Th. 3e cycle--Physiol. nerveuse et musculaire--Lille 1, 1979. N°: 782.

No description available.

Le rouissage du lin cultivé (Linum ustitatissimum L.) sur champ est un procédé naturel, rapide et semi-contrôlé durant lequel les parois végétales sont partiellement dégradées par les micro-organismes afin de faciliter l’extraction des fibres pour différents usages industriels. Le sous- et le sur-rouissage sont associés à une mauvaise qualité de fibre, il est donc essentiel de maîtriser ce processus. La microbiologique du rouissage reste encore mal caractérisée en raison d’études basées uniquement sur des approches de cultures dépendantes et d’identification phénotypique. La mise en place d’une approche de metabarcoding au cours de trois campagnes, nous a permis de caractériser l’évolution des membres et structures du domaine Bacteria et du règne Fungi, à l’échelle de son écosystème, pour la toute première fois. L’assignation taxonomique des OTUs (Operational Taxonomic Units) a permis l’identification de nouveaux taxa encore non associés au rouissage et notamment le phylum Bacteroidetes, très représenté. Grâce aux analyses multivariées et aux tests de corrélations, nous avons identifié plusieurs facteurs influençant ce processus. Nous avons démontré : (i) que le retournement des andains a un effet significatif sur les structures microbiennes, (ii) de l’existence d’un effet "terroir" avec des communautés bactériennes affectées par les précipitations et (iii) de l’existence d’un effet "millésime" avec des variations de structures fongiques expliquées par les températures. Les prédictions des CAZomes (Carbohydrate-Active-Enzymes) bactériens nous ont permis d’identifier des familles potentiellement impliquées dans la dégradation des parois cellulaires qui serviront de base pour une étude plus approfondie par méta-transcriptomique. / Flax (Linum ustitatissimum L.) dew-retting is a short-term, semi-controlled natural process during which plant cell walls are partially degraded by microorganisms to facilitate fiber extraction for various industrial applications. Under- and over-retting are associated with ‘bad fiber quality’ and it is therefore essential to master this process. The microbiology of dew-retting is poorly characterized mainly because it is currently based on the utilization of cultured approaches and phenotypic identification.The implementation of a metabarcoding approach during three independant flax dew-retting campaigns allowed us to characterize, for the first time, the bacterial and fungal community dynamics at this ecosystem level. The taxonomic assignment of OTUs (Operational Taxonomic Units) led to the identification of new taxa not previously associated with dew-retting in particular a high presence of Bacteroidetes phylum. Multivariate analysis and correlation tests identified a number of factors affecting this process. We have demonstrated : (I) that swathe turning has a significant effect on the microbial structures, (ii) the existence of a "terroir" effect and the fact that bacterial communities are affected by precipitation and (iii) the existence of a year effect and the fact that fungal communities are affected by temperature. Bacterial CAZyme (Carbohydrate-Active-Enzymes) predictions, allowed us to identify different families involved in plant cell wall degradation thereby providing a basis for future studies using a metatranscriptomic approach.

No description available.

The general aim of the research presented in this thesis is to extend the application of microstructural and microchemical analytical techniques, with the longer term objective of better informing textile conservation. The ability to identify the components of threads in historic textiles and characterise their state of degradation is essential when considering potential conservation treatments. Three particular constituents are considered here, namely metals, and plant and silk fibres. Metal threads are found in wide variety of historically important textiles, and their composite nature can complicate characterisation and treatment. Examples from a range of sources were assessed by a range of microscopic and spectroscopic techniques. It was demonstrated that these approaches allowed the determination of the general type, composition, state of degradation and likely methods of manufacture of these materials. In addition, investigations of metal threads from two specific artefacts were performed: the Jesse Tapestry, a 15th century ecclesiastical hanging; and a piece of 19th century embroidered artwork, produced in the style of the 17th century. Cellulosic fibres can prove difficult to distinguish due to their similarities in composition and structure. The work presented here describes the development of an ATR FT-IR spectroscopic technique for the characterisation of six species of commonly encountered plant fibres, using linear discriminant analysis on peak intensity ratios, to allow differentiation on the basis of characteristic lignin and cellulose contents. Further investigations using a polarised ATR technique allowed the fibre microstructure to be probed, permitting further distinction, for example of hemp and flax, on the basis of the characteristic angles and senses of winding of the cellulose fibrils. Metal weighted silk fibres, found in many important artefacts, are particularly susceptible to deterioration and so are a special area of concern. The research has concentrated on developing a micro-methodology to assess these materials, and specifically to identify spectroscopic signatures that correlate to physical properties. In order to do so, samples of habutae silk were weighted, using historically accurate methods, then aged by means of either elevated temperatures or intense illumination. Physical properties were assessed by measurement of breaking strength and Young's modulus. Subsequently TGA, HPLC, UV/Visible and ATR analyses were carried out. A good correlation was found between the physical state of the fibres and both the retention time of the major silk peak (measured in the H P L C experiment) and an orientational order parameter (derived from the pol-ATR data).

