Experimental and numerical studies of thermoregulating textiles incorporated with phase change materials

Phase change materials (PCMs) provide thermal management solution to textiles for the protection of wearer from extreme weather conditions. PCMs are the substances which can store or release a large amount of energy in the form of latent heat at certain melting temperature. This research reports practical and theoretical studies of textiles containing PCMs. Mono and multifilament filaments incorporated with microencapsulated phase change material (MPCM) have been developed through melt spinning process. Scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) have been performed for the characterisation of MPCM polypropylene filaments. The parameters for optimum fibre processing and their effect on mechanical properties of filaments with respect to the amount of MPCM have also been studied. A plain woven fabric has been constructed using the developed MPCM multifilament yarn. The heat transfer property of the multifilament yarn and fabric has been investigated using finite element method. The time dependent thermoregulating effect of yarn and fabric incorporated with MPCM has also been predicted according to the validated models. The synthesis of Nanocapsules containing mixture of paraffins and Glauber’s salt as PCM and its characterisation using DSC and SEM has also been carried out. Polypropylene monofilament incorporated with the nanoencapsulated paraffins was developed and its properties have been compared to its MPCM counterpart. Furthermore the developed nanocapsules were applied on a cotton fabric via a pad-dry-cure process and the resultant fabric was evaluated using DSC and SEM in comparison with MPCM treated fabric. The research work described in this thesis has established a better understanding of use of phase change materials in textiles, the evaluation and application. It is anticipated that this research will broaden the understanding and potential use of encapsulated phase change materials in textiles especially in the field of active smart textiles

Decontamination of Wearable Textile Electrodes for Medical and Health Care Applications

In the medical and health care environment ‘intelligent’ clothing must endure all the same treatments and procedures as standard hospital textile; that is laundry, disinfection and sterilization. The decontamination level depends on the end-use of the product. The smart garment system for long term body monitoring must be like any other technical underwear; fit well, be comfortable, elastic, vapor permeable, and have easy-care properties capable of enduring multiple cycles of laundry washing. Thus the use of man-made fibers, instead of traditionally used natural fibers, in a body monitoring garment would be more reasonable.The research focuses on disinfected and sterilized textile electrodes which are applicable for long term body monitoring. As high elasticity, comfort and good vapor permeability are needed, the research concentrates on the electrical and mechanical properties of knitted sensors after sterilization, disinfection and water-repellent treatment. The most important mechanical features of elastic textile electrodes are elongation recovery and dimensional stability. Before sterilization the textile must be cleaned properly from body fluids like blood and sweat. Improving the easy-clean properties would consequently be desirable. By improving the stain repellent or easy cleaning properties, the need for washing can be decreased and a more protective, lower temperature program during laundry washing can be used. These factors not only save energy but also lengthen the lifetime of textile electronics.The textile surface electric resistance, abrasion resistance, dimensional change and elastic properties following decontamination processes were studied, including the evaluation of water repellent-treated electrode properties. In addition, the mechanical properties of conventional knits and elastic woven bands were observed after treatment in order to assess their use in smart wearable systems.In addition to electrodes, the research results can be applied to many other textile electronics components such as conductors, antennae, heat elements, switchers and detectors, because all these components can be achieved with same elements; conventional textile fibers combined with conductive fibers or coatings. The obvious application areas for body monitoring by using textile electrodes are hospitals, health care centers and medical research centers. The textile electrodes are more comfortable and invisible for long time body monitoring which is needed, for example, in rehabilitation after surgery or detection of chronic diseases, where they are more effective than conventional gel (Ag / AgCl) electrodes.In conclusion it can be stated that silver-plated PA fiber in a knitted or woven structure with added repellent treatment provides a highly conductive and durable solution for wearable electronics in medical and health care applications. The steel fiber and textile mixture cannot tolerate mechanical stress caused by disinfection, washing, or repellent treatment. The knitted textile with silver coating cannot tolerate sterilization, either electrically or mechanically. Based on the results of the study, the use of woven bands as an electrode would be recommended instead of knitted material because they are dimensionally more stable. The electrode dimensional changes might negatively affect the measurement quality. On the other hand, the knitted electrodes have additional useful properties like softness and flexibility, thus compromises must be made in using textile electrodes in wearable technology. All materials in the study, woven and knitted, elastic and inelastic, coated and non –coated showed clear shrinkage in the sterilization process. However, using only one heat treatment makes them much more stable. For this reason it can be assumed that man-made fibers are more useful for medical products as they are more resistant to being sterilized or disinfected than are natural fibers. The elastane fiber can be used for improving bi-directional textile material recovery, but the unrecovered elongation as a function of sterilization must be considered. The variation in unrecovered elongation (stretching) might be extremely high and success depends on raw materials and textile structures

