Carbon fibers from dry-spinning of acetylated softwood kraft lignin

An acetylated softwood kraft lignin was dry-spun into precursor fibers and successfully processed into carbon fibers with a tensile strength exceeding most values reported in prior studies on lignin-based carbon fibers. Limited acetylation of lignin hydroxyl groups enabled dry-spinning of the precursor using acetone (solvent) followed by thermo-oxidative stabilization. Resulting carbon fibers (∼7 μm diameter) displayed a tensile modulus, strength, and strain-to-failure values of 52 ± 2 GPa, 1.04 ± 0.10 GPa, and 2.0 ± 0.2%, respectively. Because of solvent diffusion during dry-spinning, fibers displayed a crenulated surface that can provide a larger specific interfacial area for enhanced fiber/matrix bonding in composite applications.     

Enhancing water resistance of welded dowel wood joints by acetylated lignin

Low molecular mass acetylated organosolv lignin from wheat straw and from depolymerised low sulphur organosolv wood lignin have been shown to markedly improve both the water resistance and the mechanical performance of welded dowel wood joints. The acetylated oligomers distribution and extent of acetylation of the two lignins were determined by Matrix assisted laser desorption ionization-time-of-flight mass spectrometry. Extensive acetylation was confirmed by CP-MAS ¹³C NMR spectrometry. Force–displacement measurements on welded dowel joints to which acetylated wood lignins were added showed a ductile behaviour. This is due to the interpenetration of the elastic acetylated lignin network into the more rigid composite network of the welded interphase.     

Light scattering from polyethylene solutions

The technique of measurement of light scattering from dilute polyethylene (PE) solutions is reviewed. Conditions are discussed under which various PE samples can be characterized. The choice of the solvent affects the accuracy of molecular weight determination. It appears that measurement with thermodynamically poorer solvents yields results subjected to a smaller error. The interpretation of light scattering data is often disturbed by the presence of supermolecular structures in PE solutions. The effect of reprecipitation on the behavior of PE samples is described. The measurements were mostly performed on PE standards and on the Czechoslovak sample Liten Macro.     

Light scattering by lead-borate melts

Specific features of changes in the intensity of light scattered by single-phase lead-borate melts containing from 0.6 to 12 mol % PbO are investigated. It is established that, under these conditions, the total intensity of light scattered by the investigated objects is mainly contributed from the concentration component, and the anisotropic scattering contribution is relatively low. Based on the obtained data with the use of the critical phenomena theory, spinodal temperatures T _s are determined, corresponding to the absolute instability limit for the investigated melts. It is found that an increase in the content of lead oxide in the melt results in a gradual development of specific features in the behavior of the light scattering intensity, which are revealed as its instability, dependence on the position of a scattering volume in the melt, and widened and textured glares from the primary light beam passed through the melt. The found effects cause irreproducible experimental results for melts containing more than 12 mol % PbO. Possible reasons for the discovered “anomalies” may be related to both lead oxide precipitation from the melt and interactions of lead-borate melts with the walls of a quartz cuvette.     

Light scattering studies of hi-impact polystyrene

Small-angle light scattering techniques have been used to evaluate the factors controlling the transparency of two hi-impact polystyrene films. These factors were found to include surface smoothness, volume fraction of the phases in the system, the difference of the refractive indices of the phases, and the sizes of the phases. The elongation of the rubber phase during processing was also determined.     

Light scattering and extinction in polydisperse systems

A simple approach to predict transmittance spectra of polydisperse systems is recalled and applied to various model systems (spinel-like particles in water, pores in a spinel-like matrix) and real systems (spinel in water, diamond in water, amorphous carbon soot in isopropanol) in order to investigate principal effects of size distributions (normal/lognormal, narrow/wide, monomodal/bimodal, shift of mode positions, shift of mode heights) and optical properties (refractive index contrast, with or without absorption) on the in-line transmittance. A comparison of predicted and measured spectra showed that size distributions with more small particles cause a more significant decrease in transmittance (at least for sufficiently short wavelengths) and that laser diffraction may seriously underestimate the amount of small particles (for absorbing particles, for which the influence on transmittance is enormous, a difference of up to 30% in absolute transmittance measured via spectrophotometry has been found against predictions based on laser diffraction results).     

