Investigation of the chemical structures of coking and non-coking coals in original and reductively alkylated solid states via 13C n.m.r. and i.r. spectroscopies

Chemical structures of four Turkish coals in original and reductively alkylated forms were investigated in the solid state by CP/MAS ¹³C n.m.r. and i.r. spectroscopies. Dilatation properties of these samples were also determined. It was observed that, while the aliphatic parts of the coking coals are mainly composed of short and straight alkyl groups and alicyclic structures, the aliphatic parts of the non-coking coals are to a larger extent composed of branched chains and/or alicyclic structures. It was concluded that ether bonds linking aromatic units are more prominent in the coking coals, whereas in the non-coking coals aromatic-O-aliphatic and/or alicyclic ethers dominate. The degree of condensation of aromatic structures was found to be higher in the coking coals, and the extent of reductive alkylations was higher in comparison with the non-coking coals. Non-coking coals were found to be alkylated preferentially at their phenolic oxygens. Difference spectra were found to be very useful in following organic chemical structural changes that accompany reductive alkylation.     

Microlayer and nanolayer tubing and piping via layer multiplication coextrusion. I. Validation

Layered annular structures produced with layer multiplication coextrusion, utilizing both a standard in-line “spider” die, and a custom annular die, are compared in structures up to 129 layers. One multilayered system, of a Dow LDPE 5004I was utilized in generating experimental results to validate the custom die design performance. It was found that the custom design demonstrates successful extrusion of high layer number annular structures with substantial benefits over the standard spider die. Moreover, a design method incorporating angular rotation was implemented within the custom die to eliminate weld lines and attain concentric layer structures to further enhance commercial viability and mechanical integrity. Results indicate angular rotation may be utilized to generate idealized annular products with concentric layer structures. Additionally, exploration of flow through the annular die land was conducted with ANSYS Polyflow in under several conditions of angular rotation. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48683.     

Silicification and Biosilicification. Part 6. Poly-L-Histidine Mediated Synthesis of Silica at Neutral pH

Biosilicification results in the formation of ornate silica structures, which are seen in diatoms, sponges, grasses and other biological systems. Proteins have been isolated from diatoms, sponges and grasses that are proposed to be responsible for biosilicification and have been sequenced and/or some of the key amino acids identified. Studies of the amino acids primary sequence in these proteins suggest that lysine, histidine, arginine, cysteine, proline and serine probably play a role in biosilicification. Homopolymers of lysine, arginine and proline have been shown to form silica structures in vitro at (or close to) neutral pH. Here we report, for the first time, the ability of poly-L-histidine (PLHis) to form silica structures from a silica precursor at neutral pH. It was observed by scanning electron microscopy that PLHis facilitates the formation of silica spheres in the size range 150–200 nm and interconnected structures make up relatively smaller particles.     

Self-condensation of oxidized lignosulfonate. II. Condensation behaviors

Studies have been made on the principal parameters that affect the self-condensation of oxidized lignosulfonate, such as lignin content, pH, temperature, time of hot pressing, and oxidation. During condensation, the hydroxyl groups in both the lignosulfonate and carbohydrate molecules could react with carboxyl, sulphonic acid, and carbonyl groups to form an ester bond and result in (hemi) ketal and (hemi) acetal structures. These structures made condensation products having excellent resistance in water and in alkaline solutions. The results also demonstrated that the oxidized lignosulfonate could be condensed at a higher rate than could the untreated one.     

H n.m.r. study on the sequence length of polysulphide linkages in the copolymer of chloroprene and sulphur

The sulphur rank distribution and the structures of chloroprene units in the chloroprene-sulphur copolymer have been investigated in detail by proton nuclear magnetic resonance spectroscopy (¹H n.m.r.). Two factors, the sulphur rank and the structures of chloroprene units, which complicate the spectrum, were elucidated by modification of the copolymer structure through partial and full reductions of the polysulphide linkages. The populations of the chloroprene units with different structures adjacent to the sulphur units were found to be different from those of the homosequence. It was found that the major sulphur unit in the copolymer is octasulphide, the next disulphide and the least common are the other polysulphides composed of 3–7 sulphur atoms. No evidence of monosulphide was found.     

