Effect of slack mercerization and tension mercerization on the breaking load distribution of cotton fibers

It has been shown that the breaking load histograms of raw, slack-mercerized, and mercerized-stretched cottons can be represented by β-distributions. The breaking load distribution is positively skewed for raw cotton. The influence of slack mercerization is to make the distributions symmetric and to reduce the variability of the breaking load by the elimination of weak links. The mode of the distribution shifts toward higher breaking load upon mercerization, and this shift increases with the extent of applied stretch. For various raw and mercerized cottons, the effect of increasing the gauge length is to reduce the mean, mode, and variability of the breaking load and to make the distributions less and less asymmetric. The application of stretch to swollen fibers influences the load distribution on the side of higher load and renders the distribution asymmetric.     

Tensile properties of cotton treated with alkali metal hydroxides

The tenacity of cotton fibers treated without tension with 5N KOH at 0°C or 21°C is greater than that of fibers treated with either 5N LiOH or NaOH. In studying the effect of changes in fine structure on the strength of cotton fibers, we suggest that strength should be given as breaking load rather than as tenacity. Evidence is given indicating that crystallite length is an important factor and should be considered with degree of crystallinity and degree of orientation when explaining the increase in breaking load of cotton fibers brought about by treatment with 5N alkali metal hydroxides.     

Effect of aqueous swelling and stretching on the structure and properties of cotton

Spectacular changes in structure and properties of cotton have been found to result from swelling and stretching treatments in water. Fibers from one variety of cotton (Sudan) were swollen in water and stretched to their limit. While one lot was dried in the stretched state, another was allowed to dry in the slack condition after being subjected to stretch. The two types of treatments produced considerable changes in structural and physical properties, the stretch drying being more drastic. Enhancement of breaking load and tenacity without much loss in extensibility improved fibrillar orientation without change in crystallinity; reduction in ribbon width wall thickness and number of convolutions, etc. are some of the changes resulting from the treatment     

Analysis of cotton fiber maturity. III. A study of breaking load distribution of single fibers

Breaking load frequency distributions have been obtained at different test gauge lengths for several raw cottons differing in fiber cell wall maturity. The curve-fitting procedure for the analysis of the shape of observed breaking load histograms is described. The procedure yields several important parameters characterizing the raw cotton, such as the mean, mode, skewness, standard deviation, and the C. V. of breaking load. It is found that for all raw cottons, the observed breaking load distributions have a positive skew and are of β type. The effect of fiber maturity and the test gauge length on the shape of observed distributions has been analyzed. The effect of weak links on the variability of breaking load in raw cotton is discussed.     

Reaction of formaldehyde with cellulose in the presence of phosphoric acid

The extent and rate of reaction between cotton yarn before and after slack mercerization and slack mercerization followed by restretching and formaldehyde in the presence of various amounts of phosphoric acid (10–70% by weight) have been studied. The reaction is very rapid beyond a concentration of 45% phosphoric acid. The reaction has also been studied on mercerized cotton voile in the presence and absence of polyols and ammonium sulfate, and the effect of these substances on combined formaldehyde value and tensile strength of the fabric has been investigated.     

Effect of Lignin on the Heat and Light Resistance of Lignocellulosic Fibers

The existence of lignin in lignocellulosic fibers increases the loss in breaking tenacity and elongation of fibers when they are exposed to heat and light. Delignification by sulfonation helps to remove some of the lignin from the fibers without affecting the breaking tenacity. The delignified fibers have higher resistance to heat and light exposure compared to the raw fibers. The effect of lignin on the heat and light resistance of kenaf and cornhusk fibers with three different lignin contents was studied in comparison to cotton at various periods of heat and light exposure. The changes in the breaking tenacity, breaking elongation and yellowness of the samples were studied.

