Longitudinal Swelling Research Articles

Dimensional stability of Douglas fir and mixed beech?poplar plywood: experimental measurements and simulations

A finite element method (FEM) numerical model predicting the warping of plywood panels from a description of the intraveneer properties in response to moisture content changes is presented and compared with experimental measurements. Thirteen three-ply plywood panels of 40×40 cm2 (1.9-mm thickness per ply) were manufactured from Douglas fir or from mixed beech and poplar. Maps of the longitudinal and tangential swelling as well as the wood density were established on the veneers before the glueing process. The shape was measured on the panels conditioned first at 17% moisture content (MC), then at the fiber saturation point, in order to calculate the maximum displacements along six profiles (three longitudinal and three tangential) on each panel. These experimental data were compared with the results of simulations based on two models. First, they were compared to a "heterogeneous" model in which all measured veneer properties were used as inputs. In this case the predicted displacements showed a close correlation (R 2=0.74) to the measured ones, but were remarkably underestimated. Second, they were compared to a "homogeneous" model in which the three layers of each panel were only described by their mean density and average swelling coefficients. For this comparison the prediction of the displacements was much less accurate in the longitudinal direction but was still satisfactory in the tangential direction.

Adamantinoma-Like Ewingʼs Sarcoma: Usefulness of Genetic Approaches in Diagnosing Small Round Cell Tumors

A 13-year-old boy had a painful longitudinal swelling over the lateral aspect of the right calf. Radiographic studies revealed a dense fibular diaphyseal lesion with an associated soft tissue mass interpreted as probable Ewing's sarcoma. In contrast to the expected small round cell tumor appearance, the biopsy tissue was composed of nests of hyperchromatic, mildly pleomorphic cells separated by a pronounced desmoplastic reaction. Immuno-phenotyping showed that the tumor cells were strongly keratinand vimentin-immunoreactive but negative for 0-13 (MIC2). Other epithelial-like features included the presence of abundant intermediate filaments (including tonofilaments) and complex desmosomal-type intercellular junctions. These histologic, immunohistochemical, and ultrastructural findings were consistent with a diagnosis of adamantinoma, an entity that is not usually considered in the differential diagnosis of Ewing's sarcoma. Genetic analysis of this patient's tumor specimen, in addition to two cases previously described in the literature as “Ewing-like adamantinomas,” revealed the presence of the 11;22 translocation [t(11; 22)(q24;q12)] and/or the associated EWS/FLI1 fusion transcript characteristic of Ewing's sarcoma and peripheral primitive neuroectodermal tumors. This case illustrates the diagnostic challenges often encountered in bone and soft tissue tumors. Recently, recognition of specific cytogenetic and molecular genetic abnormalities in these neoplasms has significantly reduced some of the associated difficulties and has provided valuable information with respect to histopathogenesis. A review of the diagnostic and prognostic usefulness of genetic studies in Ewing's sarcoma and peripheral primitive neuroectodermal tumors is presented.

Sorption and longitudinal swelling kinetic behaviour in the system cellulose acetate-methanol

The kinetics of methanol vapour sorption and concurrent longitudinal swelling of cellulose acetate membranes has been studied and interpreted in terms of ‘viscous’ swelling and differential swelling stress effects, on the basis of previous modelling work. The close parallelism of the kinetic behaviour observed here and in a previous study of the cellulose acetate-acetone system, shows that both sorption and longitudinal swelling kinetics can be understood in terms of the viscoelastic response of the plasticized polymer to an applied osmotic stress, without regard to the nature of the penetrant causing the osmotic stress and plasticization. It has also been shown that, from the first stage of two-stage absorption curves, diffusion coefficient values can be derived agreeing with those evaluated by Takizawa et al. from steady state permeation and equilibrium sorption data.

