Characterization of the Internal Pore Structures of Cotton and Chemically Modified Cottons by Gel Permeation

Abstract

The pore structures of cotton and formaldehyde-modified cottons have been characterized by applying the principles of gel permeation to chro-matographic columns formed of the finely divided fibrous cottons. Measurements were made of the relative elution volumes of suitable solutes which cover a range of known, discrete molecular weights. The solutes chosen were sugars ranging in molecular weight from 198 to 738, the elution volumes of which are in an inverse linear relationship to their molecular weights. Extrapolations of this linear relationship provide measures of the effective internal solvent volumes and the permeability limits of the cotton celluloses. Changes in these parameters are indicative of the nature and extent of the alterations of the pore structure produced by cross-linking.

Marked differences have been found in the pore structures of cotton cross-linked to progressively higher levels with the fibers in a collapsed state by a bake-cure process and with the fibers in a semidistended state by reaction in an acetic-hydrochloric acid medium. The technique will be useful for relating changes in pore structure to the modifications of physical and performance characteristics of fabrics produced by various chemical treatments.     

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.     

Zwitterions of 1-poly(oxyethylene)-2-imidazoline derivatives as anti-electrostatic agent for polyamide fiber

Summary This paper describes a group of anti-electrostatic agents 1 for polyamide fiber(Nylon 6). Agents 1 are calcium imidazolinium-carboxylates having poly(oxyethylene) chain and long alkyl group (C₁₁H₂₃ and C₁₇H₃₅). Eight derivatives of 1 were prepared by a four-step one-pot synthesis shown in Scheme 1. Nylon 6 fibers and films containing some of 1 (1.0 and 2.0 wt%) show improved anti-electrostatic property. The performance of 1 was increased by the increase of the length of poly(oxyethylene) chain.     

Partial specific volume of thermotropic polybibenzoates with different spacers

Summary Partial specific volume (v ₂ ^o ) of polybibenzoates with all-methylene and oxyethylene spacers have been determined in chloroalifatic solvents. The polybibenzoate with a heptamethylene spacer exhibits a more expanded state than the ones with one, two and three oxyethylene units in the spacer. A solvent effect on v ₂ ^o has been observed. Nevertheless, the values of v ₂ ^o in tetrachloroethane are in accord with the calculated by group contributions from rubbery polymers.     

Effect of plasma pretreatment on the wrinkle‐resistance properties of cotton fibers treated with a 1,2,3,4‐butanetetracarboxylic acid–sodium hypophosulfite system with titanium dioxide as a cocatalyst

A 1,2,3,4‐butanetetracarboxylic acid (BTCA)–sodium hypophosulfite (SHP) wrinkle‐resistance system played an important role in improving the wrinkle‐resistance properties of cotton fibers. In this study, titanium dioxide (TiO₂) was used as a cocatalyst to further enhance the wrinkle‐resistance properties of BTCA–SHP‐treated cotton fabrics, that is, those treated with (1) 5% BTCA and 10% SHP; (2) 5% BTCA, 10% SHP, and 0.1% TiO₂; and (3) 5% BTCA, 10% SHP, and 0.2% TiO₂. In addition, the effect of plasma as a pretreatment process on the wrinkle‐resistance properties of the three treatment systems was also studied. The experimental results reveal that the wrinkle‐resistance properties of cotton fibers were improved after different wrinkle‐resistance treatments. In addition, the plasma pretreatment further enhanced the wrinkle‐resistance treatments to different extents, depending on the process parameters. Scanning electron microscopy images confirmed that such plasma pretreatment conditions imparted the best crosslinking effect on the cotton fibers. However, the wrinkle‐resistance‐treated cotton specimens had lower tensile strength and tearing strength values compared to the control sample, whereas the plasma pretreatment and cocatalyst may have compensated for the reduction in the mechanical strength caused by the wrinkle‐resistance agents. In this article, the optimum conditions for the plasma pretreatment on the basis of the result of the wrinkle‐recovery angle were analyzed with an L₉(3)³ orthogonal array testing strategy technique. The results showed that plasma treatment conditions with (1) a 10 mm/s speed, (2) a 0.1 L/min oxygen flow rate, and (3) a 4‐mm jet‐to‐substrate distance together caused a significant improvement in the wrinkle‐resistance properties of the cotton fibers treated with the three different BTCA treatments. Moreover, the treatment speed was the dominant factor, followed by jet‐to‐substrate distance and oxygen flow rate, in affecting the extent of improvement. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Cellulose crystallite sizes in diploid and tetraploid native cotton