Light scattering of ideal random copolymers in bulk

Copolymerization is a useful way of modifying the physical properties of a material to meet specific needs, but it can result in a significant light scattering loss due to dielectric fluctuations in the material. Ideal random copolymers are known to be more transparent; however, the light-scattering properties of such copolymers in bulk have not been fully studied. In this paper, two representative ideal random copolymers were synthesized: methyl methacrylate (MMA)/benzyl methacrylate (BzMA) and MMA/2,2,2-trifluoroethyl methacrylate (TFEMA). The effects of copolymer composition and polymerization temperature on the light-scattering properties were investigated. Polarized light scattering (V_V) in copolymers was more sensitive to the polymerization temperature. Higher temperatures were necessary to homogenize the dielectric fluctuations and minimize excess light scattering. However, once the heterogeneous structures vanished, the copolymer bulk exhibited low scattering losses, which are comparable with homopolymers, over the entire range of copolymer compositions.     

Efficient solid‐phase synthesis of acetylated lignin and a comparison of the properties of different modified lignins

The chemical modification of lignin can greatly enhance its functionality and exploit its application areas. To avoid the difficulties of separation and environmental pollution in the traditional liquid‐phase method, we prepared acetylated lignin by a mechanical‐activation‐assisted solid‐phase synthesis (MASPS) technology with a customized stirring ball mill as a reactor and studied its structure and properties. Ultraviolet–visible analysis showed that the degree of esterification (DE) of the acetylated lignin produced by the MASPS technique was 77.59%, whereas the DEs of those produced by traditional liquid‐phase synthesis (LPS) and thermal solid‐phase synthesis (TSPS) were only 42.29 and 27.54%, respectively. Fourier transform infrared spectroscopy and NMR analyses indicated that both phenolic hydroxyls and aliphatic hydroxyls participated in the reaction, and the reactivity of the phenolic hydroxyls was higher than that of the aliphatic hydroxyl groups. The acetylation of aliphatic hydroxyl mainly happened at the γ of arylglycerol‐β‐aryl ether (β‐O‐4). Scanning electron microscopy analysis showed that the acetylated lignins prepared by MASPS and TSPS were irregular blocks with coarse surfaces and loose structures, whereas the lignin prepared by LPS consisted mostly of regular balls with a smooth surface and a compact structure. Differential scanning calorimetry and thermogravimetric analyses indicated that the glass‐transition temperatures and thermal stability of the acetylated lignin increased by orders with the processing techniques of MASPS, TSPS, and LPS. MASPS integrated the activation and reaction in the same equipment without the use of a solvent and showed advantages of a high efficiency, environmental protection, and easy operation. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44276.     

Light and neutron scattering studies of excess low-angle scattering in moderately concentrated polystyrene solutions

The light scattering (LS) and small-angle neutron scattering (SANS) behaviour of semi-dilute solutions of polystyrene has been determined in both ‘good’ and ‘theta’ solvents. Above a critical concentration related to chain overlap, an excess small-angle scattering component is in evidence for scattering vectors, q, such that qR_g < 1. Application of a number of recent solution scattering theories fails to account for the small-angle scattering observed. The inter- and intramolecular scattering functions are measured experimentally through characterization of the SANS behaviour of solutions containing mixtures of polystyrene and perdeuteropolystyrene. The resultant intermolecular scattering functions depend on the fraction of labelled chains, indicating clearly that the solutions contain large scale fluctuations. LS studies support this hypothesis and further show that the presence of these fluctuations is reproducible, yet dependent on the solution preparation procedure. Similar behaviour is observed in screening length measurements. The excess low-angle scattering is well characterized by the Debye—Bueche random two-phase model, which is subsequently used to estimate the characteristic dimensions of the long-range fluctuations.     

