The Ozonation of N,N′-Di-n-Octyl-p-Phenylenediamine and N,N′-Di-(1,1-Dimethylethyl)-p-Phenylenediamine

1991 ◽  
Vol 64 (5) ◽  
pp. 780-789 ◽  
Author(s):  
R. P. Lattimer ◽  
R. W. Layer ◽  
E. R. Hooser ◽  
C. K. Rhee
Keyword(s):  
Film Theory ◽  
Chain Scission ◽  
Protective Film ◽  
Self Healing ◽  
Reaction Products ◽  
Double Bonds ◽  
Final Theory ◽  
Rubber Compounds ◽  
Rubber Surface ◽  
Paraffin Waxes

Abstract Ozone attack on rubber compounds causes characteristic cracking perpendicular to the direction of applied stress. This degradation is caused by reaction of ozone with the double bonds in the rubber molecules. This causes chain scission and the formation of various decomposition products. The general subject of protection of rubber against ozone attack has been reviewed by a number of authors. In order to control the effects of rubber ozonation, either paraffin waxes or chemical antiozonants are added to unsaturated rubbers. The most effective antiozonants are N,N′-disubstituted-p-phenylenediamines (PPDAs), in which at least one of the side groups is alkyl (preferably sec-alkyl). Several theories have appeared in the literature regarding the mechanism of antiozonant protection. The “scavenger” model states that the antiozonant blooms to the surface and preferentially reacts with ozone so that the rubber is not attacked until the antiozonant is exhausted. The “protective film” theory is similar, except that the ozone-antiozonant reaction products form a film on the rubber surface that prevents (physically and perhaps chemically as well) ozone attack on the rubber. A third “relinking” theory states that the antiozonant prevents scission of the ozonized rubber or else recombines severed double bonds. A final theory states that the antiozonant reacts with the ozonized rubber or Criegee zwitterion (carbonyl oxide) to give a low-molecular-weight, inert, “self-healing” film on the rubber surface. Currently, the most accepted mechanism of antiozonant action is a combination of the scavenger and protective film theories.

The Reaction of Ozone with Rubber

1959 ◽  
Vol 32 (1) ◽  
pp. 269-277 ◽  
Author(s):  
Harold Tucker
Keyword(s):  
Chain Scission ◽  
Crack Development ◽  
Original Material ◽  
Protective Film ◽  
Double Bonds ◽  
Stress Strain ◽  
Ultimate Elongation ◽  
Rubber Surface ◽  
Fresh Surface

Abstract The reaction of ozone with an unsaturated elastomer is very rapid until the double bonds at the surface have reacted. Only then do the double bonds beneath the surface become available for reaction with ozone. In this respect, unstressed rubber is similar to the metals that are protected from oxidation by a film of oxide formed on the surface. When this protective film is broken and fresh surface is exposed, the reaction can continue. This is the situation that exists when the rubber is under strain. Since the entire rubber surface can be considered as under a uniform bombardment by ozone molecules, to consider cracks in stressed rubber as arising from a directed chain scission process seems unrealistic. On the assumption that the double bonds in the rubber surface are equally reactive, and that ozone does not act as a pair of chemical shears snipping double bonds at right angles to the strain, crack development must then arise from the fact that the stress-strain characteristics of the rubber-ozone reaction product are not indentical to those of the original material and that ultimate elongation decreases continuously with increasing reaction with ozone. That such a mechanism would produce the type of cracks produced by ozone reacting with rubber can be shown by modifying the nature of the surface by vulcanization.

scholarly journals SYNTHESIS OF SULFUR-CONTAINED MICROCAPSULES AND POTENTIAL APPLICATION IN RUBBER

2019 ◽  
Vol 57 (3A) ◽  
pp. 29
Author(s):  
La Thi Thai Ha ◽  
Chau Ngoc Mai
Keyword(s):  
Crucial Role ◽  
Potential Application ◽  
Urea Formaldehyde ◽  
The Self ◽  
Self Healing ◽  
Core Content ◽  
Rubber Compounds ◽  
Rubber Surface ◽  
Average Size ◽  
Vulcanize Rubber

Microcapsule-based material is potentially utilized in a variety of fields such as pharmaceuticals, food, biology, self-healing materials, etc. More remarkedly, in the rubber-related fields, this outstanding material is able to have a crucial role to play as an alternative of sulfur in compounding and vulcanizing process with regard to the self-healing ability after cracking. In this research, the interface polymerization was applied to generate microcapsules, whose shell was synthesized from Urea-formaldehyde pre-polymer modified by 0.25 wt% melamine containing sulfur (S) as a core substance. When the synthesizing process was carried out at 80 C and stirring rate of 300 rpm in 2 hours, the microcapsule product was spherical with the average size of 115 m and contained 60% of core content that was examined by FTIR, DLS, SEM, TGA and experimented the potential application. As a result, the amount of 8 phr of produced microcapsules utilized in NBR rubber compounds necessitated a longer time to vulcanize rubber at 160 C  compared to using 5 phr free S. Besides, the mechanical strength of the microcapsules-contained product was insignificantly changed but bloom-like phenomenon on the rubber surface was markedly improved. It is noticeable that the vulcanized NBR rubber with the presence of these microcapsules are well able to heal its crack or cut when heated up to 150 C in 10 minutes while the free S-vulcanized NBR rubber is definitely unable to be self-healing in the same conditions.

