Adsorption of polymers at the solution-solid interface. VI. Polyacids on nylon powder

The adsorption of some polyacids, principally poly(acrylic acid), on nylon powder has been studied. In aqueous solutions at low pH the adsorption behavior of poly(acrylic acid) is controlled by adsorbate coil dimensions rather than by electrostatic effects. Less adsorption takes place from methanol solutions but the process is much more rapid than from water. Above a critical value, increase of adsorbate molecular weight leads to a reduced adsorption, the effect being particularly evidenced by aqueous solutions. Model compounds (propionic and glutaric acids) are rapidly adsorbed from both methanol and water, but give low specific absorptions. Adsorption of poly(acrylic acids) and model compounds, is reduced, but not eliminated, by modification of the nylon adsorbent through acetylation or methoxymethylation. The adsorption of poly(acrylic acid) on nylon is not readily reversible; however, partial neutralization will release preadsorbed poly(acrylic acid) from nylon powder. The adsorption behavior of copolymers of acrylic acid with N-vinylpyrrolidone is reported, as are brief studies on some other homopolyacids. The results are generally interpreted on the basis of sorption of the macromolecules into a swollen, flexible adsorbent.     

Typical fiber structure

Model fibers of polyethylene and nylon 6 were strained in the direction of the fiber axis and the internal deformation of the samples was studied by large-angle and small-angle x-ray diffraction. The compression of samples along the fiber axis was successfully carried out, and the results obtained by x-ray methods yielded more interesting information on the structure of the fibers than was obtained in extension. A model for the structure of the fiber was constructed on the basis of the results on compressed fibers. In this model, crystals are distributed in cylindrical symmetry around the fiber axis keeping a crystal axis tangential to circles in the section normal to the fiber axis. The characteristic crystal axis is the b axis in polyethylene and the a axis in nylon 6. The chain axis of the crystals varies in orientation with respect to the fiber axis. In compression of fibers with such a structure, the crystals rotate around the characteristic axis indicated above. In the case of nylon 6 fiber, only this simple rotation seems to occur, while additional changes occur in polyethylene fibers. However, the simple rotation predominates even in polyethylene fibers. This fiber structure is correlated with the structure of thin films of the materials. This similarity proves the existence of a common mechanism for the origin of the structure of fibers and films.     

Structure and morphology of nylon 2 4 lamellar crystals: Comparison with polypeptides and relationship with other nylons

Chain-folded lamellar crystals of nylon 2 4 have been prepared from dilute solution by addition of poor solvent. Two crystal structures are observed at room temperature: a monoclinic form I, precipitated at elevated temperature, and a less-defined, orthorhombic form II, precipitated at room temperature. The unit cell parameters for both forms are similar to those reported for its isomer, nylon 3. Nylon 2 4 form II is a liquid–crystal-like or disordered phase, consisting of hydrogen-bonded sheets in poor register in the hydrogen bond direction. Form I crystals have two characteristic interchain spacings of 0.41 nm and 0.39 nm at room temperature and on heating, exhibit a structural transformation and a Brill temperature (250°C) characteristic of many other even–even nylons. Nylon 2 4 is a member of the nylon 2 Y and nylon 2N 2(N+1) families, and the form I crystals show behavior commensurate with both. We propose they contain a proportion of intersheet hydrogen bonds at room temperature, similar to that for the nylon 2 Y family, and the short dimethylene alkane segments mean that the structure consists of hydrogen-bonded a-sheets, with an amide unit in each fold, similar to that of nylon 4 6. The fold geometry and sheet structure is compared with chain-folded apβ-sheet polypeptides and nylon 3. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2401–2412, 1998     

Introduction of the trihydrated hydronium ion concept into the dyeing mechanism of nylon with polybasic dyes

Summary The adsorption isotherms of polybasic acid dyes (two dibasic dyes and two tribasic dyes) on three kinds of nylon fibers at constant p_H (3.5) have been determined at 90 °C. The nylon fibers, Nylon-1, –2 and –3 had amino group analyses of 25, 54 and 95 meq/kg, respectively. From the adsorption isotherms the saturation value of the dyes on each nylon fiber was calculated. For the dibasic dyes, the saturation value on each nylon fiber was very near the amino group content of the fiber. This indicates that these dyes are adsorbed stoicheiometrically on each nylon fiber. For the tribasic dyes, the stoichiometric behavior was observed only on Nylon-3. A crude calculation was made of the distance between amino groups in each nylon fiber. It was seen from the scale model of the dyes that the distance of sulfonic acid groups in the dye molecule is much smaller than that of amino groups in the fiber. The H₉O₄ ⁺ bridge hypothesis was proposed in order to explain how a polybasic dye can physically saturate fixed sites.