Surfactant migration on polymeric substrates

Many industrial nonwoven polymeric fabrics are coated with surfactants to provide improved wettability which is an essential attribute for disposable hygiene products, like facemasks, wipes, absorbent materials and baby nappies. These surfactant coatings on polyolefinic nonwovens appear to be typically not permanent and this fugitive nature of the surfactants is a concern for the industry. However, the interaction between organic species and complex semi-amorphous polymers as used in nonwoven products is an industrially important but poorly understood research area. Experimental studies reported here have established the mechanisms by which surfactants interact with polyolefinic surfaces, provide visualisation of 3D surfactant distributions on these nonwovens as well as their wettability, and report on the processes responsible for surfactant migration/loss from polyolefins. A novel confocal microscopy method is reported here for the non-invasive imaging of the 3D distributions of surfactants on polymeric nonwovens. Optical contrast was achieved by introducing a fluorescent dye via vaporisation at elevated temperatures, which preferentially dissolves into the hydrophilic surfactant regions of the nonwoven sample. The method is quantitative and allows the patch wise heterogenic distribution of surfactant coatings on complex 3D nonwoven materials to be visualised. To understand the interaction between surfactants and nonwoven polyolefins, several chemical properties and physicochemical descriptors of nonwoven materials were determined including wettability, specific surface area, surface energy, solvent sorption kinetics, and their surface elemental composition. Specific surface area BET measurements demonstrated that industrial nonwovens are characterised by generally low specific surface area values, in the range 0.1 - 4 m2/g and that inverse gas chromatography (IGC) offered best sensitivity and precision. The wettability of polyolefin surfaces is well described by the dispersive contribution of surface free energy γsD. Alkane probes are normally used for measuring γsD but dissolve in polyolefins invalidating the method. A new method using a series of normal alcohols was developed as part of this work, yielding γsD values in the range 20 - 40 mJ/m2. XPS analysis confirmed the hydrocarbon nature of polyolefinic nonwoven materials and the polar elements present responsible for the hydrophilic nature when the nonwovens were coated with surfactants, confirming surfactant treatment was not permanent. The solubility interactions between organic solutes and a range of amorphous and semicrystalline PP and PE were investigated by DSC, pycnometry, dynamic vapour sorption (DVS) and ellipsometry. The work confirmed that the presence of crystalline regions decreased the sorption of organic solutes in polyolefins. DVS studies of the sorption and desorption kinetics for small organic molecules in polyolefin films demonstrated that temperature increased diffusion rates and the amounts of solutes sorbed. However, increasing molecular size, or polarity, of the solute decreased the solubility. DVS combined with ellipsometry was used to determine the processes responsible for surfactant loss in thin polyolefin films. The amount of water sorbed by a polyolefin material was used here for the first time as a proxy for the amount of surfactant present on the polyolefin surface. DVS studies confirmed very slow mass losses due to surfactant evaporation from the surfactant coated polymers. However, the total rate of surfactant mass loss from the polymer surface was 10 times higher than the evaporative losses. The significant solubility of the non-polar surfactants and organic solutes in different polymer analogues was experimentally estimated. Based on these studies the hypothesis was that there are two processes causing surfactant loss from the polyolefin surface: • slow surface evaporation of the surfactants into the surrounding environment • a faster concurrent dissolution of the surfactant into the bulk polyolefin In summary, this thesis, provides new experimental insights into the interaction between liquid solutes, including surfactants, with semi-amorphous polyolefin materials including nonwoven fabrics.Open Acces

