Analysis of warp-knitted fabric structure. Part II: theoretical study on initial modulus of warp-knitted fabrics (tricot,locknit, and satin)

In the first part of this series, a 3D straight line model was presented for the geometry of two-guide-bar warp-knitted fabrics. In this part, first, the variation of unit cell geometry under uniaxial tension in the range of elastic deformation is investigated. In the present study, the energy method and Castiglianos's theorem were used to derive the fabric's initial modulus. Energy terms which are considered in this study are extension, bending, and compression energies. Also, the friction phenomenon is taken into account by using frictional energy term. For this purpose, the loop of each bar is divided into eight elements. Free-body diagrams of elements are drawn to show the relative magnitude and direction of all forces acting upon an object in a given situation. After obtaining the force details, strain energy of each element is calculated. Finally, the initial modulus of warp-knitted fabrics is obtained. To verify the model, samples of tricot fabrics were produced and tested. Results showed that the generated model can predict precisely the initial modulus of aforementioned warp-knitted structures.     

The influence of two bar warp-knitted structure on the fabric tensile stress relaxation Part I: (reverse locknit,sharkskin, queens’ cord)

Time-dependent mechanical behavior of textiles has particular importance. One of such behaviors is the stress relaxation. If a fabric is under tension over a period of time, some of the stresses in it will be relieved. During the manufacture and application of clothing and footwear, materials experience various long-lasting deformations, and relaxation process in materials arises. For example, if medical pressure garments such as compression stockings are under tension over a long period of time, some of their stresses will be relieved, with a consequent reduction in the skin and garment interfacial pressure. Thus, with theoretical and experimental study of the factors affecting stress relaxation, the ability to design and produce appropriate clothes will be increased. The aim of this study was to investigate the effect of fabric structure on the stress relaxation of two bar warp-knitted fabrics (reverse locknit, sharkskin, queens’ cord), as well as to find the effect of strain value and loading direction on the stress relaxation of the fabrics. The results reveal that the fabric structure, strain, and loading direction are important factors affecting the stress and stress relaxation percent of the fabrics. By increasing the strain and the length of underlap in the back guide bar, stress will be increased, but stress relaxation percent will be decreased. Also, stress relaxation percent in wale direction is more than course direction for reverse locknit and sharkskin3, but this is reversed for sharkskin4 and queens’ cord. Finally, among the mechanical models used to describe the stress relaxation behavior of the fabrics, three-component Maxwell’s model with parallel-connect nonlinear spring showed the best agreement with the experimental relaxation curve of the analyzed fabrics.     

Analysis of warp-knitted fabric structure part IV: modeling the initial Poisson’s ratio in elastic deformation region

The effect of Poisson’s ratio on the mechanical properties of fabrics is undeniable. In the present study, a geometrical model for the Poisson’s ratio of two-guide-bar warp-knitted fabrics is developed, based on the presented models in the previous parts of this series. For this purpose, warp-knitted fabrics are categorized into two groups, according to their structures. Thereafter, a geometrical model is presented to predict the Poisson’s ratio of each group. To verify the generated models, theoretical results are compared with the available experimental data. The results show that the generated models are a suitable guidance to consider the Poisson’s ratio of warp-knitted fabrics.     

Analysis of warp-knitted fabric structure. Part III: theoretical study on initial modulus of warp-knitted fabrics (reverse locknit,three- and four-needle sharkskin)

In the second part of this series, tensile properties of tricot structure were investigated. Then derived model was extended to locknit and satin as first group of fully thread two-needle bar warp-knitted fabrics. In the present study, tensile properties of second group of these warp-knitted fabrics, i.e. reverse locknit and three- and four-needle sharkskin, are considered using energy method and Castigliano’s theorem. For this purpose, the difference between the tensile properties of first and the second group of warp-knitted fabrics is attributed to the movement space and friction of back bar underlaps. Similar to previous part, free-body diagrams of elements are drawn to show the relative magnitude and direction of all forces acting upon an object in a given situation. Finally, the initial modulus of second group of warp-knitted fabrics is obtained.     

The role of geometry on the viscoelastic materials properties: tensile and stress relaxation of the yarn

The time-dependent mechanical behavior of textiles has particular importance. One of such behaviors is stress relaxation. When strain is applied constantly, there is a decreased stress with time in viscoelastic materials, which is called stress relaxation. The aim of this study is to investigate the effect of knot’s geometry (surgeon, square and eight) and the number of knots on the tensile and stress relaxation properties of the polyester yarn. Significant differences were observed for the tensile characteristics of the yarn in the presence of the knot. Generally, the knotted yarns demonstrated lower tensile stress and strain at failure. Moreover, the results revealed that the stress relaxation behavior of the yarn is affected by the number of knots and their geometry. The yarn without knot exhibited the highest stress relaxation percent while the yarn with the surgeon’s knot displayed the least stress relaxation percent. On the other hand, increasing the number of knots led to a decrease in the percentage of yarn stress relaxation.     

