Accelerated degradation of syntactic polysulfide in the presence of Viton A

Headspace SPME GC/MS was used to monitor the volatile degradation products generated by syntactic polysulfide alone and in the presence of Viton A at elevated temperature. This approach allowed the identification of products from two distinct degradation mechanisms. In one degradation mechanism, which is associated with lead oxide-cured polysulfide, a single cyclic disulfide compound dominated the outgassing signature. The second mechanism was evident only when the polysulfide was in the presence of Viton A at 70 °C. In as little as 24 h, the Viton-exposed polysulfide generated multiple outgassing species indicative of an acid-catalyzed degradation process. Within one week of exposure to Viton A, the syntactic polysulfide softened significantly and lost over 6% of its initial mass, and after four weeks, the polysulfide was no longer a solid material.     

Comparison of physical-mechanical features of polyethylene based polymers employed as sealants in solar cells

In this article, we compared the sealing strength, flexibility, thermal stability, and moisture-barrier properties of two polymeric films, both based on linear low density poly ethylene (LLDPE), which can be successfully used as sealant materials in electrical devices. One example is the dye-sensitized solar cell (DSSC), a low-cost third generation device, based on a photo-electrochemical system. Characterization of LLDPE modified with maleic anhydride (PE-MAH) or with ionomeric ethylene-acrylic acid co-polymer (EMAA) was carried out. Results highlighted as PE-MAH exhibits better adhesion features toward glass, higher thermal stability, and lower wet ability even at high temperatures (80?°C) compared to EMAA. Sealant’s features have been correlated to their chemical and structural composition.     

Highly Graphitized Porous Carbon-FeNi3 Fabricated from Oleic Acid for Advanced Lithium–Sulfur Batteries

Improving the electrical conductivity of sulfur, suppressing shuttle/dissolution of polysulfide, and enhancing reaction kinetics in Li–S batteries are essential for practical applications. Here, for the first time, we have used inexpensive oleic acid as a single carbon source, and have added commercial SiO₂ as a template to form a porous structure, whereas introducing Fe(NO₃)₃ and Ni(NO₃)₂ as catalysts to increase the degree of graphitization. Moreover, the dual metal salts Fe(NO₃)₃ and Ni(NO₃)₂ can also form FeNi₃ alloy, and our results show that FeNi₃ nanoparticles accelerate the kinetic conversion reactions of polysulfide. By virtue of the well-developed porous structure and high degree of graphitization, the highly graphitized porous carbon-FeNi₃ (GPC-FeNi₃) has high conductivity to ensure fast charge transfer, and the hierarchically porous structure facilitates ion diffusion and traps polysulfide. Thus, a GPC-FeNi₃/S cathode displays excellent electrochemical performance. At current rates of 0.2 and 1 C, a cathode of the GPC-FeNi₃/S composite with a sulfur content of 70 % delivers high initial discharge capacities of 1108 and 880 mA h g⁻¹, respectively, and retains reversible specific capacities of 850 mA h g⁻¹ after 200 cycles at 0.2 C and 625 mA h g⁻¹ after 400 cycles at 1 C.     

Chemical structures assigned for the low molecular weight fractions from degradation of poly(styrene sulfides)

A non-destructive analysis is performed of thermally unstable sulfur-styrene reaction products, combining preparative size exclusion chromatography (P-SEC), ultraviolet-visible (UV-vis) and nuclear magnetic resonance (NMR). The crystallizing compounds are identified as be 2,4-diphenylthiophanes with short sulfur bridge (x ∼ 2) contrary to earlier suggestions which were based on destructive analysis. A new cyclic structure (styrene polysulfide x = 1 up to 8) was assigned to the amorphous species containing a single styrene repeating unit. Comparison with the amorphous fractions suggests that the rigid ring of styrene repeating units in adjacent sequences is the characteristic feature for the crystallisability. The melting and crystallization behaviour of this crystalline component was observed, by optical microscopy (OM) and differential scanning calorimetry (DSC), to be step-wise as well as broad, due to the variation in the length of the sulfur bridge.     

Enhanced Sealing by Hydrophobic Modification of Alaska Pollock‐Derived Gelatin‐Based Surgical Sealants for the Treatment of Pulmonary Air Leaks

Pulmonary air leaks are medical complications of thoracic surgery for which fibrin sealant is the main treatment. In this study, innovative sealants based on hydrophobically modified Alaska pollock‐derived gelatin (hm‐ApGltn) and a poly(ethylene)glycol‐based 4‐armed cross‐linker (4S‐PEG) have been developed and their burst strengths have been evaluated using fresh rat lung. The developed sealants show higher lung burst strength compared with the nonmodified original ApGltn (Org‐ApGltn)‐based sealant and a commercial fibrin sealant. The maximum burst strength of the hm‐ApGltn‐based sealant is 1.6‐fold higher than the Org‐ApGltn‐based sealant (n = 5, p < 0.05), and 2.1‐fold higher than the commercial fibrin sealant (n = 5, p < 0.05). Cell culture experiments show that modification of ApGltn with cholesteryl or stearoyl groups effectively enhances anchoring to the cell surface. In addition, binding constants between hm‐ApGltn and extracellular matrix proteins such as fibronectin and fibrillin are increased. Therefore, the new hm‐ApGltn/4S‐PEG‐based sealant has the potential for applications in thoracic surgery.