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Zusammenfassung Die Adsorptionsisothermen von mehrbasischen Säurefarbstoffen (zwei dibasische Farbstoffe und zwei tribasische Farbstoffe) an Nylonfasern von dreierlei Art bei konstantem p_H (3.5) wurden bei 90 °C bestimmt. Die Nylonfasern Nylon-1, –2 und –3 ergeben bei Aminogruppenanalysen Werte von 25, 54 und 95 mäqu/kg. Aus Adsorptionsisothermen wurden die Sättigungswerte für diese Farbstoffe auf jeder Art Nylonfaser berechnet. Für die dibasischen Farbstoffe wurden die Sättigungswerte auf jeder Nylonfaser sehr nahe dem Aminogehalt in der Faser gefunden. Das zeigt, daß diese Farbstoffe auf den Nylonfasern stoichiometrisch adsorbiert werden. Bei den tribasischen Farbstoffen wurde das stöchiometrische Verhalten nur auf Nylon-3 gefunden. Die Abstände zwischen den Aminogruppen in jeder Nylonfaserart wurde näherungsweise berechnet. Aus dem Molekülmodell des Farbstoffes stellt sich heraus, daß der Abstand zwischen den Sulfonsäuregruppen im Farbstoffmolekül viel kürzer als der zwischen irgendwelchen Aminogruppen in der Faser ist. Deshalb wird eine H₉O₄ ⁺-Brücken-Hypothese vorgeschlagen, um zu klären, wie ein mehrbasischer Farbstoff feste Plätze physikalisch absättigen kann.

     

Adsorption behaviors of high-valence metal ions on desferrioxamine B immobilization nylon 6,6 chelate fiber under highly acidic conditions

Adsorption behaviors of the high-valence metal ions Zr(IV), Hf(IV), Ti(IV), V(V), Nb(V), Ta(V), and Mo(IV) on desferrioxamine B (DFB) immobilization nylon 6,6 chelate fiber was investigated under highly acidic conditions. Though the complexes of DFB and the high-valence metal ions were extracted without selectivity by solvent extraction, the only zirconium ions showed higher adsorption percentages than that of other high-valence metal ions on the DFB immobilization nylon 6,6 chelate fiber. Adsorption properties were caused that limited the freedom of DFB by chemical immobilization. Especially, hafnium ions and zirconium ions, which have similar chemical properties, showed different adsorption behavior in highly acidic aqueous solutions. Zirconium ions were quantitatively adsorbed up to 13.5 micromol/g.     

Analysis of precipitated lignin on kraft pulp fibers using atomic force microscopy

A method is presented which enables analysis of lignin precipitated on the surface of kraft pulp fibers. As experimental input, high-resolution atomic force microscopy phase images of the fiber surfaces have been recorded in tapping mode. A digital image analysis procedure—based on the watershed algorithm—is applied to distinguish between cellulose fibrils and the precipitated lignin. In this way, size distributions for the diameter of lignin precipitates on pulp fiber surfaces can be obtained. In an initial application of the method, three softwood kraft pulps were analyzed: a black liquor cook with a very high content of precipitated lignin, a bleached pulp where nearly no precipitated lignin is visible and an unbleached industrial pulp. The proposed method is suggested as an appropriate tool to investigate the kinetics of lignin precipitation and the structure of lignin precipitates in pulping and bleaching.     

Birefringence of native cellulosic fibers. Part II. Spiral structure of cotton

Interferometric studies have been made on cotton fibers as well as on twisted nylon filaments. The results so obtained provide strong evidence that the fibrils in the cotton fiber become less inclined to the fiber axis as one proceeds from the surface to the core. Also, studies on twisted nylon filaments by the fiber refractometer and Becke line techniques indicate that the latter, as practiced in this laboratory, does give values of refractive index which are heavily weighted towards the fiber periphery.     

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.     

The interaction of ions with nylon. Part I. Absorption of simple acids

The paper describes the titration relations for nylon 66 samples of different endgroup contents both for aqueous and alcohol solutions. The effect of temperature change is also considered. The results are consistent with a zwitterion structure of the nylon, carboxyl groups being protonated on acid titration. The acid groups are shown to be weaker than the corresponding monomeric acids in aqueous solution, owing to their environment inside the polymer. Individual ionic affinities are calculated from the experimental absorption isotherms and are in agreement with values obtained from a simple electrostatic theory. The low sulfate ion affinity can be explained by assuming interaction for this ion with single, fixed, isolated sites.     

Synthesis and sorption properties of porous layers of cyclames on a modified polyvinyl chloride surface

The structure and adsorption properties of the porous layers of synthesized ethanol-cyclames and sodium acetate cyclames on a surface of polyvinyl chloride (PVC) encapsulating fibers of the asbestos tissue of chrysotile asbestos are studied. It is established that PVC is linked to the silicon-oxygen chains of magnesium hydrosilicate; the capsule ensures the stability of the asbestos tissue under the action of the concentrated solutions of acids and alkalis; its exterior reproduces the fiber surface and has a typical microrelief; and there are voids in the layers. We conclude that the specific surface of layers and the volume of the adsorption space are larger than those of the initial fibers, and the statistical capacity upon the adsorption of water vapor and polar and nonpolar organic molecules depends on the nature and affinity for cyclames.     

