymer Treated Wool

Incorporating an enzyme in the alkaline peroxide treatment bath enhances wool wet-tability and the effectiveness of subsequently applied chitosan biopolymer. Wool whiteness is also significantly enhanced. Wool knitted fabric thus treated is shrink resistant at the machine-washable level, which is one of the most important end-user demands. The formation of ionic bonds between the new sulphonic groups generated on the wool fiber surface and chitosan contribute to the shrink resistance of H2O2 + enzyme/chitosan treated wool. As a result of excessive increases in enzyme concentration in the peroxide bath, the wool surface cysteic acid content decreases, thus diminishing both the efficiency of post-applied chitosan solution and the shrink resistance.

Synthesis and properties of cationic surfactants containing a disulfide bond

Two new cationic surfactants containing a disulfide bond were synthesized, and the physical chemical characteristics and the fundamental surface-active properties were determined. These new surfactants have potential applications in the textile and cosmetic field. These compounds have been prepared by condensation of a commercial Nα,Nα-dimethyl amino betaine with cystine dimethyl ester or cystamine by means of the mixed anhydride method. The study of their properties revealed that these molecules are soluble in water (stable at pH⩽8) and show surface activity with similar low critical micelle concentration values. Microscopic examination of water/surfactant systems containing these compounds shows that they form liquid crystals with patterns corresponding to typical hexagonal and lamellar structures.

FTIR analysis to study chemical changes in wool following a sulfitolysis treatment

Sulfitolysis of wool keratin is important to many industrial processes, including shrink resistance, setting, and bleaching; its extent therefore requires rapid estimation. Currently, time consuming chemical analysis is used to convert the cysteine-S-sulfonate to cysteine and then to measure total cysteine colorimetricaily. Using ftir and the attenuated total reflectance (atr) method, our experiments quantify the relative amount of cysteine-S-sulfonate on the wool fiber surface. The cysteine-S-sulfonate (Bunte salt) shows a strong symmetrical stretching vibration at 1022 cm−1; working in the absorbance mode and taking second derivatives to enhance resolution allows changes in the amount of Bunte salt to be followed. The keratin Bunte salt is stable to acid but labile in alkali; a treatment with ammonium thioglycolate at pH 7.6 completely removes the Bunte salt. Results show the same trend as those obtained using the classical chemical method.

Antimicrobial Activity of Wool Treated with a New Thiol Cationic Surfactant

Wool can be an appropriate medium for growing and transferring microorganisms under favorable temperature and humidity conditions. These microorganisms can result in wool damage, skin irritation, or infections. A new and effective quaternary ammonium surfactant, N-dodecyl-N, N-dimethyl glycine cysteamine hydrochloride (DABM), has recently been synthesized. DABM can react with wool by means of its thiol group, either with cysteine-S-sulphonate residues (Bunte salts) of sodium bisulphite pretreated wool or with the disulfide bond of cystine wool, forming an asymmetrical disulfide bond. The antimicrobial activity of bisulphite-pretreated and untreated wool, both treated with DABM, is studied against gram-positive and gram-negative bacteria by means of the protective antibacterial AATCC, test method 100-1989 and SEM observation. Both wool samples show biocide activity against B. pumilus and bacteriostatic activity against S. aureus. The absence of gram-positive and gram-negative bacteria attached to the wool surface fibers is observed by SEM.