Influence of noncontractile motion of plasmalemma upon cotton fiber cell wall structure

Unusual noncontractile motion in vivo within the fibers growing on cotton ovules was found for four cotton genotypes. Structural investigations have shown that, in addition to the active motion related to fiber cell growth, a simultaneous spiral rotation of the cytoplasmic membrane occurs. Due to translational growth of the fiber cell apices and spiral rotation of plasmalemma, the fibers of cotton cultivars take on a twisted, corkscrew-like external shape. Optical microphotos illustrate the formation process of the fiber cell wall at different stages of growth and noncontractile motion in cotton fiber cells.     

Morphological changes of twisted nylon 66 and poly(ethylene terephthalate) monofilaments

A comparison of the x-ray diffraction from twisted nylon 66 and poly(ethyleneterephthalate) monofilaments is made with the scatter predicated by a model assuming an affine deformation of the fiber. The x-ray diffraction of the model is characterized by an approximately constant intensity over the entire range of the azimuthal dispersion. With twisted nylon 66 fibers the (010) reflection is split into a bimodal intensity distribution about the equator, while the (100) reflection maintains a distinct maximum on the equator. It is proposed that this difference is due primarily to the fact that a plastic deformation involving rotation of crystal planes occurs more readily when the shear stress acts in [010] direction than in the case when it acts in the [100] direction. A similar behavior is found with poly(ethylene terephthalate) fiber.     

Controlled and scalable torsional actuation of twisted nylon 6 fiber

Large‐scale torsional actuation occurs in twisted fibers and yarns as a result of volume change induced electrochemically, thermally, photonically, and other means. A quantitative relationship between torsional actuation (stroke and torque) and volume change is here introduced. The analysis is based on experimental investigation of the effects of fiber diameter and inserted twist on the torsional stroke and torque measured when heating and cooling nylon 6 fibers over the temperature range of 26–62 °C. The results show that the torsional stroke depends only on the amount of twist inserted into the fiber and is independent of fiber diameter. The torque generated is larger in fibers with more inserted twist and with larger diameters. These results are successfully modeled using a single‐helix approximation of the twisted fiber structure. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1278–1286     

The bonding of a hydroxy-functional organophosphorus oligomer to nylon fabric using the formaldehyde derivatives of urea and melamine as the bonding agents

In this research, we studied the mechanism of bonding a hydroxy-functional organophosphorus oligomer (HFPO) to nylon 6.6 fabric using the formaldehyde derivatives of urea and melamine, including dimethyloldihydroxyethyleneurea (DMDHEU) and trimethylolmelamine (TMM), as the bonding agents. The nylon fabric treated with HFPO/DMDHEU or HFPO/TMM retained significant amount of phosphorus after multiple launderings. The laundering durability of the HFPO applied to nylon was probably attributed to the formation of a crosslinked polymeric network on the nylon fiber. The nylon fabric treated with HFPO/DMDHEU showed higher percent phosphorus retention than that treated with HFPO/TMM. The percent phosphorus retention of the treated nylon increased as the DMDHEU or TMM concentration was increased, and the nylon fabric's stiffness follows the same trend. The micro-scale combustion calorimetry and thermal analysis data indicate that the HFPO bound to nylon reduced peak heat release rate and heat release capacity of the nylon fabric, decreased decomposition temperature and promoted the char formation of the treated fabric. The nylon/cotton blend military fabric treated with HFPO/DMDHEO or HFPO/TMM demonstrated flame retardant performance after 10 laundering cycles.     

