Synthesis and Stability of Aryl Bis(nitrile oxides) With Potential as Curing Agents for Polysulfide Sealants

1989 ◽  
Vol 42 (2) ◽  
pp. 287 ◽  
Author(s):  
PJ Hanhela ◽  
DB Paul
Keyword(s):  
Nitrile Oxides ◽  
Liquid Polymers ◽  
Convenient Route ◽  
Curing Agents

Several aromatic bis( nitrile oxides) have been prepared as potential curing agents for sealants produced from thiol -terminated polysulfide liquid polymers. All were obtained by dehydrohalogenation of α-halo oximes and the requisite aldehydes were synthesized from either the dimethyl derivatives or the chloromethylated hydrocarbons. The direct chloromethylation of naphthalene which offered a convenient route to the naphthalene-1,4- and 1,5-bis(carbonitrile oxides) was re-examined. Also prepared were naphthalene-2,6-bis(carbonitri1e oxide), anthracene-9,10-bis(carbonitri1e oxide) and 4,4′-sulfonylbisbenzonitrile dioxide. The course of the reaction between naphthalene-2,3-dicarbaldehyde and hydroxylamine was established and shown to differ from that involving phthalaldehyde. Stabilities of the nitrile oxides at -15�, 4� and 25� were assessed by spectroscopic means.

Organic Curing Agents for Polysulfide Sealants. III. A Mechanistic Interpretation of the Thermal Degradation of Nitrile Oxide-Cured Polysulfide Sealants

1990 ◽  
Vol 43 (1) ◽  
pp. 109 ◽  
Author(s):  
BC Ennis ◽  
PJ Hanhela ◽  
DB Paul
Keyword(s):  
Thermal Analysis ◽  
Acid Group ◽  
Spectroscopic Studies ◽  
Nitrile Oxide ◽  
Side Chain ◽  
Polymer Backbone ◽  
Nitrile Oxides ◽  
Liquid Polymers ◽  
Curing Agents ◽  
Group B

Sealants obtained by cure of polysulfide liquid polymers with aryl bis ( nitrile oxides) possess the thiohydroximic acid ester structural feature. Unexpectedly these materials were found to exhibit poor thermal stability: when heated at 60° they soften within days and liquefy in 3 weeks. Products obtained with excess nitrile oxide degraded faster than those produced with equimolar amounts of reagents. Interpretations considered included (A) dissociation of the thiohydroximic acid group, (B) reaction between nitrile oxide and a reactive centre in the polysulfide structure, and (c) addition of nitrile oxide to the side chain. It was shown that neither of the first two possibilities was applicable. Moreover, spectroscopic studies demonstrated that, after an initial rapid addition between nitrile oxide and thiol , a second slower reaction occurred which consumed additional nitrile oxide. Although aldehyde oximes and a- chloro oximes do not participate in such processes unless catalysts are present, thiohydroximic acid derivatives were shown to react with nitrile oxides at ambient temperature to form 1,2,4-oxadiazole 4-oxides and alkyl thiol . For the case of a polysulfide sealant the equivalent rupture of a C-S bond to form the thiol involves cleavage of the polymer backbone. Continuation of the process would lead to degradation of the sealant. These observations were supported by thermal analysis studies on the polysulfide sealants and model polymers.

Organic Curing Agents for Polysulfide Sealants. II. Additions of Thiols to Nitrile Oxides: Scope, Relative Reactivities and Application to the Cure of Polysulfide Sealants

1989 ◽  
Vol 42 (8) ◽  
pp. 1257 ◽  
Author(s):  
PJ Hanhela ◽  
DB Paul
Keyword(s):  
Ambient Temperature ◽  
Elevated Temperatures ◽  
Barium Oxide ◽  
Free Products ◽  
Ambient Temperatures ◽  
Nitrile Oxides ◽  
Curing Agents ◽  
In Situ Generation ◽  
Long Chain

