Ozone Resistance of Natural Rubber Vulcanizates. Part III. Influence of Accelerators and Antioxidants

1958 ◽  
Vol 31 (4) ◽  
pp. 882-895 ◽  
Author(s):  
B. I. C. F. van Pul
Keyword(s):  
Natural Rubber ◽  
Ozone Concentration ◽  
Static Conditions ◽  
Natural Rubber Vulcanizates ◽  
Ozone Resistance ◽  
Phenylene Diamine

Abstract An investigation of the ozone protection given to natural rubber vulcanizates by different accelerators and antioxidants has shown that, of the accelerators investigated, the thiuram derivatives appear to be the best antioxidants, when they are used as vulcanizing agents; of the large number of antioxidants examined. NN′-di-sec-octyl p-phenylene diamine appears to be the best antiozonant. Vulcanizates containing this material showed no cracks after being exposed for 400 hours to an ozone concentration of 25×10−8 ml/ml under static conditions; it was far superior to all other materials examined.

Ozone Resistance of Natural Rubber Vulcanizates. Part II. Influence of Fillers and Waxes

1958 ◽  
Vol 31 (4) ◽  
pp. 874-881 ◽  
Author(s):  
B. I. C. F. van Pul
Keyword(s):  
Natural Rubber ◽  
Side Chains ◽  
Melting Points ◽  
Dynamic Conditions ◽  
Static Conditions ◽  
Natural Rubber Vulcanizates ◽  
Ozone Resistance

Abstract Commerical waxes whose melting points, refractive indexes and numbers of side chains are within the ranges described seem likely to give good ozone protection under static conditions. All waxes lead to worse cracking under dynamic conditions than if none had been included and it is clearly better to use no wax if the rubber is likely to be submitted to intermittent stretching.

Ozone Resistance of Natural Rubber Vulcanizates. Part I. Apparatus for Exposure at Low Ozone Concentration

1958 ◽  
Vol 31 (4) ◽  
pp. 866-873
Author(s):  
B. I. C. F. van Pul
Keyword(s):  
Natural Rubber ◽  
Ozone Concentration ◽  
Cracking Resistance ◽  
Dynamic Conditions ◽  
Ozone Concentrations ◽  
Natural Rubber Vulcanizates ◽  
Ozone Resistance

Abstract An apparatus is described for evaluating the cracking resistance of rubber specimens exposed under static or dynamic conditions to ozone concentrations between 5 and 50×10−8 ml/ml of air. Ozone concentration is kept constant automatically however much is destroyed at the walls of the cabinet or at the surfaces of the rubber testpieces. Temperature can be regulated between 20° and 100° C.

Aging of Natural Rubber Vulcanizates in the Presence of Dithiocarbamates

1959 ◽  
Vol 32 (3) ◽  
pp. 739-747 ◽  
Author(s):  
J. R. Dunn ◽  
J. Scanlan
Keyword(s):  
Stress Relaxation ◽  
Natural Rubber ◽  
Protective Action ◽  
Dicumyl Peroxide ◽  
Vulcanized Rubber ◽  
Aging Properties ◽  
Photochemical Aging ◽  
Natural Rubber Vulcanizates

Abstract The thermal and photochemical aging of extracted dicumyl peroxide-, TMTD (sulfurless)- and santocure-vulcanized rubber, in presence of a number of metal and alkylammonium dithiocarbamates, has been investigated by measurements of stress relaxation. The dithiocarbamates have a considerable protective action upon the degradation of peroxide- and TMTD-vulcanizates, but they accelerate stress decay in santocure-accelerated vulcanizates. The reasons for this behavior are discussed. It is suggested that the excellent aging properties of unextracted TMTD vulcanizates are due to the presence of zinc dimethyldithiocarbamate formed during vulcanization.

High-Resolution Latex-State 13C-NMR Spectroscopy for Natural Rubber Vulcanizates

2007 ◽  
Vol 80 (5) ◽  
pp. 751-761 ◽  
Author(s):  
Seiichi Kawahara ◽  
Jinta Ukawa ◽  
Junichiro Sakai ◽  
Yoshimasa Yamamoto ◽  
Yoshinobu Isono
Keyword(s):  
Nmr Spectroscopy ◽  
High Resolution ◽  
Natural Rubber ◽  
13C Nmr ◽  
Multiple Bond ◽  
Natural Rubber Latex ◽  
13C Nmr Spectroscopy ◽  
Rubber Latex ◽  
Aliphatic Carbon ◽  
Natural Rubber Vulcanizates

Abstract Crosslinking junctions of natural rubber vulcanizates were characterized by high-resolution latex-state 13C-NMR spectroscopy. Vulcanized natural rubber latex was prepared by two methods: i.e., vulcanization of the rubber latex and cryogenic crushing of a rubber sheet vulcanized on a hot press. High-resolution latex-state 13C-NMR spectroscopy was attained even after vulcanization of the rubber latex, as is evident from no background in spectrum and narrow half width of signals independent of vulcanization time. Small signals at 44 ppm and 57 ppm in the aliphatic carbon region were assigned by measurements of both Distortionless Enhancement by Polarization Transfer (DEPT) and Attached Proton Test (APT) to secondary and tertiary carbons of crosslinking points. The assignment was proved by high-resolution solution-state NMR spectroscopy of vulcanized liquid cis-1,4-polyisoprene as a model, in which DEPT, APT, 2-dimensional 1H-1H correlation (H-H COSY), 2-dimensional 1H-13C correlation (H-C COSY) and 2-dimensional heteronuclear multiple bond correlation (HMBC) measurements were applied.

Influence of Crosslink Characteristics Induced by Aromatic-Based Antioxidants on the Swelling and Stress-Strain Behavior of Natural Rubber Vulcanizates

2003 ◽  
Vol 76 (2) ◽  
pp. 334-347 ◽  
Author(s):  
Tarek M. Madkour ◽  
Rasha A. Azzam
Keyword(s):  
Natural Rubber ◽  
Crosslinking Agent ◽  
Oxidative Degradation ◽  
Thermal Oxidative Degradation ◽  
Stress Strain ◽  
Strain Behavior ◽  
Strain Induced Crystallization ◽  
Elastomeric Chains ◽  
Natural Rubber Vulcanizates ◽  
Induced Crystallization

Abstract Stress-strain measurements were performed on dry and swollen natural rubber vulcanizates prepared using both sulfur as the crosslinking agent and aromatic-based bound antioxidants acting as a second crosslinking agent. The aromatic-based antioxidants were synthesized and analyzed spectroscopically in order to relate the final behavior of the vulcanizates to the nature of the crosslink characteristics. The anomalous upturn in the modulus values of these networks in response to the imposed stress was shown to persist in the dry as well as the swollen state. Since the swollen elastomeric chains cannot undergo a strain-induced crystallization, the abnormal upturns in the modulus values in an absence of a filler were explained on the basis of the limited extensibility of the short chains of networks prepared using two different crosslinking agents in line with earlier modeling predictions. Remarkably, the swelling experiments revealed the increase in the crosslink density of the networks in the early stages of the thermal oxidative degradation procedure indicating a post-cure of the chemically bound antioxidants to the elastomeric chains, which incidentally corresponds to a maximum in the modulus values of the networks. The rheological and other mechanical properties such as the hardness were shown not to have been affected as a result of the incorporation of the chemically bound antioxidants.

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