Pyrolysis of kenaf (Hibiscus cannabinus L.) biomass: influence of ashless treatment on kinetics and thermal behavior

Journal of Thermal Analysis and Calorimetry - Recently, ashless pretreatment of lignocellulosic biomass prior to pyrolysis has been used for removing mineral matters to prevent slagging and...     

Dithieno[2,3‐d:2',3'‐d']benzo[1,2‐b:4,5‐b']dithiophene (DTBDAT)‐based copolymers for high‐performance organic solar cells

P(BDT‐TCNT) and P(DTBDAT‐TCNT) , which has an extended conjugation length, were designed and synthesized for applications in organic solar cell (OSCs). The solution absorption maxima of P(DTBDAT‐TCNT) with the extended conjugation were red‐shifted by 5–15 nm compared with those of P(BDT‐TCNT) . The optical band gaps and highest occupied molecular orbital (HOMO) energy levels of both P(BDT‐TCNT) and P(DTBDAT‐TCNT) were similar. The structure properties of thin films of these materials were characterized using grazing‐incidence wide‐angle X‐ray scattering and tapping‐mode atomic force microscopy, and charge carrier mobilities were characterized using the space‐charge limited current method. OSCs were formed using [6,6]‐phenyl‐C₇₁‐butyric acid methyl ester (PC₇₁BM) as the electron acceptor and 3% diphenylether as additive suppress aggregation. OSCs with P(BDT‐TCNT) as the electron donor exhibited a power conversion efficiency (PCE) of 4.10% with a short‐circuit current density of J_SC = 9.06 mA/cm², an open‐circuit voltage of V_OC = 0.77 V, and a fill factor of FF = 0.58. OSCs formed using P(DTBDAT‐TCNT) as the electron donor layer exhibited a PCE of 5.83% with J_SC = 12.2 mA/cm², V_OC = 0.77 V, and FF = 0.62. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3182–3192     

Effects of directed architecture in epoxy functionalized prepolymers for photocurable thin films

Cationic photopolymerization has become increasingly important in thin‐film applications for advantages including no oxygen inhibition and rapid polymerization rates. Photocurable cationic thin film properties are often modulated by incorporation of oligomeric and prepolymer materials, but little work has directly examined the effect of prepolymer structure and reactive group placement on the thermomechanical properties of the final material. To explore the role of molecular architecture, epoxy functionalized butyl acrylate gradient copolymers were synthesized with reactive groups in end segments or randomly distributed along the prepolymer chain. Polymerized end functionalized formulations exhibit moduli almost double that of random functionalized oligomer formulations. In addition, inclusion of end functionalized prepolymers decreases creep of resulting thin films by a factor of 10. Furthermore, decreasing the concentration of the cross‐linking diluent in end functionalized prepolymer systems results in amorphous networks with significantly lower mechanical strength. Increasing reactive groups at the ends of prepolymers produces stronger materials without affecting tensile elongation at break. These properties indicate that the structured oligomers facilitate the formation of continuous hard domains with high cross‐link density with inclusions of soft, flexible domains of low cross‐link density. This study demonstrates that the prepolymer architecture governs network formation and ultimate properties. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 144–154     

Pd/C‐Catalyzed Carbonylative Esterification of Aryl Halides with Alcohols by Using Oxiranes as CO Sources

A carbonylative esterification reaction between aryl bromides and alcohols, promoted by Pd/C and NaF in the presence of oxiranes, has been developed. In this process, oxiranes serve as sources of carbon monoxide by their conversion to aldehydes through a palladium‐promoted Meinwald rearrangement pathway. Intramolecular versions of this process serve as methods for the synthesis of lactones and phthalimides.     

Effect of burn-up on the radioactivation behavior of cladding hull materials studied using the ORIGEN-S code

The effect of fuel burn-up on the radioactivation behavior of cladding hull materials was investigated using the ORIGEN-S code for various materials of Zircaloy-4, Zirlo, HANA-4, and HANA-6 and for various fuel burn-ups of 30, 45, 60, and 75 GWD/MTU. The Zircaloy-4 material is the only one that does not contain Nb as an alloy constituent, and it was revealed that ¹²⁵Sb, ^125mTe, and ⁵⁵Fe are the major sources of radioactivity. On the other hand, ^93mNb was identified as the most radioactive nuclide for the other materials although minor radioactive nuclides varied owing to their different initial constituents. The radioactivity of ⁹⁴Nb was of particular focus owing to its acceptance limit against a Korean intermediate-/low-level waste repository. The radioactivation calculation results revealed that only Zircaloy-4 is acceptable for the Korean repository, while the other materials required at least 4,900 of Nb decontamination factor owing to the high radioactivity of ⁹⁴Nb regardless of the fuel burn-up. A discussion was also made on the feasibility of Zr recovery methods (chlorination and electrorefining) for selective recovery of Zr so that it can be disposed of in the Korean repository.     

Electrically conductive transparent papers using multiwalled carbon nanotubes

We describe a novel class of electrically conductive transparent materials based on multiwalled carbon nanotubes (MWCNTs). Transparent nanocomposites were fabricated by incorporating an aqueous silk fibroin solution into bacterial cellulose membranes. The transparent nanocomposites had a high transmittance in the visible and infrared regions, regardless of the bacterial cellulose fiber content, due to the nanosize effect of the bacterial cellulose nanofibrils. This phenomenon allowed the preparation of a novel electrically conductive transparent paper. The high dispersity of the MWCNTs was realized by utilizing a bacterial cellulose membrane as a template to deposit them uniformly, thereby achieving electrically conductive transparent papers with outstanding optical transparency. The light transmittance and electrical conductivity varied according to the concentration of the MWCNT dispersion. Good optimal transparency and electrical properties were obtained with a light transmittance of 70.3% at 550 nm and electrical conductivity of 2.1 × 10^?3 S/cm when the electrically conductive transparent paper was fabricated from a 0.02 wt % aqueous MWCNT dispersion. In addition, the electrically conductive transparent papers showed remarkable flexibility without any loss of their initial properties. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1235–1242, 2008     

Characterization of thin polymer‐like films formed by plasma polymerization of methylmethacrylate: A neutron reflectivity study

The microstructure of the plasma‐polymerized methylmethacrylate (ppMMA) films is characterized using neutron reflectivity (NR) as a function of the plasma reaction time or film thickness. Variation in the crosslink density normal to the substrate surface is examined by swelling the film with a solvent, d‐nitrobenzene (dNB). In the presence of dNB, uniform swelling is observed throughout the bulk as well as at the air surface, and silicon oxide interfaces. The results indicate that the MMA film prepared by plasma polymerization (ppMMA) has a uniform crosslink density from air surface to substrate surface. Additionally, the scattering length density of the plasma‐polymerized MMA film (SLD ≈ 0.750 × 10⁻⁶ Å⁻²) is much lower than that of a conventional PMMA film (SLD = 1.177 × 10⁻⁶ Å⁻²). The increase in film thickness following dNB sorption is 7.5% and at least 36% for the ppMMA and PMMA films, respectively. This suggests that the films formed by plasma polymerization are different from conventional polymers in chemical structure. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2522–2530, 2004