Dana Křemenáková

Enhancing side illumination of plastic optical fiber by using TiO2 particles and CO2 laser

Plastic optical fiber (POF) is highly appreciated for its applications in glowing textiles. However, fabricating thin POF with good side illuminating effect is a challenge due to the complicated manufacturing processes. CO2 laser treatment is normally applied to enhance the surface roughness without significant influence on other properties of materials. Titanium dioxide (TiO2) is widely studied for its high photo activity and thermal stability. The surface modification combined with TiO2 particles and CO2 laser treatment was carried out to investigate the side illuminating effect of POF. The images of surface morphology show that TiO2 particles reduce the thermal damage of POF surface during CO2 laser treatment. The results from side illumination testing prove that the employment of TiO2 particles, combined with CO2 laser treatment, could enhance the side illumination of POF for longer lasting application. Cyclic CO2 laser treatment can decrease the heat accumulation in POF and may have adverse effect on...

Evaluation of Illumination Intensity of Plastic Optical Fibres with Tio2 Particles by Laser Treatment

Abstract CO2 laser treatment can increase the surface roughness of plastic optical fibres (POFs) with the diameter of 0.5 mm and enhance the input intensity and attenuation coefficient accordingly, which is supposed to weaken the side emission of POFs in long distance above 375 mm. TiO2 particles were applied to improve the increasing optical loss of POFs by laser treatment. POFs were first modified with fine TiO2 particles and then treated by CO2 laser with the pixel time from 30 to 120 ìs. The surface morphology was observed by scanning electron microscopy to investigate the changes of micro-structure before and after laser treatment and the distribution of TiO2 particles. The illumination intensity and attenuation coefficient were calculated and compared in two methods. It is visible that the evaluation by model LLF2 with two parts is more suitable for the fitting of experimental data and shows higher input intensity and lower attenuation than that by standard power function. Both the evaluation methods exhibit that the utilization of TiO2 particles could play an active role in the enhancement of side emission of POFs treated by CO2 laser.

Characterization of side emitting plastic optical fibers light intensity loss

The main role of polymer optical fibers is to transmit light or optical signal to a specified spot. In the case of side emitting plastic optical fibers the light leaks out from their surface. This sidelight can be used for creation of optically active textile structures providing opportunities to highlight people and objects without the need for external exposure. Due to the transmission loss, the intensity of radiation emitted in any direction decays exponentially along the fiber axis with increasing distance from the light source. The main aim of this contribution is evaluation of side emitting plastic optical fibers light intensity in dependence on the distance from light source. The special device for measurement of surface and cross section light intensity in various distances from light source was developed. The dependence of surface and cross section light intensity on the distance from light source will be expressed by the exponential type model with attenuation factor as the rate parameter. The i...

Improvement and evenness of the side illuminating effect of side emitting optical fibers by fluorescent polyester fabric

A strong and even side illuminating effect is required for plastic optical fibers (POFs) in illuminating applications. In consideration of good flexibility and illumination, side emitting POFs with 2 and 3 mm core diameters are preferred, especially in active illuminating safety textiles. However, the side illumination intensity of side emitting POF varies significantly along the fiber length. Fluorescent polyester (PET) fabric rather than traditional surface modifications is employed to enhance and even the side illuminating effect of POFs based on the emitting principle of phosphors. Two testing methods of side illumination intensity are carried out on semi-automatic devices. The results indicate that 2 mm side emitting POFs might take the place of 3 mm side emitting POFs by using fluorescent PET fabric, with a similar side illuminating effect in applications under certain circumstances.

Micro-lensed polymeric optical fiber by CO2 laser cutting

Thin polymeric optical fiber (POF) with good illumination is appreciated when POF is utilized as the luminous element in fabric structure. The CO2 laser cutting is employed to create a micro-lens in POF end to optimize the light gathering or light distribution in textile fields. The image analysis implies that the end shape varies from a polynomial to a lens with increasing laser energy, and meanwhile, the POF axis shifts gradually away from the central axis, which could be optimized by fiber rotation. A ball lens of POF end could be obtained at 1 μs mark speed and 850 rpm rotation speed.Thin polymeric optical fiber (POF) with good illumination is appreciated when POF is utilized as the luminous element in fabric structure. The CO2 laser cutting is employed to create a micro-lens in POF end to optimize the light gathering or light distribution in textile fields. The image analysis implies that the end shape varies from a polynomial to a lens with increasing laser energy, and meanwhile, the POF axis shifts gradually away from the central axis, which could be optimized by fiber rotation. A ball lens of POF end could be obtained at 1 μs mark speed and 850 rpm rotation speed.