Crystal structure of nylon 12

The crystal structure of nylon 12 prepared by polymerization of dodecalactam has been determined by x-ray diffraction. Nylon 12 fiber exhibits only the γ form as its stable crystal structure. The unit cell of nylon 12 was determined with the aid of the x-ray diffraction pattern of a doubly oriented specimen. The unit cell is monoclinic with a = 9.38 Å, b = 32.2 Å (fiber axis), c = 4.87 Å and β = 121.5° and contains four repeating monomer units. The chain is planar zigzag for the most part but is twisted at the position of amide groups, forming hydrogen bonds between neighboring parallel chains. The chain conformation is similar to that of the γ form of nylon 6 proposed by Arimoto. It was deduced from the calculations that there are two chain conformations statistically coexistent according to the direction of twisting. In each conformation, hydrogen bonds are formed between parallel chains to make pleated sheetlike structures. The sheets are nearly parallel to (200) and in the sheet the directions of the neighboring chains are antiparallel, as is the case with nylon 6.     

Studies of tensile failure in oriented polymeric fibers by quantitative fractography

For some fibers, such as the nylon monofilaments studied here, quantitative information may be obtained from scanning electron micrographs of fracture surfaces. On these surfaces the segment of the cross section that supports the load at the instant of rupture is seen distinctly, and its area can be measured. Normalizing breaking load by this area provides a breaking stress characteristic of the final supporting segment. “Ultimate” breaking stresses calculated in this way indicate (i) For notched filaments, the ultimate breaking stress is almost constant with notch depth and also with strain rate. (ii) For un-notched filaments, there is an increase of breaking load with strain rate, due in part to the extent of the slow cleavage that precedes failure; however, the ultimate breaking stress increases as rate of strain decreases. These two findings are incompatible with mechanisms of failure based on growth of microcracks by heat- and stress-activated chain breakage. A possible explanation involves rearrangement of microfibrils within the fiber which alters their strength distribution. (iii) The apparent strength reduction on wetting nylon filaments in water is due to a faster rate of growth of the slow-cleavage area; the ultimate breaking stress is unchanged, except at high rates of strain.     

Melting behavior and morphology of drawn nylon 6

Thermal analysis has been carried out on drawn nylon 6 filaments annealed at various temperatures between 150 and 210°C and then methoxymethylated to various degrees. It is shown that the melting point inherent to the morphology of drawn nylon 6 can be obtained from samples in which the reorganization of defect crystallites in the course of thermal analysis is prevented by a proper degree of methoxymethylation of amorphous regions. The melting point thus obtained is in linear relation with the reciprocal crystallite size in the direction of fiber axis which has been obtained from small-angle x-ray data and crystallinity. The extrapolation and the slope of this linear relation give the equilibrium melting point of nylon 6 as 245°C and an end-surface free energy of 42 erg/cm². The results seem to provide strong support for the presence of chain-fold surfaces in the drawn and annealed polymers.     

Adsorption of polymers at the solution-solid interface. VII. Poly(acrylic acids), model compounds,and vapors on nylon fibers

Nylon fibers of various draw ratios have been used as the adsorbents in the adsorption of low molecular weight acids and of polyacrylic acids from solution. Polymer adsorption is lower than on a precipitated nylon and decreases with fiber orientation; however, propionic acid and glutaric acids do not show this dependence on nylon structure. The structural alterations consequent on fiber drawing also reduce swelling in hydroxylated liquids. The greater accessibility of the precipitated nylon is shown by vapor sorption and extends to nonhydroxylated vapors; however, the differences in behavior between polyamide powder and fiber cannot be fully attributed to the former possessing a porous structure, in the sense normally employed in surface chemistry.     

Fibers from polyblends containing nylon 6 as basic component. I. Melt spinning and physical properties of blend fibers

Five series of two-component blend filaments, comprising nylon 6 (N6) and nylon 66 (N66), nylon 610 (N610), nylon 11 (N11), nylon 12 (N12), or poly(ethylene terephthalate) (PET), were prepared by using a research spinning machine and a conventional drawing machine. The microstructure and the physical properties of the resultant filaments were evaluated with a tensile tester, a optical microscope, a density-gradient column, and a DTA instrument. When both components were mixed homogeneously so that they would form a three-dimensional network, the tensile properties of the blend filament were at least equivalent to the values predicted from those of both components. On the other hand, as in the cases of 30/70 and 70/30 N6–PET, when the minor component was discretely distributed as short fibrils in the matrix of the major component, the blend filament had an extremely weak tenacity. A supertenacity filament was obtained from 50/50 N6–N610. The marked increase of the tensil strength and the initial modulus of 50/50 N6–N610, about 12 g/den and 520 kg/mm², respectively, may be due to a significant increase in the crystallinity and the orientation of the blend.     