The effect ofN,N-dimethylformamide and polymer grafting on the morphology of polyester fibers in fabric substrate

Photo-induced graft polymerization of acrylic acid (AA) and methyl acrylate (MA) in the liquid and vapor phase, respectively, onto N,N-dimethyformamide (DMF)-pretreated poly(ethylene terephthalate) (PET) fibers in fabric substrate was studied. The effect of various synthesis conditions and DMF pretreatment on the graft yields on PET was investigated. The internal morphology and properties of DMF-pretreated and grafted PET fibers in the fabric were characterized using density and birefringence measurements, differential thermal analysis (DTA), Fourier transform infrared spectroscopy (FTIR), dyeing methods, and critical dissolution times. The grafting was promoted by increasing DMF pretreatment temperature and the amount of DMF retention in the PET. Increasing biacetyl and monomer flow time and irradiation time enhanced grafting. DMF pretreatment resulted in increases in total void content, degree of crystallinity, trans-isomer content, chain folding, segmental mobility, and molecular packing of the PET, but caused decreases in its amorphous orientation, intermolecular forces, and individual void size through longitudinal shrinkage, lateral swelling, and removal of oligomers. Subsequent graft copolymerization led to further changes in the internal morphology and properties of the PET. PET grafted with AA had a higher cohesive energy density, lower degree of molecular packing, and larger individual void size, but less total void content, lower segmental mobility, less chain orientation, and a lower degree of crystallinity. PET grafted with MA showed increases in total void content, individual void size, segmental mobility, and molecular packing, but showed decreases in chain orientation and degree of crystallinity. © 1996 John Wiley & Sons, Inc.

A detailed study of the viscoelastic nature of vapor sorption and transport in a cellulosic polymer. II. Sorption and longitudinal swelling kinetic correlations

AbstractLongitudinal swelling kinetics of cellulose acetate films sorbing acetone vapor at 30°C were studied under various conditions and correlated with the corresponding sorption kinetic measurements reported in Part I. The results were analyzed in the light of (1) previous theoretical studies of simple viscoelastic polymer‐penetrant model systems and (2) mechanical stress‐strain data on the cellulose acetate‐acetone system, which are also reported here. The conclusions drawn from this analysis confirm and/or amplify (particularly as regards the effect of longitudinal differential swelling stresses) our previous interpretations based on sorption kinetic analysis, concerning the physical nature and causes of various features of the non‐Fickian kinetic behavior of cellulosic polymer‐micromolecular penetrant systems. History‐dependent long‐term aging effects were also observed and investigated. © 1995 John Wiley & Sons, Inc.

Modeling for Suppression of Moisture/Temperature Induced Dimensional Changes in Fibrous Composite Structures

Suppression of dimensional change induced by moisture and or temperature changes of several fibrous systems each composed of at least one hygroscopic component has been studied. This paper deals with the simplest case, that of a balanced parallel structure assembled with perfect bonding. Its dimensional behavior is modeled taking into account such parameters as the preloading condition at the time of assembly, initial moisture content and temperature, area ratio of the components, molecular orientation, and modulus decaying factor. The results showed that two factors played a major role in moisture/temperature induced dimensional change: longitudinal swelling/shortening which determines the longitudinal dimensional change, and material softening/stiffening which influences the restricting ability of the less moisture/temperature sensitive component. Whether the two factors add their effects to each other or compete against each other depends on the initial moisture content and temperature. The effectiveness of the suppression of dimensional change relies on the area of the two components. Molecular orientation of the moisture/temperature sensitive component affects its longitudinal swelling as well as its modulus.

Control of thickness of collenchyma cell walls by pectins

Near-isotropic stresses were generated within collenchyma cell walls of celery (Apium graveolens L.) by exchanging K(+) for Ca(2+) ions, varying the ionic strength and de-esterifying the pectic carboxyl groups, treatments that changed the free-charge density of the pectic polysaccharides. The collenchyma strands swelled radially with increasing free-charge density but there was very little longitudinal swelling. Depolymerising the pectins by β-elimination also induced much more radial than longitudinal swelling. Supported by earlier work on Nitella, these results indicate that pectins control the interlamellar spacing in cell walls and hold them together across their thickness, particularly against turgor stresses tending to delaminate the walls at the cell corners.

