Majda Sfiligoj Smole

X-ray study of pre-treated regenerated cellulose fibres

Abstract. Regenerated cellulose fibres have had an important role to play in the man-made fibre field. The very special characteristics of different types of regenerated cellulose fibres, e.g. mechanical properties, sorption characteristics, and aesthetics were conditioned by the differences in their fine structure due to fibre formation processes. Additionally, the finishing processes could influence the fibre structure. A study was done of the crystalline structures of a solvent-spun cellulose fibre type (Lenzing Lyocell), made according to the NMMO process, and two conventional cellulosic fibre types, made by the viscose process (Lenzing Viscose and Lenzing Modal). The fibres were pre-treated (bleached and slack mercerised) and structural changes were followed by wide angle and small angle x-ray scattering (WAXS and SAXS), respectively. The periodical structure, determined by long spacing, was nearly the same in all the different types of fibres. A slight increase was observed after the treatment of viscose and modal fibres, but an unpronounced fall of a long period accompanied the pre-treatment of lyocell fibres. Some changes in crystallinity and crystalline orientation occurred due to the treatment conditions. The structural changes were correlated to the iodinesorption and mechanical properties.

The effect of heat treatment conditions using the drawing process on the properties of PET filament sewing thread

For the production of drawn poly(ethylene terephthalate) (PET) filament threads it is useful to determine the relationship between the drawing process conditions and the resulting product properties. Drawing at an elevated temperature over a defined time usually causes changes of the polymer structural parameters that influence the mechanical properties of the filaments. In order to elucidate the physical background of the drawing process for developing the production process of PET filament sewing thread, the thread was drawn by varying the treatment temperature and contact time. The effect of the treatment conditions on the structural and mechanical properties of the drawn threads was investigated, such as the birefringence, crystallinity, and dynamic mechanical properties of the threads’ filaments, as well as the mechanical properties and shrinkage of the treated threads. Using the drawing process, higher temperature and contact time up to the critical values (T2 = 220°C, n2 = 9 turns) change the structural parameters and, consequently, any modifications influence changes in the mechanical properties of the threads. Namely, a higher treatment temperature and contact time increases the degree of crystallinity, the birefringence, and the maxima of the loss tangent and loss modulus temperature, and a significant increase in the breaking tenacity, elastic modulus and the thread’s tension at the yield point, and a decrease of the breaking extension is achieved. The observed deterioration of the thread’s mechanical properties above the critical treatment conditions is attributed to the destructive phenomena of the supra-molecular structure, resulting in an imperfect structure of the thread’s filaments.

Study of PES sewing thread properties

The properties of 100 % PES core-spun threads were studied before and after the sewing process at different stitching speeds, by determination of the threads tensile force during the sewing process and by changes of the mechanical and thermo-mechanical properties after the sewing process. This analytical method is especially advantageous when monitoring contemporary thermal and mechanical effects, as is the case when loading the sewing thread. Loadings during the sewing process cause structural changes in the thread-twisted fibres. This is confirmed by changes in the thermo-mechanical properties after the sewing process. Simultaneously, changes in the threads mechanical properties after sewing were also observed.

Characterisation of modified polypropylene fibres

Due to excellent mechanical properties, high chemical stability and processability polypropylene fibres are mostly used in different technical fields. However, because of low surface energy, lack of reactive sites and sensitivity to photo or thermal oxidation the polymer properties are insufficient for some applications. Therefore several techniques for fibres modification are reported, e.g., plasma treatment, chemical modification etc.To alter the chemical and physical properties hydrophobic polypropylene monofilament fibres were surface modified and the sulphonation with concentrated sulpuric acid was used. The sulfonation was performed at different conditions, e.g., different temperatures and varying period of time and a detailed study of treatment conditions influence on the fibre properties was carried out. The sulphur content on fibres was determined by mass spectroscopy. The sulfonic acid cation exchange polypropylene fibres were characterised in terms of elektrokinetic and mechanical properties.

Polymer Nanocomposite Hydrogels for Water Purification

Contamination of water, due to the discharge of untreated or partially treated industrial wastewaters into the ecosystem, has become a common problem for many countries [1]. In various productions, such as textiles, leather, rubber, paper, plastic and other industries, the dyeing processes are among the most polluting industrial processes because they produce enormous amounts of coloured wastewaters [2-4]. In addition to their colour, some of these dyes may degrade to highly toxic products, potentially carcinogenic, mutagenic and aller‐ genic for exposed organisms even at low concentrations (less than 1 ppm) [5]. They contami‐ nate not only the environment but also traverse through the entire food chain, leading to biomagnifications [6-9]. The removals of such compounds particularly at low concentrations are a difficult problem.

