Overview on natural dyes and their IR-spectra – Part I: Plant based dyes with naphthoquinone and anthraquinone structure

This is the first paper of a series of review articles reporting on natural dyes, their origin and infrared spectra (IR spectra). One aim of this review series is to compare IR spectra of natural dyes from different origin and discuss if this spectroscopic method can be used as versatile tool for the identification of natural dyes and their origin. This part I of the review series is related to four natural dyes based on the chemical structures of naphthoquinone and anthraquinone. Especially discussed are Lawson, juglone and alizarin, which are related to the natural products henna, walnut hull and madder root. Also, the natural dye based on alkanna root is investigated. Compared are the IR spectra of these natural dyes gained from different suppliers with the IR spectra of the pure chemical substances related to the natural dyes. A discussion with spectra from literature is supported. The aim of this review paper is to support infrared spectroscopic data of natural materials (natural dyes) to enable further material identification and also quality control supporting people working in the fields of fiber analytics or with production processes using natural dye

Textile study courses – evaluation of student performance over one complete decade

The success of students and their performance are influenced by manifold parameters. The current study focusses especially on the correlation between study duration and the student performance. Investigated are the numbers of two textile related courses (bachelor and master) over the complete time frame of one decade. Data of more than 800 students are considered. Data evaluation is done with the final marks of the students and by using a calculated value – the student performance index PI. Especially discussed is the behavior of long-time students needing more than the double of the regular study duration. In this study only results of students are discussed which successfully finished the study course with a degree. Students leaving without a degree are not considered. For the bachelor course a correlation of their final grades with larger study duration can be determined. In contrast, for the master course nearly no influence of the study duration on the student performance is determined. A possible explanation for these different results can be discussed with the different reasons for longer study duration. For master course it is obviously the situation that the studying is combined with part-time or even full-time jobs. This combination of job and study course leads even for excellent students to prolonged study duration. With this background, for future developments a special designed part time master study course should be developed and offered for students who like the combination of a job carrier with gaining simultaneously a master degree

Conversion of a conventional to a digital lecture under the conditions of Covid19 – an example from a bachelor lecture on finishing, dyeing & printing

Due to the Covid-19 pandemic situation during the years 2020 and 2021, the necessity occurred to convert conventional university lectures into digital ones, to avoid personal contacts between people and by this minimizing the spreading of the disease. Beside lectures, also exams have to be transferred to minimize personal contacts. This paper reports on a lecture in a bachelor course with more than 100 students and its conversion to digital format. The lecture is related to textile finishing processes – especially to dyeing and printing. The experience get during the digital lecture are compared with the results gained during the last decade with the same lecture in conventional style. Main tools of the digital format are video conferences and digital worksheets. Challenging are the contact to students by e-mail and the time management of the students especially during the final digital homework. In conclusion, digital lecture and exam are valuable tools to increase the number of participating students and their success in the exam. These tools could be also used successfully in post-corona times especially for lectures given for experienced students in higher semester

Comparison of conventional and digital lectures and examinations with respect to the conditions after COVID-19 period – an example for a bachelor lecture on textile finishing

Due to the appearance of COVID-19, many lectures and examinations at universities are forced to digital formats. In the first post-pandemic semester again, the change from digital to conventional lectures was demanded. By this background the question arises, what is the better format for lecture and exam – digital or conventional? This question is discussed on the example of a bachelor lecture on textile finishing for the time period from 2019 to 2023. The combination of digital lecture and digital exam leads to strong participation numbers and by this to more successfully passing students. If the exam is done as conventional written text, the influence if the lecture is digital or conventional is weak. Also, the numbers of passing students or the finally achieved mark are mainly not dependent on the type of lecture format. Finally, it can be state that a digital lecture is more successful if there are also digital parts in the examination. Also, the return to conventional lectures and exams after the pandemic period is possible without influencing the student performance compared to pre-pandemic situation

High-Performance Fibres – A Review of Properties and IR-Spectra

High-performance fibres are fibre materials that exhibit at least one extraordinary property compared to conventional fibre materials. That extraordinary property is frequently related to excellent fibre stability against certain influences such as fire, heat, chemicals or light. Also, a high mechanical strength is often a property of high-performance fibres. Nevertheless, it should be noted that high-performance fibres exhibit certain weaknesses in addition to their advantages. This review presents a broad overview of the most important high-performance fibres, with a special emphasis on their chemical structure and related infrared spectra (IR-spectra). The categorization of the fibres according to chemical substance classes was performed to make it easy for the reader to find a fibre of interest. The main categories are polyethylene (PE) fibres, polyacrylonitrile (PAN) fibres, polyvinylalcohol (PVAL) fibres, polyester-based fibres, polyamide-based fibres, polyetheretherketone (PEEK) fibres, polyimide (PI) fibres, halogen-containing fibres, polyphenylene sulfide (PPS fibres), resin-based fibres and finally inorganic fibres. Competing materials are also discussed, and structural related materials can be easily identified. In addition to discussing fibre properties and selected applications, one of the main aims is to present a various number of IR-spectra as a tool for structural understanding and to help identify unknown fibres. Here, beside the IR-spectra of high-performance fibres, the reference IR-spectra of common fibres are presented for comparison