Light scattering studies of the stability of liquid fuels

Storage stabilities of upgraded coal-derived liquids (H-coal and SRC-II), JP-5 jet fuels derived from petroleum and oil shale, and a petroleum-derived diesel fuel were compared using laser light scattering measurements. The most severely hydrotreated coal-derived liquids have stability characteristics comparable to the jet fuels derived from petroleum and oil shale. Fuel degradation was monitored in the presence of added specific heteroatomic compounds. Very pronounced enhancement of light scattering intensity has been observed for coal-derived liquids containing the following additives: 1. phenol + pyridine + Cu; 2. 2,6-di-tertbutylphenol (DTBP) + pyridine + Cu; 3. phenol + dimethylquinoline, (DMQ) + (Cu; and 4. 2,5-dimethylpyrrole (DMP) + thiophenol. Previous studies have shown that phenolic oxidative coupling is an important reaction responsible for the ageing of coal-derived liquids and this observation is confirmed here. Pyridine and DMQ complexed with Cu are shown to be effective catalysts for oxidative coupling. DMP by itself is deleterious to fuel stability, in that it promotes sediment formation and light scattering. During accelerated ageing of upgraded H-coal in the presence of DMP a sediment formed with empirical formula C₇H₈NO_1.3, which was further characterized by solid-state C 13 n.m.r. and X-ray photoelectron spectroscopy.     

Light scattering studies on crystallization in polyethylene terephthalate

The light scattering from the spherulites of polyethylene terephthalate grown near the glass transition temperature has been investigated. The Hv scattering profiles can be reproduced by the sum of the ideal spherulite scattering with the distribution of spherulite radius and the isotropic scattering from randomly oriented crystallites. The ratio of optical anisotropies in the isotropic scattering to the ideal spherulite scattering is obtained by the method established to eliminate the effects of the number density of spherulites and the coefficient depending on the experimental conditions. It is found that the anisotropy ratio is almost independent of the crystallization time and of temperature above 106 °C, while it is larger at a crystallization temperature of 103 °C. The spherulitic structure is discussed in terms of the anisotropy ratio.     

Light scattering studies on the ripening of viscose solution

Investigations were made on cellulose xanthate molecular weights by light scattering during the ripening of the solutions of (a) viscose-containing colored thio salts and (b) pure cellulose xanthate separated from viscose. Though an apparent reduction in molecular weight was recorded with time of ripening for the viscose solution, no such fall was observed with pure cellulose xanthate. The apparent fall of molecular weight in the case of viscose has been shown to be due to the increasing absorption of the incident beam and to the change in the value of dn/dc with progressive color formation. Reproducible results can be obtained for cellulose xanthate solutions freed from color. Intrinsic viscosity of the viscoses and the degree of polymerization (D.P.) of the regenerated cellulose from viscoses during ripening were also measured and found to be constant. The results indicate that no degradation of alkali cellulose molecule takes place during the ripening process, irrespective of the state of degradation of alkali cellulose from which the viscose is made.     

Light scattering Rayleigh linewidth measurements on some dextran solutions

Light scattering Rayleigh linewidth measurements have been made upon eight fractions of dextran from Leuconostoc mesenteroides B512 with molecular weights ranging from 10 to 500 kg/mol and the relationship D₂₀ = 2.25 × 10^?4M^?0.45 (D in mm²/s, M in kg/mol) was established. No concentration dependence of diffusion constant was detected within experimental error (±3%). The measurements were corrected for the polydispersity of the fractions. The results are compared with diffusion constants obtained by conventional techniques and with viscosity data.     

