Andreja Rudolf

The Influence of Thread Twist on Alterations in Fibers' Mechanical Properties

In order to design high-quality threads, it is necessary to know the properties of threads and fibers, as well as the loadings and deformations which may occur during the sewing process. Thread properties depend on the mechanical properties of the fiber and the constructional parameters of the thread and its surface treatment, which directly influence sewing performance. The mechanical properties of a thread primarily depend on the fiber mechanical properties and the amount of twist. Knowledge of the thread dynamic loadings during the sewing process, depending on the number of turns and the lubrication method, is important for planning the required processing properties of the thread. This paper presents research into the influence of thread twist and the lubrication method on the mechanical properties and dynamic load of PES core-spun thread and its fibers. Research into the mechanical properties of the different twisted and surface treated threads, and separated fibers was carried out for this purpose. The influence of thread dynamic load during a sewing process was also researched regarding any alterations in the mechanical properties of the threads and separated fibers. Analyses of the results show that the amount of twist depends on the mechanical properties of the thread and its constituent fibers, whilst the method of surface treatment is based on the specific mechanical properties of the thread. A dynamic load causes greater or smaller thread deformations, which is reflected in changes in the thread and fiber mechanical properties. The occurred changes depend on dynamic load, amount of twist, and the lubrication method, which is confirmed with statistical analysis of the measured results.

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.

Study of the relationship between deformation of the thread and built‐in fibres

Presents the study of the relationship between the deformation of the sewing thread and built‐in fibres as a consequence of a thread loading in the sewing process. The influence of the stitching speed and different twist numbers of PES thread on the alteration of the mechanical properties of the fibres twisted in the thread was studied for that purpose. On the basis of the received results it was found that with an increase in the number of the thread twist, the breaking tenacity and initial elasticity modulus of the fibres decrease, while the resulting deformation of the sewing thread between the sewing process was reflected as a decrease in the fineness and breaking extension of the fibres and as an increase in the value of the initial elasticity modulus of the fibres.

Study regarding the virtual prototyping of garments for paraplegics

The sitting position is very common in everyday life and therefore any garment should be comfortable in that positon. It is especially important for those who are disabled and are confined to a sitting position throughout life. These include paraplegics whose restricted movements are due to paralysis of the lower limbs and restrict them to a wheelchair. Garments for a sitting position should meet certain particular needs like the body dimensions and postures of each individual. Design considerations should provide ergonomic comfort in a sitting position and include functional requirements due to limitations of strength and mobility in such a way that they do not cause additional health problems to paraplegics, e.g. skin irritations, pressure sores, obstruction of the blood flow etc., but rather to improve the quality of life for paraplegics. Today, the development of garments is practically impossible to imagine without the assistance of 3D CAD systems for the virtual prototyping of garments, which usually provide only the 3D body models in a standing position. The aim of this study was to explore the possibilities for the virtual prototyping of garments in regard to the sitting position, using the OptiTex 3D commercial CAD system. For this purpose 3D scans of subjects in sitting position were performed using a general-purpose ATOS II 3D optical scanning system. In addition, processing techniques of the human body mesh modeling and surface reconstruction techniques were involved to obtain a sitting 3D body model. The garments’ basic pattern designs for a standing position were constructed according to the rules of the M. Müller&Sohn construction system. Their reconstruction into garments’ basic pattern designs for a sitting position were performed by using the virtual measured dimensions of the scanned 3D body model in a sitting position, and virtual prototyping of the garments. Comparisons between the dimensions of the real and the 3D body models were carried out, as well as a comparison between the real sewn and virtually developed garments. The research showed that a reliable sitting 3D body model was achieved by used scanning technology, modeling and reconstruction techniques, as well as the usefulness and effectiveness of the virtual prototyping of the garments for a sitting position. In this study fully mobile individuals were involved to avoid unnecessary burdening of paraplegics in this stage of the research. The experiences gained from this study will enable us to include paraplegics within the study during the scanning and anthropometric survey with the aim of designing a general parametric 3D body model. Its body dimensions and postures would be possible for adapting from able-bodied persons with the purpose of developing individual garments for paraplegics.