Resources Protection: Towards Replacement of Cotton Fiber with Polyester

L'abstract è presente nell'allegato / the abstract is in the attachmen

Polymer Blends and Compatibilization

The market is continuously looking for substitutes for expensive polymers or tailor made polymers for specific applications. Therefore, polymer blends are gaining more interest since they possess a great potential to fulfill these needs. Blending not only results in better final properties, but can also improve the processing behavior and reduce costs. In the field of polymer blends, there are numerous parameters that influence the morphology, e.g., viscosity ratio, blend composition, shear conditions, and blend ratio. There is still a great deal of potential to scientifically exploit the possibilities of blend technology, which is necessary to obtain a foundation based on science, engineering, technology, and applications in order to make it possible to tailor polymer blends as desired. However, combining two or more different polymers to receive favorable properties by blending often results in immiscible polymer blends. This immiscibility goes hand-in-hand with phase separation leading to weak mechanical properties. The high interfacial tension causing this can be reduced by compatibilization of polymer blends. There are different methods to achieve this, such as adding block and graft copolymers, reactive polymers to form block and graft copolymers, nanoparticles or organic molecules. Using suitable compatibilizers, not only is the interfacial adhesion between matrix and its blends reduced, but also the dispersion of the dispersed phase is improved, the adhesion between the phases is enhanced and the morphology is stabilized. This can lead to improved mechanical and morphological properties. Designing new polymer blends or improving the properties of immiscible polymer blends by compatibilization is very challenging, but an excellent way to exploit the full potential of polymers for applications and their varied needs. This Special Issue is a source of information on all recent aspects of polymer blend technology

Advances and Applications of Nano-antimicrobial Treatments

Nowadays, great concerns are associated with the resistance demonstrated by many microorganisms towards the conventional antibiotic therapies. The failure of traditional antimicrobials, and the increasing healthcare costs, have encouraged scientific research and the development of novel antimicrobial agents. Particularly, there is a great deal of interest in nanotechnologies and in antibacterial products obtained through the incorporation of antibacterial agents or the deposition of antibacterial coatings for prevention of biofilm-associated infections. The main focus of the forthcoming Special Issue is, therefore, to present the most recent efforts in scientific research in the development of advanced antimicrobial materials, with special attention to nature-inspired antimicrobial agents and antimicrobials nanomaterials and nanocoatings. For this purpose, we intend to collect original research articles and reviews on the synthesis and characterization of antimicrobial agents, as well as on the development of antimicrobial products for different applications

WATER REPELLENT BREATHABLE PET/WOOL FABRIC VIA PLASMA POLYMERISATION TECHNOLOGY

Water-repellent textiles are usually prepared by application of hydrophobic polymers such as fluorocarbons on fabrics using padding or spraying methods followed by drying and curing steps. These procedures impart hydrophobicity to the fabric, but harm the physical and handle properties of the fabric. In this study, low-pressure plasma was employed for the polymerization of 1H,1H,2H,2H-Perfluorooctyl acrylate on PET/Wool fabric for obtaining water-repellent properties with minimum effect on other desirable properties. To compare the results with the conventional industrial processes, a sample was treated with a commercial water-repellent agent using pad-dry-cure method. The water contact angle, bending length, tensile strength, air permeability, and surface morphology of the samples were compared. The plasma-treated sample showed similar water contact angle and higher fastness properties compared with the sample prepared by the conventional method. The tensile strength of the samples was similar, while the air permeability of the plasmatreated sample was higher and the coating was more uniform compared with the sample prepared by the paddry- cure method.</jats:p