Efficient addition between various nitrile oxides and both short (C2) and long chain (C16) alkyl thiols , aliphatic dithiols and aryl thiols occurred rapidly at ambient temperature with the formation of thiohydroximic acid derivatives. Competitive experiments with bis( nitrile oxides) showed that for terephthalonitrile oxide the second addition proceeded more readily than the first whereas with anthracene-9,l0-bis(carbonitrile oxide) elevated temperatures were needed to obtain the diadduct. Relative reactivities of a number of thiols with nitrile oxides were also determined spectroscopically . Reaction between prop-2-ene-1-thiol and p-nitrobenzonitrile oxide afforded products resulting from both cycloaddition and 1,3-addition with the latter predominating. The polysulfide prepolymer LP-2 was cured effectively at ambient temperatures by both terephthalonitrile oxide and 4,4'-sulfonylbisbenzonitrile dioxide at CNO to SH ratios of 1.5 and higher giving tack-free products within 0.5 h and 90% cure in under 4 h. For the less highly cross-linked LP-32-based sealants, curing was a little slower. Unreinforced sealants produced in this manner were firm elastomers with hardness of 35-40 (Rex A). The naphthalenebis (carbonitrile oxides) afforded softer products while anthracene-9,10- bis(carbonitrile oxide) was ineffective. One-part formulations involving in situ generation of nitrile oxide from hydroximoyl chlorides and barium hydroxide (formed by action of water vapour on barium oxide) were also produced.

Extraction and identification of fillers and pigments from pyrolyzed rubber and tire samples

1996 ◽  
Vol 54 ◽  
pp. 174-175
Author(s):  
P. Sadhukhan ◽  
J. B. Zimmerman
Keyword(s):  
Zinc Oxide ◽  
Electron Microscope ◽  
Carbon Black ◽  
Natural Rubber ◽  
Transmission Electron Microscope ◽  
Rolling Resistance ◽  
Synthetic Polymers ◽  
Nitrogen Atmosphere ◽  
Transmission Electron ◽  
Curing Agents

Rubber stocks, specially tires, are composed of natural rubber and synthetic polymers and also of several compounding ingredients, such as carbon black, silica, zinc oxide etc. These are generally mixed and vulcanized with additional curing agents, mainly organic in nature, to achieve certain “designing properties” including wear, traction, rolling resistance and handling of tires. Considerable importance is, therefore, attached both by the manufacturers and their competitors to be able to extract, identify and characterize various types of fillers and pigments. Several analytical procedures have been in use to extract, preferentially, these fillers and pigments and subsequently identify and characterize them under a transmission electron microscope.Rubber stocks and tire sections are subjected to heat under nitrogen atmosphere to 550°C for one hour and then cooled under nitrogen to remove polymers, leaving behind carbon black, silica and zinc oxide and 650°C to eliminate carbon blacks, leaving only silica and zinc oxide.

Diacylfuroxans Are Masked Nitrile Oxides That Inhibit GPX4 Covalently

2019 ◽  
Author(s):  
John Eaton ◽  
Richard A. Ruberto ◽  
Anneke Kramm ◽  
Vasanthi S. Viswanathan ◽  
Stuart Schreiber
Keyword(s):  
Molecular Mechanism ◽  
Mechanism Of Action ◽  
Therapeutic Target ◽  
Biologically Active ◽  
Drug Resistant ◽  
Nitrile Oxides ◽  
Molecular Mechanism Of Action

<div><div><div><p>GPX4 represents a promising yet difficult-to-drug therapeutic target for the treatment of, among others, drug-resistant cancers. While most GPX4 inhibitors rely on a chloroacetamide moiety to modify covalently the protein’s catalytic selenocysteine residue, the discovery and mechanistic elucidation of structurally diverse GPX4-inhibiting molecules has uncovered novel electrophilic warheads that bind and inhibit GPX4. Here we report our discovery that diacylfuroxans can act as masked nitrile oxides that inhibit GPX4 covalently. These observations illuminate a novel molecular mechanism of action for biologically active furoxans and also suggest that nitrile oxides may be uniquely suited to targeting GPX4.</p></div></div></div>

scholarly journals Effect of Curing Agents on Electrical Properties of Low-Temperature Curing Conductive Coatings and Thermodynamic Analysis