溶剂和添加剂对尼龙6鬃丝结构形态和道明性的脸响

The transparency of nylon 6 filaments is changed by spherulites formed by Solvent Induced Crystallization (SINC) in quenching bath. The long carbon chains in alkyl diamides additives can prevent Solvent (water) Induced Crystallization so that the transparency of nylon 6 filaments is improved. The nylon 6 filaments were examined by Scanning Electron Microscopy (SEM), Small-Angle Light-Scatting (SALS), polarized microscope, light transmission rate, contact angles and others.     

溶剂和添加剂对尼龙6鬃丝结构形态和道明性的脸响

针对增加鱼网丝的透明性,各国都进行了大量的工作。一种措施是在生产尼龙6鬃丝的过程中,用不同的溶剂代替水作凝固浴,例如四氯化碳,氢氧化钠的水溶液,己烷,白油等。水的影响已引起人们的重视。另一种措施是在纺丝时向尼龙6切片中加入某种添加剂,例如氯化钠、十八烷基胺、硬脂酸锌共同使用,N,N′-双十八烷基对苯酰     

Synthesis of natural rubber-g-maleic anhydride and its use as a compatibilizer in natural rubber/short nylon fiber composites

Natural rubber grafted maleic anhydride (NR-g-MAH) was synthesized by mixing maleic anhydride (MAH) and natural rubber (NR) in solid state in a torque rheometer using dicumyl peroxide (DCP) as initiator. Then the self-prepared NR-g-MAH was used as a compatibilizer in the natural rubber/short nylon fiber composites. Both the functionalization of NR with MAH and the reaction between the modified rubber and the nylon fiber were confirmed by Fourier transform infrared spectroscopy (FTIR). Composites with different nylon short fiber loadings (0, 5, 10, 15 and 20 phr) were compounded on a two-roll mill, and the effects of the NR-g-MAH on the tensile and thermal properties, fiber-rubber interaction, as well as the morphology of the natural rubber/short nylon fiber composites were investigated. At equal fiber loading, the NR-g-MAH compatibilized NR/short nylon fiber composites showed improved tensile properties, especially the tensile modulus at 100% strain which was about 1.5 times that of the corresponding un-compatibilized ones. The equilibrium swelling tests proved that the incorporation of NR-g-MAH increased the interaction between the nylon fibers and the NR matrix. The crosslink density measured with NMR techniques showed that the NR-g-MAH compatiblized composites had lower total crosslink density. The glass transition temperatures of the compatibilized composites were about 1 K higher than that of the corresponding un-compabilized ones. Morphology analysis of the NR/short nylon fiber composites confirmed NR-g-MAH improved interfacial bonding between the NR matrix and the nylon fibers. All these results signified that the NR-g-MAH could act as a good compatilizer of NR/short nylon fiber composites and had a potential for wide use considering its easy to be prepared and compounded with the composites.     

An elastomeric conducting composite based on polyaniline coated nylon fiber and chloroprene rubber

Chloroprene rubber-polyaniline (PANI) coated nylon fiber composites containing PANI powder were prepared by mechanical mixing on a two-roll mill. PANI was synthesized by chemical polymerization of aniline in presence of hydrochloric acid. PANI coated nylon fiber was prepared by in situ polymerization of aniline on nylon fiber. The cure parameters cure kinetics, filler dispersion, mechanical properties, DC electrical conductivity and thermal degradation parameters of the composites were evaluated. Cure rate index and cure reaction constants indicated that the rate of cure reaction changes on filler addition. Filler addition at higher loadings led to agglomeration. The tensile strength and modulus values increased suggesting a reinforcement effect. The conductivity, thermal characteristics and thermal degradation kinetic parameters are also presented.     