Mechanisms of Ozonation of N-(1,3-Dimethylbutyl)-N′-Phenyl-p-Phenylenediamine

1983 ◽  
Vol 56 (2) ◽  
pp. 431-439 ◽  
Author(s):  
R. P. Lattimer ◽  
E. R. Hooser ◽  
R. W. Layer ◽  
C. K. Rhee
Keyword(s):  
Amine Oxide ◽  
Film Theory ◽  
Nitroxide Radical ◽  
Side Chain ◽  
Low Molecular Weight ◽  
Protective Film ◽  
Oxide Formation ◽  
Chain Oxidation ◽  
Rubber Compounds ◽  
Ozonation Product

Abstract The ozonation products of a common rubber antiozonant, N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (HPPD), have been separated by liquid chromatography and identified by mass spectrometry. Three principal mechanisms appear to govern the ozonation of HPPD. Amine oxide formation leads to observed nitrosoaryl and nitroaryl products. Side-chain oxidation leads to several low molecular weight products, including some that contain an amide moiety. Nitroxide radical formation leads to a nitrone that is the most abundant ozonation product; a dinitrone is also formed. Ozonation of HPPD occurs mainly with degradation of the alkyl portion of the molecule. The results of this study are consistent with a combined “scavenger-protective film” theory of antiozonant protection of rubber compounds.

On the Reaction of 2,5-Dihydroxy-[1,4]-benzoquinone with Diamines – Strain-induced Reactivity Effects

2020 ◽  
Vol 24 ◽  
Author(s):  
Hubert Hettegger ◽  
Andreas Hofinger ◽  
Thomas Rosenau
Keyword(s):  
Nucleophilic Substitution ◽  
Product Structure ◽  
Carbonyl Groups ◽  
Reaction Products ◽  
Double Bonds ◽  
Oh Groups ◽  
Natural Geometry ◽  
Quinoid Structure ◽  
Bond Localization

: The regioselectivity of the reaction of 2,5-dihydroxy-[1,4]-benzoquinone (DHBQ) with diamines could not be explained satisfactorily so far. In general, the reaction products can be derived from the tautomeric ortho-quinoid structure of a hypothetical 4,5-dihydroxy-[1,2]-benzoquinone. However, both aromatic and aliphatic 1,2-diamines form in some cases phenazines, formally by diimine formation on the quinoid carbonyl groups, and in other cases the corresponding 1,2- diamino-[1,2]-benzoquinones, by nucleophilic substitution of the OH groups, the regioselectivity apparently not following any discernible pattern. The reactivity was now explained by an adapted theory of strain-induced bond localization (SIBL). Here, the preservation of the "natural" geometry of the two quinoid C–C double bonds (C3=C4 and C5=C6) as well as the N–N distance of the co-reacting diamine are crucial. A decrease of the annulation angle sum (N–C4–C5 + C4–C5–N) is tolerated well and the 4,5-diamino-ortho-quinones, having relatively short N–N spacings are formed. An increase in the angular sum is energetically unfavorable, so that diamines with a larger N–N distance afford the corresponding ortho-quinone imines. Thus, for the reaction of DHBQ with diamines, exact predictions of the regioselectivity, and the resulting product structure, can be made on the basis of simple computations of bond spacings and product geometries.

scholarly journals Thermodynamic simulation of oxidation process of the Moss-Mo3Si hypoeutectic alloy, doped with scandium or neodymium

2019 ◽  
Vol 57 (2) ◽  
pp. 90-100
Author(s):  
Alexey V. Larionov ◽  
◽  
Ludmila Y. Udoeva ◽  
Vladimir M. Chumarev ◽  
◽  
...  
Keyword(s):  
Oxidation Process ◽  
Thermodynamic Simulation ◽  
Oxidation Products ◽  
Hypoeutectic Alloy ◽  
Protective Film ◽  
Chemical Transformations ◽  
Reaction Products ◽  
Moist Air ◽  
Condensed Product ◽  
Hsc Chemistry

