Stress Relaxation during the Photoxidation of Peroxide Crosslinked Rubber

1960 ◽  
Vol 33 (2) ◽  
pp. 433-444
Author(s):  
J. R. Dunn ◽  
J. Scanlan ◽  
W. F. Watson
Keyword(s):  
Stress Relaxation ◽  
Natural Rubber ◽  
Physical Properties ◽  
Chemical Reactions ◽  
Small Extent ◽  
Organic Peroxides ◽  
Physical Measurement ◽  
Crosslinked Networks ◽  
Photochemical Aging ◽  
Natural Rubber Vulcanizates

Abstract The chemical reactions involved in the thermal and photochemical aging of natural rubber vulcanizates are largely unknown. Experimental difficulties have precluded direct chemical investigation owing to the insolubility of the crosslinked networks and the small extent of reaction required for a great deterioration in physical properties. Accordingly recourse has been made to physical measurement. Tobolsky et al. (e.g. Ref. (1)) have shown that the relaxation in stress on holding a rubber strip at constant extension during aging is a convenient experimental measure capable of interpretation in terms of network breakdown. In photochemical studies the opacity of conventional sulfur vulcanizates provides a further complication. In the present work, the stress relaxation technique has been used in a study of the degradation by 365 mµ radiation of the comparatively transparent and chemically simple rubber networks obtained after crosslinking by organic peroxides.

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.

Oxidative Aging of Natural Rubber Vulcanizates. Part III. Crosslink Scission in Monosulfidic Networks

1969 ◽  
Vol 42 (3) ◽  
pp. 924-935 ◽  
Author(s):  
T. Colclough ◽  
J. I. Cunneen ◽  
G. M. C. Hrggins
Keyword(s):  
Natural Rubber ◽  
Physical Properties ◽  
Chemical Structure ◽  
Spectroscopic Methods ◽  
Chemical Probes ◽  
Conjugated Diene ◽  
Strain Measurements ◽  
Oxidative Aging ◽  
Tert Butyl Hydroperoxide ◽  
Natural Rubber Vulcanizates

Abstract A natural rubber vulcanizate containing almost entirely monosulfidic crosslinks was oxidized in oxygen and with tert-butyl hydroperoxide. The changes in physical properties due to oxidation were followed by stress—strain measurements, and the changes in chemical structure were investigated with chemical probes, and by spectroscopic methods. The results show that when the oxidized vulcanizates are heated at 75° C, the monosulfidic crosslinks are broken, that crosslinks containing two sulfur atoms are formed, and that conjugated diene and triene structures are introduced into the main polyisoprene chains.

Aromatic and Epoxidised Oil Curing and Rebound Resilience Characteristic and their Humidity Effect of Hardness on NR Vulcanizates

2013 ◽  
Vol 812 ◽  
pp. 138-144 ◽  
Author(s):  
Mohamed Rahmah ◽  
Wan Zain Norazira ◽  
Shafie Nur Ashyikin ◽  
Mohd Nurazzi Norizan
Keyword(s):  
Natural Rubber ◽  
Physical Properties ◽  
Room Temperature ◽  
Rubber Compound ◽  
Humidity Effect ◽  
Humidity Level ◽  
Cure Time ◽  
Humidity Chamber ◽  
Overall Performance ◽  
Natural Rubber Vulcanizates

Recently, aromatic oil (AO) is one of the substances that is typically used as a processing aid especially for high filler loadings in formulating rubber compound. Aromatic oil has disadvantages in that, it is hazardous to environment, toxic and has been labeled as carcinogenic. In this research, an epoxidised oil (EO) and aromatic oil were used to investigate the effect incorporation of oil onto the SBR/NR natural rubber vulcanizates (NR). From the result obtained, EO showed shorter cure time and scorch time as the oil loading were increased up to 20 pphr of EO. Physical properties such as hardness and rebound resilience of NR/EO vulcanisate were also investigated upon exposure to different humidity level in humidity chamber. At room temperature, the hardness of EO loading onto the SBR/NR vulcanisate is lower than AO loadings. Hardness was slightly decreased with increasing rate of humidity. There is great difference in hardness and rebound resilience values between AO and EO. Both hardness and rebound resilience were not affected by humidity. This implies the existence of good filler interaction with EO and rubber which do not impart changes in the hardness and resilience properties of rubber compound. Epoxidised oil has great promising potential to replace the carcinogenic aromatic oil as it has good overall performance and renewable in nature .

Stress Relaxation of Peroxide and Sulfur Vulcanizates of Natural Rubber

1956 ◽  
Vol 29 (2) ◽  
pp. 398-408
Author(s):  
J. P. Berry ◽  
W. F. Watson
Keyword(s):  
Stress Relaxation ◽  
Natural Rubber ◽  
Chemical Reactions ◽  
Network Structure ◽  
Small Proportion ◽  
Polymeric Networks ◽  
Relaxation Curves ◽  
Physical Changes ◽  
Direct Proportionality ◽  
Experimental Difficulty

Abstract Direct chemical investigation of the degradation of polymeric networks is usually impracticable owing to the experimental difficulty of insolubility and to the fact that reaction at only a small proportion of network units is sufficient to cause marked alteration of network structure. Resort has, therefore, to be made to the measurement of physical changes brought about by the chemical reactions. Change of tension at constant extension is a useful measure for this purpose, since statistical elasticity theory predicts a direct proportionality between the tension and the number of chains supporting the stress. The present purpose is: (1) to describe a stress relaxometer possessing certain advantages over previous models; (2) to report on the stress relaxation of peroxide-crosslinked rubber, which can be considered from a chemical viewpoint to be the simplest possible rubber network; (3) to point out some complications in the relaxation behavior of sulfur vulcanizates, and (4) to interpret the shapes of stress relaxation curves.

Effect of Carbon Blacks on Swelling of Neoprene GRM-10 Vulcanizates

1949 ◽  
Vol 22 (3) ◽  
pp. 812-819 ◽  
Author(s):  
N. L. Catton ◽  
D. C. Thompson
Keyword(s):  
Carbon Black ◽  
Natural Rubber ◽  
Physical Properties ◽  
Compression Modulus ◽  
Tension Stress ◽  
Limited Extent ◽  
Carbon Blacks ◽  
Reinforcing Fillers ◽  
Swelling Characteristics ◽  
Natural Rubber Vulcanizates

Abstract Reinforcement of elastomers with fillers has generally been measured by physical properties, such as tension stress-strain, tear resistance, hardness, and compression modulus. To a more limited extent, swelling in solvents has been recognized as associated with reinforcement. In natural-rubber vulcanizates it has been demonstrated that reinforcing fillers impart greater resistance to solvents and oils than do nonreinforcing types. Addition of the latter gives only the reduction in swelling attributable to elastomer dilution. In the case of Neoprene vulcanizates, Catton and Fraser reported that fillers function only as elastomer diluents and that those fillers commonly considered as of the reinforcing type impart no greater resistance to solvents than the nonreinforcing type. More recently, however, Buist and Mottram, in describing the effects of carbon blacks on the physical properties of natural rubber and Neoprene, reported that with both of these elastomers compounds containing thermal type carbon black gave slightly greater swelling in benzene than compounds containing equal loadings of other types of carbon black. With Neoprene, they reported good correlation between moduli and swelling characteristics.

Sign in / Sign up

Export Citation Format

Share Document