New Approaches for Field Analyses of Cotton Quality by Means of Near-IR Spectroscopy Supported by Chemometrics

There is a strong economic interest in routine measurements of cotton quality as production processes and final products depend on it. An important cotton property is “micronaire,” a parameter that is indicative of the fibers' maturity and its fineness. Currently, micronaire is normally measured in laboratories with equipment that prohibits routine field analyses. The goal of this study is a proof-of-principle demonstrating that cotton quality as determined via fiber micronaire is correlated to fiber properties and that these properties can be determined by near-infrared (NIR) reflection spectroscopy using portable instrumentation in conjunction with Principal Component Regression for micronaire prediction. A set of 191 cotton samples was acquired from over 100 different upland cotton varieties, and initial spectroscopic studies confirmed the feasibility of NIR spectroscopy to measure cotton micronaire in the laboratory with portable NIR instrumentation. Sample reproducibility was an issue which has been resolved with two approaches, that is, model spectral artifacts, mainly baseline shifts, by means of chemometric calibrations or application of second derivative spectroscopy to suppress baseline drifts. Results from this study demonstrated in up to 90% of the test samples that the micronaire values fall into the acceptance range. Thus, a promising new approach for field analyses is on the horizon and has been assessed in this study. Further, the acceptance range could be reduced to ±0.2 m.u. and still ≥70% of the samples fell inside the restricted acceptance range. Up to 60% of the samples fell inside an acceptance range of ±0.1 m.u.     

Adsorption thermodynamic and kinetic of disperse dye on cotton fiber modified with tolylene diisocyanate derivative

Adsorption thermodynamic and kinetic study of disperse dye on cotton fiber modified with tolylene diisocyanate derivative was carried out under the condition of pH value 6.0 ± 0.2, initial dye concentration 0.01–3.0 g/L and liquor ratio 2,000:1. The result showed the equilibrium adsorption isotherm of disperse dye on modified cotton fiber was Langmuir—Nernst mixed Model and the saturated adsorption capacity of the turning point was 7.1429 mg/g. The calculation of the thermodynamic parameters indicated that the Van der Waals’ forces played a major role between the disperse dye and the modified cotton fiber, and the adsorption of disperse dye on the modified cotton fiber was exothermic process. Compared with the diffusion coefficient and the activation energy of disperse dye on various fibers, the disperse dye diffusion in modified cotton fiber was more difficult than that in original cotton. Meanwhile, it was found that the adsorption kinetics of disperse dye on modified cotton fiber was well agreed with a pseudo second-order kinetic model.     

Scroll wave filaments terminate in the back of traveling fronts

Experiments with the 1,4-cyclohexanedione Belousov-Zhabotinsky reaction demonstrate that three-dimensional scroll waves can rotate around filaments that end in the wake of a traveling excitation pulse. The vortex structures nucleate during the collision of three nonrotating excitation pulses. The nucleation process and the wave-termination of filaments are direct consequences of the system's anomalous dispersion relation. Vortex filaments are found to expand with about twice the speed of their anchoring wave fronts. Filament expansion is accompanied by the build-up of phase differences in spiral rotation creating strongly twisted wave structures. Experiments employ optical tomography for the reconstruction of the three-dimensional wave patterns.     