The effect of drawing on PET filament sewing thread performance properties

A drawn PET filament sewing thread for the automotive industry was used for this research. This study concerned itself with the draw ratio’s influence regarding certain physical properties of the threads, the tensile properties during sewing and the mechanical properties after sewing in order to estimate the drawn thread’s sewing performance. An increase in the draw ratio caused a decrease in the linear density, and thread twist. In addition, the tenacity, elastic modulus and tension at the yield point were increased when drawing, whilst the breaking extension decreased. It was found that tensile fatigue and heat loading during the sewing process cause changes in the threads’ mechanical properties, depending on the draw ratio. The tenacity, elastic modulus and tension at the yield point had decreased after the sewing process, whilst the breaking extension decreased for those threads drawn at lower draw ratios, and increased for those drawn at higher draw ratios. The results show that those threads drawn at higher draw ratios displayed inappropriate sewing performance, resulting from inadequate elastic and surface characteristics.

Medical textiles based on viscose rayon fabrics coated with chitosan-encapsulated iodine: antibacterial and antioxidant properties

Adsorption of chitosan nanoparticles with embedded iodine was implemented onto pristine and oxidized cellulose viscose fabrics in order to introduce antimicrobial and antioxidative functionalization. The adsorption capacity, charging behavior and electrokinetic response of differently functionalized viscose at different pH values were analyzed by determining their zeta potential. Desorption studies, besides zeta potential measurements, were supported by polyelectrolyte titration. Finally, the antimicrobial properties were evaluated by the standard ASTM E2149 method, whilst antioxidative properties were determined by 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) radical cation decolorization assay. It was found that the oxidation of viscose fabrics further modified by chitosan–iodine nanoparticles dispersion was a very promising functionalization process, providing good coating stability along with antimicrobial and antioxidant properties.

Textile Forms’ Computer Simulation Techniques

Computer simulation techniques of textile forms already represent an important tool for textile and garment designers, since they offer numerous advantages, such as quick and simple introduction of changes while developing a model in comparison with conventional techniques. Therefore, the modeling and simulation of textile forms will always be an important issue and challenge for the researchers, since close‐to‐reality models are essential for understanding the performance and behavior of textile materials. This chapter deals with computer simulation of different textile forms. In the introductory part, it reviews the development of complex modeling and simulation techniques related to different textile forms. The main part of the chapter focuses on study of the fabric and fused panel drape by using the finite element method and on development of some representative textile forms, above all, on functional and protective clothing for persons who are sitting during performing different activities. Computer simulation techniques and scanned 3D body models in a sitting posture are used for this purpose. Engineering approaches to textile forms’ design for particular purposes, presented in this chapter, show benefits and limitations of specific 3D body scanning and computer simulation techniques and outline the future research challenges.

Investigations Regarding the Effects of Simulating Parameters During 3D Garments' Drape Simulations

This paper presents research into simulating parameters effects on 3D garment drape simulations with the aim of examining influential parameters regarding the accuracies of the appearances of virtual garments. The effects on the modified appearances of 3D virtual garments due to the simulated parameters, i.e. the solver setting, soft bending and resolution were investigated. Drape simulations of fabrics and garments were analysed by using the OptiTex 3D commercial CAD system for different fabrics, of which low-stress mechanical properties were measured by using the FAST measuring system and drape parameters by a Cusic Drape Tester. A comparison between the orthogonal projections of the real and virtual fabric drapes based on the Cusic method was performed and between the appearances and dimensions of the real and 3D virtual garments. The simulation parameters observed influence drape simulations of the 3D virtual fabrics and 3D garments depending on the fabric properties and pattern piece sizes. The results reveal that there is still a fundamental problem regarding the introduction of real fabric physical and seam properties during garment drape simulation. Therefore further consistent studies are needed for resolving limitations in this area on the synergistic effects of simulation parameters on 3D garment drape simulation.