Sorption—longitudinal swelling kinetic correlations in polymer film—vapor systems

It is pointed out that the correlation between sorption and longitudinal swelling kinetics provides a noteworthy new method of characterization of polymer film—penetrant vapor systems. A model previously developed for linear viscoelastic media is extended here to include non-linear viscoelastic behavior. Calculations based on this model are used to investigate the salient characteristics of the aforementioned correlation curves as a function of the diffusion and viscoelastic properties of the polymer—penetrant system. Deviations from a linear correlation are generally caused by “softening” effects, which may reflect plasticization of the polymer by the penetrant and/or non-linear viscoelastic behavior in the form of “stress softening”. Elucidation of the chief characteristics of these two types of effect provides considerable insight into the behavior of real systems. Examination of data on Nylon 6—water, in particular, yields evidence of non-linear viscoelastic behavior, which can explain previous difficulty in interpreting these data in terms of a simpler linear model.

Technological value of whole-tree-chips for the particleboard industry

The percentage of bark and small branches was analysed for the main Belgian hardwood species. 288 homogeneous UF-bonded boards were made on a laboratory scale from the wood, bark and small branches of four wood species and their mixing. The physical and mechanical properties of these boards were determined. The addition of bark and small branches leads to a decrease in the mechanical properties of the boards and an increase in longitudinal swelling. The technological value of whole-tree chips depends on the quality of the particles made from them and on their percentage of bark and small branches.

Longitudinal Swelling in Water of Heat-Treated Nylon 66 Yarns and Fabrics

Longitudinal swelling in water of nylon 66 multifilament yarn and fabric has been measured before and after heat setting. It is shown that relatively large increases in longitudinal swelling of the nylon occur as a result of setting. The swelling produced is to a large extent of reversible nature, which results in considerable stresses being produced in heat-set specimens dried at constant extension.

2—HYGRAL CHANGES IN CURVATURE AND LENGTH IN SET KERATINS

The set developed in various wools and hairs when strained in boiling water or in monoethanolamine sulphite (MEAS) has been measured, together with the longitudinal swelling of set fibres on wetting. The changes in curvature of merino fibres on wetting are enhanced by setting in boiling water or in cold MEAS but diminished by setting in boiling 1% MEAS. The interpretation of these changes of curvature in terms of ortho–para differences throws into question the supposition that there is a specific para-type keratin (exemplified by human hair) and a specific ortho-type keratin (kid mohair). Some technological treatments diminish the hygral changes in curvature.

26—THE KINETICS OF WATER-VAPOUR SORPTION IN WOOL: PART I: AN IMPROVED SORPTION VIBROSCOPE

An improved design of the sorption vibroscope previously developed for wool–water-sorption studies is described. In particular, the improved equipment incorporates a novel vibration-detection transducer and a linear differential transformer, which allows simultaneous measurement of longitudinal swelling with moisture uptake. The accuracy of the sorption vibroscope for studies of the sorption kinetics of the wool-water system is assessed.

Set/Supercontraction Characteristics and Longitudinal Swelling of Keratin Fibers

The longitudinal swelling of three different sorts of wools, when permanently set, has been studied. It has been observed that, when progressively set, Mohair fibers, which acquire a set much more readily, show retarded swelling, compared to Blackface wool fibers. The effect of setting time reveals that the structure of Mohair fiber opens up at a much faster rate, but the swelling is high in the case of Blackface wool fiber which exhibits poor settability. Moreover, in each case, fibers, on acquiring a certain set, show a decrease in longitudinal swelling due to bond re-formation. It appears that the increase in longitudinal swelling, which is due to changes in the cortical regions, is influenced not only by the setting strain or the setting time; the number of strained bonds initially present and the ease of bond re-formation also determine the extent of swelling.