Irregular structures in polyvinylchloride II. Unsaturated structures

In the present paper, considerations are made on the mechanism of the dehydrochlorination of PVC, mainly from information summarized from studies with unsaturated model compounds. A semi-empirical evaluation of the activation energy has been carried out for the monomolecular elimination of hydrogen chloride involving unsaturated structures in PVC. The semi-empirical method proposed by VEDENEYEV was used to study the C-Cl, C-H and C-C bonds in PVC. Activation energies for elimination of hydrogen chloride were calculated on the basis of the additivity of bond energies of the four-centre activated complex for various irregular structures in the polymer chain such as branching, head-to-head or tail-to-tail addition, and double bonds. From a number of possible structural abnormalities controlled by polymerization conditions only a few give a contribution to the initiation of the thermal dehydrochlorination but internal allyl type chlorine and branched structures having a tertiary chlorine appear to have significant effect as the initiators of the decomposition, while abnormal structures at the chain ends are rather stable. It should be pointed out that increasing delocalization or resonance stabilization in the case of unsaturated internal-irregular structures will lower the activation energy of elimination of hydrogen chloride in consequence of decreased thermal stability of PVC.     

Electrical Aspects of Adsorbing Colloid Flotation. XIX. Viscosity and the Structures of Mixed Micelles

Abstract

Viscosity measurements on mixed surfactant solutions containing the nonionic surfactant Triton X-100 and a number of other cosurfactants (dodecanoic acid, dodecyl amine, sodium dodecylsulfate, dodecyltrimethylammonium chloride, dodecyl alcohol, and sodium dodecylphosphate) indicate the presence of two quite different ‘types of micelles’. Solutions containing an electrically neutral cosurfactant exhibit very large viscosities, indicating the presence of extended micellar structures. Solutions containing a charged cosurfactant exhibit much lower viscosities, indicating that the micelles in these solutions are small spherical or ellipsoidal structures. Evidently coulombic repulsions destabilize the extended structures when charged surfactants are present in the micelles. The effects of pH and ionic strength are consistent with this interpretation.     

Oberflächenstrukturierung polymerer fasern durch UV-laserbestrahlung. 11. Oberflächenstrukturierung von polypropylen-folien und -geweben

It is shown that weakly UV-absorbing polymers like polypropylene (PP) become amenable to laser treatment by impregnation with strong absorbers like benzophenone. The high absorption coefficients of the doped polyolefines allow an efficient etching by laser irradiation. In addition, roll-like structures of the surface are obtained as they are known from laser-treatment of polyester and polyamide fibers. The dimensions of these structures on fibers are in the region of 10 to 25 μm with a depth of about 3 °m. Using biaxially stretched PP-foils, drop-like structures are obtained, thus indicating a predominance of thermal effects. On weakly absorbing systems like dyed PP-fibers only fusions of single filaments are obtainable. By mechanical contact of an undoped PP-foil with poly(ethyleneterephthalate) (PETP) foils laser irradiation creates roll-like structures on the PP-surface.     

Cover Chem. Eng. Technol. 6/2014

Nanotechnology Chip. Courtesy of DuPont. Nanotechnology is the science and technology for manipulating chemistry and biology at molecular and atomic levels. It involves the ability to create and adjust molecular structures to create new materials, devices, machines or objects.     

Silicification and Biosilicification. Part 4. Effect of Template Size on the Formation of Silica

Silicification at neutral pH and under ambient conditions is of growing interest due to its close relationship with biosilicification. In diatoms biosilicification has been reported to occur at (or close to) neutral pH and it has been shown that protein molecules act as catalysts/templates/scaffolds for this elegant materials chemistry. In this investigation various catalysts/templates have been studied for their role in silicification in vitro. We have used functionalized C₆₀ fullerene, R5 (an important polypeptide from the amino acid sequence of a silaffin protein), poly-l-lysine (PLL) and two poly(allylamine hydrochloride) (PAH) samples having different molecular weights. An aqueous silica precursor was used and ordered silica structures were produced in each of the systems studied. The sizes of the silica structures appear to correlate with the size, in solution, of the templating/scaffolding agents. Biological systems exhibit hierarchical structures with remarkable control of morphologies over different length scales. The use of templating/scaffolding agents having different sizes and shapes is one possible paradigm for the production of such structures in vivo.     

