Oxidative Stress Relaxation of Natural Rubber Vulcanizates at High Strains

1966 ◽  
Vol 39 (5) ◽  
pp. 1577-1583
Author(s):  
C. L. M. Bell
Keyword(s):  
Oxidative Stress ◽  
Tensile Strength ◽  
Stress Relaxation ◽  
Natural Rubber ◽  
High Strain ◽  
Oxidative Degradation ◽  
Relaxation Measurement ◽  
Premature Failure ◽  
Surface Flaws ◽  
Natural Rubber Vulcanizates

Abstract The effect of high strain on the oxidative stress relaxation of several natural rubber vulcanizates has been investigated. In peroxide and CBS accelerated vulcanizates, the rate of stress relaxation increases with increasing strain, and this increase appears to be due to an increase in the rate of oxidation of the network. TMTD and MBT vulcanizates showed marked premature failure at high strains and no oxidative stress relaxation measurement could be made. The tensile strength of a TMTD vulcanizate was at least 20 per cent higher in vacuum than in oxygen, due, it is believed, to stress-induced oxidative degradation at the tip of surface flaws in the rubber.

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.

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.

HXNBR Coating for Improving Aging Resistance of Natural Rubber Products

2006 ◽  
Vol 79 (4) ◽  
pp. 553-560 ◽  
Author(s):  
Rani Joseph
Keyword(s):  
Mechanical Properties ◽  
Natural Rubber ◽  
Room Temperature ◽  
Oxidative Degradation ◽  
Thin Coating ◽  
Oil Resistance ◽  
Aging Resistance ◽  
Natural Rubber Vulcanizates ◽  
Good Heat ◽  
Accelerator System

Abstract HXNBR (Hydrogenated Carboxylated Nitrile Rubber) has very good heat ageing resistance and oil resistance. A novel accelerator system is designed to bring about the vulcanization of HXNBR at room temperature. The room temperature cured samples showed good mechanical properties equivalent to those of high (150 °C) temperature cured samples. Natural rubber vulcanizates are highly prone to oxidative and ozone degradation. The oil resistance of natural rubber vulcanizates is also very low. The oil resistance, ozone and oxidative degradation resistance of natural rubber vulcanizates are considerably improved by placing a thin coating of HXNBR over it.

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.

Correlation of Blooming and Tensile Properties in Surfactant-Loaded Natural Rubber Vulcanizates

2016 ◽  
Vol 705 ◽  
pp. 35-39 ◽  
Author(s):  
Bryan B. Pajarito ◽  
Jimyl Arabit
Keyword(s):  
Tensile Strength ◽  
Natural Rubber ◽  
Tensile Properties ◽  
Tensile Strain ◽  
Tensile Modulus ◽  
Adhesive Tape ◽  
Taguchi Design Of Experiment ◽  
Convection Oven ◽  
Maximum Tensile Strain ◽  
Natural Rubber Vulcanizates

Tensile properties of surfactant-loaded natural rubber (NR) vulcanizates are investigated in correlation with blooming. Rubber sheets are compounded using an L12 orthogonal array of Taguchi design of experiment, where ingredients are treated as factors varied at low and high loadings. Blooming experiments are carried out by placing NR sheets in a natural convection oven set at 50 °C for 20 days. The amount of bloom on the surface is removed using adhesive tape and is monitored with time. Tensile properties of rubber dogbone samples are also measured with time. Results show that 5 out of 12 formulations show blooming to be significantly related to tensile modulus (0.005 < p < 0.039). It is observed that the tensile modulus increases with blooming (0.898 < r < 0.973). Three formulations indicate significant correlation of blooming with tensile strength (0.022 < p < 0.047). As observed, tensile strength decreases with blooming (-0.884 < r < -0.930). Five formulations signify blooming to have significant correlation with maximum tensile strain (0.000 < p < 0.011), which decreases with blooming (-0.957 < r < -0.995). Two formulations imply significant negative (-0.960 < r < -0.963) correlation between blooming and tensile set (p= 0.009).