STUDIES ON THE SELECTIVE UNIPLANAR ORIENTATION OF (101) PLANES OF CELLULOSE II CRYSTALS IN REGENERATED FIBERS

In the first paper on this series attention has been drawn to the selective uniplanar orientation of (101) planes in films. The purpose of this work is to investigate the above orientation of (101) planes in fibers. In order to determine whether preferencial orientation of (101) planes takes place or not, the micro X-ray examination were carried out on model bristles. These specimens having a diameter of 300_??_700μ were prepared by extruding viscose into several kinds of spinning baths through a glass nozzle. The thickness of cross-sectioned specimen was 30_??_50μ. Diffraction patterns were taken for several cross sections of undrawn and drawn bristles on different radial regions. The collimeter diameter was 50μ in each case.No preferred orientation of (101) planes is observed in Toramomen type filament. It may be concluded that crystallites lie in all possible directions in this case, since the micro X-ray diagram agrees with the powder pattern. On the other hand, in the case of undrawn Muller type filament it is confirmed that the (101) planes have a preferencial orientation parallel to the fiber surface in a skin region, while random orientation in a core region. The degree of orientation becomes more pronounced with increasing sulfate in the bath. This orientation behavior is essentially identical with that described on films in the previous work of this series.Undrawn Muller type cellulose filament exhibits smaller tangential and longitudinal swelling by wetting, and shrinkage by drying than Toramomen type filament. It seems reasonable to explain swelling properties on the basis of the preferred orientation of (101) planes parallel to the filament surface as in the case of films, keeping in mind that hydroxyl groups concentrate mostly on the (101) surfaces of cellulose crystallites. Fiber can be considered as the structure made from films concentrically multi-layered. Irregular shapes of cross section of viscose rayons, depending on the spinning bath, are discussed in relation to the preferencial orientation of (101) planes and anisotropic swelling and shrinkage behavior.The change of the orientation of (101) planes with drawing are also examined by the micro X-ray method. The filament has a tendency to maintain the selective uniplanar orientation in spite of tangential decrease in dimension. This tendency is in good agreement with that found for drawn cellophane.

The Mechanical Properties of Wool Fibers in Water at Temperatures Above 100° C

The mechanical properties of normal and of chemically modified wool fibers in water were examined for temperatures up to 140°C. Marked changes in the mechanical properties of normal wool fibers occurs at temperatures around 130°C. At this tempera ture the Hookean modulus of the load-extension curve approaches zero, the x-ray diffraction pattern shows that the organized α-keratin structure of the wool is replaced by a randomized β-structure, unstrained fibers supercontract and the longitudinal swelling from dry to wet increases. Chemical modification of the fibers can alter the temperature at which these physical property changes occur. The set, dry-wet longi tudinal swelling and load-extension curves in water at 20°C of fibers held extended in water at temperatures up to 140°C were also examined. It is concluded that the α-helices stabilize the structure of the wool fibers longitudi nally by opposing both extension and swelling. The disappearance of the α-keratin structure for normal fibers at around 130°C results in a loss of this longitudinal stability. During setting of normal fibers, for temperatures less than 130°C, the modification only occurs in the unfolded structural components. The maximum modification (the best setting condition) occurred at 120°C, which was the highest temperature used below the "melting" temperature of 130°C.

The Relation Between Longitudinal Swelling and Water Sorption by Keratin Fibers

Longitudinal swelling of keratin fibers has been measured as a function of time following abrupt humidity changes in the environment of the fibers. The equilibrium length change and the shape of the longitudinal swelling vs. relative humidity isotherm for horse hair and Corriedale and Lincoln wool fibers is dependent on the fiber type. The increase of length is associated with the disruption of the fiber microfibrils. At high humidities there is an overshoot in the length swelling accompanying the water absorption. For interval absorption at high humidities, the entire length increase for Corriedale fibers is transient, and the length returns to the value before the step was applied. For horse hair, only a part of the length increase is transient. The corresponding interval desorp tion causes no change of length. An effect on the longitudinal swelling due to the load on the fiber is observed for loads sufficiently large to extend the fiber into its yield region , in water. The observed relationship between longitudinal swelling and water content during sorption steps is discussed.

