Search

Organic single crystals with elastic bending capability and potential applications in flexible devices and sensors have been elucidated. Exploring the temperature compatibility of elasticity is essential for defining application boundaries of elastic materials. However, related studies have rarely been reported for elastic organic crystals. Now, an organic crystal displays elasticity even in liquid nitrogen (77 K). The elasticity can be maintained below ca. 150 °C. At higher temperatures, the heat setting property enables us to make various shapes of crystalline fibers based on this single kind of crystal. Through detailed crystallographic analyses and contrast experiments, the mechanisms behind the unusual low-temperature elasticity and high-temperature heat setting are disclosed.

Poly(e-caprolactone)/poly(e-caprolactone-co-lactide) (PCL/PLCL) blend filaments with various ratios of PCL and PLCL were prepared by melt spinning. The effect of PLCL content on the physical properties of the blended filament was investigated. The melt spinning of the blend was carried out and the as spun filament was subsequently subjected to drawing and heat setting process. The addition of PLCL caused significant changes in the mechanical properties of the filaments. Crystallinity of blend decreased with the addition of PLCL as observed by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). Scanning electron microscopy (SEM) revealed that the fracture surface becomes rougher at higher PLCL content. It may be proposed that PCL and PLCL show limited interaction within the blend matrix. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Summary Washing cod mince in water containing both CaCl2 and MgCl2 improves the functional properties of the resultant surimi. Gel strength, frozen shelf-life, and colour, important quality factors for the further processing of surimi, were measured after different heat setting regimes for surimi pastes prepared with or without CaCl2 and MgCl2 addition. the surimi was stored frozen for up to 12 months. the positive effect of setting at low temperatures was far more pronounced when the surimi was processed with 7.5 mM CaCl2 and 15 mM MgCl2 added to the wash water. After 12 months of frozen storage, the gel strength of the salt-washed surimi was reduced, but was still higher than the control. the lightness of the cooked surimi model product was reduced when salt-washed. the positive effect of the ions was abolished when lysine, an inhibitor of transglutaminase, was included. Hence, the positive effect of Ca2+ and Mg+2 ions on the functional properties of surimi may be caused by a transglutaminase-type enzyme present in cod mince.

A study has been conducted into the effect of heat setting on the dimensional stability and dyeing properties of spun and false-twist texturised poly(lactic acid) yarn. It has been shown that acceptable levels of dimensional stability can be achieved after heat setting for 30-45 s at 130 °C, false-twist texturised yarn exhibiting greater shrinkage than spun yarn. The exhaustion level and visual colour yield of a number of disperse dyes have been evaluated on each type of poly(lactic acid) yarn and shown to be essentially independent of the time of heat setting.

The anisotropic structures found in drawn poly(lactic acid) films are strongly correlated to their overall dimensional stability. Several aspects of this relationship can be efficiently characterized by Raman spectroscopy. We determined the degree of orientation in these drawn films by measuring the relative intensity of the polarized and depolarized components and the shift in the relative band positions. The bandwidth and specific band frequency also correlated well with the degree of sample crystallinity. These aspects make the Raman method amenable for the online monitoring of orientation and crystallinity in commercial processes. A molecular understanding of heat setting to reduce film shrinkage is also proposed. Raman data from films that were heat-set while physically constrained suggest that amorphous-phase relaxation does not occur during heat setting. Rather, the level of crystallinity increases substantially, indicating that the cause of low shrinkage in the films was due to crystalline network formation rather than amorphous-phase relaxation. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2497–2505, 2001

The purpose of this article is to study the fast structural changes that take place during the deformation and heat setting of uniaxially preoriented poly(ethylene 2,6-naphthalate) films. For this purpose, an online birefringence measurement system coupled with a heat-setting oven was used. In the online birefringence system, whose details were reported previously (H. Venkatesvaran and M. Cakmak, SPE ANTEC Tech Pap 1993, 39, 257; H. Venkatesvaran and M. Cakmak, Polym Eng Sci 2001, 41, 341), a green and red laser is passed through the films being annealed in a heat-setting chamber; the resulting data are analyzed for the details of structural mechanisms that take place during this process. This technique is shown to be capable of detecting reversals in birefringence development; as a result, complex sequences of structural evolution can be tracked. The design of this system allows one to observe not only the increase or decrease in birefringence during the course of the heat-setting process but also the rate dependencies on processing variables. In this study, we establish that the rate of structural rearrangement, as detected by birefringence, depends strongly on the state of the pre-existing chain orientation and the level of crystallinity. Increased levels of preorientation in the films results in decreases in the rate of birefringence change during heat setting. This is primarily attributed to the increased levels of steric hindrance developed with the increase in orientation and crystallinity in the preoriented samples. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 1107–1121, 2001