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.     

Selective degradation of nylon 6,6. II. Application of the degradation technique to commercially drawn fibers

Treatement with hydrazine was used to investigate the crystalline morophology of commercially drawn nylon 6,6 fibers. Electron microscopic investigation revealed a stacked lamellar structure for the debris of a highly oriented, rapidly drawn fiber. However, the high molecular weight range of the gel permeation chromatogram of this same oriented fiber indicated the presence of high molecular weight material. This is thought to be due to the production of rod-like, partially extended regions during drawing.     

Electrokinetic and Thermodynamic Analysis of the Dyeing Process of Polyamide Fabric with Mordant Black 17

An electrokinetic and thermodynamic analysis of the dyeing process of polyamide 6.6 (nylon 6.6) by the dye Palatine chrome black (PCB) is described in the present work. The electrokinetic study was performed by means of electrophoretic mobility measurements on bare and dyed fiber. The most significant result is the increase in electrokinetic potential, zeta, toward more negative values as the dye concentration in the dispersion medium is raised. Given the molecular structure of PCB, which contains a sulfonate group per molecule, it is feasible that such increase in |zeta| is due to the adsorption of the negatively charged, dissociated dye entities. The uptake of PCB by the fiber is experimentally determined at two temperatures: the strong increase in the amount of dye incorporated into the fiber as the initial concentration of PCB is larger, and also the fact that higher temperatures favor the dyeing process is an indication of the existence of strong interactions between both interfaces. From a different point of view, the efficient coverage of Nylon by PCB is also demonstrated by the changes experienced by the surface free energy of Nylon upon treatment with PCB. Copyright 2001 Academic Press.     

聚砜-尼龙6嵌段共聚物结构的研究

<正> 以金属钠作催化剂合成的聚砜-尼龙6嵌段共聚物对尼龙6的吸水性有一定的改善,而且可以作为聚砜与尼龙共混物的相容剂,但共聚物中聚砜组分的含量都不超过25％。这可能与共聚物的结构有关。近年来的工作表明:反相气相色谱法(IGC)是高聚物结构分析的有用的工具之一。我们试图用反相气相色谱法,通过观察嵌段共聚物     

Solution‐blown nylon 6–chitosan core–shell nanofiber for highly efficient affinity adsorption

A facile spinning‐based strategy was developed to fabricate chitosan (CS) surface nanofiber‐based affinity membranes for protein adsorption. The core–shell nanofiber mat of nylon 6–CS was prepared via coaxial solution blowing process. The nanofibers have a diameter range of 60–300 nm. The core–shell structure was confirmed by transmission electron microscopy, and CS was observed as a thin layer that uniformly adhered to the core. The dye ligand of cibacron blue F3GA (CB F3GA) was further covalently immobilized on the nanofibers with a content of 425 µmol/g. The pristine and CB F3GA‐attached mats were studied in protein adsorption. High bovine serum albumin adsorption capacities of 91.9 and 219.6 mg/g were obtained for pristine and CB F3GA‐attached mats, respectively. Given its properties of high flux rate and low pressure drop, CB F3GA‐attached nylon 6–CS nanofiber mat meets the requirements of highly effective affinity membrane chromatography. Copyright © 2016 John Wiley & Sons, Ltd.     

Polymorphic forms of nylon 3

The crystal structure of nylon 3 was studied, and four crystalline modifications were observed. Modification I, as determined from the x-ray diffraction pattern of drawn fibers, is similar to the α crystal structure of nylon 6. The unit cell is monoclinic; a = 9.33 Å, b = 4.78 Å, (fiber identity period), c = 8.73 Å, and β = 60°. The theoretical density for nylon 3 with four monomeric units in the unit cell is 1.39 g/cm³, and the observed density is 1.33 g/cm³. The space group is P2₁. The nylon 3 chains are in the extended planar zigzag conformation. Although other odd-numbered nylon form triclinic or pseudohexagonal crystals when oriented, drawn nylon 3 crystals are monoclinic. In addition to modification I, modifications II, III, and IV were studied. Lattice spacings of modifications II and III are equal to those of modification I. However x-ray diffraction intensities are different. Infrared spectra of those forms indicate an extended planar zigzag conformation of the chains. Modification IV is thought to correspond to the so-called smectic hexagonal form. No γ crystals were found, and it appears that polyamide chains with short sequences of methylene groups cannot form crystals of this type.     