Investigation of stretch on air permeability of knitted fabrics part II: effect of fabric structure

The structure of a fabric plays vital role in determining its air permeability. So, the study and comparison of air permeability of various fabric structures have their own significance. A detailed study is carried out here on various fabric structures to understand the effect of fabric structure on air permeability at their dry, wet and fully relaxed states. An automatic fabric stretching device has been designed and fabricated as an attachment with air permeability tester to test the air permeability of fabric samples under dynamic condition for this investigation. It is a fully automatic stretching equipment to stretch the fabric samples as per the preset value. The stretching device can be set with a predetermined degree of fabric stretch either in percentage or in mm and rate of extension also can be preset in mm per minute. From the results, it is clear that fabric structure has explicit impact on air permeability both in the unstretched and stretched states of the samples. Loose fabric structure and porous fabric structure show maximum air permeability under both sedate state and incrementally stretched states and vice versa.     

改性野蚕丝取向态与力学松弛特征研究

通过对不同用量助剂溶液处理的野蚕丝纤维取向态结构、力学松弛特征和性能等方面的研究,探讨不同用量助剂溶液对野蚕丝纤维分子运动、结构和力学特性的影响及其内在联系,为改善野蚕丝纤维服用性能提供理论依据.     

Understanding the influence of fibre,yarn and fabric parameters on UV protection of wool-knitted fabrics

This work investigated the influence of fibre, yarn and fabric parameters on the UV protection of fabrics. It proposed a model for UV interaction based on a theoretical hypothesis, targeted experimentation and statistical analysis. Undyed and untreated wool-knitted fabrics with varying mean fibre diameter, yarn linear density, yarn twist, fabric cover factor and fabric structure were examined. A statistical model was presented to report the relationship between fibre/yarn/fabric parameters and fabric UPF values. An optical model on the interaction between the UV light and a single jersey fabric was constructed to understand the penetration of UV light. The models were verified by the UV transmittance results of knitted wool fabrics. The results obtained from the statistical and optical models were used to propose a set of optimized parameters for lightweight summer/spring UV-protective knitted fabrics. Testing confirmed that these fabric parameters provided both high UV protection and good tactile comfort.     

Analysis of warp knitted fabric structure. Part V: experimental study on the initial modulus of warp knitted fabrics

In the previous parts of this series, tensile properties of warp knitted fabrics were investigated using energy method. For this purpose, the geometry of fully threaded two-guide bar structures, i.e. tricot, locknit, reverse locknit, satin and sharkskin were modeled by considering the fabric density, yarn diameter and the number of front and back bar underlaps. Then, the theoretical models for the initial modulus of aforementioned structures were obtained. In the present study, the initial modulus of actual fabrics has been calculated using presented models in previous parts. Then, a new test method was defined for tensile testing of warp knitted fabric, specifically. Thereafter, the initial modulus of prepared samples has been measured by using tensile tester in order to compare with theoretical values, based on derived test conditions. Reasonable agreements between theoretical and experimental results showed that generated models are capable to predict the initial modulus of fully threaded two-guide bar warp knitted fabrics, adequately.     

日晒对织物（纤维）色牢度和力学性能影响的研究

服装在服用过程中将经受日晒而老化,研究日晒对织物性能的影响具有重要意义。回顾和总结了日晒对织物（纤维）色牢度和力学性能影响的国内外研究,明确研究中存在的空白点和有待进一步研究的方向。     

扁平截面形状对纤维及其纤网结构的影响

纤维截面扁平化可以克服圆形截面纤维的某些缺点,赋予产品优良的性能和用途.从扁平粘胶纤维的结构性能、力学性能和纤网缠结模型分析了截面形状对纤维及其相关制品性能的影响,指出扁平粘胶纤维是一种应用前景广阔的异形纤维.     

改性羧甲基纤维素(MCMC)对聚氨酯PU防水透湿织物性能的影响研究

在用湿法生产高档防水透湿织物时,为改善成品性能,降低成本,经常要在涂覆液中添加一定量的填料如木粉、纸浆、纤维等产品.为了提高该产品透湿防水性.本实验采用改性羧甲基纤维素(MCMC)作为填充剂,制成聚氨酯PU微孔膜织物,并利用透湿杯、FX3000、TEXTESTAG测试透湿量、耐静水压等,探讨了改性羧甲基纤维素对聚氨酯PU微孔膜织物性能的影响.结果表明:以改性羧甲基纤维素为填充剂可改善织物的防水透湿性能.     