     

棉浆和木浆掺混纺醋酸纤维素纤维结构与性能的分析

对棉浆和木浆三种掺混纺比例(棉浆与木浆的掺混纺比例为0∶100,50∶50,100∶0)的醋酸纤维素纤维的结构与性能进行了测试分析。采用光学显微镜观察、纤维图形分析软件计算、X射线衍射和强伸性能测试,对比分析了三种掺混纺比例纤维的截面形态、结晶度、取向度、断裂伸长率、断裂强度以及初始模量,为棉浆与木浆掺混纺醋酸纤维素纤维的广泛应用提供了理论依据。实验结果表明:三种掺混纺比例纤维的截面形态指标无显著差异,内部晶体基本结构相同,随着棉浆与木浆掺混纺比例的增加,结晶度、取向度以及强伸性能呈现出略微增大的趋势。     

Studies on swelling of cotton fibers in alkali metal hydroxides. I. Influence of variations in fine structure on tensile behavior

A study on cotton fibers swollen slack at ambient temperature in different concentrations of LiOH and KOH indicates that fibers swollen in KOH have higher disorder. Conversion to cellulose II results from swelling in both the reagents, although, with KOH swelling, it begins at a lower concentration. Further, retention of tenacity is higher at all gauge lengths after KOH swelling. Analysis of the influence of fine structure on tensile properties showed some specificity, mainly attributable to cationic size differences of the swelling agents.     

Effect of silane treatment on physicochemical properties of lignocellulosic C. indica fiber

Present work deals with the mercerization of Cannabis indica fibers and their subsequent surface modification by aminopropyl triethoxysilane. The reaction parameters like time and concentration of the sodium hydroxide for mercerization were optimized. C. indica fibers treated with different silane concentration solutions were subjected to evaluation of some of their properties like swelling behavior in different solvents, moisture absorbance under different humidity levels, and resistance toward chemicals such as sodium hydroxide and hydrochloric acid. C. indica fibers treated with 2% aminopropyl triethoxysilane solution have been found more resistant toward moisture, water, and chemicals when compared with that of untreated fibers. Morphological, structural changes, thermal stability, and crystallinity of both silane treated and mercerized fibers have been studied by SEM, FTIR, TGA, and XRD techniques. Silane treatment has been found to cause decrease in crystallinity but increase in the thermal stability of the fibers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

FTIR spectroscopic study of the effect of microwave heating on the transformation of cellulose I into cellulose II during mercerization

Fourier transform infrared (FTIR) spectroscopy techniques were used in the study of the effect of microwave (MW) heating on the structural properties of cotton fibers and on the mercerization mechanism of these fibers. Samples of the fibers were microwave heated for different times and different microwave powers. Also, mixtures of cotton fibers and aqueous solution of NaOH with different concentrations were exposed to microwave radiation for different times and different powers. It was found that microwave heating of cotton fibers under these experimental conditions causes no observable changes in their spectral features apart from slight changes in the intensities of the absorption bands. The determined values of the absorbances ratio A1375 cm^?1/A2900 cm^?1 revealed that microwave heating for short periods and at low powers decreases the crystallinity of cotton as the result of the drying effect of microwave heating, while microwave heating for longer periods and at higher power results in recristallyzation of the fibers. The analysis of the experimentally obtained data revealed that microwave heating that causes molecular motions by migration of ions and rotations of the dipoles produces no considerable effects on the mechanism of mercerization but only reduces the concentration of NaOH in the solution and the time of treatment which are needed for the complete transformation of cellulose lattice type I into cellulose lattice type II without any heating. Also it was found that the magnitude of reductions depends on the applied power. Moreover the results proved that the deconvolution and the second derivatives of the FTIR spectra of cotton fibers can be used as a useful tool for distinguishing cellulose lattice type II from cellulose lattice type I. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Reaction of formaldehyde with cellulose in the presence of sulfuric acid

The extent and rate of reaction between cotton yarn before and after slack mercerization and slack mercerization followed by stretching and formaldehyde, in the presence of various amounts of sulfuric acid (5–60% by weight) were studied. Beyond a concentration of 45% sulfuric acid, the reaction takes place very rapidly, and an explanation is put forward in terms of the extent of swelling of the fiber in sulfuric acid solutions. The reaction was also studied in the presence of glycerin, when the combined formaldehyde value is shown to decrease with an increasing concentration of glycerin.     

