Mourad Krifa

Fiber Length Distribution in Cotton Processing: Dominant Features and Interaction Effects

This study investigated the unique shape of cotton fiber length distribution and explored its main features. One prominent feature revealed by the examination of a multitude of distributions measured on a wide range of cotton samples was the modality of the distribution pattern. Based on the experimental data, significant interactions were identified and highlighted between the distribution modality (quantitatively described as a measure of departure from unimodality), some fundamental properties of cotton fiber including maturity and strength, and the extent/aggressiveness of the mechanical processes undergone by the cottons.

Compact spinning effect on cotton yarn quality : Interactions with fiber characteristics

Compact or condensed spinning technology is widely considered as the new benchmark for staple yarn quality. The enhanced structure of compact yarn typically results in a lower hairiness and improved mechanical properties. The present study examines these two key benefits of compact technology when applied to short-to-medium staple cotton. The main focus is on interaction effects involving various raw fiber properties rather than on the overall effects. The results show that, with some combinations of fiber characteristics, using the compact technology does not lead to significant hairiness reduction. However, yarn tensile properties (strength and elongation values) do not appear to be directly affected by these interactions.

Centrifugal force spinning of PA6 nanofibers – processability and morphology of solution-spun fibers

Forcespinning™ is a newly developed process that employs centrifugal force to spin nanofibers from polymer solutions or melts. Nanofibers and nanofibrous structures have remarkable properties due to their small diameter and high surface area to volume ratio. The ability to control the average value and dispersion of fiber diameter is critical for applications such as filtration and tissue engineering scaffolds, where the performance of the nanofiber membranes depends on fiber diameter. This research investigates the interactions among polymer fluid viscosity and Forcespinning parameters, and their impact on fiber morphology and diameter using PA6 as a spinning material. The results indicate a positive relationship between spinning solution viscosity and fiber diameter. Increasing the solution viscosity both shifts the diameter distribution and increases its spread toward higher values, which results in the alteration of its shape. In addition to fiber diameter, viscosity appeared to also play a major role in determining the spinnability of the solution. Other spinning parameters, i.e. spinneret speed and spinning nozzle gage, played a minor role relative to the polymer solution viscosity, in determining both processability and fiber diameter distribution.

Fiber Length Distribution in Cotton Processing: A Finite Mixture Distribution Model

This paper introduces a new approach to modeling and parameterizing cotton fiber length distribution. The approach uses finite mixture models to derive a parametric expression of the fiber length probability density function. The model was applied to a multitude of empirical length distributions and proved to adequately parameterize the complex distribution patterns, as well as express the intrinsic and process-related factors determining their shape.

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.

Seed coat fragments : the consequences of carding and the impact of attached fibers

Seed coat fragments (SCF) are extremely difficult contaminants to remove from cotton fibers because of the fibers attached to them. Literature data suggest that carding is the most effective cleaning step during which a significant proportion of the SCF is eliminated. In the study described here, different detection methods are used to evaluate the ability of carding to clean SCF-Contaminated cottons. Variations in SCF number and size distribution are evaluated. The amount of fibers attached to the SCF is measured by image analysis, and it appears to have a significant effect on the ability of the card to remove SCF.

Flame retardant polyamide 6/nanoclay/intumescent nanocomposite fibers through electrospinning

Flame retardant polyamide 6 (nylon 6) nanocomposite nanofibers containing montmorillonite clay (MMT) platelets and intumescent non-halogenated flame retardant (FR) additives were processed by electrospinning. Different methods of mixing nano fillers before electrospinning were explored and compared. It was found that high loadings of nanoclay particles affected the electrospinnability of the nanocomposite material. Good dispersion and exfoliation of nanoclay platelets within individual nanofibers was verified by transmission electron microscopy. The degradation temperature of nanocomposite samples was lower than pristine nylon 6 samples. However the degradation of all nanocomposite formulations was overall slower. Moreover, the difference in residual char weight after decomposition was significant. Microscale combustion calorimeter results show that FR particles played a major role in reducing flammability of the material in both solution- and melt-compounded samples, while MMT nanoclay was effective in improving char residue and in reducing flammability in high-shear melt premixed samples.

Morphology and pore size distribution of electrospun and centrifugal forcespun nylon 6 nanofiber membranes

The porosity and high surface-area-to-volume ratio of nanofiber membranes offer potential for diverse applications, including high-efficiency filters and barrier fabrics for use in protective textiles. The objective of this research is to examine the morphology and pore size distribution of nanofiber membranes prepared using two spinning methods, that is, electrospinning and forcespinning. The results indicate that fiber diameter is impacted by spinning solution viscosity in an analogous way for both spinning methods. Higher concentrations resulted in larger fiber diameters in both electrospun and forcespun membranes. Fiber diameter and membrane areal density were found to significantly impact membrane pore size distribution. A theoretical model was used to describe pore size variation and was found to agree with the empirical patterns in the case of electrospun membranes.

Occurrence and morphology of bead-on-string structures in centrifugal forcespun PA6 fibers

This research aimed at investigating the morphology and frequency of bead-on-string occurrences on forcespun nano- and sub-micron fibers. The formation of bead-on-string structures was observed on a range of fiber samples forcespun in varied conditions from PA6 solutions of different concentrations. Bead-on-string structures were characterized for morphology using SEM micrographs, and were counted on all samples. Two major factors appeared to affect both the morphology and the bead count, namely spinning solution concentration, i.e. viscosity, and spinning needle gage or diameter. Low viscosity solutions resulted in large numbers of mostly spherical beads. Solutions with higher viscosity appeared to suppress the fluid jet instability thus resulting in significantly fewer beads with exclusively elongated spindle-like shapes. Spinning needle diameter also had a significant impact on beading behavior, with the larger diameter exhibiting higher bead counts. A significant interaction between the two factors was detected and its impact on the competition between the fluid jet visco-elastic relaxation and the Rayleigh instability is discussed.

Fiber length distribution variability in cotton bale classification: Interactions among length, maturity and fineness:

Proper classification and bale selection are prerequisites to success in a modern cotton spinning operation. Currently, for crops where automatic High Volume Instrument (HVI) classification is the norm, fiber selection is done based on HVI data which does not include adequate characterization of fiber length distribution. This research evaluates the effectiveness of current cotton fiber classification and selection procedures in controlling for variability in fiber length distribution and presents a new approach to adequately clustering cotton bales into homogenous groups based on empirical length distributions. The results show that using the common HVI parameters to group the bales produces categories with uncontrolled length distribution variability. Differences in distribution patterns appeared related to the potential for bales with the same micronaire levels to differ significantly in maturity and thus in propensity to break.