Light scattering from polymer spherulites in crystal growth simulation

A three-dimensional simulation is carried out in the growth process of a polymer spherulite and the Hv light scattering intensity is calculated. In the simulation, a crystallite is represented by a thin disk with the optical axis perpendicular to the disk. In a growth step, each crystallite generates new crystallites, the optical axes of which are fluctuated. The simulation results reproduce prominent features observed in the light scattering experiments on polymer spherulites: the scattering intensity that consists of a fourfold-symmetry intensity component and an isotropic intensity component, the scattering angle dependence, the relative magnitude and the development with crystallization time of these intensity components. A new interpretation is proposed for the Hv light scattering intensity from the polymer spherulites in the growth process.     

Light scattering from dilute solutions of critically branched epoxy resins

Summary Critically branched polymers were prepared from the bifunctional 4,4-diglycidyl-2,2-diphenylpropane (diglycidyl ether of Bisphenol A) and tetrafunctional poly(oxypropylene)diamine (Jeffamine D-400) at different distances from the gel point. Solutions of these samples in dimethylformamide were studied by static and dynamic light scattering. The results are discussed in terms of the classical Flory-Stockmayer theory and the percolation theory of gelation. The experimental results were found to be in agreement with the classical theory. The distribution functions of relaxation times were experimentally determined by the analysis of time autocorrelation functions obtained by quasielastic light scattering measurements on critically branched polymer solutions.     

Light scattering in polycrystalline alumina with bi-dimensionally large surface grains

Alumina ceramics with high in-line transmittance at 0.5–1.0 mm-thickness were prepared with different doping additives by sintering at 1850 °C in vacuum for 1–8 h. Depending on the additive contents and sintering variables bi-dimensionally large surface grains, caused by surface evaporation of MgO, had grown parallel to the surface with ～100 μm thickness and lateral sizes up to the millimeter range. The abnormal grain-growth process also resulted in the formation of pores entrapped inside the large surface grains within a narrow zone at 10–20 μm distance from the surface. The fraction of these pores is thickness-invariant. Scattering factors associated to the pores entrapped inside the bi-dimensionally large surface grains, second-phase particles, grain-boundaries, and microstructural surface defects are derived from the results of in-line transmission (at 600 nm) and are used together with microstructural characteristics to explain the light transmittance in these materials.     

Light scattering Rayleigh linewidth measurements on some solutions of cellulose trinitrate

Light scattering Rayleigh linewidth measurements have been made upon three cellulose trinitrate samples in ethyl acetate by obtaining the autocorrelation function of fluctuations in scattered intensity. The weight average degrees of polymerization (DP_w) were in the range 2400 to 3300 and $\text{DP}{}_{\mathrm{w}}\text{DP}{}_{\mathrm{n}}\text{～ 1.3}$. Measurements were made at concentrations below 2 × 10^?3 g/ml and no concentration dependence was detected within experimental error (±7%). No effects due to internal motion of the polymer chains were observed even though current theories predict that these effects should be quite large. Reasons for this are discussed and it is suggested that the effects of internal motion are diminished when the second virial coefficient is large and positive. Absolute values of translational diffusion constant calculated from the results lie well within the range of those obtained by other authors using conventional techniques. Over the limited range of degrees of polymerization investigated the equivalent hydrodynamic diameter per monomer unit was found to be $\text{0.45 ± 0.03}\text{A}\text{?}$. The effects of polydispersity on the results are discussed.     

Light scattering Rayleigh linewidth measurements on some globular protein solutions

An apparatus previously described for investigating the Rayleigh linewidth of light scattered from macromolecular solutions by means of the optical homodyne technique has been modified so as to obtain the autocorrelation function of the fluctuations in scattered intensity. Its operation is described and some results presented for three commercially obtainable globular proteins: chymotrypsinogen, bovine plasma albumin and urease. Measurements were made in unbuffered 0.2M NaCl aqueous solutions and the diffusion constants, D_20w, found to be 7.4±0.3×10^?7cm²s^?1, 5.8±0.1×10^?7cm²s^?1 and 3.4±0.1×10^?7cm²s^?1 respectively. There was no detectable concentration dependence. In each case the results agreed well with theoretical predictions both as regards angular variation and shape of the autocorrelation function. The effects of polydispersity are discussed.