EFFECT OF CURE EFFICIENCY ON PROPERTIES OF GUM AND BLACK FILLED NATURAL RUBBER VULCANIZATES

2011 ◽  
Vol 84 (2) ◽  
pp. 229-242 ◽  
Author(s):  
Gary R. Hamed ◽  
Kanoktip Boonkerd
Keyword(s):  
Electron Microscopy ◽  
Tensile Strength ◽  
Natural Rubber ◽  
Crosslink Density ◽  
Cure Time ◽  
Cracking Pattern ◽  
Natural Rubber Vulcanizates ◽  
Scanning Electron ◽  
Fracture Specimens ◽  
Strength Effect

Abstract Effects of the sulfur cure efficiency on the reversion behavior and the normal and edge-cut tensile strength of gum and black filled natural rubber (NR) vulcanizates were studied. N, N-dicyclohexyl-2-benzothiazole sulfenamide (DCBS) was used as an accelerator. A series of five vulcanizates with high to low cure efficiencies was prepared by increasing the sulfur (S) to DCBS ratios within the range of 0.26–6.66. All vulcanizates were formulated to have the same crosslink density. The degree of reversion (%) calculated from cure curves of gum and black filled NR at 20 min above the cure time (tc100) passed through maximum with decreasing cure efficiencies. For both gum and black filled NR, the highest degree of reversion (%) was observed at the S/DCBS ratio of 1.17. The normal tensile strengths of gum and black filled NR were directly proportional to the cure efficiency. For gum NR vulcanizates, the edge-cut tensile strength was markedly influenced by cure efficiency. Similar to the normal tensile strength, the gum NR vulcanizates cured with the lowest cure efficiency showed the lowest edge-cut tensile strength. Effect of the cure efficiency on the edge-cut tensile strength was less in the case of black filled NR vulcanizates. However, the black filled NR vulcanizates cured with the lowest cure efficiency also showed the lowest edge-cut tensile strength. The cut tip characteristics of the fracture specimens were investigated using scanning electron microscopy. The gum specimens showed only the simple lateral cracking pattern, while all black filled specimens showed the longitudinal cracking pattern. Four different cracking patterns of the black filled specimens were identified. The distribution of cracking patterns depended strongly on the size of precut and the cure efficiency.

Polymeric Antioxidant Based on Natural Rubber Grafted with N-(4-Hydroxyphenyl)maleimide

2012 ◽  
Vol 488-489 ◽  
pp. 211-215 ◽  
Author(s):  
Pairote Klinpituksa ◽  
Sittaporn Somkieowan ◽  
Wae Asae Waehamad ◽  
Natinee Lopattananon
Keyword(s):  
Tensile Strength ◽  
Maleic Anhydride ◽  
Natural Rubber ◽  
Ftir Spectroscopy ◽  
Accelerated Aging ◽  
Elongation At Break ◽  
Optimal Amount ◽  
Melt Grafting ◽  
Natural Rubber Vulcanizates

A novel rubber bound antioxidant NR-g-HPM was prepared by melt grafting HPM (N-(4-hydroxyphenyl)maleimide) onto natural rubber in a brabender plasticorder. HPM was synthesized from p-aminophenol and maleic anhydride. The yield was found to be over 80%. The grafting products were observed with FTIR spectroscopy and TGA. The ageing resistance of natural rubber vulcanizates using NR-g-HPM was studied. It was found that an optimal amount of NR-g-HPM (6 phr) gave about 25% better tensile strength and elongation at break as compared with conventional BHT addition, for filled natural rubber after 48 h of accelerated aging.

The Degradation of Elastomers. 2. Oxidative Degradation of Natural Rubber Vulcanizates at Different Elongations and Temperatures. II

1959 ◽  
Vol 32 (3) ◽  
pp. 759-769 ◽  
Author(s):  
Karl-Heinz Hillmer ◽  
Walter Scheele
Keyword(s):  
Activation Energy ◽  
Natural Rubber ◽  
Oxidative Degradation ◽  
Zero Order ◽  
Relaxation Rates ◽  
Good Qualitative Agreement ◽  
Kcal Mole ◽  
Pure Nitrogen ◽  
Natural Rubber Vulcanizates ◽  
Constant Activation Energy

Abstract The results of measurements of stress relaxation in natural rubber vulcanizates are reported. In the earlier work, the conditions were denned under which the drop in tension of a vulcanizate—after a pre-relaxation in pure nitrogen—follows a zero order law when tested in oxygen. The temperature dependence of the rate of relative tension relaxation was determined for 8 different vulcanizates. With a constant activation energy of about 29 kcal/mole, the vulcanizates differed in their relative relaxation rates at most by two powers of ten. Several general observations on the course of tension relaxation under different conditions were made on the grounds of experimental evidence. Good qualitative agreement was found with relations reported by Berry and Watson.

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