The influence of Fusarium infection and growing location on the quantitative protein composition of (Part II) naked barley (Hordeum vulgare nudum)

The effect of the fungal infection Fusarium graminearum and Fusarium culmorum on naked barley cultivars (n = 7) with respect to the barley’s total protein content and the content of the protein fractions albumins + globulins, prolamins (hordeins) and glutelins (hordenins) was investigated. A summer barley cultivar (n = 1) was used for comparison. The total protein content of the whole grain flours was very variable, ranging from 125 to 225 g kg^?1. The influence of Fusarium infection showed that the content of hordeins and hordenins was slightly reduced, while the albumins and globulins were not affected. In addition, the effect of the two different growing locations on the protein content of the naked barley was also evaluated. It could be shown that the C-hordeins, γ-hordeins and D-hordenins were significantly positively affected by increasing nitrogen supply, whereas the B-hordenin content was significantly negatively influenced. Nitrogen availability seems to be a factor that promotes gene expression for hordeins but reduces the synthesis of the main B-hordenins.     

Analysis of spinning process using the Taguchi method. Part IV: Effect of spinning process variables on tensile properties of ring,rotor and air-jet yarns

Abstract

The yarn samples prepared for migration study were tested for tensile properties. Furthermore, the effect of drafts of the spinning machines on yarn strength and breaking elongation (%) was studied. The effect of spinning position, doff position and material conditioning during testing on yarn tensile properties were also accounted for. The ring yarn was seen to have the highest tensile properties, whereas air-jet yarns the lowest. The low elastic recovery of viscose fibres is the cause of weakest and least extensible air-jet yarns.     

The influence of modified atmospheres and their interaction with water activity on the radial growth and fumonisin B(1) production of Fusarium verticillioides and F. proliferatum on corn. Part II: The effect of initial headspace oxygen concentration

This paper is the second in a series of two that describe the effect of modified atmospheres on the growth and mycotoxin production of Fusarium verticillioides and Fusarium proliferatum on corn. In this part, the effect of initial headspace (IH) oxygen concentration and its interaction with water activity (a(w)) on growth and fumonisin B(1) production was investigated. In addition, the impact of vacuum packaging and in-cooperation of O(2) scrubbing sachets was also studied. It was observed that at all a(w) values studied, reduction of IH O(2) concentration from 20 to 2% had no significant effect on the colony growth rate (g, mm d(-1)) and lag phase duration (lambda, d). However, g and lambda were positively and negatively correlated to a(w). The IH O(2) concentration was determined to have a a(w) dependent effect on the oxygen consumption rate. Although the maximum colony diameter (D(max), mm) decreased with the reduction of the IH O(2) level, the greatest mycelial density occurred at 10% IH O(2) for both isolates. This observation was accompanied by a trend of a decrease in the value of the IH O(2) level at which the most fumonisin B(1) was produced from 15 to 5% when the a(w) was decreased from 0.976 to 0.930 for F. verticillioides. For F. proliferatum the optimum conditions for fumonisin B(1) production shifted from 20% at a(w) 0.976 to 10% at both 0.951 and 0.930. Vacuum packaging and the in-cooperation of O(2) absorbing sachets completely inhibited the growth of both isolates. These results together with those reported in Part I of the study indicate that O(2) should preferably be completely excluded from modified atmospheres that are employed to protect stored corn from fungal growth and mycotoxin production.     

The response of phenylalanine ammonia‐lyase,polyphenol oxidase and phenols to cold stress in the olive tree (Olea europaea L. cv. Picual)

BACKGROUND: In this study the activities of phenylalanine ammonia‐lyase (PAL) and polyphenol oxidase (PPO) and the concentrations of hydroxytyrosol, tyrosol and oleuropein in olive tree (Olea europaea L. cv. Picual) leaves were investigated before and after cold stress by freezing. The air temperature fell to below ?7 °C and, according to the specific field conditions, four categories of orchard were selected: not cold stressed (NS), lightly cold stressed (LS), moderately cold stressed (MS) and heavily cold stressed (HS). RESULTS: In LS and MS samples the PAL specific activity at saturated substrate concentration rose 4.8‐ and 1.9‐fold respectively compared with NS samples. In HS samples the PAL activity declined by 47% compared with NS samples. A low level of PAL protein was detected in all samples affected by cold stress. In LS, MS and HS samples the PPO specific activity at saturated substrate concentration was 1.9‐, 4.4‐ and 9.8‐fold higher respectively than in NS samples. K_m values also increased after cold stress. In MS and HS samples the concentration of oleuropein was 69 and 82% higher respectively than in NS samples, while the concentrations of hydroxytyrosol and tyrosol decreased. CONCLUSION: The response of PAL activity may be part of a recovery process of the olive leaf against cold stress, while the response of PPO and oleuropein may be part of an antioxidant protection mechanism. Copyright © 2009 Society of Chemical Industry     

