Decomposition of Elastomers at High Temperatures

1949 ◽  
Vol 22 (3) ◽  
pp. 667-679 ◽  
Author(s):  
Glenn S. Skinner ◽  
James H. McNeal
Keyword(s):  
Double Bond ◽  
Natural Rubber ◽  
Hydrogen Cyanide ◽  
Rapid Rise ◽  
Hydrogen Atoms ◽  
Acrylonitrile Copolymer ◽  
Rapid Action ◽  
Exothermic Decomposition ◽  
Gaseous Hydrocarbons ◽  
Pilot Light

Abstract All of the elastomer compositions tested from natural rubber, GR-S, butadiene-acrylonitrile copolymer, and Neoprene undergo an exothermic decomposition when rapidly heated. Increase in the heating rate enhances the abruptness and magnitude of the exothermic rise. Long heating at 190–200° C eliminates exothermic action. The rapid action also takes place in an atmosphere of nitrogen. Various compounding agents may modify this behavior, but they do not eliminate it. The exothermic action is therefore characteristic of the elastomers in the stocks. The only known structural characteristic common to all these elastomers is the residual double bond. The exothermic activity is, therefore, ascribed primarily to this source. This interpretation is further supported by the work of Midgley and Henne, which showed that the C—C bond in the 1–3 position to the residual double bond in crepe rubber is most readily cleaved. It is rendered still more probable by the evolution of products from the gum stocks tested, which require active hydrogen atoms for their formation. Very little hydrogen chloride is evolved before rapid action begins, and the rate of evolution increases sharply at the peak of exothermic action. Similarly, the butadiene-acrylonitrile copolymer yields hydrogen cyanide, and natural rubber yields saturated gaseous hydrocarbons. The evolution of smoke does not necessarily parallel the exothermic action. Smoke densities sufficient to cause 50 per cent extinction are always obtained before the beginning of the rapid rise in temperature. Complete extinction of the light in the apparatus occurs at a point between the beginning and the peak of the exothermic action. The smoke just above the sample of some stocks may clear completely during the exothermic action. Stocks containing zinc and magnesium oxides give colored smokes of a greatly increased order of density during the exothermic action. Phosgene cannot be detected in the smoke from Neoprene stocks. The outside heating temperatures at which the smoke and volatile gases flash are very similar for the four elastomers in the gum stocks. The initial flash occurs at the beginning of the exothermic rise. The smoke from Neoprene extinguishes the pilot light, while the other samples are ignited and continue to burn.

THE REACTION OF ACTIVE NITROGEN WITH PROPYLENE

1952 ◽  
Vol 30 (12) ◽  
pp. 915-921 ◽  
Author(s):  
G. S. Trick ◽  
C. A. Winkler
Keyword(s):  
Double Bond ◽  
Nitrogen Atom ◽  
Hydrogen Cyanide ◽  
Atomic Hydrogen ◽  
Atomic Nitrogen ◽  
Active Nitrogen

The reaction of nitrogen atoms with propylene has been found to produce hydrogen cyanide and ethylene as the main products, together with smaller amounts of ethane and propane and traces of acetylene and of a C4 fraction. With excess propylene, the nitrogen atoms were completely consumed and for the reaction at 242 °C., 0.77 mole of ethylene was produced for each mole of excess propylene added. For reactions at lower temperatures, less ethylene was produced. The proposed mechanism involves formation of a complex between the nitrogen atom and the double bond of propylene, followed by decomposition to ethylene, hydrogen cyanide, and atomic hydrogen. The ethylene would then react with atomic nitrogen in a similar manner.

Chlorination of Natural Rubber in Solution with Gaseous Chlorine

1953 ◽  
Vol 26 (4) ◽  
pp. 902-911 ◽  
Author(s):  
C. S. Ramakrishnan ◽  
D. Raghunath ◽  
J. B. Pande
Keyword(s):  
Double Bond ◽  
Natural Rubber ◽  
Cyclization Reaction ◽  
Double Bonds ◽  
Chlorine Atoms ◽  
Reaction Stage ◽  
Stage 1 ◽  
Additive Reaction