No description available.

After reviewing past work into the geometry of the symmetrical idealised plain knit loop, an account is given of the present knowledge of loop distortion, which represents one of the major problem areas of the knitting industry. The shortcomings of this knowledge are shown to be that, although a large number of processing variables have been demonstrated to be associated with loop distortion, there have been no systematic studies of the defect and there have been virtually no attempts to explain it in terms of fundamental physical characteristics of the yarn. Eleven yarn production and processing variables are examined within the framework of factorially designed experiments. The influence of these independent variables is statistically related both to ranked levels of loop distortion and to values of yarn physical characteristics. The two latter groups of data are also inter-related by rank correlation. It is shown that loop distortion is dependent upon at least three yarn characteristics which, in turn, are dependent upon particular production and processing variables. These three are yarn bending hysteresis, bending rigidity, and count regularity. The greater propensity for wool to distort in comparison to acrylic is explained in relation to these characteristics, and to their different changes during processes such as steam setting and package dyeing. The work is finally reviewed both from the point of view of the manufacturer, who wishes to be able to predict the likelihood that a particular yarn will cause distortion, and the textile technologist who is not only interested in choosing the optimum yarn production conditions for minimum distortion, but would like to improve the fabric appearance by changes or additions to established production routes.

Polyacrylonitrile (PAN) hollow fibres have been spun by a dry-jet wet spinning technique, using a commercial PAN polymer (Courtelle) redissolved in dimethylformamide (DMF). After failure to produce satisfactory porous hollow fibres from PAN/DMF solutions, a series of studies on the porous substructure of PAN cast films prepared with a variety of additives in the casting solution and at varying temperatures of the coagulation bath were carried out. A porous and flexible PAN cast film was produced when it was precipitated in water at 55 °C with CuSO4 present in the casting solution. Hollow fibres produced from a spinning solution composed of 25wt% PAN, 70wt% DMF and 5wt% CuSO4 were more porous and flexible than those produced from 25wt% PAN and 75wt% DMF spinning solution, and appeared to be more suitable for gas separation studies. The permeability of the PAN hollow fibre membranes to single gases was studied. The experimental results showed that the calculated pore radius on the surface of the fibre was in the range of 4- 32 nm. After coating with silicone rubber, the membranes showed very poor gas permeability and selectivity. Since PAN has a low intrinsic gas permeability, the low permeability observed is ascribed to a thick skin layer. The low selectivity of the membranes is related to their high surface porosity (> 10-4), or to the large pores present which are imperfectly blocked. With such fibres, little or no gas will pass through the membranes by solution-diffusion in the PAN. In order to reduce the surface porosity on the skin layer of the hollow fibres, a dualbath coagulation spinning system was used. The gas permeability of H2 in these membranes is lower than that obtained by the single bath coagulation system, while the gas permeability of the other gases, such as CO2 and CH4, were too low to measure. These results indicate that a high selectivity can be obtained by the dual bath coagulation spinning system although the selectivity is accompanied by too low a permeability, which is itself caused by too thick a skin layer. Surface modifications of PAN hollow fibre were carried out in order to modify the surface porosity of the fibres. After the treatments, the hollow fibre membranes did not give significant improvement in gas permeability and selectivity. But, when PAN hollow fibres were treated with cuprammonium hydroxide solution at room temperature, the fibres became coloured and no longer soluble in the usual solvents. The insolubility of the fibres is presumed to be due to a newly-formed crosslinked structure. The crosslinking of the fibres is reversed when the fibres are treated with EDTA solution. It has been observed that the presence of the copper in the fibres increases the tensile strength and decreases the elongation of the hollow fibres. The interaction of the PAN fibre with the cuprammonium hydroxide gave no improvement in gas separation performance but might be the basis for general acrylic fibre modification.

