Protección ultravioleta proporcionada por los textiles:estudio de la influencia de las variables más significativas y aplicación de productos específicos para su mejora

La componente ultravioleta de la radiación solar, beneficiosa a pequeñas dosis, puede ser muy nociva por su efecto acumulativo sobre la piel. Los dermatólogos aconsejan protegerse de cantidades excesivas de radiación UV. Generalmente se piensa en la protección de la piel no cubierta, pero hay que tener en cuenta también la protección proporcionada por los tejidos, en particular en prendas ligeras.El objetivo de esta tesis doctoral es el estudio de la protección ultravioleta proporcionada por los tejidos. Mediante diversas técnicas, fundamentalmente la determinación de la transmitancia espectral difusa de radiación ultravioleta, se estudia la influencia de las variables más significativas de las que depende el factor de protección ultravioleta (UPF) de los tejidos.En la primera parte de la tesis, se trata la influencia de la estructura del tejido sobre el UPF. Mediante técnicas estadísticas de planificación de experiencias, se han diseñado tres series de tejidos de Algodón, Modal y Modal Sun, formadas por 27 muestras con una gradación en su estructura. La compacidad del tejido tiene una importante influencia sobre el bloqueo de la radiación UV y el análisis estadístico de los resultados permite su cuantificación. Se obtienen modelos estadísticos que relacionan el UPF de los tejidos con algunos de los principales parámetros de fabricación (título del hilo de urdimbre, título del hilo de trama y densidad de pasadas). Asimismo, se modeliza la influencia sobre el UPF de otros parámetros estructurales de amplio uso en la industria textil (peso por unidad de superficie, cobertura y espesor). Debido a que los resultados muestran que el UPF puede variar muy significativamente en función del tipo de fibra, mediante la técnica FT-IR se analiza la causa del diferente comportamiento de las tres fibras. También se ha estudiado la influencia de las condiciones de uso de las prendas. El UPF puede variar cuando los tejidos se llevan en estado mojado o cuando son sometidos a las tensiones habituales en su contacto con el cuerpo. Se ha obtenido un modelo estadístico para cada fibra que cuantifica la variación del UPF en función de la tensión y humedad, así como del UPF inicial del tejido en estado relajado y seco (representante de la estructura inicial).A partir de tejidos seleccionados en la primera parte, se ha estudiado la aplicación de algunos productos textiles que pueden mejorar el nivel de protección.Se ha estudiado la influencia de la coloración sobre el UPF. Aunque cuando se habla de color se piensa en la región del visible, el espectro de absorción de colorantes también se extiende a las longitudes de onda del UV, por lo que pueden mejorar el UPF. Para cuantificar la influencia de este parámetro, se han aplicado tres colorantes, de una tricromía de colorantes directos, a diferentes concentraciones sobre varios tejidos de Algodón, Modal y Modal Sun, obteniéndose muestras con una gradación de color correspondiente a diferentes intensidades estándar. Se analiza también la influencia de la aplicación, a varias concentraciones, de dos blanqueadores ópticos de diferente estructura química. Estos productos pueden disminuir la transmisión en el UV debido a su capacidad de absorber este tipo de radiación. Del mismo modo se estudia la mejora del UPF mediante el tratamiento con un producto de acabado absorbente de radiación UV, en función de su concentración. Como complemento a este estudio, las imágenes SEM permiten dilucidar si el tratamiento produce modificaciones en la superficie de la fibra. También se analiza la permanencia del efecto de acabado y el impacto ecotoxicológico del tratamiento con el producto.En todos los casos, se han obtenido modelos estadísticos que relacionan el valor de la respuesta UPF con las variables de control en cada una de las partes: el tipo de colorante/blanqueador óptico, la intensidad de la tintura/concentración de producto y el UPF inicial del tejido. Los modelos permiten diseñar tejidos con UPF preestablecido.The ultraviolet component of the solar radiation, beneficial in small doses, can be very harmful due to its accumulative effect on the skin. Dermatologists recommend the protection of the skin against excessive amounts of UV radiation. Generally, people think in the protection of the uncovered skin, but the protection provided by fabrics should be also taken into account, particularly in light garments.The objective of this doctoral thesis is the study of the ultraviolet protection provided by textiles. By the use of several techniques, fundamentally the determination of the diffuse spectral transmittance of the ultraviolet radiation, the influence of the more significant variables on the ultraviolet protection factor of the fabrics (UPF) is studied. The first part of the thesis deals with the influence of the fabric structure on the UPF. By means of statistical techniques for experiments planning, three sets of fabrics made with Cotton, Modal and Modal Sun are designed. Each set is composed by 27 samples of fabrics with a gradation in their structure. The compaction of the fabric has shown to have an important influence on the blocking of the ultraviolet radiation and the statistical analysis makes possible its quantification. Three statistical models, one for each fibre type, that describe the UPF of the fabrics as a function of some of the main manufacturing parameters (warp yarn number, weft yarn number and weft thread count) have been obtained. Likewise, the influence of other structural parameters widely used in the textile industry (weight per surface unit, percent cover and thickness) on the UPF is modelled. Due to the fact that the results show that the UPF can vary very significantly because of the type of fibre, the cause of the different behaviour of the three studied fibres is analysed by the FT-IR technique. The influence of the wearing conditions of the garments has been studied as well. The UPF can vary when the fabrics are worn in wet state or when they underwent the usual tensions in their contact with the body. A statistical model for each fibre has been obtained, which quantifies the variation of the UPF due to the tension, wetness and the initial UPF of the fabric in relaxed and dry state (which represents the initial structure of the fabric). Taking some fabrics selected in the first part of the thesis, the application of some textile chemicals that can improve the protection level has been investigated. The influence of the coloration on the UPF of the fabrics has been studied. Although when speaking about colour one thinks in the visible range of wavelengths, the absorption spectra of the dyestuffs extends in some part to the UV wavelengths, so they are likely to improve the UPF. To quantify the influence of the colour on the UPF, three dyes of a trichromie of direct dyes have been applied under different concentrations to fabrics made with Cotton, Modal and Modal Sun, therefore obtaining samples with a gradation in colour corresponding to different standard intensities.The influence of the application under several concentrations of two whitening agents of different chemical structure has been as well analysed. These chemicals are likely to decrease the transmittance in the UV region due to their capability to absorb this range of radiation.Likewise, the improvement on the UPF by means of the finishing treatment with an UV absorber under different concentrations has been studied. As a complement to this study, SEM images have been obtained to determine if the treatment produces a modification of the fibre surface. The permanence of the finishing effect and the ecotoxicological impact of the treatment with the UV absorber have been as well analysed.In all the cases, statistics has been use to model the relationship between the response UPF and the control variables in each one of the different parts of the study: the type of dyestuff / whitening agent, the dyeing intensity / concentration of the chemical and the initial UPF of the fabric. The models allow to design fabrics with a pre-established UPF.Postprint (published version

