Kinetics and mechanism of the ozone degradation of nitrile rubbers in solution

Anachkov, M.P.; Rakovsky, Slavcho; Stefanova, R.; Шопов, Д.

doi:10.1016/0141-3910(87)90031-0

Cited by 18 publications

(11 citation statements)

References 7 publications

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“…The integrated intensity of that signal compared with the signal of aldehyde protons at 9.70–9.79 ppm was about 10%. Similar signal at 2.75 ppm has been registered in the spectra of ozonized butadiene–nitrile rubbers, in which the 1,4‐trans double bonds are dominant 23…”

Section: Resultssupporting

confidence: 76%

“…The φ values, determined by viscometric measurements, do not correspond to the real extent of the degradation efficiency of the elastomers 16, 19, 22, 23. The discrepancy between the viscometric data and those obtained by functional group analysis is a result of uneven distribution of the degradation process in the bubbling reactor.…”

Section: Resultsmentioning

confidence: 90%

“…and22. In the case of 1,4‐ cis ‐polybutadiene, because of the very high values of its rate constant with ozone (6 × 10 4 L mol −1 s −1 2), the instantaneous volume of the polymeric solution layer in which the reaction takes place is about 1.1 × 10 −3 cm 3 (0.007% from the total volume)23; the frequency of replacement of the boundary surface of the liquid phase is about 250 times per second 22. The intensive progress of the reaction in a very small volume determines the formation of significant amount of low‐molecular‐mass fragments which in practice cannot be viscometrically detected.…”

Section: Resultsmentioning

confidence: 99%

“…It has been found that the crosslinks of polymers containing double CC bonds in the side chain have peroxide nature 29. The kinetics of the crosslinking process during ozonolysis of polymers with double bonds has been studied in Refs 23. and31.…”

Section: Resultsmentioning

confidence: 99%

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Does combination of lipid formulation of amphotericin B and echinocandins improve outcome of invasive aspergillosis in hematological malignancy patients?

Mihu

Kassis

Ramos

et al. 2010

Cancer

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BACKGROUND:In vitro and in vivo studies suggested that combination of lipid formulation of amphotericin B (L‐AMB) and echinocandins may have a synergistic or additive effect against Aspergillus. Furthermore, clinical studies suggested that this combination may improve response of invasive aspergillosis (IA).METHODS:Between August 1993 and June 2008, the authors identified a total of 159 patients with hematological malignancies who received salvage therapy for IA, with L‐AMB alone, echinocandins alone, or a combination of L‐AMB and echinocandins. Clinical characteristics, response to salvage therapy, and death up to 12 weeks after initiation of salvage therapy were retrospectively determined for all patients.RESULTS:Seventy patients received salvage therapy with L‐AMB, 18 patients received echinocandins alone (89% of whom received caspofungin), and 71 patients received the combination therapy of amphotericin B and echinocandins (90% of who received caspofungin). The 3 salvage treatment groups were comparable in regard to clinical characteristics; graft versus host disease was more frequently encountered in the echinocandin group, whereas more patients in the L‐AMB and combination groups had neutropenia and received immunotherapy. The response to salvage therapy was better in the echinocandin group (9% L‐AMB, 28% echinocandins, and 21% for combination therapy). The 3 groups had a comparable rate of Aspergillus‐related death (58%‐64%) and overall mortality (61%‐67%).CONCLUSIONS:The combination of L‐AMB and echinocandins offered no advantage in terms of improving response or reducing mortality over either drug alone. Hence, this combination will only add to the cost of therapy without any improvement in outcome in patients with hematological malignancies. Cancer 2010. © 2010 American Cancer Society.

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Section: Resultssupporting

confidence: 76%

Section: Resultsmentioning

confidence: 90%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

See 2 more Smart Citations

Does combination of lipid formulation of amphotericin B and echinocandins improve outcome of invasive aspergillosis in hematological malignancy patients?

Mihu

Kassis

Ramos

et al. 2010

Cancer

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“…Moreover, the presence of this highly oxidizing gas within the hollow insulator was thought to be responsible for the corrosion observed on the metallic parts. It was also thought to induce the mechanical breaking of the nitrile piston seal, known for poor ozone resistance [36][37][38].…”

Section: Failure Mechanismsmentioning

confidence: 99%

Effects of electric partial discharges on the rheological and chemical properties of polymers used in HV composite insulators after railway service

Habas

Arrouy

Perrot³

2009

IEEE Trans. Dielect. Electr. Insul.

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The origin and the consequences of the electric failure of in-service composite hollow insulators used in railway transportation were investigated. Direct electrical measurements made it possible the detection of partial discharges (PD) and UV emissions allowed of identifying the location of the PD at the interface between metal braids and a silicone liner. To investigate the effects of the damaging PD activity, physicochemical properties of the different polymers were investigated and compared to new samples. The thermomechanical properties of the HTV and RTV silicones showed important alterations in the polymers structure. The chemical analyses of the silicones and nitrile rubber conducted using ATR-FTIR spectroscopy revealed that the polymers were oxidized after electrical failure. The results indicated that the ozone production and UV emission were due to the surface electrical activities. The breakdown of alumina trihydrate (ATH) in the inner HTV silicone liner demonstrated that undesired electrical discharges induced an significant increase of temperature and the formation of moisture in the air present in the hollow insulator. Laboratory artificial aging performed on the silicones and nitrile rubber showed similar degradation as in service. Further electrical experiments conducted on empty hollow insulators enabled the detection of internal PD located in micro-voids present in the adhesive used to bond the HTV silicone liner to the inner composite tube.

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Ozonolysis of polybutadienes with different microstructure in solution

Anachkov

Rakovsky

Заиков

2007

J of Applied Polymer Sci

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ABSTRACT:The reaction of ozone with 1,4-cis-polybutadiene and polybutadiene having the following linking of the butadiene units: 1,4-cis (47%), 1,4-trans (42%), 1,2 (11%) was investigated in CCl 4 solution. It was found out by means of IR-spectroscopy and 1 H-NMR spectroscopy that the basic ozonolysis products of both elastomers are ozonides and aldehydes. The aldehyde:ozonide ratio was 11 : 89 and 27 : 73 for E-BR and BR, respectively. In addition, epoxide groups were detected, only in the case of BR, and their yield was about 10% of that of the aldehydes. On the basis of BR ozonolysis it was established that the ozonide yield from 1,4-trans units is about 50%. By using the aldehyde yields, an evaluation was made of the efficiency of ozone degradation of the two polybutadienes, according to which the respective value of BR is considerably higher than that of E-BR. A reaction mechanism is proposed, which explains the formation of the identified functional groups and the differences in the ozone degradation of the studied elastomers.

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Kinetics and mechanism of the ozone degradation of nitrile rubbers in solution

Cited by 18 publications

References 7 publications

Does combination of lipid formulation of amphotericin B and echinocandins improve outcome of invasive aspergillosis in hematological malignancy patients?

Does combination of lipid formulation of amphotericin B and echinocandins improve outcome of invasive aspergillosis in hematological malignancy patients?

Effects of electric partial discharges on the rheological and chemical properties of polymers used in HV composite insulators after railway service

Ozonolysis of polybutadienes with different microstructure in solution

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