The chemical composition of commercial BF/sub 3/:amine complexes are variable and contain BF/sub 4//sup -/ and BF/sub 3/(OH)/sup -/ salts together with other unidentified highly reactive species. The BF/sub 3/:amine complexes, which are susceptible to hydrolysis, also partially convert to the BF/sub 4//sup -/ salt (i.e. BF/sub 4//sup -/NH/sub 3//sup +/C/sub 2/H/sub 5/) upon heating. This salt formation is accelerated in dimethyl sulfoxide solution and in the presence of the epoxides that are present in commercial prepregs. Commercial C fiber-epoxy prepregs are shown to contain either BF/sub 3/:NH/sub 2/C/sub 2/H/sub 5/ or BF/sub 3/:NHC/sub 5/H/sub 10/ species together with their BF/sub 4//sup -/ salts and a variety of boron-fluorine or carbon-fluorine prepreg species. Considerable variation in the relative quantities of BF/sub 3/:amine to its BF/sub 4//sup -/ salt was observed from prepreg lot to lot, which will cause variable viscosity-time-temperature prepreg cure profiles. It is concluded that the chemically stable and mobile BF/sub 4//sup -/ salt is the pre-dominant catalytic species, acting as a cationic catalyst for the prepreg cure reactions. During the early stages of cure the BF/sub 3/:amine catalyst converts to the BF/sub 4//sup -/ salt in the presence of epoxides, whereas the BF/sub 3/-prepreg species are susceptiblemore » to catalytic deactivation and immobilization.« less

Diaminodiphenyl sulfone (DDS) cured tetraglycidyl 4,4' diaminodiphenyl methane (TGDDM) epoxies are the most-common composite matrices utilized in high-performance fibrous composites. Our recent studies on the characterization of these epoxies from the processing and durability viewpoints are described. The effects of DDS concentration, BF/sub 3/:NH/sub 2/C/sub 2/H/sub 5/ catalyst composition, TGDDM impurities, and prepreg mixing conditions on the processing of the composite, cure reactions, and the resultant chemical and physical structure of TGDDM-DDS epoxies are presented. 8 figures.

The requirements of protective coatings for corrosion control of offshore structures are given and a comparison is made of the relevant properties of high build vinyl and chlorinated rubber paints with high build traditional epoxies. While improvement of the weak points of vinyl or chlorinated rubber paints can not be made because they are physical drying paints, it is possible to improve the curing characteristics of epoxy resins at low temperatures. Experience with polyamide adduct cured epoxy coatings and isocyanate cured epoxies in zero and sub-zero conditions is summarised.

Results from spectroscopic investigations are presented that demonstrate the effect of oil cracking on shale oil composition. Techniques used include infrared spectroscopy, capillary column gas chromatography/mass spectroscopy and /sup 13/C nuclear magnetic resonance. We show that cracking causes an increase in aromatic and alkene content of the oil. We compare our results for oils prepared in the laboratory with oils prepared in the TOSCO-II semi-works and in modified and true-in-situ combustion retorts. We demonstrate that the napthalene/2-methyl-naphthalene ratio is a good indicator of cracking conditions in an oil shale retort.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTKinetics of Thermal Decomposition of Liquid Nitric AcidC. W. Tait, J. A. Happe, R. W. Sprague, and H. F. CordesCite this: J. Am. Chem. Soc. 1956, 78, 12, 2670–2673Publication Date (Print):June 1, 1956Publication History Published online1 May 2002Published inissue 1 June 1956https://doi.org/10.1021/ja01593a003RIGHTS & PERMISSIONSArticle Views196Altmetric-Citations8LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (474 KB) Get e-Alerts Get e-Alerts

DDS and TGDDM epoxies are currently the most commonly used matrices for high performance fibrous composites. Systematic Fourier - transform infrared spectroscopy (FTIR) studies of the cure reactions of these epoxies are reported as a function of cure conditions, DDS concentration and the presence or absence of BF/sub 3/ catalyst. From these studies, the TGDDM epoxide was found to undergo homopolymerization to form either (CH/sub 2/OH)CH-CH(CH/sub 2/OH) or ether linkages in the absence of DDS. Such reactions are accelerated by epoxide impurities and a BF/sub 3/ catalyst and also occur in the presence of DDS. For TGDDM-DDS systems epoxide-amine addition reactions occur in which all primary amine and approx. 50% secondary amine groups are consumed. The BF/sub 3/ cured systems are more ductile relative to the noncatalyzed systems because they contain less network defects in the form of unreacted epoxide groups. Inhomogeneous mixing of the components together with the catalytic activity of the BF/sub 3/ catalyst in commercial TGDDM-DDS epoxies are also discussed.