The effects of a controlled heat-setting treatment on the properties and microstructure of biaxially stretched poly(ethylene terephthalate) (PET) and poly(ethylene-2,6-naphthalene dicarboxylate) (PEN) films are described. Substantial changes in crystalline fraction, crystallite size, glass transition temperature and significant enhancement in dimensional stability are observed for both film types upon increase in heat-set temperature. A distinct melting peak in the vicinity of the heat-set temperature, observed in differential scanning calorimetry thermograms for both materials, is shown to be an effective marker of the heat-setting process underlying the dual nature of the morphology of the heat-treated films. We also observe that the PET films undergo significant molecular realignment on heat setting, while the orientation of the PEN films is only weakly modified by the heat-set conditions. A morphological transition is detected for both films at high heat-set temperatures (T HS * ) near the onset of the p melting range, marking a qualitative change in the physical response of the biaxially oriented films; Measurable drop in planar orientation and glass transition temperature, and a sharp rise in crystallite size are noted for films heat-treated above T HS * . The morphological models of previous workers (Schultz et al. and Fischer and Fakirov), invoking the idea of fibrillar-to-lamellar transformation, are used to explain some of our observations.

The modifications of macromolecular entanglements in polyacrylonitrile copolymer fibers by heat setting in different mediums such as steam, hot air, and inert liquid are reported. The effects of applied tension, frozen internal stress, temperature, time, medium, crystallization, etc., during heat setting on the modification of entanglements are investigated in detail. These experimental results elucidate clearly the mechanism of entanglement and disentanglement and confirm fully the DSC method of swelling polymers for studying entanglement in solid polymer, as was previously published in Part I of this paper. © 1993 John Wiley & Sons, Inc.

Nylon 6 fibers were submitted to three types of heat treatments at different temperatures and times in order to find the best conditions to achieve structural stability. The boiling water treatment proved to be more effective in promoting profound structural modifications than the other treatments (dry treatment and the dry treatment followed by a 5-h boiling water heat setting). Also, the fibers reached their maximum structural transformations after 1 h of treatment. Thus, a 5-h boiling water treatment was chosen to heat-set the fibers. Then, the heat-set fibers were submitted to dyeing and migration experiments with different disperse dyes. The obtained results demonstrate that the discontinuities observed in the curves of migration factor versus square root of time might be related to the mechanism of the migration experiments. The different solubilities of the disperse dyes in water helped the understanding of this mechanism. Also, this study with nylon 6 fibers reveal that the proposed model can be used for leveling time prediction, and the discontinuities mentioned above can for practical purposes be neglected. © 1992 John Wiley & Sons, Inc.

A sample of high-elastic-textured poly(ethylene terephthalate) (PET) yarns were subjected to different conditions of heat-setting, i.e., different temperatures and overfeeds. The structural changes were characterized by different physical methods. The orientation factors of crystalline and amorphous regions were calculated. The yarn tensions acting during the SET process were measured and corrected to the structural data. The results obtained show that two processes take place during the SET process: relaxation of the molecule segments in amorphous regions and change of crystallite orientation in microfibrils. A simple model for explanation of the structural changes in simultaneously draw-textured PET yarns is proposed.

Fibers spun from blends of small percentage of plastic grade polypropylene (HMPP) with fiber grade polypropylene (PP) are studied for drawing behavior. A factorial design of experiment is used for a two-stage drawing process with variables, such as percent of HMPP component, first stage draw ratio and temperature, and second stage temperature. Optimization is carried out for breaking stress and modulus of drawn filaments. Breaking stress of up to 0.74 GPa and initial modulus of 7.34 GPa is possible by such an optimization process. These properties are observed for 6% HMPP blend composition. Heat setting of drawn filaments show little changes up to 140°C heat-setting temperature. Large scale structural changes with rapid drop in mechanical properties is observed for 150-160°C heat-set samples.