Radical-initiated copolymerization of carbon monoxide and ethylenimine in the presence of ethylene

The radical-initiated copolymerization of carbon monoxide and ethylenimine in the presence of ethylene was studied quantitatively. Carbon monoxide copolymerized with difficulty with ethylenimine with α,α′-azobisisobutyronitrile as radical initiator. In the presence of a small amount of ethylene, however, a remarkable amount of crystalline powdery poly-β-alanine (nylon 3) was obtained. The crystalline copolymer, which mainly consists of nylon 3 and contains a small amount of nylon 5 and other substances of higher homologous nylon structure, was obtained in the presence of a large amount of ethylene. This copolymer scarcely contained any ketone structure. Increasing the total feed of the equimolar mixture of the monomers increased the conversion of total monomer and nylon 3 content in the copolymer formed. The effect of increasing carbon monoxide content in this system was to increase both the conversion and the nylon 3 content in the copolymer. In both cases the copolymers were almost identical with nylon 3. Increased ethylene content in the monomer feed, however, increased the conversion and the content of higher homologous nylon structures, such as nylon 5 and 7. From the results it was concluded that ethylene was involved not only in the propagation reaction but also particularly in the initiation reaction.     

Structures for monodisperse oligoamides. A novel structure for unfolded three-amide nylon 6 and relationship with a three-amide nylon 6 6

Three-amide oligomers of nylon 6 and nylon 6 6 have been investigated using electron microscopy (imaging and diffraction), X-ray diffraction, and computational modeling. A new crystal structure has been discovered for the three-amide oligomer of nylon 6. This material crystallizes from chloroform/dodecane solutions into an unfolded crystal form that has progressively sheared hydrogen bonding in two directions between polar (unidirectional) chains. This structure is quite different from the usual room temperature α-phase structure of chain-folded nylon 6 crystals, in which alternatingly sheared hydrogen bonding occurs between chains of opposite polarity in only one direction. The occurrence of this new structure illustrates the extent to which progressively sheared hydrogen bonding is preferred over alternatingly sheared hydrogen bonding. Indeed, the progressive hydrogen bonding scheme occurs in the three-amide nylon 6 material even though it requires a disruption to the lowest potential energy all-trans conformation of the chain backbone, and requires all the chains in each hydrogen-bonded layer to be aligned in the same direction. We believe the presence of chain folding, which necessarily incorporates adjacent chains of opposite polarity into the crystal structure, prevents the formation of this new crystal structure in the nylon 6 polymer. In contrast, the three-amide nylon 6 6 crystal structure is analogous to the polymeric nylon 6 6 α-phase structure, found in both fibers and chain-folded crystals, and consists of progressive hydrogen-bonded sheets which stack with a progressive shear. In both structures, the molecules (≈ 3 nm in length) form smectic C-like layers with well-orchestrated stacking of 2.2 nm to form a three-dimensional crystal. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2849–2863, 1998     

三元乙丙橡胶/尼龙高性能弹性体结构与性能的研究

通过DSC、DMA、TEM及SEM研究了三元乙丙橡胶 /尼龙 (EPDM /PA)共混物结构与性能 ,按照各级结构形态的特点 ,可大致分为三个层次的结构 :初级结构即氯化聚乙烯 (CPE)锚入或镶嵌在PA中形成分散相颗粒中的结构 ;中级结构指分散颗粒在基体中的采取的微纤状形态 ;高级结构是外力作用下共混物形成的由一定数量微纤组成的可传递应力的聚集体结构 .这种多层次结构决定了共混体系兼具EPDM与PA的优点 ,综合性能优异 .物理机械性能及热氧老化性能比较表明 ,PA改性的EPDM是理想的高性能弹性体     

Structural characteristics and moisture sorption behavior of nylon‐6/clay hybrid films

The structure of nylon‐6 hybrids with synthetic or natural clays was investigated for melt‐pressed films with Fourier transform infrared spectroscopy, wide‐angle X‐ray diffraction, and differential scanning calorimetry in comparison with the nylon‐6 homopolymer. In contrast to the development of familiar α‐form crystals in plain nylon‐6 film, the hybrid films produced γ‐form crystals when nylon‐6 was conjugated with synthetic mica, whereas the hybridization with natural montmorillonite gave rise to both α‐ and γ‐crystalline modifications. The degree of crystallinity of the nylon‐6 hybrid with synthetic mica was the highest of the three series. Moisture sorption isotherms obtained for these nylon‐6‐based films were all typically sigmoid‐shaped, although the prevalence of a higher crystallinity in the hybrid samples lowered the degree of moisture regain. The sorption behavior was analyzed well in terms of the parameters of a Brunauer–Emmett–Teller multiplayer adsorption model and a Flory–Huggins treatment. It was also observed that the cluster formation of the water adsorbed into the nylon‐6 matrix tended to be restricted by the hybridization with clay. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 479–487, 2002; DOI 10.1002/polb.10106