Effect of different dispersing agents in the non-isothermal kinetics and thermomechanical behavior of PET/TiO2 composites

This work is based on the analysis of the influence of dispersing agents on the non-isothermal kinetics, thermomechanical behavior and dispersing action of PET/TiO2 nanocomposites. The influence of two montanic waxes and an amide wax used as dispersing agents in the nucleating effect of the nanoparticles is studied. The dispersing agents are the following: a) a partly saponified ester of montanic acids (PSEMA), b) an ester of montanic acids with multifunctional alcohols (MAWMA) and c) an amide wax based on N,N '-Bisstearoyl ethylenediamine (AW). The non-isothermal kinetics based on the Avrami method revealed that MAWMA and PSEMA favors the nucleating effect of the nanoparticles when are included in PET. Birefringence microscopy points out the good dispersing capacity of MAWMA and AW and the termomechanical analysis confirmed that the ester of montanic acids with multifunctional alcohols MAWMA shows the best dispersing properties and best promotes the nucleating effect of the TiO2 nanoparticles when used for PET/TiO2 nanocomposites productionPostprint (author's final draft

Effect of the presence of an ester of montanic acids with multifunctional alcohols in the composites of titanium dioxide nanoparticles with poly(ethylene terephthalate) in their non-isothermal crystallization

The effect of the addition of an ester of montanic acid with multifunctional alcohols in the effectiveness of the dispersion and compatibility of TiO2 nanoparticles when included as filler in poly(ethyleneterephthalate) for composite production is studied through the study of the non-isothermal crystallization by differential scanning calorimetry (DSC). The application of the Avrami method enables to evaluate the compatibility and the level of dispersion/aggregation of the nanofiller in the poly(ethylene terephthalate) by the analysis of the temperature and enthalpy of crystallization, the kinetic parameters and the half-crystallization timePostprint (author's final draft

Microstructure variations of polylactide fibres with texturing conditions

The characterization of the microstructure of synthetic fibres is necessary to identify changes in properties produced by differences in the production variables. To this end, two physico-chemical tests (iodine sorption and differential solubility), which are easy and rapid to implement were employed to study the differences in the microstructure of polylactide false-twist textured multifilaments. The results enabled us to identify variations in microstructure induced by texturing conditions and were related to processing variables. These tests were compared with more expensive and complicated techniques to quantify crystallinity and orientation of filaments. Both tests enabled us to identify microstructure variations between substrate

Microstructure variations of polylactide fibres with texturing conditions

The characterization of the microstructure of synthetic fibres is necessary to identify changes in properties produced by differences in the production variables. To this end, two physico-chemical tests (iodine sorption and differential solubility), which are easy and rapid to implement were employed to study the differences in the microstructure of polylactide false-twist textured multifilaments. The results enabled us to identify variations in microstructure induced by texturing conditions and were related to processing variables. These tests were compared with more expensive and complicated techniques to quantify crystallinity and orientation of filaments. Both tests enabled us to identify microstructure variations between substrate

Time-dependent vortices and monopoles

Available from British Library Document Supply Centre- DSC:3630.84(DIAS-STP--86-42) / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo

Effect of surface treatment of titanium dioxide nanoparticles on non-isothermal crystallization behavior, viscoelastic transitions and cold crystallization of poly(ethylene terephthalate) nanocomposites

The effect of untreated and tri-n-octylphosphine oxide (TOPO) surface-treated TiO2 nanoparticles when included as filler in poly (ethylene terephthalate) on its compatibility, non-isothermal crystallization behavior, viscoelastic transitions and cold crystallization has been studied. The effectiveness of the surface treatment has been studied using infrared spectrophotometry (FTIR) and thermogravimetric analysis (TGA). The effect of the untreated and surface-treated nanofiller content in the polymer, added by an extrusion process, on the non-isothermal crystallization has been studied by differential scanning calorimetry (DSC). The influence on the viscoelastic transitions and cold crystallization of PET nanocomposites has been studied through thermomechanical analysis (TMA). The surface treatment and the concentration of nanofiller influence the non-isothermal crystallization behavior, the viscoelastic transitions and the cold crystallization of the PET nanocomposites, enables us to evaluate the compatibility and the level of dispersion/aggregation of the nanofiller in the poly(ethylene terephthalate)

Guía per a l'avaluació de les competències en els laboratoris de ciències i tecnologia (AQU)

Postprint (published version