We continue a previous study of the α and α′ mechanical relaxation processes in oriented poly(ethylene terephthalate) by means of heat-setting experiments on drawn filaments between room temperature and the melting region. Both processes were exhibited in both torsion and bending deformations, but heat setting was found consistently to be greater in bending than in torsion: this was accounted for by the known anisotropy of the α relaxation. In both modes of deformation, increasing strain level gave reduced recovery, and results suggested this arose from high stresses activating at room temperature the stress relaxation mechanisms, which at low stresses occurred only at elevated temperatures (α if as-drawn, α′ if preset). Results were found to be independent of whether blown air or stirred oil was used as heat transfer medium, in contrast to some previous reports in the literature; the reason lay in differences in the precise sequences of deformation and temperature employed.

Apparent diffusion coefficients of two disperse dyes for so-called easily dyeable/cationic-dyeable polyester (ED-CDPET) and cationic-dyeable polyester (CDPET) fibres of identical linear density and sulphonic acid group content have been calculated. It was found that the diffusion coefficients of dyes for ED-CDPET were far greater than those of dyes for CDPET. The dyeability at the boil without carrier, using disperse and cationic dyes on various ED-CDPET and CDPET fibres, has been studied. ED-CDPET was found to have higher dyeability at all levels of heat setting (irrespective of the dye used). The finest ED-CDPET fibres showed maximum dye uptake as a result of increased surface area. Heat setting in the taut condition reduced dye uptake.

Heat-set yarns are being used increasingly in cut-pile carpets, and these treatments entail particular attention to dye selection, whether the fibre is dyed before or after setting. Some of the adverse effects of heat setting e.g. colour changes due to dye instability, are immediately obvious, but others, e.g. an increased sensitivity of the dye to certain agencies encountered during wear, are more insidious. A number of these effects have been studied with particular reference to variations in the setting temperatures appropriate to each fibre.

In the existing literature various values are given for the intrinsic birefringence of the crystalline and the amorphous phases in poly(ethylene terephthalate) (PET). These values have either been calculated theoretically or obtained from experimental data on the basis of certain models. In this investigation, using the Samuels two-phase model which correlates sonic modulus with structural parameters, intrinsic birefringence values for the crystalline (Δnc) and amorphous (Δna) phases have been determined by studying 30 PET samples prepared by heat setting to have a wide range of structures; the results are Δnc = 0.29 and Δna = 0.20. These values are discussed along with others in the literature and it is concluded that in the light of the present work, the values used by many authors need reexamination.

The presence of carriers in polyester fabric reduces the temperature at which creases become permanently set. The magnitude of the effect depends on the concentration of the carrier in the fibres, the time and temperature of heat-setting and the chemical structure of the carrier.

Strain recovery of polyester and nylon 66 monofilaments, following stress relaxation at constant strain, has been measured under two types of temperature history. In the first (experiments here called type A), the monofilament, extended at an elevated temperature, was held at constant strain at that temperature, and then air-quenched to room temperature while still under stress. The stress was later removed with the fiber at ambient temperature, and the recovery from strain determined. In the second (experiments of type B), the monofilament was also extended at an elevated temperature, but it was then allowed to recover, under zero load, at the same temperature, prior to quenching. A cylindrical heater is described which surrounded the fiber specimen and which could be removed suddenly to permit rapid air quenching of the specimen. Recovery was characterized by the percent of applied strain which was recovered 100 sec after load removal. The percent recovery, in type A experiments, decreased to low values with increasing stretch temperature. Recovery in type B experiments, however, was markedly different, and showed a minimum value at stretch temperatures in the vicinity of the glass transition. At higher temperatures, recovery was high, but it decreased rapidly as TM was approached due to the onset of viscous flow. There was thus a discontinuity in recovery behavior as the time of quenching increased through the time of unloading (transition between type A and type B conditions). The results were interpreted to show that the achievement of good heat setting (poor recovery) is critically dependent on the temperature of the fiber during both stretching and recovery periods.

In the finishing of Terylene–linen fabrics, the shrinkage characteristics of the constituent yarns must be given careful consideration. Established methods for open-width processing of 100% linen fabrics may be applied to the blend and, according to the choice of yarn, a predominance of either flax or Terylene fibre on the fabric surface can be produced. Good stability to laundering is achieved by processing the fabric under minimum tension and heat setting at some stage in the finishing sequence. Terylene–linen fabrics may be dyed to solid colours by a two-bath process, using a variety of techniques. The possibility of differential abrasion must be considered when producing cross-dyed effects. The use of crease-resist resins is recommended for those fabrics made from the 67/33 blend intended for outerwear. Provided that an amount appropriate to the fabric weight is applied, good crease recovery can be produced with various classes of resin.