Treatment of Kynol fiber materials – Part 1: dyeing processes

Kynol fibers are excellent flame-retardant materials used for manifold applications. These fibers exhibit originally an orange coloration. Up to now, dyeing processes for Kynol fibers are less reported, and the functionalization of these fibers by finishing processes is less investigated. With this background, the main aim of this paper is the evaluation of different dyeing processes for Kynol fiber materials – a woven fabric and a non-woven material. The following types of dyestuff are evaluated – direct dyes, vat dyes, disperse dyes and color pigments. The reached color quality is determined by CIE L*a*b* indices. Dry and wet rubbing fastness is measured. Finally, best results are gained by application of disperse dyes. The gained results could be used in future also to develop other functional treatments of Kynol fibers in different fields for, e.g., light protection, UV-stability, water repellency or antistatic properties

Treatment of Kynol fiber materials – Part 2: antistatic and water-repellent functionalization

Kynol fibers are flame retardant high performance fibers. Without further treatment they do not exhibit significant antistatic or water-repellent properties. With this background, several conventional antistatic agents and one hydrophobic finishing agent are evaluated to introduce these properties to Kynol fiber materials. Also, the combination of both properties is investigated to realize bifunctional fiber materials. By application of antistatic finishing agents, the electric surface resistance of Kynol fiber materials can be decreased to values smaller 108 W, which is a good value related to antistatic properties. By application of the hydrophobic agent, water repellent properties can be introduced to Kynol fiber materials. However, simultaneously the antistatic properties are decreased. The combination of both types of agents in a kind of bifunctional finishing can lead to intermediate antistatic effects combined with an intermediate water repellency. Nevertheless, in bifunctional application no single excellent property is gained. The flame retardant properties are tested on selected samples after the finishing processes. No change in flame retardant properties is determined, if the finishing agents are applied. For this, the presented results can be the starting point for development of functionalized flame retardant Kynol fiber products

Sol-gel coatings with the fluorescence dye Rhodamine B for optical modification of cotton

The sol-gel method is a versatile tool for the modification and functionalization of textiles. This method can be also used to support the application of dyes on textile materials. This paper is related to the application of the fluorescence dye Rhodamine B together with an industrial sol-gel component. Beside fluorescence spectroscopy, also scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) are used for the investigation of the produced textile samples. The realized fluorescence effects are strongly related to the applied dye concentration and can be drastically enhanced by presence of the applied sol-gel system. By use of sol-gel method also the dry and the wet rubbing fastness can be improved. These results could be the starting point for future development of new fluorescent textile materials

Exemplarily view on selected fluorescence textile products

Fluorescent materials emit light of higher wavelength, in case of illumination with light exhibiting lower wavelength. In many commercial applications, fluorescent materials transfer non-visible ultraviolet (UV) light into visible light. By this an additional color effect and higher visibility is reached. One typical field for application of fluorescence dyes is the textile area. Here, fluorescent textile products are manifold used and offered, e.g. for brightening effects, light effects and UV protection. With this background, the aim of the current study is the investigation of typical commercially available textile products with fluorescent properties. For this, four different polyester fiber-based materials of different coloration and purpose are selected for investigation. Investigations are performed by illumination under different illumination arrangements with UV light and visible light. CIE-Lab measurements are done. Further, scanning electronic microscopy (SEM) and Fourier Transform infrared (FT-IR) spectroscopy are used. Light emission and excitation of the samples is recorded by fluorescence spectroscopy. 2D fluorescence spectroscopy is performed. The chemical composition of the investigated textile samples is determined by using electron dispersive spectroscopy (EDS). For all investigated commercial textile products, the light emission during illumination with UV light is extraordinary strong. The color appearance can be enhanced strongly by this fluorescence effect. Beside the absorption of UV light by the present fluorescence dyes, also the presence of titanium dioxide supports an UV protective property of the textile samples. Finally, it can be concluded that fluorescent fiber materials are well established products for advanced and functional textiles. These materials can be even found in cost effective and everyday consumer products

HT process for treatment of PET fabrics with chitosan containing recipes

Polyester is the leading man-made fiber in the field of textiles and clothing. Polyester is usually dyed and finished using a process temperature in the range of 120 to 135 ºC. Such a process is known as a high-temperature (HT) process. The application of chitosan on cellulosic materials is an interesting approach to textile functionalization. In contrast, the application of chitosan by the HT process for the functional treatment of polyester is less investigated. With this background, the present study is related to the surface characteristics of different polyester fabrics with implemented chitosan after performing the HT process