Thermal Insulation and Porosity—From Macro- to Nanoscale

Porosity of textiles is one of the main factors influencing their thermal conductivity and insulation. Porosity in textile fabrics is the combination of fiber porosity, yarn packing density, and voids due to fabric construction. It is shown that assemblies from very fine fibers tend to suppress radiation and convection heat transfers because of huge total surface area, which restricts the free flow of air passing through them. For effective thermal insulation especially at low temperatures, it should be selected sufficiently high thickness of textile layer as well. Porosity is therefore decisive parameter for the evaluation of thermal comfort expressed in special units “clo.” The main aim of this chapter is the prediction of the effect of porosity of fabrics and fibers on the thermal conductivity and insulation. The changes of thermal comfort due to the use of hollow fibers and multilayer corrugated nonwovens are described. The thermal properties of highly porous aerogel structures are discussed. Enhancement of insulation by their inclusion into textiles is investigated as well.

Properties Of Viscose Vortex Yarns Depending On Technological Parameters Of Spinning

Abstract This paper analyzes the relationship between technological parameters of spinning of 100% CV Vortex yarns of different counts and its selected geometrical parameters (a lead of helix of wrapping fibre ribbon, yarn diameter) as well as yarn properties. The number of twist of wrapping fibre layer is determined. The effect of the yarn delivery speed, hollow spindle diameter, and the main draft on the hairiness, mass irregularity, tenacity, elongation, resistance to abrasion and bending rigidity of Vortex yarn is observed. The yarn properties are compared with the properties of open-end rotor spun yarns. Slivers of the same spinning lot were used for the production of both kinds of yarn. The results showed that the delivery speed in combination with spindle diameter affects yarn diameter, hairiness and abrasion resistance. Mass irregularity and imperfections of yarn is mainly affected by the main draft of drafting unit. Technological parameters of spinning do not affect the level of bending rigidity of the Vortex yarn. Tested rotor spun yarns had a larger diameter, higher hairiness, lower tenacity and higher elongation, lower mass irregularity and number of imperfections, higher abrasion resistance and lower bending rigidity compared to tested Vortex spun yarns.

Flex Fatigue Behavior Of Plastic Optical Fibers With Low Bending Cycles

Abstract Flex fatigue behaviour of plastic optical fibres (POFs) with the diameters of 0.2 and 0.3 mm under different pretensions is measured with fatigue life curve by flexometer. The fatigue sensitivity coefficient is calculated by the linear fitting curve of normalised stress versus logarithm of bending cycles. The residual modulus is investigated during the flex fatigue processes. The results exhibit the exponential relationship between applied pretension and numbers of bending cycles at break. It is indicated that the flex fatigue of POFs might be sensitive with high swing angle or swing speed. There is an evident loss of modulus for two POFs with pretensions of 4 and 10% of ultimate tensile strength during 10-times bending cycles. The values of residual modulus of two POFs almost keep constant after 10-times bending cycles.

Complex criterion for computer aided textileles design

The purpose of the paper is to describe the construction of utility value U based criterion suitable for expressing pseudodistance in the area of computer aided textile design. The possibility to use of this approach for evaluation of generalized distance between properties of target fabrics and properties of fabrics created by computer aided textile design will be discussed. The application of U and corresponding pseudodistance is demonstrated on the example of characterization of the effect of catalysts on the quality of crease resistant finished fabrics under laboratory conditions. The target fabric was selected according to the requirements to minimize the influence of finishing on the loss of mechanical properties and surfaeabrasion on one hand and improve the recovery angles on the other hand. The program complex written in MATLAB is briefly mentioned.

Illumination intensity changes of side emitting optical fibers

The main aim of this work is evaluation of side emitting plastic optical fibers (POF) illumination intensity changes in dependence on the distance from light source. Illumination intensity is measured along straight and bent fibers. The special devices for these measurements realization are described. The dependence of light intensity on the distance from light source for straight optical fibers is expressed by the exponential type model with two parameters, i.e. illumination intensity at the input into fiber and fiber attenuation factor. Preliminary results of measurement of light intensity in bent state are discussed. Influence of ratio between fiber diameter and bending cylinder diameter on the illumination intensity changes is presented.