Drawn and undrawn nylon 6 fibers subjected to dry heat setting or steam setting were dyed with an acid dyestuff and a direct dyestuff. The dye uptake of these fibers was determined, and the rate of diffusion of a disperse dyestuff was evaluated by the method of Kramer. For the drawn nylon 6, the dye uptake and the diffusion coefficient are generally increased by the steam setting. This tendency increases with the temperature of the steam setting. However, dry heat setting up to about 160°C. gives the reverse tendency. In both types of setting treatments, the diffusion coefficient decreases with increasing tension of the sample during setting. For the undrawn nylon 6, the same effects of the heat setting are observed. Therefore the change of dyeability on steam setting is not attributable to a decrease in the orientation of crystallites but is caused by loosening of the molecular packing in the amorphous region as a result of inclusion of water. The change of dyeability resulting from dry heat setting, however, results from the increase in crystallinity and also closeness of packing in the amorphous regions.

The swelling and dissolution of heat-set nylon 6 fiber in aqueous sulfuric acid were examined. Steam-set fiber having good dyeability swells with much more difficulty than the dry-heat-set and unset fibers. Similar phenomena are seen in the examination of density of nylon 6 fiber subjected to heat setting, and it is found that the resistance to swelling depends on the crystalline region rather than on the amorphous region.

Orientation by x-ray diffraction, dichroic orientation, and orientation by birefringence were measured on nylon 6 fibers subjected to stress relaxation or dry heat setting after stress relaxation. Orientation in the crystalline and noncrystalline regions increases with tension to an especially great extent in heat setting. Dyeability of the fibers subjected to stress-relaxation treatment is only slightly affected by tension, and dyeability of fibers subjected to dry heat setting or steam setting decreases with tension. The larger the molecular weight of dye used, the more marked the behavior becomes. Thus, depending on the dyes used, tension variations in weaving or knitting of nylon 6 fibers may be a cause of stripiness of dyed fabrics.

The degree of penetration, the diffusion constant, and the uptake of dyestuffs of different molecular sizes were measured in undrawn and drawn nylon 6 filament, heat-set under various conditions in order to determine the pore structure in the amorphous regions. Unset and dry-heat-set nylon 6 can be penetrated only with difficulty by the dyestuffs having molecular lengths above about 30 and 25 A., respectively. The apparent diffusion coefficients and molecular weight of dyestuffs are approximately hyperbolic. The relations are considerably different, depending on the degree of drawing and conditions of the heat setting. Further, the relations among molecular size, amount of absorbed dyestuffs, and fraction of amorphous region capable of being penetrated by dyestuff are discussed with reference to the lateral-order distribution of nylon 6, as evaluated from the accessibility to D2O vapor.

The relative viscosity and amino and carboxyl endgroup contents for unset, dry-heat-set, and steam-set nylon 6 fiber were determined. The results for the heat-set fibers are almost the same as those for the unset fibers. Therefore, it is difficult to explain the increase of dye uptake in steam setting on the basis of hydrolysis of nylon molecules. The differences in amino endgroup contents as determined by the p-toluenesulfonic acid and 2,4-dinitrofluorobenzene methods indicate that 20–30% of the amino groups might be occluded in the crystalline regions after steam setting.

Studies have been made of the dependence of saturation limits, rates of diffusion, rates of dyeing, and migration properties of a number of disperse dyes on polyester fibres upon the temperature at which the fibres have been heat-set. Use of pure, crystalline dyes was found to give erratic results and therefore ultra-dispersed commercial dyes were used in the investigation. The saturation limit and the average diffusion coefficient showed a minimum at a particular heat-setting temperature. Values were calculated for heat of dyeing, heat of solution, and entropy change in dyeing; these values tended to a maximum or minimum for fibre set at 150C. The findings suggest that the minimum tinctorial yields obtained at such temperatures are due to (a) increasing transformation of the fibre structure on heat setting and (b) preferential loosening of unset fibre by swelling agents in a heated medium. Degree of setting was found to have virtually no influence on migration. The causes of unlevel dyeings are discussed.

