A novel UV-light stabilizer (UVLS), 3′-(2H-benzotriazol-2′′-yl)-1,1,1-tris(4′-hydroxyphenyl)-ethane or simply tris(hydroxyphenyl)ethane benzotriazole (THPE-BZT), that can be copolymerized with engineering plastic monomers has been synthesized in three steps. The compound has two solid forms, a hydrate and an anhydrous form. Surprisingly, the hydrated form is more soluble in organic solvents such as acetone. Infrared spectra reveal that the hydrated form loses water of hydration upon heating and then forms a coplanar ring structure with a strong intramolecular hydrogen bond (IMHB) between one benzotriazole nitrogen and the adjacent phenolic OH. The NMR and UV-vis spectra in less polar organic solvents are also in accordance with the IMHB structure of THPE-BZT. In polar organic solvents such as DMSO and DMF and in MeOH/water at pH >10, the IMHB is disrupted, and the disrupted form exists in equilibrium with the planar or nondisrupted form. However, THPE-BZT copolymerized into low molecular weight polysulfones and polycarbonates retains the planar IMHB structure, as indicated by the UV absorption peak at ∼335 nm. These copolymers have greater UV stability than those without any THPE-BZT because of dissipation of photon energy by molecular vibrational relaxation in the planar form. Also, polysulfone copolymers containing THPE-BZT in the range of 0.25-1.5 mol % have greater UV light stability than polysulfone containing additive-type UVLS such as 2-(2′-hydroxy-5′-t-octylphenyl)benzotriazole (Cyasorb 5411). For polycarbonates, preliminary results show that copolymers of THPE-BZT have UV-light stability comparable to or only slightly less than that of polycarbonates blended with Cyasorb 5411 or THPE-BZT as additives. But the copolymers should escape the problems of surface "blooming" and leaching by extraction experienced by noncopolymerized UVLS additives. Thermogravimetric analysis indicates that THPE-BZT is more stable than the commercial benzotriazoles 2-(2′-hydroxy-5′-methylphenyl)benzotriazole (Tinuvin P), Cyasorb 5411, and the industrial standards2-[2′-hydroxy-3′,5′-bis (1-methyl-1-phenylethyl)phenyl]benzotriazole (Tinuvin 900)sand therefore might offer superior performance, even as an additive.

The absorption characteristics of ethiofos were studied using the rat in situ intestine circulating perfusion technique. Slow absorption kinetics were observed for ethiofos with varying rates of absorption and metabolism/degradation in situ as a function of buffer and absorption enhancers. In most cases less than 10 per cent of the radiolabeled compound is lost from the circulating perfusate in 90 min. In addition, over the same time period greater than 40 per cent of the intact parent compound was lost by degradation. Much of the difference can be accounted for in the formation of the free thiol metabolite. WR-1065, suggesting ester hydrolysis or metabolic activity. Good stability was observed in all perfusate systems ex vivo indicating that the degradation occurs in situ. The disodium salt of ethylenediaminetetraacetic acid (EDTA) was shown to be an effective absorption enhancer of ethiofos. The enhancement of intestinal absorption by EDTA was dose-dependent resulting in a 20-fold increase in blood levels of ethiofos in the portal blood. Follow-up studies in the rhesus monkey confirm this observation. Salicylate and dimethylsulfoxide (DMSO) also resulted in absorption enhancement although to a lesser degree than that seen after EDTA treatment. Addition of several alkaline phosphatase inhibitors did not significantly improve absorption of ethiofos in the rat small intestine. Proposed mechanism(s) for intestinal absorption and absorption enhancement of ethiofos are discussed.

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Chemical methods of processing ceramics have the potential to overcome many of the processing-related obstacles that have hindered widespread commercialization. The Southwest Research Institute (SwRI) has focused on the development of polymeric precursors to silicon nitride (Si3N4). One such precursor, perhydropolysilazane (or PHPS), has been shown to be a useful binder for Si3N4 powder processing, a useful matrix precursor for the polymer infiltration/pyrolysis (PIP) processing of fiber-reinforced Si3N4, and a useful ceramic coating precursor for the repair of oxidation protection coatings on carbon-carbon composites. While conventional, thermal pyrolyses of these preceramnics has been sufficient to demonstrate their potential, substantial cost savings could be realized if the polymer-to-ceramic conversion could be instigated with electromagnetic energy. We have investigated the use of millimeter wave heating as a means of converting PHPS into Si3N4, and report here the results of our efforts to produce bulk compacts, coatings, and fiber-reinforced ceramics.