In order to study the effect of yttrium additives on the oxidation of molybdenum silicide alloys, thermodynamic modeling of the interaction in Mo-Mo3Si-Sc5Si3 и Mo-Mo3Si-NdSi systems with dry and moist air was performed in the temperature range 25-2000 °C. The calculations were performed using the HSC Chemistry 6.12 software, into the database of which the calculated missing thermochemical characteristics silicates, molybdates of scandium and neodymium were entered. Based on the obtained dependences of the composition of phases on temperature and charge of the oxidant (air or vapor-air mixture), the sequence of phase formation was determined and the compositions of oxidation products were estimated. It is shown that, under equilibrium conditions, the oxidation process with dry and moist air proceeds almost equally, since the interaction of the components of the alloy with oxygen is thermodynamically preferable than with water vapor. According to the obtained thermodynamic models, the oxidation process of the Mo-5Si-3(Sc, Nd) (wt.%) alloys involves a sequence of the following chemical transformations: at the beginning Mo and Sc (Nd) silicides oxidize forming Sc2O3 ( Nd2O3), SiO2 and elemental Mo, then molybdenum is oxidized to MoO2 and Sc2O3 or Nd2O3 interacts with SiO2 with the formation of appropriate silicates Sc2Si2O7 или Nd2Si2O7. As a result of the complete oxidation of the alloy, MoO3 and Sc2(MoO4)3 or Nd2Mo4O15 are added to the condensed product, and molybdenum oxide (MoO3)n vapor appears in the gas phase. In addition, the formation of Nd2Mo2O7 and Nd2 (MoO4)3 is possible. During the oxidation of the Mo-5Si-3Nd alloy at T> 1700 oC, Nd(OH)3 can be formed in the condensed reaction products. According to the results of complete thermodynamic analysis, the formation of silicates and molybdates of scandium and neodymium can promote to the formation of a protective film on the surface of the alloys, which limits the diffusion of oxygen in them, and as a result, the oxidation resistance of alloys should increase.

scholarly journals Cellulose microfibers (CMFs) reinforced smart self-healing polymeric composite coatings for corrosion protection of steel

2020 ◽  
Author(s):  
Muddasir Nawaz ◽  
Sehrish Habib ◽  
Adnan Khan ◽  
Abdul Shakoor ◽  
Ramazan Kahraman
Keyword(s):  
Corrosion Resistance ◽  
Immersion Time ◽  
Electrochemical Impedance ◽  
Composite Coatings ◽  
Polymeric Composite ◽  
Protective Film ◽  
Self Healing ◽  
Ph Change ◽  
Smart Coatings ◽  
Cellulose Microfibers

The use of organic coating for the metals has been widely being used to protect the surface against corrosion. Polymeric coating incorporated with Nanocontainers loaded with inhibitor and self-healing provides better corrosion resistance. Cellulose microfibers (CMFs) used as smart carriers were synthesized and loaded with dodecylamine (DOC)-inhibitor and polyethyleneimine (PEI)-both inhibitor and self-healing agents. Smart polymeric coatings were developed by mixing CMF/DOC and CMFs/PEI into the epoxy matrix. Reference coatings (that has only CMFs) were also prepared for a compersion. Scanning electron microscope (SEM), X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR) and thermal gravitational analysis (TGA) were used to confirm the loading of DOC and PEI onto the CMFs. UV-vis analysis indicates that the self-release of inhibitor from CMFs is sensitive to pH of the solution and the immersion time. Recovery of controlled surface damage confirms the decent self-healing ability of the prepared smart coatings is due to the efficient release of inhibitor (DOC) and self-healing agent (PEI) in the damaged area leading to the formation of a protective film. Electrochemical impedance spectroscopy (EIS) results demonstrate that corrosion resistance of the smart coating increases with an increase in immersion time which is due to the progressive release of inhibitors from CMFs in response to the pH change. Therefore, smart coatings demonstrate superior properties as compared to the reference coatings. The study reveals the polymeric composite coatings have potential to inhibit the corrosion of steel for oil and gas industry.

scholarly journals Cerium Dioxide Nanoparticles as Smart Carriers for Self-Healing Coatings

Nanomaterials ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 791 ◽  
Author(s):  
Sehrish Habib ◽  
Eman Fayyad ◽  
Muddasir Nawaz ◽  
Adnan Khan ◽  
Rana A. Shakoor ◽  
...  
Keyword(s):  
Corrosion Inhibition ◽  
Cerium Dioxide ◽  
Electrochemical Impedance ◽  
Protective Layer ◽  
Vital Role ◽  
Epoxy Coating ◽  
Gravimetric Analysis ◽  
Protective Film ◽  
Self Healing ◽  
Vis Spectroscopy