Graft copolymerization of acrylamide on cotton cellulose in a limited aqueous system following pretreatment technique

Graft copolymerization of acrylamide on cotton (dialdelyde cellulose, DAC) fibers and fabrics was studied in a limited aqueous system using K₂S₂O₈ as the initiator. Grafting parameters under different sets of conditions were determined and the mechanism of graft copolymerization discussed. Optimum conditions for grafting were established and the effect of polyacrylamide grafting on tenacity, modulus, breaking elongation, and stiffness of the cotton (DAC) fabrics and on their dyeability and moisture regain properties were also studied; 9–10% grafting of polyacrylamide on (DAC) fabric at _pH 7–10 imparts an improved balance in its mechanical and other properties. © 1995 John Wiley & Sons, Inc.     

Enhanced enzymolysis of never-dried cotton fibers belonging to different species

Enzymolysis of cotton cellulose in their never-dried state, belonging to all the four cultivated species of cotton, was carried out with the enzyme derived from penicillium funiculosum F₄. Hydrolysis to reducing sugars was almost complete for all the cottons in 6 h, though glucose percentage varied. X-ray characterizations of the residues obtained, which were both after enzyme and acid hydrolysis, showed significant differences between both hydrolyses, as well as differences in the behavior of different cotton fibers towards enzyme action. These differences have been attributed to the different structural organization of cellulose in the secondary cell wall of cotton fibers.     

Studies on swelling of cotton fibers in alkali metal hydroxides. II. Influence of morphology and fine structure on tensile behavior

Cotton fibers varying widely in gravimetric fineness but having nearly same percentage mature fibers have been subjected to swelling in 4.5N LiOH, NaOH, and KOH at room temperature and 0°C. The resultant changes in fine structure are analyzed by X-ray diffraction and infrared absorption methods while variations in surface morphology are followed by scanning electron microscopy. Extent of swelling measured by changes in gravimetric fineness follows the order LiOH ≥ NaOH ≥ KOH, the exact gradation being dependent on the variety. Analysis of tensile data shows that whereas moderate swelling leads to an increase in tenacity at 3.2 mm gauge length, excessive swelling leads to a decrease of the same, the extent of decrease being a function of swelling. KOH treatment produced uniform swelling and gave better retention of T₀ and T₃ for all varieties. Tensile behavior after slack swelling in the various reagents could be interpreted on the basis of fine structural variations produced by them. However, the differential response of cottons to a swelling agent is explained by postulating variations in the packing of structural elements along the radii.     

Antibacterial functionalization of cotton fabrics by electric‐beam irradiation

An N‐halamine precursor monomer, 2,2,6,6‐tetramethylpiperidinyl acrylate (TMPA), was synthesized and successfully grafted onto cotton fibers via an impregnation process (IP) and electron‐beam irradiation (EB). The grafted cotton fibers could provide antibacterial efficacy after chlorination through a dilute sodium hypochlorite solution. The antibacterial efficacy was challenged against Staphylococcus aureus and Escherichia coli. The cotton fibers grafted with TMPA and acrylic acid by EB inactivated all of the bacteria within 30 min of contact, whereas the samples grafted with TMPA via an IP could not completely kill the bacteria with 60 min. The breaking strength and UVA light stability also improved significantly. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42023.     

Resistance of Valonia cellulose to mercerization

The mercerization behavior at 20°C. of Valonia macrophysa cellulose of Japanese origin was investigated by x-ray, moisture regain, and infrared spectrographic methods. The NaOH concentration range necessary for mercerization was 16–20%, which is higher than those required for wood pulp (8–11%), ramie or cotton (11–14%), and even the animal cellulose, Tunicin (14–16%). Treatment with the alkaline solution of the ordinary concentration (17.5%) for 4 days could not mercerize it, and even mercerization with a 19% solution brought about the presence of the reflection from (101)_II along with those from (101 )_I and (101)_I after regeneration. Such a high resistance to mercerization of the Valonia cellulose may be due to its larger crystallite size rather than the crystalline content.     

