Maria Rosaria Massafra

Surface modification of poly(ethylene terephthalate) fibers induced by radio frequency air plasma treatment

The surface chemical and physical modifications of poly(ethylene terephthalate) (PET) fibers induced by radiofrequency air plasma treatments were correlated with the characteristics of the discharge parameters and the chemical composition of the plasma itself, to identify the plasma-induced surface processes prevailing under different operating conditions. Treated polymer surfaces were characterized by water droplet absorption time measurements and XPS analysis, as a function of the aging time in different media, and by AFM analysis. They exhibited a remarkable increase in hydrophilicity, accompanied by extensive etching and by the implantation of both oxygen- and nitrogen-containing polar groups. Etching was mainly a consequence of ion bombardment, yielding low molecular weight, water soluble oxidation products, while surface chemical modifications were mainly due to the action of neutral species on the plasma-activated polymer surface.

Characterisation of poly(ethylene terephthalate) and cotton fibres after cold SF6 plasma treatment

Poly(ethylene terephthalate) (PET) and cotton fibres, treated in an appositely set up RF SF6 plasma reactor under different operating conditions, were characterised by XPS, EPR, DSC, XRD, ATR analyses, water contact angle and water droplet roll-off angle measurements. The ageing of plasma-treated samples was also investigated under different post-treatment conditions. Plasma treatment led to efficient implantation of fluorine atoms on the surface of both polymers; this resulted in water repellence without altering the bulk properties of the polymers. The radical species formed in the plasma-activated polymer surface were involved in its fluorination and in the subsequent uptake of atmospheric oxygen. Surface reorganisation of polymer segments, tending to reduce the interfacial energy between the polymer and the phase in contact with it, induced the surface modifications observed under ageing and in samples plasma-treated several times. An increase in the depth of the fluorinated layer, leading to outstanding stable hydrorepellence, was achieved by repeated SF6 plasma treatments, followed by surface rearrangements favoured by swelling.

Structure and properties of bombyx mori silk fibers grafted with methacrylamide (MAA) and 2‐hydroxyethyl methacrylate (HEMA)

Silk fibers were graft-copolymerized with methacrylamide (MAA) and 2-hydroxyethyl methacrylate (HEMA) in aqueous media, using a chemical redox system as an initiator. High weight gains (300%) were obtained with both monomers, the weight gain being linearly related to the amount of monomer contained in the reaction system. The reaction efficiency attained 95–100%. The extent of homopolymerization was negligible for the MAA grafting system, while large amounts of poly-HEMA covered the surface of silk fibers beyond 70% weight gain. The fiber size increased linearly with the weight gain. The moisture content of MAA-grafted silk fibers was highly enhanced by grafting. The severe grafting conditions caused a partial degradation of the tensile properties of silk fibers, as well as of the degree of fiber whiteness. Following grafting, the breaking load slightly increased, while elongation at break and energy decreased. The decomposition temperature of grafted silk fibers shifted upwards. The Raman spectra of untreated silk fibers showed strong lines at 1667 (amide I), 1451, 1227 (amide III), 1172 and 1083 cm−1. Overlapping of the lines characteristic of both silk fibroin and grafted polymer was observed in the spectra of grafted silk samples. The vibrational mode of the amide III lines of silk fibroin was significantly modified by grafting.

A SF6 RF plasma reactor for research on textile treatment

This research concerns the development of a SF6 RF discharge at low pressure in a small reactor for industrial applications. The plasma is produced in the pressure range 0.05-1 mbar by a RF supply. The pumping system sustains a flowrate of about 50 cm s-1, with residence time in the discharge of about 0.2 s at a pressure of 0.1 mbar. The discharge parameters were measured at a low operation power. Measurements were performed by means of movable electrostatic probes and a photodiode. Particular care in the analysis of the data proved to be necessary due to the presence of a substantial amount of negative ions. The reactor has been employed for textile treatment in order to modify the surface properties of the fibres. Favourable operating conditions leading to an improved hydrophobicity of the textiles were achieved.

Surface Modifications of Silk by Cold SF6 Plasma Treatment

Silk samples, treated in an appositely set-up radio frequency SF6 plasma reactor under different operation conditions, were characterized by XPS, EPR, DSC, XRD, ATR analyses and water contact angle measurements, also as a function of storage time after the treatment. Efficient attachment of fluorine atoms on the polymer surface occurred during the plasma treatment, imparting water repellence to it. Also the percentage of surface oxygen increased after the treatment, partially as a consequence of radical scavenging by molecular oxygen and the formation of peroxides. An increase in silk crystallinity during the treatment seems to contribute to ensuring durable water repellence properties.

Structure and properties of tussah silk fibers graft‐copolymerized with methacrylamide and 2‐hydroxyethyl methacrylate

Tussah silk fibers were graft-copolymerized with methacrylamide (MAA) and 2-hydroxyethyl methacrylate (HEMA) in aqueous media, using a chemical redox system as an initiator. High weight gain values were obtained with both grafting agents (up to 175%). The extent of homopolymerization was negligible for the MAA grafting system over the entire range of monomer–silk ratios examined, while polymer deposition on the fiber surface occurred when the HEMA–silk ratio exceeded 0.5% (w/w). The moisture content of poly(MAA)-grafted silk fibers was enhanced by grafting. Breaking load, elongation at break, and energy decreased at low weight gain (0–20%) and then remained rather constant. The DSC curves of poly(MAA)-grafted silk showed a new endotherm at about 280°C, due to the melting of poly(MAA) chains. The loss modulus peak of poly(HEMA)-grafted silk fibers broadened and shifted to a lower temperature, showing a tendency to split into two peaks at high weight gain. On the other hand, grafting with poly(MAA) induced a noticeable upward shift of the loss peak. The TMA curves showed that grafting with poly(MAA) resulted in a higher extent of fiber contraction from room temperature to about 250°C. Moreover, the intensity of the final contraction step at about 350°C decreased with increasing weight gain and shifted to a lower temperature. The Raman spectra of grafted fibers were characterized by overlapping of the characteristic lines of both silk fibroin and polymer, the latter showing an intensity proportional to the amount of weight gain. Among the conformationally sensitive vibrational modes of tussah silk fibroin, the amide III range was significantly modified by grafting with both poly(MAA) and poly(HEMA).

Characterization of plasma processing for polymers

Abstract Some selective plasma treatments are described, aiming at modifying specific surface properties of textile polymeric materials, such as their hydrorepellence and dyeability. The prevailing plasma–polymer interactions were identified by correlating the physico-chemical modification of treated polymer surfaces to the characteristics of the plasma sources.

Marking of Cellulose Yarn by Vinyl Monomer Grafting

Marking consists of adding a mark on a product for the purpose of its identification. The use of methacrylamide (MAam) and 2-hydroxyethylmetacrylate (HEMA) as markers for cellulose yarn (flax) has been studied. Grafting of a reactive monomer onto cellulose chains has been carried out using a redox system with a chemical initiation technique. The products were characterized by Fourier transform infrared (FT-IR) spectroscopy. HEMA has been chosen due to its more pronounced characteristic band. The major factors affecting HEMA polymerization, including concentration, reaction time and temperature, were studied to establish the optimum grafting conditions. We note that the grafting does not affect the mechanical properties of the yarn.