Abstract The chlorination of rubber solutions by gaseous chlorine was followed by isolating the partially chlorinated products and preparing their ozonides. The ozonides were hydrolyzed, and the acids and aldehydes formed on hydrolysis were determined. By a comparison with the amounts of acids and aldehydes obtained from ozonides of unreacted rubber, the amount of residual isoprenic double bonds present was found. The loss of double bonds attending the introduction of chlorine atoms into the molecule of rubber indicates four definite stages in chlorination : (1) initial substitutive attack by chlorine, with concomitant cyclization, resulting in a loss of one double bond between two isoprenic units, (2) substitution, (3) additive reaction, and (4) essentially substitution. Chlorination of aged rubber solutions differs from the above in that the cyclization reaction (stage 1) seems to be absent.

Photolyse du butène-1 dans l'ultraviolet à vide

1973 ◽  
Vol 51 (17) ◽  
pp. 2853-2859 ◽  
Author(s):  
Guy J. Collin
Keyword(s):  
Double Bond ◽  
Hydrogen Atom ◽  
Kinetic Energy ◽  
Thermal Energy ◽  
Hydrogen Atoms ◽  
Excited Molecules

The vacuum u.v. photolysis of 1 -butene was studied in the 147–105 nm region. The main products formed from the fragmentation of excited molecules are allene, 1,3-and 1,2-butadienes, ethylene, and acetylene. The addition of a hydrogen atom to the double bond produces mainly secondary butyl radicals (91%) at 147 nm. At 123.6 nm, this proportion becomes 82%. Thus at shorter wavelengths (10 and 11.6–11.8 eV), hydrogen atoms are produced with a kinetic energy higher than the thermal energy.

Cis-trans Isomerization in Polyisoprenes. Part VII. Double Bond Movement During Isomerization of Natural Rubber and Related Olefins

1967 ◽  
Vol 40 (3) ◽  
pp. 921-927
Author(s):  
J. I. Cunneen ◽  
G. M. C. Higgins ◽  
R. A. Wilkes
Keyword(s):  
Double Bond ◽  
Sulfur Dioxide ◽  
Natural Rubber ◽  
Structural Modification ◽  
Anaerobic Conditions ◽  
Aerobic Conditions ◽  
Trans Isomerization ◽  
Acidic Compounds

Abstract When trans-3-methyl-2-pentene or trans-3-methyl-3-hexene is treated with butadiene sulfone, thiolbenzoic acid, and dibenzoyl disulfide under anaerobic conditions, the olefin undergoes only cis-trans isomerization. However, similar reactions in the presence of oxygen or peroxides also cause changes in the position of the double bond. The latter structural modification is probably caused by acidic compounds formed by oxidation of the isomerization reagents. With natural rubber the nonrubber substances prevent movement of the double bond, and cis-trans isomerization is the sole change, even when the reaction with sulfur dioxide is carried out under aerobic conditions.

Photolyse de pentène-1 dans l'ultraviolet à vide

1973 ◽  
Vol 51 (5) ◽  
pp. 724-731 ◽  
Author(s):  
Patrick M. Perrin ◽  
Guy J. Collin
Keyword(s):  
Double Bond ◽  
Low Pressure ◽  
Hydrogen Atoms ◽  
Ethyl Radical ◽  
Excited Molecules

Photolysis of 1-pentene molecules at 8.4 eV (xenon photolysis) and 10.0 eV (krypton photolysis) was studied. Excited molecules decompose to produce mainly ethylene, propadiene, 1,3-butadiene, acetylene, and other minor products. Hydrogen atoms add to the double bond of the monomer and the resulting excited pentyl radical decomposes at low pressure (P < 1 Torr) into propene and ethyl radical. Isomerization of excited 1-pentene molecules is unimportant at these energies.