Meeting of the Midlands Region, held at the Post House, Sandiacre, on 8 November 1972, MrH. W. Partridge in the chair. The manufacture, characteristics and fibre properties of Vincel 64 (Courtaulds) high-wet-modulus fibre are discussed. The general dyeing behaviour of this fibre is described and compared with that of Fibro (Courtaulds). Information is given on the preparation of Vincel 64-cotton blends by batchwise and continuous techniques, followed by dyeing on winch or Jet machines with the usual classes of dye for cellulose. Attention is drawn to the importance of selecting dyes with good partition between the two fibres. Details are given of suitable chemical finishes which can be applied to impart improved easy-care properties and dimensional stability. The preparation, heat setting, dyeing and finishing of Vincel 64-polyester single- and double-jersey fabrics are described with particular reference to practical techniques.

The effects of dry-heat setting and pressure-steam setting on the dyeing behaviour of nylon yams are considered. Measurements have been made of the influence of the temperature and duration of dry-heat setting on the rates of dyeing of nylon 6.6 yarns and fabrics with the direct dye Chlorazol Violet R (C.I. Direct Violet 3) and the 1:2 metal-complex dyes Irgalan Red 3G (C.I. Acid Red 220) and Irgalan Grey BL (C.I. Acid Black 58). Similar measurements were carried out on steam-set nylon 6.6 yarns to examine the influence of presteaming conditions, steam pressure, steam quality, and variation of the steam-setting procedure. The practical implications of the results are discussed, especially with regard to uniform setting and subsequent dyeing behaviour of nylon yarns and fabrics. The effects of dry-heat and pressure-steam setting are interpreted in terms of the proposed molecular mechanism of setting, which considers especially the influence of moisture on the fine structure of nylon.

The dry heat setting of Terylene filament fabrics is considered in relation to dimensiond Stability, wet creasing, stiffness and recovery from dry creasing, and dyeing properties. The effects of aqueous heat are also discussed. Setting machines are described, and the setting conditions for Terylene fabrics outlincd.

Practical aspects of the preparation and dyeing of polyester-cotton fabrics are considered. The processes dealt with are: Singeing; desizing; scouring, including solvent scouring; bleaching; mercerising; heat setting; and dyeing. The polychromatic dyeing process is mentioned.

Crystalline content, crystalline orientation, and long period of heat-set nylon 6 fibers were investigated. Fibers subjected to dry heat setting or steam setting, have x-ray diffraction patterns which suggest that an increase of crystallinity occurs on treatment, especially in the case of steam setting. The degree of crystalline orientation does not decrease greatly in either dry heat setting or steam setting. Therefore, the increased dyeability of nylon 6 fiber on heat setting is not attributable to a decrease of orientation of crystallites. The large increase of long period produced by steam setting corresponds to the increase in density noted.

The origin and distribution of oil stains have been analysed. During the last ten years oil stains have become slightly less prevalent, but dirty knots in continuous–filament fabrics and spinning stains in spun fabrics still present a serious problem. Suggestions are made as to how the manufacturers could improve the cleanliness of filament fabrics. The main factors impeding the removal of oil stains are: long time of storage, heat setting, and inaccessibility of the dirt. The relative merits of different hand–cleaning appliances (cleaning pen, spray gun, and vibrators) are discussed, and it is stated that hand cleaning (with agitation) is much more effective than spotting with a brush. Suitable agents are suggested for spotting and pad–scouring. The paper explains how cleaning patches are formed and how to eliminate them, as well as giving the costs of the materials required. Methods and recipes for improved scouring of fabrics which have not been hand cleaned are given, and the technique of stain removal from finished cloth and from cloth finished in loomstate is described.

Two different methods of effecting modification of the fibre structure, namely, heat treatment and solvent treatment, have been investigated. Heat setting and solvent treatement led to improvement in the crystallinity of the poly(ethylene terephthalate) fibres. Pretreatment in dimethyl formamide and acetonitrile resulted in reduced tensile strength. Die Struktur von Polyethylenterephthalatfasern wurde durch Warmebehandlung bzw. Losungsmitteleinwirkung modifiziert. Beide Methoden bewirkten eine Erhohung der Kristallinitat der Fasern. Die Behandlung mit Dimethylformamid oder Acetonitril fuhrte zu einer Verringerung der Reisfestigkeit.