X‐ray diffraction methods in the study of the effect of microwave heating on the transformation of cellulose I into cellulose II during mercerization

X‐ray diffraction (XRD) techniques were used in the study of the effect of microwave (MW) heating on the structural properties of cotton celluloses I and II and on the mercerization mechanism of cotton fibers. Samples of celluloses I and II were MW heated at 900 W for different times ranging from 10 to 40 min. The obtained data revealed that MW heating of cellulose II in opened glass tubes produces no significant effects on the resolution of its XRD patterns, whereas the most evident effects occur when cotton fibers (cellulose I) are heated in opened tubes at 900 W for 10 and 20 min. Also, mixtures of cotton fibers and aqueous solution of NaOH with different concentrations were exposed to MW radiation for different times and different powers. It was found that MW heating has no considerable effects on the mechanism of transformation of cellulose I into cellulose II during mercerization. On the other hand, MW heating of cotton fibers during mercerization reduces the values of concentration of NaOH in the aqueous solution and the time of treatment that are needed for the complete transformation of cellulose lattice type I into cellulose lattice type II without any heating. Also it was found that the magnitude of reductions depends on the applied power. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Structure‐mechanical properties relationship of poly(ethylene terephthalate) fibers

The correlation between the fiber structure and mechanical properties of two different poly(ethylene terephthalate) fiber types, that is, wool and cotton types produced by three producers, was studied. Fiber structure was determined using different analytical methods. Significant differences in the suprastructure of both types of conventional textile fibers were observed, although some slight variations in the structure existed between those fibers of the same type provided by different producers. A better‐developed crystalline structure composed of bigger, more perfect, and more axially oriented crystallites was characterized for the cotton types of PET fibers. Crystallinity is higher, long periods are longer, and amorphous domains inside the long period cover bigger parts in this fiber type in comparison with the wool types of fibers. In addition, amorphous and average molecular orientation is higher. The better mechanical properties of cotton PET fiber types, as demonstrated by a higher breaking tenacity and modulus accompanied by a lower breaking elongation, are due to the observed structural characteristics. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3383–3389, 2003     

Thermal behavior of cellulosic graft copolymers. II. Cotton grafted with binary mixtures of vinyl acetate and methyl acrylate

Thermal degradation of cotton, mercerized cotton, cotton grafted with vinyl acetate-methyl acrylate mixtures at different compositions, and mercerized cotton grafted with vinyl acetate–methyl acrylate mixture at a composition of 60 : 40 has been investigated using the techniques of thermogravimetric analysis (TGA) and differential thermal analysis (DTA) in nitrogen. The kinetic parameters E, n, and A have been obtained following several methods of thermogravimetric analyses. The mercerization shows a little effect upon thermic properties of cotton cellulose, making cotton thermally more stable. Graft copolymerization of vinyl acetate-methyl acrylate mixture makes cotton thermally less stable if the composition of the copolymer grafted is 100, 90, and 70 mol % VA, while in the case of cellulose graft copolymers with compositions of VA–MA of 80 : 20, 20 : 80, 5 : 95, and 0 : 100 the thermal stability is higher than that of original cotton. The thermal stability of the mercerized cotton grafted with vinyl acetate-methyl acrylate mixture with a composition of 60 : 40 depends on the percent grafting yield. The thermal stability of mercerized cotton grafted with the monomer mixture is higher than that of cotton grafted with that monomer mixture. The degradation of cellulose and cellulose graft copolymers is complex as is shown by DTA thermograms and kinetic parameters.     

聚丙烯高强丝防老化母粒的研制和应用

：将加入了防老化母粒的聚丙烯高强丝进行人工加速老化试验和户外大气暴露试验,讨论了防老化母粒在高强丝上的应用。结果表明：添加２％的防老化母粒,经１年的户外大气暴露试验,聚丙烯高强丝的断裂强度保持率高达８０．２％,断裂伸长保持率达７９．０％;而未加防老化母粒的聚丙烯高强丝,户外暴露５个月,断裂强度保持率降至４６．７％,断裂伸长保持率降至３６．４％。同时还对添加防老化母粒与使用耐候级聚丙烯专用料的耐候性、不同母粒添加量的耐候性做了对比。