Probability models are developed for the failure of parallel brittle fibres embedded in a relatively soft plastic matrix. A loss of load-bearing occurs in the region surrounding a fibre break, resulting in a concentration of stress in neighbouring fibres. These stress concentrations cannot be measured directly, but by assuming them to be a chosen function of unknown parameters, the failure of the composite may be modelled. It is then shown how the stress concentration parameters may be estimated using the method of maximum likelihood. The technique is illustrated using experimental data for different materials, and in particular, it is shown how the stress concentration parameters vary with fibre spacing. The appearance of breaks along a fibre is, in nature, a point process. Load-sharing between two fibre processes will lead to a degree of nearly coincidental breaks. The degree to which 'coincidences' or 'matchings' occur in two independent point processes is examined. An unusually high degree of matching can be defined, and used to infer that processes are not independent. The exact analysis for a fibre-break process is intractable, but several approximate alternatives are studied, and compared with real and simulated data. The probability models for composite failure rely on assumptions about the underlying strength of the fibres. Principally, the 'weakest-link' property is assumed, frequently characterised by use of the Weibull distribution. A non-parametric test of this property is devised, and specially designed experiments show that weakest-link is apparently open to considerable doubt. It is shown that the existence of different causes of failure, all of which may not be present all of the time, give rise to some new types of failure model. It is demonstrated that these do not have the weakest-link property, even when based on the Weibull distribution, and that they are consistent with some experimental results.

Cette étude s’inscrit dans le cadre du projet FILAIRCO et consiste à développer des fibres fines pour la filtration de l’air. L’objectif final est d’augmenter l’efficacité de filtration en diminuant le diamètre des fibres des médias filtrants. Le filage bicomposant permet d’associer des polymères selon des morphologies « segmentée » et « îles-en-mer ». Ces structures favorisent la diminution du diamètre des fibres après la séparation des composants. Un procédé d’hydroliage permet la séparation, mais elle nécessite une morphologie avec une interface stable et faible. Des viscosités équivalentes et une différence de température de cristallisation entre les matériaux sont identifiées comme les paramètres pertinents influant sur les morphologies. Le polypropylène (PP) et le polyamide (PA6) sont mis en œuvre selon les deux morphologies. Ils doivent éviter l’encapsulation du polymère le plus visqueux par le moins visqueux, et présentent la cohésion la plus faible, pour une meilleure séparation. Selon le placement des matériaux, la cohésion est plus ou moins forte. L’association PPîlesPA6mer avec une morphologie d’interface faible favorise la fracturation. Les fibres PA6îlesPPmer et PPîlesPA6mer (diamètre ~ 26 µm) sont transformées en voiles nontissés par des procédés de cardage et spunbond, puis dissociées. L’analyse de la perméabilité à l’air et l’observation microscopique (MEB) ont révélé une fracturation facilitée des fibres PPîlesPA6mer. Leur diamètre final passe de 3,6 à 1,1 µm avec le passage de 37 à 300 îles. Enfin, l’influence de l’étirage sur la cohésion des composants et la diminution du diamètre initial des fibres a permis d’optimiser les paramètres de filage. / This study is part of the project FILAIRCO which consists in the development of fine fibers for air filtration. The ultimate goal is to increase filtration efficiency by decreasing diameter of fibers in nonwoven webs. Bicomponent melt spinning allows polymers combination according to “segmented pie” and “islands-in-the-sea” morphologies. Thus, subsequent fiber splitting is promoted by hydroentanglement process. However, components splitting requires a fiber morphology with stable and poor interface. Equivalent viscosities and difference of crystallization temperatures are the relevant parameters influencing morphologies fibers. Polypropylene (PP) and polyamide 6 (PA6) were performed within the two morphologies. Polymers are evenly distributed to avoid encapsulation phenomenon of the most viscous polymer by the less viscous one. Polymers don’t need cohesion to allow fiber splitting by hydroentanglement process. Depending on polymers localization within “islands-in-the-sea” morphology, polymers cohesion is more or less strong. PPislandsPA6sea association with poor interface enables fiber splitting unlike PA6islandsPPsea fiber. Both fibers PA6islandsPPsea and PPislandsPA6sea (diameter ~ 26 µm) are performed using carding and spunbond processes and fiber splitting is allowed with hydroentanglement process. Air permeability and SEM analysis show fiber splitting is promoted for PPislandsPA6sea couple. Decrease of fiber diameter from 3.6 to 1.1 µm is allowed with increase of islands in the morphology from 37 to 300. Finally, influence of draw ratio on polymers cohesion and decrease of fiber diameter are studied to optimize bicomponent melt spinning process parameters.