Mercerization of cellulose. I. X-ray diffraction evidence for intermediate structures

A study of the mercerization of ramie cellulose was begun using x-ray diffraction, in order to determine the types of alkali–cellulose structures that occur as intermediates during the conversion of cellulose I to cellulose II. A total of five unique alkali–celluloses (Na–celluloses) could be generated reproducibly, depending only on the alkali concentration used. The reproducibility was enhanced by slowing down the mercerization process, by laterally compressing the fibers in capillary tubes. The five structures, named Na–celluloses I, IIA, IIB, III, and IV, were of two types based on their crystallographic fiber repeats. The first type was represented by Na–celluloses I, III, and IV, all exhibiting a ca. 10 Å repeat. The second type was represented by Na–celluloses IIA and IIB, with a ca. 15 Å repeat. The latter structures are possibly based on a threefold helical chain conformation, which has not been seen in crystalline celluloses. All Na–cellulose structures exhibited a reasonable degree of crystallinity and high degree of fibrous orientation. They formed a definite interconversion scheme, marked by crystalline-to-crystalline phase transformations.     

Structural analysis of Aleksinac oil shale kerogen by high-resolution solid-state C n.m.r. spectroscopy

A sample of kerogen from Aleksinac oil shale was examined by high-resolution solid-state ¹³C n.m.r. spectroscopy. The presence and relative proportions of kerogen structural units were estimated using a combination of NQS and T_1C methods with a peak-synthesis technique applied to the ¹³C CP—MAS spectrum. Relaxation parameters from these experiments were used to estimate differences in relative ‘mobility’ of various structural units. The kerogen was found to be highly aliphatic and to contain 79% long-chain aliphatic plus alicyclic structures, as well as 9% aromatic structures. These findings are in good agreement with the characterization of the same kerogen from its oxidation products.     

Thermoplastic urethane elastomers. III. Effects of variations in isocyanate structure

The dynamic mechanical properties of thermoplastic urethane elastomers have been compared for materials based on different diisocyanate structures, either 4,4′-diphenylmethane diisocyanate (MDI) or an isomeric ratio of tolylene diisocyanate (TDI). Two comparable series of polymers were prepared with a polycaprolactone diol as the soft segment and varying concentrations of hard segments based on the respective diisocyanates and 1,4-butanediol. Over the composition range studied, the polymer glass transition temperatures increased for the TDI-based polyurethanes, but remained relatively constant for the series containing MDI. Differences in the degree of macroscopic order within the hard segments, due to variations in the symmetry of the diisocyanate structures, are suggested as an explanation of these dynamic mechanical properties.     

Structures and properties of injection moldings of crystallization nucleator-added polypropylenes. II. Distribution of higher-order structures

Flexural test specimens were injection-molded from polypropylenes added with 0.5 wt % calcium carbonate, talc, p-tert-dibutyl-benzoic acid monohydroxy aluminum, or p-dimethyl-benzylidene sorbitol under cylinder temperatures of 200–320°C. Distributions in the flow direction of higher-order structures such as a^*-axis-oriented component fraction [A^*] and crystalline orientation functions and distributions in the thickness direction of higher-order structures such as crystallinity, β-crystal content, the degree of b-axis orientation to the thickness direction, [A^*], and crystalline orientation functions were studied. These higher-order structures are inhomogeneous in the flow and thickness directions, which strongly influences the product properties such as mechanical and thermal properties.     

Hydrogenation of linolenate. XI. Nuclear magnetic resonance investigation

Nuclear magnetic resonance (NMR) spectra have been obtained during the hydrogenation of methyl linolenate with platinum, nickel and sulfur-poisoned-nickel catalysts and during the reduction of linolenic acid with hydrazine. Structural changes have been studied by “proton counting” techniques and include those for the total unsaturation (olefinic protons), 15,16-double bond (β-olefinic methyl protons), 1,4-pentadienes (di-α-olefinic methylene protons) and allylic methylene (α-olefinic methylene protons). The number of olefinic protons is inversely related to the degree of saturation as determined by iodine value, GLC and hydrogen absorption. Amounts of double bonds in the 15,16-position and in the 1,4-pentadiene structures decrease linearly with increasing saturation, but the slopes of lines differ for specific catalysts. Sulfur-poisoned pickel has the most negative slope, followed by electrolytic nickel, and then platinum and hydrazine. Amounts of α-olefinic structures with increasing saturation are roughly constant for hydrazine and platinum during reduction with the first mole of hydrogen; they fall to zero at complete saturation. For the two nickel catalysts, the α-olefinic structures increase during absorption of the first mole and a half of hydrogen before dropping to zero. The possibility of substituting NMR measurements for iodine value, alkali-isomerization spectrophotometric determination and other structural analyses is discussed. Presented at AOCS Meeting in Minneapolis, 1963. A laboratory of the No. Utiliz. Res. & Dev. Div., ARS, USDA.     