Nanofibrous polysaccharide hydroxyapatite composites with biocompatibility against human osteoblasts

Regenerative medicine has a high demand for defined scaffold materials that promote cell growth, stabilize the tissue during maturation and provide a proper three dimensional structure that allows the exchange of nutrients. In many instances nanofiber composites have already shown their potential for such applications. This work elaborates the development of polysaccharide based nanofibers with integrated hydroxyapatite nanoparticles. A detailed study on the formation of electrospun nanofibres from aqueous mixtures of carboxymethyl cellulose polyethylene oxide was performed. The influence of different processing conditions and spinning solution properties using a nozzle-less electrospinning device was systematically studied. Optimized parameters were used to incorporate hydroxyapatite nanoparticles into the fibers. Nanofibers were additionally hydrophobized with alkenyl succinic anhydride (ASA) to render them insoluble in water. The nanofiber webs were thoroughly investigated with respect to morphology, chemical composition and inorganic content. Time dependent biocompatibility testing of the materials with human bone-derived osteoblasts showed no significant reduction in cell viability for the developed materials composed of carboxymethyl cellulose/polyethyleneoxide. Cells grown on hydrophobized materials show similar viability as those grown on a commercial collagen/apatite matrix.

Electrokinetic properties of surface modified PETP fibres

Abstract.The microporous structure of unmodified poly(ethylene terephthalate) PETP fibres was investigated by small-angle X-ray measurements in order to determine the content, size and shape of micro-voids in the fibres. Because of the compact and highly crystalline morphology of the chemically weakly reactive PETP fibres, the rate of diffusion within the fibres or adsorption on the surface is very low. Therefore a technique for modifying polyester fibre surface to change the dyeability, water sorption properties and electrokinetic characteristics have been suggested and used. It includes the adsorption of some electrolytes on the fibre surface. In order to study the obtained fibre surface changes the zeta-potential ζ was determined by streaming potential measurements as a function of pH. PETP fibres exhibit high negative ζ plateau value, due to their strong hydrophobicity and non-ionic character. The application of the surfactant changes the electrokinetic properties with respect to the adsorption process conditions.

Electrokinetic Properties of Nanocomposite Fibres

Nanocomposite fibres are becoming of great importance since organic–inorganic nanoscale composites frequently exhibit unexpected hybrid properties synergistically derived from the two components. The incorporation of one-, twoand three-dimensional nano particles, e.g. layered clays, nano-tubes, nano-fibres, metal containing nano-particles, carbon black, etc. is used to prepare nanocomposite fibres. However, the preparation of nanocomposite fibres offers several possibilities, i.e. creation of nanocomposite fibres by dispersing of nanoparticles into polymer solutions, the polymer melt blending of nanoparticles, in situ prepared nanoparticles within a fibre, the intercalative polymerization of the monomer, introduction of nanoparticles from dispersion into a porous polymer, preparation of nanocoatings by different techniques, e.g. sol-gel process, etc. With the respect to nanoparticles organization in / on fibres, respectively nanocoated fibres and fibres with nanoinclusions can be divided. Nanocomposite fibres demonstrate improved applicable properties, e.g. mechanical, flammability, electromagnetic, electro-conductive, sorption properties, and/ or obtain additional functional properties, like antimicrobial, self-cleaning, shielding, UV protective properties, etc. Combining polymer fibre and nanopaticles of different structures and characteristics influences also fibre’s surface properties, i.e. morphological properties and electrokinetic behaviour. In order to analyse fibre’s surface charge, the zeta potential is often determined through streaming potential measurements as a function of pH. These properties are generated by the electrochemical double layer (EDL), which exists at the phase boundary between a solid and a solution containing ionic moieties. By variation of the solution’s pH value and electrolyte content it is possible to estimate the acidic / basic and polar / nonpolar character of the solid surface from zeta potential data. Some examples of nanocomposite fibres (e.g. nanofilled PP fibres, SiO2 – nanocoated different types of fibres) regarding their electrokinetic properties are presented in the contribution. In addition to, the influence of nanocomposite fibres preparation procedure conditions on their zeta potential values is demonstrated.

Properties of nanocomposite PP fibres

PP-based nanocomposite fibres were prepared by direct polymer melt intercalation. With the intention to determine the size and dispersion of nanoparticles in the polymer matrix, fibres were plasma etched and SEM observations were performed. The influence of nanofiller content and coupling agent on electrokinetic properties was studied. PP monofilament fibres exhibit hydrophobe character with negative zeta potential value. The zeta potential value of co-polymer PP fibre decreases with increasing PPAA content and the isoelectric point IEP of co-polymer samples shifts towards acid region. Addition of modified montmorillonite due to the particles electropositive character, affects the reduction of zeta potential value and a slight shift of IEP towards neutral region is observed. Nano-particles content influences electrokinetic fibres properties, i.e. ZP value is changed, however IE point is not significantly changed by different concentrations of nanofiller. In addition to, mechanical properties of nanocomposite fibres were determined.

Polysaccharide Fibres in Textiles

Besides naturally grown cellulose fibres like cotton, hemp or flax, interest in textile fibres made up from regenerated cellulose is growing. By sure the use of a polymer material, which is provided by nature in huge amounts, favours its use as more sustainable material compared to oil-based products. However, a much stronger argument is the high variability of the properties that can be achieved, which allows design an extremely wide range of products.