Studies on the drawing of polyamide fibers. IV. Effect of drawing on the degree of longitudinal swelling

AbstractThe longitudinal dimensional change of dried nylon 6 monofilaments of various draw ratios swollen in the atmosphere of 24°C. and 100% R.H. was studied. The degree of longitudinal swelling in equilibrium changes with the conditions of drawing and the draw ratio of the sample; for the samples drawn immediately after spinning, it increases, passes through a maximum near a draw ratio of 2, and gradually decreases as the draw ratio increases; for the samples drawn many days after spinning the maximum point is at a draw ratio near 2.8, while for the samples drawn after heat‐treatment the degree of longitudinal swelling does not change appreciably with the draw ratio of the sample. The rate of longitudinal swelling remains nearly constant or increases slightly in the range of draw ratios of 1–3. It then decreases with the draw ratio at draw ratios higher than 3.

Longitudinal Swelling of Permanently Set Wool Fibers

The longitudinal swelling of permanently set wool fibers was measured by a desorption method as a function of the time the fibers were held in the extended state. It was found that, after a setting treatment involving extensions below 40%. the longitudinal swelling, following an initial rapid increase, was independent of setting time and the dimensional changes of the fiber resulting from the setting process. At a setting ex tension of 60%, a maximum in longitudinal swelling is reached, which is followed by a rapid decrease and then by a gradual decrease with increasing times of setting. The results are interpreted in terms of differences in the stabilization mechanism for the extended configuration, depending on the strain level. Elimination of free sulfhydryl groups, before the fibers are released from extension, decreases chain mobility and, therefore, decreases disordering during the subsequent recovery step.

Dimensional Stability of Woven Wool Fabrics: Hygral Expansion

In worsted fabrics, one factor contributing to lack of dimensional stability is the reversible change of dimensions that takes place with regain changes, here termed hygral expansion. The hygral expansion of ten worsted fabrics is studied, and it is shown that the yarn and fabric behavior can be explained in terms of the bending and straightening of single fiber arcs. The observed change of arc radius from dry to wet is about 50%, and when this figure is applied to the geometry of the weave, quantitative predictions of the hygral expansion of the yarn can be satisfactorily made. Such a large change of curvature in single fibers cannot arise from radial swelling alone, and it is suggested that with regain changes, the fibers behave in a way that is analogous to the behavior of bimetal strips with temperature changes. Such a mechanism is possible because of the bilateral structure of the fibers, with different longitudinal swelling of the two segments. Since the fibers are preferentially oriented in the fabric, this mechanism can play a dominant role in yarn and fabric behavior. The hygral expansion increases with increased setting, probably because the yarns no longer tend to revert to their straight form at high regain. Correspondingly, there is a reduction in the reaction forces between yarns at the points of intersection; the higher these reaction forces are, the greater the restriction that is put upon hygral expansion. Some applications of hygral expansion—to measurements of relaxation shrinkage and assessment and effectiveness of mill machines—are discussed.

Permanent Set and Keratin Structure

When a normal wool fiber is held extended in boiling distilled water, the force due to bonds opposing the extension falls rapidly in the first few minutes to a steady value of force, which has been shown to he purely entropic. Accompanying this breakdown of bonds opposing extension is the reduction of the ability of the fiber to return, on release, to its native configuration. The loss of organization in the released fiber suggested by mechanical fiber tests is confirmed by birefringence measurements and also by the irrecoverability of the a-keratin structure, as measured by the x-ray diffraction pattern. The longitudinal swelling on wetting dry fibers increases as the setting exten sion increases and with increased time of setting; these observations are also consistent with structural disorganization of the fiber. The equilibrium state after release of the keratin fiber changes in the first few minutes of being held extended in the boiling water from the native state to a supercontracted state. This state, on further boiling, is replaced by that of the set fiber.