Diana Gregor-Svetec

Preparation and characterization of chitosan coatings onto regular cellulose fibers with ultrasound technique

Regenerated cellulose fibers—viscose fibers—were coated with chitosan using an ultrasound technique to improve their accessibility, reactivity and sorption properties. The main purpose of our research was to study the modification of viscose fibers and to determine the effect of the application of chitosan onto viscose fibers. Samples were obtained by treating the fibers with chitosan in a dilute acetic acid solution in an ultrasonic bath. The influences of the chitosan coating on the changes in morphology, supramolecular structure, sorption and tensile properties were studied. The spectra (FTIR analysis) of the treated viscose fibers showed changes and new absorption bands that revealed the existence of the chemical interactions with the chitosan. The scanning electron microscope images confirmed that the surface of the fibers was covered with the chitosan. A decrease in the water retention value and increase in the absorption and moisture content with an increasing concentration of chitosan was noted. Furthermore, the differences in tensile behavior were analyzed using an Instron tensile testing machine. The chitosan coating had no effect on the tensile strength of the viscose fibers, but influenced the tensile strain. Some changes, though not significant, were noted in the structure (crystallinity, orientation) of the treated viscose fibers.

Influence of enzymatic treatment on the structural, sorption and dyeing properties of viscose and chitosan/cellulose fibers

The research focused on the structural, sorption and dyeing properties of enzymatically treated viscose fibers and chitosan/cellulose fibers compared to the untreated fibers. First, both fibers were treated with cellulase enzymes for 30 minutes and 90 minutes and afterwards were dyed with the commercial sample of CI Reactive Red 238 at three different dye concentrations. Comparison of the structural and sorption properties of untreated and enzymatically treated fibers showed that the enzymatic treatment lowered the degree of polymerization, as well as crystallinity degree and influenced the surface structure of fibers, resulting in enhanced sorption properties and dyeability of enzymatically treated fibers. Although the values of exhaustion and fixation were higher for chitosan/cellulose fibers because of their initial less-ordered crystalline structure, the 90 minutes of enzymatic treatment has increased the moisture content and water retention capability more for the viscose fibers and hence their dyeability compared to chitosan/cellulose fibers. The 90-minute enzymatically pretreated viscose fibers reached the same exhaustion and fixation values at lower dye concentrations as chitosan/cellulose fibers.

Homogeneity of Poly(Propylene) and Poly(Ethylene Terephthalate) Fibers

Diffuse small-angle X-ray scattering is caused by inhomogeneity in the electron density distribution of a material and is often attributed to the existence of microvoids in polymers. The content, dimensions and relative surfaces of the microvoid system can be determined thereby. The dimensions of the coherently scattering domains and the sizes of the inhomogeneities are related by the form, or shape factor (f). Changes in this factor highlight structural changes in polymer fibers caused by different treatments. In the present paper the microvoid system of differently treated poly(ethylene terephthalate) (PET) and poly(propylene) (PP) fibers were studied after subjugation to different treatments. PP fibers were spun from two different polymers and drawn at different temperatures, whereas PET fibers were treated in different media. The form factors found for PET and PP fibers were rather high. For PP fibers, drawn at different temperatures and draw ratios, the form factors were between 2 and 5. Untreated PET samples had form factors of about 6. A supercritical fluid treatment could increase the form factor up to 8. Conventional water dyeing and hot air treatments caused considerable changes in the microvoid system and increased the form factor to values even larger than 8.