Cellulose crystallite sizes in directions perpendicular to (101), (101 ), and (002) planes, have been estimated from X-ray powder diffraction patterns. The diffraction peaks were resolved using the FIT X-ray diffraction data analysis program (written by SOCABIM, Siemens DIFFRAC AT Software System, Siemens, Germany). The complete data for all the three equatorial planes was analyzed for 2θ, d values, full width at half-maximum (FWHM), and the normalized area under the three diffraction peaks, for seven cotton cultivars grown at four different locations in India in different crop years. The mean crystallite sizes were determined using the Scherrer equation. The reference standard included degummed and purified ramie fibers for relative crystallinity estimation in cotton cultivars. It has been observed that, though the computed crystallite sizes corresponding to (101), (101 ), and (002) planes vary within individual varieties with location and year of growth, the combined average crystallite size corresponding to (101) and (101 ) planes taken together for individual varieties from all locations and crop years is close to the combined average crystallite size corresponding to the (002) planes, irrespective of the species of cotton. The values of the average relative crystallinity with respect to highly oriented degummed and purified ramie fibers of individual varieties from all locations and crop years do not significantly vary between varieties and species of cotton. It is visualized that variations in crystallite sizes arise as a result of the differences in the amount of cellulose synthesized within fibers of individual varieties and their disposition within the matrix of their developing fibers. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 2107–2112, 1998     

Synthesis, characterization and electrostatic dissipating ability of poly(oxyethylene) block polyesteramides

Poly(oxyethylene)diamines were included in the copolymerization of ethylene glycol and dicarboxylic acids, such as terephthalic, adipic and sebacic acid, to produce a series of hydrophilic polyether-ester-amides. With the addition of poly(oxyethylene)diamines (average molecular weight of 2,000) to PET in the amounts of 3.2, 6.6, 12 and 16 wt%, melting points of these polymers dropped accordingly, from 240 °C to around 227 °C, and the electronic resistivity decreased from 1×10¹³ to approximately 8×10⁸ ohm/sq. For comparison, the introduction of hydrophilic PEG-2000 or a low molecular weight diamine, such as triethyleneglycol diamine, has less effect on electronic resistivity. Molecular weight, polymer rigidity and ageing are other factors affecting the surface resistivity. The degree of hydrophilicity was measured by the moisture absorption of the fibers made from these polyether-ester-amides. A weight gain of 0.96% was observed for 12 wt% poly(oxyethylene)diamine modified polyether-ester-amides in comparison with 0.40% for the unmodified polyethylene terephthalate). These results are explained by a mechanism involving moisture absorption on the polymer surface through the formation of hydrogen bonding with amide and-(OCH₂CH₂)-functionalities on the polymer surface.     

Crystallinity and fusion of low molecular weight α, ω-alkoxy-poly(ethylene oxide): methoxy to octadecoxy end-groups

Samples of α,ω-alk oxy-poly (ethylene oxide) with oxyethylene inner blocks of 70 to 150 chain atoms and end blocks ranging from C₁ (methoxy) to C₁₈ (octadecoxy) have been prepared and characterized. Several experimental methods have been used to investigate their crystalline structure and melting behaviour. The polymers crystallize into stacked structures in which crystalline and non-crystalline layers alternate. The methylene chains are in the non-crystalline layers together with a significant fraction (about 0.2) of the oxyethylene inner block. The crystalline layers contain extended or folded oxyethylene chains, depending upon the relative lengths of the inner and end blocks. The melting points either are roughly independent of methylene block length (extended-chain crystals) or increase with methylene block length (folded-chain crystals). This melting behaviour is explained by a combination of two important effects: conformational restriction of the cilia emerging into the non-crystalline layer and mixing of the methylene and oxyethylene chains in the melt.     