The influence of the herbs sage and wormwood on the migration of Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae) populations

The repellent or attractant effects of adding powdered sage, Salvia officinalis, or wormwood, Artemisia absinthium, to wheat on the migratory behaviour of the lesser grain borer Rhyzopertha dominica was investigated. Under conditions permitting the migration of adult R. dominica, the addition of powdered sage to wheat grain resulted in a lower colonisation of this substrate. It was also found that emigration from grain containing sage was very high, especially in the initial period of grain infestation. This leads to the conclusion that sage is a strong repellent. On the other hand, the addition of pulverised wormwood to wheat did not seem to cause significant mortality or migration activity. Females demonstrated a higher sensitivity to the action of herbal chemicals than males, as confirmed by their higher mortality. This resulted in a change in the sex ratio of the population.     

Influence of light exposure, ethanol and copper(II) on the formation of a precursor for xanthylium cations from tartaric acid

The production of xanthylium cation pigments was greatly increased when an aged, tartaric acid buffered, 12% (v/v) aqueous ethanol solution was used in a model white wine system. This suggested the formation of a precursor to the pigments during the ageing of the tartaric acid solution. On examining factors responsible for the generation of tartaric acid oxidation products in wine-like solutions it was observed that on exposure of samples to sunlight, glyoxylic acid, a known precursor to xanthylium cations, was produced. The production of glyoxylic acid was achieved in both the absence and presence of ethanol and copper(II). Hydrogen peroxide was also detected in these solutions. The results were consistent with the presence of glyoxylic acid in the aged tartaric acid buffered, 12% (v/v) aqueous ethanol solution that had frequent aeration and periodic exposure to sunlight throughout its storage. Studies on the role of hydrogen peroxide in the production of glyoxylic acid were also investigated. On the addition of hydrogen peroxide to tartaric acid solutions, with heating at 45°C in darkness, glyoxylic acid was only determined in solutions without ethanol.     

Effects of temperature on development of the azuki bean weevil,Callosobruchus chinensis (Coleoptera: Bruchidae) on two leguminous seeds

The azuki bean weevil, Callosobruchus chinensis L., is one of the most serious stored product pests in the world. The temperature driven stage-specific development of C. chinensis was examined at eight constant temperatures of 15.97, 18.31, 22.09, 26.15, 30.50, 34.39, 38.00, and 40.00 °C on azuki bean (Vigna angularis [Wild.] Ohwi & Ohashi) and cowpea (Vigna unguiculata L.) seeds. Parameters for stage-specific development such as threshold temperatures and thermal constants were determined by linear and nonlinear models. The total developmental time (egg - adult) decreased with increasing temperature from 14 to 38 °C on both seeds. However, total developmental time varied from 127.93 to 122.25 days at 15.97 °C to 19.31 and 19.17 days at 38.00 °C on azuki bean and cowpea seeds, respectively. The nonlinear Logan-6 and Performance models estimated optimal temperatures as 37.3, 37.0, 36.5 and 37.1 °C on azuki bean, and as 36.7, 36.4, 34.5 and 36.6 °C on cowpea for egg, larva, pupa and egg to adult, respectively. The linear model estimated the lower temperature thresholds (T_min) of egg, larva, pupa and egg to adult as 16.97, 10.47, 1.36, and 10.28 °C on azuki bean, respectively, and 16.84, 10.33, 10.92, and 9.83 °C on cowpea, respectively. The thermal constants (K) for each stage completion was 35.13, 255.21, 233.11, and 503.41° days (DD) for egg, larva, pupa, and egg to adult on azuki bean, respectively and 32.45, 246.50, 107.04, and 490.02 DD for egg, larva, pupa, and egg to adult on cowpea, respectively. Temperature also influenced the adult longevity. These findings on thermal requirements and temperature thresholds can be used to predict the occurrence, number of generations and population dynamics of C. chinensis.     

The influence of saline irrigation and organic waste fertilisation on the mineral content (N,P, K,Na, Ca and Mg) of tomatoes

Tomato plants were grown in a calcareous soil supplemented with two organic wastes (sewage sludge and epicarp-mesocarp of the almond tree fruit). They were irrigated at three levels of salinity caused by the addition of sodium chloride. N, P, K, Na, Ca and Mg were determined in the soil and tomato fruits. The treatments had a significant incidence on mineral content in fruit and soil.