Jean-Yves Drean

Effect of needle length, electrospinning distance, and solution concentration on morphological properties of polyamide-6 electrospun nanowebs

Nowadays, thanks to the electrospinning process, polymeric fibers in nanoscale diameters (10–500 nm) are easily producible. During the last decade, the electrospinning technique has been greatly investigated and developed. One of the most important fields of study on the electrospinning process is the influence of effective parameters on electrospun nanofibers and nanoweb properties. In this study, using polyamide-6 (PA-6)/formic acid polymer solution, three important parameters of the electrospinning process, including polymer solution concentration, needle-tip-to-collector distance, and needle length, were precisely studied. The solution concentration is a very important parameter that affects the nanowebs’ homogeneity and nanofibers’ diameter evenness. Scanning electron microscopy (SEM) analysis of the electrospun nanowebs showed that among five polymer solution concentrations (5, 10, 15, 20, and 25 wt%), 25 wt% was more suitable and provided the homogeneity and reproducibility of PA-6 nanowebs. It has been found that the needle-tip-to-collector distance had a considerable influence on the nanofibers’ diameter and the nanoweb collection zone. Morphological investigation and statistical studies showed that the nanofibers’ diameter increased with the reduction of the needle-tip-to-collector distance. Moreover, the average diameter of the nanoweb collection zone decreased by the reduction of this distance. The effect of needle length on the nanofibers’ morphology and nanowebs’ collection zone was investigated. Statistical analysis of the obtained results revealed that the increase of needle length significantly increased the average nanofibers’ diameter. Inversely, the diameter of the nanoweb collection zone reduced when needle length increased. All previously mentioned studies helped to define the optimal electrospinning condition to produce the bead-free, non-branched, and homogeneous PA-6 electrospun nanofibers and nanowebs.

PREDICTING THE MECHANICAL PROPERTIES OF NONWOVEN GEOTEXTILES WITH THE FINITE ELEMENT METHOD

A new computer model is developed to predict the tensile behavior of nonwoven fabrics from the stress-strain behavior of their constituent fibers and distributions of fiber orientation angles. The finite element method is used to calculate the numerical solution of stress and strain distribution in different regions of the samples during tensile deformation. Stress-strain curves of fabrics are simulated. Tensile testing is done on several nonwoven fabrics to verify the simulated results, which are in a good agreement with those obtained from tensile experiments.

Optimization of automated online fabric inspection by fast Fourier transform (FFT) and cross-correlation:

Fabric inspection has an importance to prevent the risk of delivering inferior quality product. Until recently, the process was still undertaken offline and manually by humans, which has many drawbacks. The continuous development in computer technology introduces the automated fabric inspection as an effective alternative. In our work, Fast Fourier Transform and Cross-correlation techniques, i.e. linear operations, are first implemented to examine the structure regularity features of the fabric image in the spatial domain. To improve the efficiency of the technique and overcome the problem of detection errors, further thresholding operation is implemented using a level selection filter. Through this filter, the technique is able to detect only the actual or real defects and highlight its exact dimensions. A software package such as Matlab or Scilab is used for this procedure. It is implemented firstly on a simulated plain fabric to determine the most important parameters during the process of defect detection and then to optimize each of them even considering noise. To verify the success of the technique, it is implemented on real plain fabric samples with different colors containing various defects. Several results of the proposed technique for the simulated and real plain fabric structures with the most common defects are presented. Finally, a vision-based fabric inspection prototype that could be accomplished on-loom to inspect the fabric under construction with 100% coverage is proposed.

Mechanical Characterization and Behavior in Spinning Processing of Milkweed Fibers

As part of a study of milkweed fibers, various blends of cotton and milkweed were created and the physical fiber and yam properties analyzed. The study included a unique investigation of transverse properties of wall thickness and linear density. Spin ning trials of blends with very high percentages of milkweed fibers revealed new data on specific problems with milkweed because of its smoothness and brittleness. These particular problems also prevented the manufacture of a pure milkweed yarn.

Effect of Seed Coat Fragments on Cotton Yarn Strength: Dependence on Fiber Quality

Contaminants in cotton fibers cause yam regularity defects that alter their structure. The effect of these alterations on yarn strength is discussed with particular focus on seed coat fragments (SCF), one of the primary cotton contaminants from the fiber to the finished product. This paper presents the results of an experimental study showing that, in certain cases, the presence of SCF has a significant effect on yarn strength. This effect is closely correlated with fiber quality, and a discussion of this interaction is presented on the basis of different statistical methods.