Effect of mode of agent removal on pore structure of liquid ammonia treated cotton cellulose

The pore structures of three liquid-ammonia-treated cottons were compared via a reverse gel permeation chromatographic technique. Cotton battings were treated with liquid ammonia which was removed by volatilization at ambient temperature or at elevated temperature and by water exchange. Three series of water-soluble solutes were used to study the elution characteristics of whole fiber columns prepared from these battings. The solutes were oligomeric sugars, ethylene glycols, and glymes (ethylene glycol dimethyl ethers) having molecular dimensions in the range of conventional finishing agents for cotton. All three liquid ammonia treatments increased the internal pore volumes accessible to small molecules. The greatest increase was noted when the ammonia was removed by water exchange and the least when volatilization at elevated temperature was employed. Ambient temperature volatilization had an intermediate effect. Decreases in the volumes of large pores were effected by ammonia treatments followed by volatilization at ambient or elevated temperature. Water exchange of the ammonia resulted in an increase in the volume of large pores as well as of the small pores.     

Investigation of Properties of Polymer/Textile Fiber Composites

Polymer-based composite structures have advantages over other materials. The most important advantage is the higher mechanical properties obtained from the composites when supported by fiber reinforcement. The mechanical and thermal properties of fiber-reinforced composite structures are affected by the amount of fibers in the structures, orientation of the fiber and fiber length. Silk and cotton fibers are used in many fields but especially in clothing and textiles. However, there is not enough research on their usage as reinforcement fibers in composite structures. Silk fibers as a textile material have better physical and mechanic properties than other animal fibers. It is very important that the improvement of the mechanical and physical properties of the composite structures allows them to be used in many areas. From economical, technological and environmental points of view, the improved the mechanical and physical properties of polymeric materials are receiving much attention in the recent studies.

In this study, various lengths (1 mm–2.5 mm and 5 mm) of waste silk and waste cotton fibers were added to high-density polyethylene (HDPE) and polypropylene (PP) polymer in the mixing ratios of (polymer:fiber) 100%:0%, 97%:3%, and 94%:6% to produce composite structures. On the other hand, known lengths (1–2.5–5 mm) of waste silk and waste cotton fibers were added to recycled polyamide-6 (PA₆) and polycarbonate (PC) polymers in mixing quantities of 100%-0%, 97%-3%. A twin-screw extruder was employed for the production of composites. Tensile strength, % elongation, yield strength, elasticity modulus, Izod impact strength, melt flow index (MFI), heat deflection temperature (HDT), and Vicat softening temperature properties were determined. In order to determine the materials' thermal transition and microstructure properties, differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) were used. Results have shown that cotton and silk fibers behave differently than in the composite structure. Waste silk fiber composites give better mechanical properties than waste cotton fiber.     

Antistatic modification of synthetic fibers by blend-spinning of polymers containing zwitterionic antistatic modifiers and their copolymers

New poly(oxyethylene) derivatives (S-betaine) having a zwitterionic structure of ammoniumsulfonate were prepared by the reaction of oxirane (EO) adducts of stearylamine with sodium chloromethanesulfonate and examined as blending antistatic modifiers for poly(ethylene terephthalate) (PET) and polyamide 6 (PA6) fibers. The blend PET and PA6 fibers containing 2.0 wt.-% of S-betaine exhibited a decreased half-life time of leakage of electrostatic charge (t_1/2) and a surface area resistivity (R_s) compared with those of the control PET and PA6 fibers. However, their antistatic properties were almost lost after repeated washings, because of the extraction of the agents. To increase the resistivity to washing, copolyester-type modifiers comprising both S-betaine and poly(ethylene glycol) were synthesized and incorporated into PET fibers. It was found that the antistatic properties of the blend PET fibers obtained can be retained even after dyeing and repeated washings.     

Synthesis of carbon nanocoils on substrates made of plant fibers

Carbon nanocoils (CNCs) with different shapes and coil diameters have been synthesized on three kinds of substrates made of plant fibers, i.e. tissue, cotton cloth and bamboo fiber cloth, using Fe₂ (SO₄)₃/SnCl₂ catalyst by a thermal chemical vapor deposition method. The average coil diameters of the CNCs on the tissue, cotton cloth and bamboo fiber cloth substrates are 560, 183, and 510 nm, respectively. It is found that the organization difference in the plant fiber substrates results in the difference in the aggregation states of catalyst particles on the fiber surfaces, which has a crucial effect on the morphology and production of the grown CNCs. The tight organization of the carbon fibers in the tissue and cotton cloth substrates can promote the catalyst aggregations to fabricate high yield CNCs. For the bamboo fiber cloth substrate, a relatively small number of catalyst particles are deposited on the surface and tend to be isolated, leading to the growth of a certain amount of the carbon nanofibers and carbon nanotubes. In addition, the catalyst adsorption ability of the bamboo fiber can be improved by coating calcium chloride particles to achieve high production of the regular CNCs.     