The utilization of self-healing cerium dioxide nanoparticles (CeO2), modified with organic corrosion inhibitors (dodecylamine (DDA) and n-methylthiourea (NMTU)), in epoxy coating is an efficient strategy for enhancing the protection of the epoxy coating and increasing its lifetime. Fourier transform infrared (FTIR) spectroscopy analysis was used to confirm the loading and presence of inhibitors in the nanoparticles. Thermal gravimetric analysis (TGA) measurement studies revealed the amount of 25% and 29.75% w/w for NMTU and DDA in the nanoparticles, respectively. The pH sensitive and self-release behavior of modified CeO2 nanoparticles is confirmed through UV-vis spectroscopy and Zeta potential. It was observed, through scanning electron microscopy (SEM), that a protective layer had been formed on the defect site separating the steel surface from the external environment and healed the artificially created scratch. This protective film played a vital role in the corrosion inhibition of steel by preventing the aggressiveness of Cl− in the solution. Electrochemical impedance spectroscopy (EIS) measurements exhibited the exceptional corrosion inhibition efficiency, reaching 99.8% and 95.7% for the modified coating with DDA and NMTU, respectively, after five days of immersion time.

Halogenation of Ethylene Propylene Diene Rubbers

1971 ◽  
Vol 44 (4) ◽  
pp. 1025-1042 ◽  
Author(s):  
R. T. Morrissey
Keyword(s):  
Natural Rubber ◽  
Double Bonds ◽  
Optimum Amount ◽  
Ethylene Propylene ◽  
Rubber Compounds ◽  
Rubber Part ◽  
Curing Agents ◽  
Diene Rubbers ◽  
Curing Systems

Abstract The ethylene propylene diene rubbers (EPDM) have been modified by halogenation. The reaction has been considered as one mainly of addition to the double bonds of the diene portion of the rubber. Dehydrohalogenation may occur to varying degrees, depending on the conditions of the reaction and the diene present in the rubber. Part of the halogen is believed to be in the allylic position. The halogenated EPDM may be vulcanized by sulfur as well as many of the curing agents used for other halogen-containing polymers. Both types of curing systems can function in the same compound. Therefore, the halogenated EPDM rubbers can be covulcanized with the highly unsaturated elastomers such as natural rubber, cis polybutadiene, and the SBR rubbers. The excellent properties, resistance to ozone, and flexing, of the halogenated EPDM can be imparted to these elastomers using standard curing systems. Also, the uncured tack of halogenated EPDM can be improved by increasing amounts of natural rubber. In addition, other advantages are adhesion of these blends to other rubber compounds and metal. It has been shown that the cure compatibility properties of the halogenated EPDM can be varied as the halogen is increased in the rubber. Evidence has been presented which shows there is an optimum amount of halogen necessary for the best properties in mixtures with other elastomers.

Functional Complementation in Escherichia coli of Different Phytoene Desaturase Genes and Analysis of Accumulated Carotenes

1991 ◽  
Vol 46 (11-12) ◽  
pp. 1045-1051 ◽  
Author(s):  
Hartmut Linden ◽  
Norihiko Misawa ◽  
Daniel Chamovitz ◽  
Iris Pecker ◽  
Joseph Hirschberg ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Rhodobacter Capsulatus ◽  
Phytoene Desaturase ◽  
Reaction Products ◽  
Double Bonds ◽  
E Coli ◽  
Synechococcus Pcc 7942 ◽  
Lycopene Cyclase ◽  
Pcc 7942 ◽  
Cis Isomer

Three different phytoene desaturase genes, from Rhodobacter capsulatus, Erwinia uredovora, and Synechococcus PCC 7942, have been functionally complemented with a gene construct from E. uredovora which encodes all enzymes responsible for formation of 15-cis phytoene in Escherichia coli. As indicated by the contrasting reaction products detected in the pigmented E. coli cells after co-transformation, a wide functional diversity of these three different types of phytoene desaturases can be concluded. The carotenes formed by the phytoene desaturase from R. capsulatus were trans-neurosporene with three additional double bonds and two cis isomers. Furthermore, small amounts of three ζ-carotene isomers (2 double bonds more than phytoene) and phytofluene (15-cis and all-trans with + 1 double bond) were detected as inter- mediates. When the subsequent genes from E. uredovora which encode for lycopene cyclase and β-carotene hydroxylase were present, neurosporene, the phytoene desaturase product of R. capsulatus, was subsequently converted to the monocyclic β-zeacarotene and its mono- hydroxylation product. The most abundant carotene resulting from phytoene desaturation by the E. uredovora enzyme was trans-lycopene together with a cis isomer. In addition, bisdehy-drolycopene was also formed. The reaction products of Synechococcus phytoene desaturase were two cis isomers of ζ-carotene and only small amounts of trans-ζ-carotene including 15-cis. The I50 values for flurtamone and diphenylamine to inhibit phytoene desaturation were determined and differential inhibition was observed for diphenylamine.

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