Morphological Characterization of Individual Fiber of Agave americana L.

The fine structure of Agave americana L. fiber was studied using scanning electron microscopy (SEM) analysis. The individual fibers have a helical structure whose axis can be considered as parallel to the main axis of the bundles of ultimate fibers. Individual fibers are extracted from the technical one with the help of a 3.8% NaOH alkali solution at 130°C. SEM analysis of an individual fiber, using image analysis software, shows that the shape of an individual fiber can be likened to a ribbon with a main transverse dimension around 3.1 μm which can be considered as very small in comparison with other individual natural fibers. The SEM analysis has also shown the fiber to have a helical structure composed of square-shape spirals which were also examined. In this study, an attempt is made to explain some of the physical and mechanical properties of the bundles of ultimate fibers, such as its high strain (49%) and its low density (1.36), through the morphological characterization of individual Agave fibers.

Anisotropic Mechanical Behavior of Nonwoven Geotextiles Stressed by Uniaxial Tension

The complex behavior of nonwoven structures can be studied by tensile tests. To understand the influence of mesoscopic phenomena on macroscopic behavior, the whole thermomechanical behavior was considered. During uniaxial tensile tests three parameters were measured: the load, the strain, and the temperature on the surface of the specimen. Mesoscopic phenomena corresponding to a rise of temperature are said to be dissipative. Two nonwoven structures were considered: a needlepunched and a thermo-bonded fabric. The needlepunched structure was quite anisotropic in terms of the strain field as well as the temperature. The dissipative phenomena involved were the anelastic extension of filaments and their failure. The thermo-bonded structure was more isotropic but was also a locked structure. The mechanical behavior was similar in the two directions and a rise of temperature was noticed during the whole test as a consequence of the failure of the bonded points, the anelastic extension, and the failure of filaments.

Textile Surfaces Analysis and Modeling based on Statistical Methods: Variance Analysis and Autocorrelation Functions

Statistical analysis using between-variance are usually used in various industries. In this paper we propose to apply these statistical analysis tools to textile surfaces. Based on early theories [1— 9] statistical tools have been developed to take into account periodic and random defects observed on linear textiles. Indeed, in the textile industry the raw material presents a strong random unevenness and moreover each processing step introduces its own periodic irregularity (e.g. faults due to an elliptic roller or defective gear). A method for determining these irregularities is developed whereby it is possible to define the function of the variance-mass per unit area of the fibrous web if the overall mass variance of the web produced during the industrial process is known. Indeed, with the help of the autocorrelation function, the between-area-density variance function B(S) of the fibrous web can be predicted and the shape of the B(S) curve is determined. The two types of irregularities have also been examined and analyzed. Random irregularities were developed based on the functions of the most common distributions (isoprobable, equiprobable, uniform distributions). Then, the periodic irregularities have been developed and generalized. Finally, we discussed the actual industrial case known as a superposition of periodic and random irregularities.

A New Method of Measurement of the Inter-fiber Force

The friction and cohesion forces are some of the most important parameters that affect the yarn spinnability and tenacity. A new and simple device was carried out in order to quantify the friction and cohesion forces during a quasi-static fiber slippage in a sliver. This device was composed of two identical small carriages. One of them was fixed, whereas the second was moving on a linear guide. A piece of sliver was put down in the carriage channel in zero-gage position. The sliver was compressed with the upper carriage sides, where two identical weights were loaded. This apparatus was tested under different loads, sliver counts and speeds. The results were analyzed in order to check out the parameters which characterized the friction force during inter-fiber slippage.

Macro and Micro Characterization of Biopolymers: Case of Cotton Fibre

This chapter’s aim is to give the reader an overview of different methods used to characterise biopolymers based on the case of cotton fibre. It is not meant to be an exhaustive list of methods, but to give examples that illustrate as clearly as possible the most used and most efficient methods. The cotton fibre is a very complex biopolymer whose properties depend on varietal and environmental conditions. Cotton fibre is a very well adapted example to describe the different methods to characterise the morphology, the mechanical properties on single fibres or on fibre bundles and the surface properties. Reference methods are described as well as more advanced methods based on experiments which have been carried out by the authors and their co-workers.