甲基丙烯酸锌增强弹性体的相态研究 II.硫化胶料(英文)

利用扫描电子显微镜(SEM)和透视电子显微镜(TEM)研究了甲基丙烯酸锌增强多种弹性体(包括BR,SBR,EPDM,NBR,EPM,POE和HNBR)的微观相态结构。发现在各体系的硫化胶料中均存在两类基本分散结构:纳米分散结构和微米分散结构。其中纳米增强结构是在胶料过氧化物交联过程中由ZDMA原位聚合生成的;而微米结构就是残余的ZDMA颗粒。这两种结构的尺寸及相对含量因不同的复合体系而不同。对于BR和SBR体系,其微米分散结构较其他体系更多,且纳米分散结构的尺寸相对略小。而在EPDM,NBR,EPM,POE,HNBR中,微米分散结构较少,且纳米分散结构的尺寸相对较大。还研究了ZDMA颗粒的原生尺寸对硫化胶料的相态结构的影响,发现在POE体系,较大的ZDMA原生尺寸将造成其硫化胶料中微米分散结构的大量增多;而EPDM,EPM,NBR,HNBR胶料的相态则对ZDMA原生尺寸的变化不敏感。硫化胶料的微观相态的差异必将对其物理机械性能产生直接的影响。     

Microlayer and nanolayer tubing and piping via layer multiplication coextrusion. II. Rheologically mismatched systems

An advanced technology, presented in Part 1, was utilized with a custom annular die to produce structures having 9–129 layers. Two material systems were chosen to produce layer structures of viscosity and elasticity stratified type both with/without the application of a rotating boundary wall within the annular land. A maximum rotation window for nine-layer structures was determined to maintain the layer structure while minimizing the appearance of the weld lines and achieving concentric layers. ANSYS Polyflow was utilized in conjunction to study trilayered systems of generic material properties in stratified forms, along with replication of the experimental systems. Combination of experimental and simulation approaches herein are allowing for the achievement of high layer number, low layer thickness, systems in annular form for the first time. The continued development of this technology can lead to application areas of tubes/pipes with advanced properties such as optical filtering, pressure resistance, and permeation reduction. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48684.     

Rheological control in foaming polymeric materials: I. Amorphous polymers

The influence of rheological properties, especially melt strength, on foam structures, such as cell size, cell density and cell size distribution, of amorphous polymer was investigated. The rheology of polystyrene (PS) was controlled by molecular modification with free radical reaction, and PS with long chain branching (LCB) level ranging from 0.15 to 1.6 branching point per 10⁴ carbon atom was gotten. The shear and elongational rheology were found to be dependent on the LCB structure, and the strain hardening behavior of modified samples in transient elongational viscosity confirmed the existence of long branched chain. The effects of chain structure and foaming conditions such as temperature and pressure were studied by the analysis on the foam structures obtained by supercritical CO₂. The experimental results revealed that increasing LCB level would decrease cell size, make cell size distribution narrower and slightly increase cell density. The effects of chain topology on the foam structures were also investigated by numerical simulation, where Pom-Pom model was used to describe the effect of backbone length and arm length. The dependence of cell size on the arm length was consistently observed in experiments and simulation. It suggested that the arm length had greater influence on the cell radius than the backbone length. Therefore, the relationship among foam structures, rheological properties and molecular structures can be established from both experiments and simulation, which can be used as a guidance to control the foam structure by designing and controlling the molecular structures and the corresponding rheological properties.     

Second moment of n.m.r. line for the Wiser model of coal

The Wiser model of coal structure was tested using the Van Vleck moment of theory of n.m.r. lines the second moment of rigid and rotational structures being calculated. The results correspond to the second moment of the Gaussian component of free induction decay (FID) observed experimentally in some coals.     

Investigation of pyridine extracts and residues of coals by solid-state 13C n.m.r. spectroscopy

The ¹³C n.m.r. technique of cross polarization with magic angle spinning was applied to seven coals in their original states and the components obtained after pyridine extraction. It was observed that for the higher rank coals, short and straight alkyl groups are preferentially transferred to the extracts, while long-chain alkyl groups, branched alkyl groups or alicyclic structures are concentrated in the residues. Aliphatic ether or ester moieties were also observed to be concentrated in the residues. For all coals the computer-generated composite extract-residue spectra differed appreciably from the spectra of the original coals, indicating that some structures may be lost or that some structural conversion may occur during the extraction procedure. It was concluded that caution should be used in trying to determine detailed organic structural information of a coal from data obtained on its pyridine extract.