Diffusion of gases and vapors through methacrylates with oxyethylene units in the pendent chain

The diffusion of He, Ar, O₂, N₂, CO₂, CH₄, CH₃CH₃ and CH₂CH₂ has been determined in three polymethacrylates with one, two and three oxyethylene units as side chains. For these three rubbery polymers we have used the acronyms PEEMA, PDEMA and PTEMA, respectively. The results have been compared to those of poly(ethyl methacrylate) on one hand, and on the other with previous results on methacrylates of varying length alkyl side chains. It has been found that the oxyethylene units side chains methacrylates show diffusion coefficients which are slightly lower than those methacrylates bearing alkyl side chain, when comparing polymers with the same number of atoms in the side chain. These diffusion data are put in relation to relevant structural features such as the glass transition temperature and the fractional free volume of both families of rubbery methacrylates.     

X-ray studies of regenerated cellulose fibers wet spun from cotton linter pulp in NaOH/thiourea aqueous solutions

Regenerated cellulose fibers were fabricated by dissolution of cotton linter pulp in NaOH (9.5 wt%) and thiourea (4.5 wt%) aqueous solution followed by wet-spinning and multi-roller drawing. The multi-roller drawing process involved three stages: coagulation (I), coagulation (II) and post-treatment (III). The crystalline structure and morphology of regenerated cellulose fiber was investigated by synchrotron wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) techniques. Results indicated that only the cellulose II crystal structure was found in regenerated cellulose fibers, proving that the cellulose crystals were completely transformed from cellulose I to II structure during spinning from NaOH/thiourea aqueous solution. The crystallinity, orientation and crystal size at each stage were determined from the WAXD analysis. Drawing of cellulose fibers in the coagulation (II) bath (H₂SO₄/H₂O) was found to generate higher orientation and crystallinity than drawing in the post-treatment (III). Although the post-treatment process also increased crystal orientation, it led to a decrease in crystallinity with notable reduction in the anisotropic fraction. Compared with commercial rayon fibers fabricated by the viscose process, the regenerated cellulose fibers exhibited higher crystallinity but lower crystal orientation. SAXS results revealed a clear scattering maximum along the meridian direction in all regenerated cellulose fibers, indicating the formation of lamellar structure during spinning.     

Synthesis and application of cotton‐based chelate fibers grafted with poly(1‐vinyl‐1,2,4‐triazole) side chains

Cotton‐based chelate fibers grafted with poly(1‐vinyl‐1,2,4‐triazole) (PVTAZ) side chains were synthesized facilely by ozone‐induced graft polymerization of 1‐vinyl‐1,2,4‐triazole (VTAZ) monomer onto cotton fibers. The synthesis conditions were optimized to improve the yield and mechanical strength of the products. The obtained cotton‐g‐PVTAZ fibers were characterized and evaluated for batch adsorption of heavy metal ions from aqueous solutions. The maximum adsorption capacity of Ag(I), Pb(II), and Cu(II) on the fibers at pH 6.8 was 522, 330, and 184 mg/g, respectively. At 30% graft yield, the Young's modulus of cotton fiber increased about 26.5%, and its adsorption capacities of Ag(I), Pb(II), and Cu(II) increased about 2.6, 1.9, and 1.4 times, respectively. After washed with 0.1 mol/L HNO₃ solutions, the adsorbed metal ions were eluted, and the regenerated cotton‐g‐PVTAZ fibers could be used repeatedly for water treatment. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41617.     