Coatings ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 656
Author(s):  
Junjie Shu ◽  
Yang Wang ◽  
Bei Guo ◽  
Weihua Qin ◽  
Lanxuan Liu ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Low Temperature ◽  
Surface Resistance ◽  
Advanced Manufacturing ◽  
Curing Time ◽  
Conductive Coatings ◽  
Exponential Factor ◽  
Design Expert ◽  
Surface Method ◽  
Curing Agents

Silver-based high-conductivity coatings are used in many advanced manufacturing equipment and components, and existing coatings require high-temperature curing. This paper studies the effects of different curing agents on the electrical properties of low-temperature curing (<100 °C) conductive coatings, and analyzes the effects of different curing temperatures and curing time on the surface resistance, square resistance and resistivity of conductive coatings. The response surface method in Design Expert was used to construct the model, and the curing thermodynamics of different curing agents were analyzed by DSC. It was found that curing agents with lower Tm and activation energy, higher pre-exponential factor and more flexible segments are beneficial to the preparation of highly conductive coatings.

scholarly journals Selective growth of Ti3+/TiO2/CNT and Ti3+/TiO2/C nanocomposite for enhanced visible-light utilization to degrade organic pollutants by lowering TiO2-bandgap

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jeasmin Akter ◽  
Md. Abu Hanif ◽  
Md. Akherul Islam ◽  
Kamal Prasad Sapkota ◽  
Jae Ryang Hahn
Keyword(s):  
Visible Light ◽  
Structural Integrity ◽  
Carbon Layer ◽  
Wide Bandgap ◽  
Blue Dye ◽  
X Ray Diffraction ◽  
Experimental Conditions ◽  
Excellent Photocatalytic Activity ◽  
Convenient Route ◽  
Walled Carbon Nanotubes

AbstractA convenient route was developed for the selective preparation of two stable nanocomposites, Ti3+/TiO2/CNT (labeled as TTOC-1 and TTOC-3) and Ti3+/TiO2/carbon layer (labeled as TTOC-2), from the same precursor by varying the amount of single-walled carbon nanotubes used in the synthesis. TiO2 is an effective photocatalyst; however, its wide bandgap limits its usefulness to the UV region. As a solution to this problem, our prepared nanocomposites exhibit a small bandgap and wide visible-light (VL) absorption because of the introduction of carbonaceous species and Ti3+ vacancies. The photocatalytic efficiency of the nanocomposites was examined via the degradation of methylene blue dye under VL. Excellent photocatalytic activity of 83%, 98%, and 93% was observed for TTOC-1, TTOC-2, and TTOC-3 nanocomposites within 25 min. In addition, the photocatalytic degradation efficiency of TTOC-2 toward methyl orange, phenol, rhodamine B, and congo red was 28%, 69%, 71%, and 91%, respectively, under similar experimental conditions after 25 min. Higher reusability and structural integrity of the as-synthesized photocatalyst were confirmed within five consecutive runs by photocatalytic test and X-ray diffraction analysis, respectively. The resulting nanocomposites provide new insights into the development of VL-active and stable photocatalysts with high efficiencies.

scholarly journals Self-healing Ability of Epoxy Vitrimer Nanocomposites Containing Bio-Based Curing Agents and Carbon Nanotubes for Corrosion Protection

2021 ◽  
Author(s):  
Narubeth Lorwanishpaisarn ◽  
Natwat Srikhao ◽  
Kaewta Jetsrisuparb ◽  
Jesper T. N. Knijnenburg ◽  
Somnuk Theerakulpisut ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Corrosion Protection ◽  
Self Healing ◽  
Curing Agents

scholarly journals Synthesis, characterization and CO2 sorption capacity measurements of selected ionic liquid polymers

2020 ◽  
Author(s):  
A. Vijaya Bhaskar Reddy ◽  
Muhammad Moniruzzaman ◽  
Bidyut Baran Saha ◽  
N. Bakthavatchala Reddy ◽  
Grigory V. Zyryanov
Keyword(s):  
Ionic Liquid ◽  
Sorption Capacity ◽  
Co2 Sorption ◽  
Liquid Polymers
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