Plasma Induced Graft Polymerization of Three Hydrophilic Monomers on Nylon 6,6 Fabrics for Enhancing Antistatic Property

In this study, three hydrophilic monomers; 2-acrylamido-2-methyl-1-propanesulfonic acid, 2-hydroxyethyl methacrylate, diallyldimethylammonium chloride (DADMAC) were selected and their performance as an antistatic finish on nylon 6,6 fabrics was investigated. A non-thermal, high density atmospheric pressure plasma was used to graft polymerize the monomers on nylon 6,6 fabrics. Fabrics were first treated with solutions of monomer in water, air dried and then treated with helium plasma to graft polymerize the monomer on the fiber surface. Surface resistivity values were measured before and after soxhlet extraction with water. Results showed that the DADMAC monomer provided better antistatic properties to fabrics. Further studies with DADMAC monomer were made; effects of plasma post exposure time, plasma pre-exposure time, plasma power, concentration of the monomer and existence of a crosslinker were investigated. Higher plasma power, higher concentration of the monomer and longer post exposure times all gave better antistatic properties to the nylon 6,6 fabrics. Acid dye staining, UV–Vis and FT-IR measurements were conducted and results confirmed a grafted poly-DADMAC layer on the fabric surface.     

Growing degree days is the dominant factor associated with cellulose deposition in cotton fiber

Two field experiments were conducted to study the effect of temperatures on the cellulose content of cotton fiber at various stages of fiber development. In the first study, cotton was sown on three different dates so that temperatures were different during fiber development. In the second study, cotton was grown in semi-mobile chambers and night-time temperatures were controlled within the chambers. During the period from anthesis until the onset of rapid cellulose deposition, the average cellulose deposition rate was significantly correlated with growing degree days (GDD) and daily minimum temperature. The onset time of rapid cellulose deposition was significantly affected by GDD and daily maximum temperature. During the period of rapid cellulose deposition, the duration of rapid cellulose deposition and the average rate of cellulose deposition were significantly correlated with GDD. Therefore, GDD had the largest effect on cellulose deposition cotton fiber. The requisite number of GDD during cellulose synthesis must be reached during two stages of cotton fiber development in order to maximize cellulose content. The average cellulose deposition rate between anthesis and the onset of rapid cellulose deposition can be increased by warmer daily minimum. Warmer daily maximum temperatures advanced the onset of rapid cellulose deposition. The cellulose content of cotton fiber is also be affected by conditions during the period of rapid cellulose deposition. Cellulose contents are highest when cellulose accumulates at moderate rates during this period and when the duration of rapid cellulose deposition is long as possible.     

Swelling of nylon 6 film due to water sorption

Dimensional changes in nylon 6 film on absorption and desorption of water were studied as functions of time and the amount of absorbed water. For absorption, a plot of film expansion versus the square root of time was sigmoidal in the initial region and did not coincide with the sorption curve: the latter was linear in the same region. This behavior is very similar to that reported for nylon 6 fiber by Kunzman. A theoretical analysis based on certain assumptions about the molecular state of nylon 6 gave good agreement with experimental results. By this analysis it was shown that the characteristic swelling behavior arises from instantaneous relaxation of the polymer molecules and is not connected with a time lag between water absorption and expansion of the polymer, as Kunzman proposed.     

Physicochemical properties of chemically and enzymatically modified cellulosic surfaces

Surface characteristics of modified cotton fibers have been studied using electrokinetic analysis (EKA), inverse gas chromatography (IGC) and dynamic contact angle (DCA) determinations. Modifications of cotton surfaces included mercerization, water-proofing, cross-linking, dyeing with a bifunctional reactive dye and cellulase biopolishing. Comparisons are made to linen as an example of a natural cellulosic fiber other than cotton and to rayon as a representative of a regenerated cellulosic fiber. Generally all cellulosic surfaces were bipolar with a slightly higher acidic contribution in the case of the cotton samples. EKA indicated ion dissociation as the predominant mechanism for surface charge in aqueous medium for all cellulosic samples, with the exception of greige cotton and the cotton sample with the hydrophobic finish. Results from EKA and IGC showed good correlation, while DCA yielded unreasonably high basic contributions most likely due to fiber swelling.