Wetting properties of nonionic surfactants of homogeneous structure C12H25(OC2H4)xOH1

The wetting of cotton skeins by aqueous solutions of individual surfactants of structure C₁₂H₂₅(OC₂H₄ )_XOH, where x = 4-8, with homogeneous head groups, and of a Poisson distribution mixture containing an average of 5.5 oxyethylene groups, has been measured at various temperatures using the Draves technique. An individual compound with a homogeneous polyoxyethylene head group is a more effective wetting agent than a Poisson distribution mixture with the same average number of oxyethylene units. Loglog plots of wetting time vs surfactant concentration are linear in the concentration range of 0.25 to 1 g/L. The best wetting agents at any temperature have slopes in the -1.5 to -1.6 range and Y-intercepts from +0.6 to +0.7. Wetting in these systems appears to be diffusion-controlled. The wetting time at 1 g/L concentration is a measure of the wetting effectiveness of the surfactant, because it is roughly inversely proportional to the diffusion constant of the surfactant at that concentration. For materials 30 C or more below their cloud point, temperature increase causes an increase in wetting effectiveness. As the cloud point of the surfactant solution is approached, however, both the slope and the Y-intercept of the log-log plot of wetting time vs surfactant concentration change sharply. The absolute value of the negative slope decreases and the positive value of the Y-intercept increases, resulting in greatly reduced wetting effectiveness.     

Single step room temperature oxidation of poly(ethylene glycol) to poly(oxyethylene)-dicarboxylic acid

Poly(oxyethylene)-dicarboxylic acids were obtained in high yields by room temperature oxidation of poly(ethylene glycol)s of molecular weights in the 4000–100,000 range using Jone's reagent (CrO₃ and H₂SO₄) as the oxidizing agent. Oxidation by-products from the reaction mixture were eliminated by adsorbing chromium salts onto activated charcoal. The acid values of poly(oxyethylene)-dicarboxylic acids so synthesized were in agreement with the theoretical values. Poly(oxyethylene)-dicarboxylic acids were characterized by ¹H-NMR, IR spectroscopy. Spectral data were in agreement with the proposed structures of products. In summary, a convenient, one pot method for the synthesis of a wide range of poly(oxyethylene)-dicarboxylic acids was developed. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 883–890, 1998     

Facile synthesis of flexible and free-standing cotton covered by graphene/MoO2 for lithium-ions batteries

It is necessary to build flexible and free-standing materials for flexible/wearable electronics in high-performance lithium-ions batteries. Herein, we design and fabricate a flexible and free-standing 3 D carbon/MoO₂ composite through a facile immersing method followed by an annealing process. The carbon framework is supported by non-woven cotton totally covered by graphene sheets. The nanosized MoO₂ particles were uniformly anchored on cotton fibers and graphene sheets. The structure has several advantages, such as an interconnected 3D electronically conductive network, plenty of channels for electrolyte solution cross, and more active points for the electrode reaction. Compared with cotton/MoO₂ (C/MoO₂) without graphene sheets, the CGN/MoO₂ composite (cotton covered by graphene/MoO₂) showed much better thermal stability and excellent cycling performance. The proposed synthesis process paves a new way as promising electrode materials for high power battery applications such as roll-up displays and wearable devices.     

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。     

Thermoreversible hydrogels. XIX. Synthesis and swelling behavior and drug release behavior for the N‐isopropylacrylamide/poly(ethylene glycol) methylether acrylate copolymeric hydrogels

A series of thermosensitive copolymeric hydrogels were prepared from various molar ratios of N‐isopropylacrylamide (NIPAAm) and poly(ethylene glycol) methylether acrylate (PEGMEA_n), which was synthesized from acryloyl chloride and poly(ethylene glycol) mono methylether with three oxyethylene chain lengths. Investigation of the effect of the chain length of oxyethylene in PEGMEA_n, and the amount of the PEGMEA_n in the NIPAAm/PEGMEA_n copolymeric gels, on swelling behavior in deionized water was the main purpose of this study. Results showed that the swelling ratio for the present copolymeric gels increased with increasing chain length of oxyethylene in PEGMEA_n and also increased with increase in the amount of PEGMEA_n in the copolymeric gels. However, the gel strength and effective crosslinking density of these gels decreased with increase in swelling ratio. Some kinetic parameters were also evaluated in this study. Finally, the drug release and drug delivery behavior for these gels were also assessed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1683–1691, 2003