     

Flame retardancy and thermal degradation of halogen-free flame-retardant biobased polyurethane composites based on ammonium polyphosphate and aluminium hypophosphite

In this work, based on castor oil (CO), flame retardant polyurethane sealants (FRPUS) with ammonium polyphosphate (APP) and aluminum hypophosphite (AHP) were prepared. The synergistic flame retardant effects between APP and AHP on flame retardancy, thermal stability, and flame retardant mechanisms of FRPUS were investigated. It was found that when the mass ratio of APP and AHP was 5:1, the limiting oxygen index (LOI) value of FRPUS increased to 35.1%, In addition, at this ratio, the parameters from cone calorimeter testing (CCT) were reduced; these parameters include peak heat release rate (PHRR), total heat release (THR), smoke production rate (SPR) and total smoke production (TSP). The thermal decomposition behavior of the FRPUS was investigated by thermogravimetric analysis (TGA). The results showed that AHP improved the thermal stability of the PUS/APP system and increased char residue at high temperatures. Moreover, the residual carbon was investigated by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscope (SEM), gas phase pyrolysis products were investigated by thermogravimetric analysis/infrared spectrometry (TG-IR) and thermogravimetric analysis/mass spectrometry (TG-MS). It was observed that the flame retardant mechanisms of the APP/AHP system was the combination of gas and condensed phase flame retardant mechanisms.     

New synthesis of liquid polysulfide polymers in the presence of hydrazine. I. Synthesis of linear polysulfide polymers from 1,1′-[methylenebis (oxy)]-bis-[2-chloroethane] and sodium tetrasulfide

The results of our studies show that liquid linear polysulfide polymers of an average molecular weight 4260–1030 g mol⁻¹ can be obtained by the reaction of sodium tetrasulfide and 1,1′-[methylenebis(oxy)]-bis-[2-chloroethane] in the presence of 2.0–5.0 mol of hydrazine and at least 4.0 mol of sodium hydroxide/mol of hydrazine in a one-step procedure. The disulfide polymers in the form of sodium mercaptide are soluble in the supernatant liquid from which they are separated by acidification of the solution to a pH value of about 4. The average molecular weight and the content of sulfur in the obtained linear polymers were determined and their IR spectra were recorded. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1363–1367, 1997     

液流储能电池技术研究进展

液流储能电池技术是一种高效、大规模电化学储能技术,在风能、太阳能等可再生能源发电、智能电网建设等方面有着广阔的应用前景。本文重点对全钒、多硫化钠-溴和锌-溴液流储能电池的工作原理、特点、国内外研究现状及发展趋势进行了综述,并对其他探索性液流储能电池体系进行了介绍。提出了制约液流储能电池技术发展瓶颈问题,展望了液流储能电池未来发展趋势。     

Preparation of a Carbon Nanotube-Reinforced UV/Heat Dual-Curable Adhesive for Liquid Crystal Displays

Abstract

There is strong demand for narrow-bezel liquid crystal displays (LCDs) in the display industry. Adhesive materials for narrow-bezel LCDs require excellent adhesive properties in order to provide the same level of adhesive strength as conventional sealants, even when applied in small amounts. In this study, we prepared a previously unknown, highly adhesive, carbon nanotube-reinforced (CNT-reinforced) UV/heat dual-curable adhesive for narrow-bezel LCDs. Single-walled and multi-walled CNTs (SWCNTs and MWCNTs) were employed as fillers, resulting in superior adhesive properties; in particular, the inclusion of SWCNTs improved both adhesion and resistance to water permeability compared to a conventional adhesive.     

Phenol‐Derived Carbon Sealant Inspired by a Coalification Process

Recently, emerging functions utilizing phenolic molecules, such as surface functionalizing agents or bioadhesives, have attracted significant interest. However, the most important role of phenolic compounds is to produce carbonized plant matter called “coal”, which is widely used as an energy source in nearly all countries. Coalification is a long‐term, high‐temperature process in which phenols are converted into conducting carbonized matter. This study focuses on mimicking coalification processes to create conducting sealants from non‐conducting phenolic compounds by heat treatment. We demonstrate that a phenolic adhesive, tri‐hydroxybenzene (known as pyrogallol), and polyethylenimine mixture initially acts as an adhesive sealant that can be converted to a conducting carbon sealing material. The conductivity of the phenolic sealant is about 850 Ω^?1 cm^?1, which is an approximately two‐fold enhancement of the performance of carbon matter. Applications of the biomimetic adhesives described herein include conducting defect sealants in carbon nanomaterials and conducting binders for metal/carbon or ceramic/carbon composites.