Oxidative Stress Relaxation of Natural Rubber Vulcanized with Di-Tertiary-Butyl Peroxide

1956 ◽  
Vol 29 (3) ◽  
pp. 1043-1046 ◽  
Author(s):  
Svein Ore
Keyword(s):  
Oxidative Stress ◽  
Stress Relaxation ◽  
Carbon Black ◽  
Natural Rubber ◽  
First Grade ◽  
Main Reaction ◽  
Reaction Products ◽  
Hydrogen Atoms ◽  
Tertiary Butyl ◽  
Butyl Peroxide

Abstract It has been shown by Farmer and Moore that natural rubber can be vulcanized with di-tert.-butyl peroxide (DTBP), Presumably the free radicals formed by the unimolecular decomposition of the peroxide abstract some of the more labile (e.g., α-methylenic) hydrogen atoms, leading to direct C—C crosslinks between the rubber molecules, with tert.-butanol and acetone as the main reaction products. This preliminary communication presents some of the results of an investigation of the oxidative stress relaxation of the following types of DTBP vulcanizates. (A) First grade pale crepe, DTBP, and carbon black (MPC) mixed on the mill and vulcanized in a press. The carbon black was added to minimize the deleterious effect of impurities. (B) Purified rubber vulcanized: (1) in aqueous heating media; (2) in the press; (3) in DTBP vapor.

scholarly journals Quinine dihydrochloride hemihydrate

IUCrData ◽  
2021 ◽  
Vol 6 (4) ◽  
Author(s):  
Grace I. Anderson ◽  
Sophia Bellia ◽  
Matthias Zeller ◽  
Patrick C. Hillesheim ◽  
Arsalan Mirjafari
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Double Bond ◽  
Long Range ◽  
Title Compound ◽  
Asymmetric Unit ◽  
Hydrogen Atoms ◽  
Non Covalent Interactions ◽  
Long Range Ordering ◽  
Covalent Interactions

Numerous non-covalent interactions link together discrete molecules in the crystal structure of the title compound, 2C20H26N2O2 2+·4Cl−·H2O {systematic name: 4-[(5-ethenyl-1-azoniabicyclo[2.2.2]octan-2-yl)(hydroxy)methyl]-6-methoxyquinolin-1-ium dichloride hemihydrate}. A combination of hydrogen bonding between acidic H atoms and the anions in the asymmetric unit forms a portion of the observed hydrogen-bonded network. π–π interactions between the aromatic portions of the cation appear to play a role in the formation of the long-range ordering. One ethylene double bond was found to be disordered. The disorder extends to the neighboring carbon and hydrogen atoms.

Site of H Atom Attack on Uracil and Its Derivatives in Aqueous Solution

1985 ◽  
Vol 40 (3-4) ◽  
pp. 292-294 ◽  
Author(s):  
Suresh Das ◽  
David J. Deeble ◽  
Clemens von Sonntag
Keyword(s):  
Aqueous Solution ◽  
Double Bond ◽  
Pulse Radiolysis ◽  
Hydrogen Abstraction ◽  
Methyl Groups ◽  
Oh Radicals ◽  
Hydrogen Atoms ◽  
Sugar Moiety ◽  
Reducing Properties

Hydrogen atoms from the radiolysis of water at pH 1.6 add to the 5,6-double bond of pyrimidines. The preferen­tial site of attack is the C(5) position (values in brackets) in the case of 6-methyluracil (87%), 1,3-dimethyluracil (71%), uracil (69%) and poly(U) (60%). This reaction yields a radical of reducing properties which can be monitored by its reaction with tetranitromethane in a pulse radiolysis experiment. In thymine (37%), thymidine (32%) and 1,3-dimethylthymine (25%) H-addition no longer pre­ferentially occurs at C(5), but addition is now mainly at C(6). Hydrogen abstraction from the methyl groups or the sugar moiety is negligible (≦ 5.5%). A comparison is made with literature values for the equivalent reactions of OH radicals.

THE REACTION OF HYDROGEN ATOMS WITH METHYL CYANIDE

1955 ◽  
Vol 33 (12) ◽  
pp. 1814-1818 ◽  
Author(s):  
W. Forst ◽  
C. A. Winkler
Keyword(s):  
Discharge Tube ◽  
Hydrogen Cyanide ◽  
Main Product ◽  
Initial Step ◽  
Methyl Radicals ◽  
Methyl Radical ◽  
Hydrogen Atoms ◽  
Methyl Cyanide ◽  
Secondary Reactions

Hydrogen atoms produced in a discharge tube were found to react with methyl cyanide to produce hydrogen cyanide as the main product, together with smaller amounts of methane and ethane. The proposed mechanism involves the formation of hydrogen cyanide and a methyl radical in the initial step; methane and ethane are attributed to secondary reactions of the methyl radicals.

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