The effect of crosslink structure on the tensile strength and oxygen absorption characteristics of natural rubber vulcanizates

1967 ◽  
Vol 16 (6) ◽  
pp. 3391-3399
Author(s):  
Joginder Lal
Keyword(s):  
Tensile Strength ◽  
Natural Rubber ◽  
Oxygen Absorption ◽  
Natural Rubber Vulcanizates ◽  
Absorption Characteristics

The Effect of Crosslink Structure on the Tensile Strength and Oxygen Absorption Characteristics of Natural Rubber Vulcanizates

1969 ◽  
Vol 42 (5) ◽  
pp. 1412-1419
Author(s):  
J. Lal
Keyword(s):  
Tensile Strength ◽  
Natural Rubber ◽  
Chemical Nature ◽  
Oxygen Absorption ◽  
High Tensile Strength ◽  
Modulus Curve ◽  
Natural Rubber Vulcanizates ◽  
Absorption Characteristics ◽  
Control Samples

Abstract The chemical nature of crosslinks in natural rubber—sulfur—diphenylguanidine vulcanizates was modified by reaction with triphenylphosphine under nitrogen to determine the effect of this change on tensile strength and oxygen absorption characteristics of the vulcanizates. The vulcanizates were characterized by organically combined sulfur and polysulfidic sulfur. Polysulfidic crosslinks, i.e., crosslinks containing three or more sulfur atoms in the crosslink, were found not to be essential for the attainment of high tensile strength in these vulcanizates. Data for the samples which had lost significant amounts of polysulfidic crosslinks by reaction with triphenylphosphine fitted the tensile strength versus 300% modulus curve for the control samples. Vulcanizates which had been reacted with triphenylphosphine for 16 days at 80° C, had lost 95–99.6% of their polysulfidic sulfur. These triphenylphosphine-reacted vulcanizates exhibited significantly lower rates of oxygen absorption at 100° C as compared to the untreated vulcanizates. This suggests that polysulfidic structures in the original vulcanizates act as oxidation initiators.

Effect of Crosslink Structure on Properties of Natural Rubber

1970 ◽  
Vol 43 (3) ◽  
pp. 664-686 ◽  
Author(s):  
Joginder Lal
Keyword(s):  
Tensile Strength ◽  
Natural Rubber ◽  
Chemical Nature ◽  
Relative Concentration ◽  
Oxygen Absorption ◽  
Dicumyl Peroxide ◽  
High Tensile Strength ◽  
Failure Envelope ◽  
Chemical Crosslinks ◽  
Absorption Characteristics

Abstract Natural rubber-sulfur-diphenylguanidine vulcanizates were allowed to react with triphenylphosphine under nitrogen to convert polysulfidic crosslinks principally to di- and monosulfidic crosslinks and to assess the effect of this change in the chemical nature of the crosslinks on tensile strength, flex life, and oxygen absorption characteristics. The vulcanizates were analyzed for organically combined sulfur and polysulfidic sulfur. Data obtained by this approach were treated statistically and showed that polysulfidic crosslinks are not essential for attaining high tensile strength or superior flex life. In another approach, polysulfidic crosslinks were introduced into dicumyl peroxide-cured vulcanizates containing carbon-carbon crosslinks to yield two-stage vulcanizates. Data for these vulcanizates fitted the curve of tensile strength as a function of 300% modulus for the precursor samples. It was further shown that the reduced failure envelope for natural rubber gum vulcanizates is independent of the type and relative concentration of chemical crosslinks. An interesting observation was made that the tensile strengths of dicumyl peroxide-cured samples were enhanced on extraction with acetone. Vulcanizates which had lost 95–99 per cent of their polysulfidic sulfur due to reaction with triphenylphosphine exhibited significantly lower rates of oxygen absorption at 100° C as compared to the untreated vulcanizates. This suggests that polysulfidic structures in the original vulcanizates act as oxidation initiators.

Rubber Oxidation and Aging Studies Safe Limits of Sample Thickness

1951 ◽  
Vol 24 (4) ◽  
pp. 999-1016
Author(s):  
George W. Blum ◽  
J. Reid Shelton ◽  
Hugh Winn
Keyword(s):  
Natural Rubber ◽  
Accelerated Aging ◽  
Sample Thickness ◽  
Oxygen Absorption ◽  
Absorption Data ◽  
Synthetic Rubber ◽  
Constant Rate ◽  
Aging Studies ◽  
Safe Limits ◽  
Natural Rubber Vulcanizates

Abstract Safe limits of sample thickness for rubber oxidation and aging studies, such that the chemical reaction rather than the rate of diffusion will be rate-controlling have been investigated for natural-rubber vulcanizates and for four synthetic-rubber types. For studies involving the entire range of oxidation, including the autocatalytic stage of rapid oxygen absorption, the conventional 0.075-inch thickness is frequently not satisfactory for accelerated aging and oxidation studies if it is desired to avoid limitation by diffusion. Only in the GR-S black stock was this thickness found to be satisfactory up to a temperature of 100° C. The other stocks, including natural rubber, Butaprene-NXM, and Neoprene black and gum stocks all require thinner samples to ensure that the observed rate of oxygen absorption is free of limitation by diffusion. A method of calculating the probable limiting value of sample thickness, above which the rate of oxidation in the autocatalytic stage is limited by diffusion, has been developed on the basis of volumetric oxygen absorption data obtained with GR-S. The method has also been applied to natural-rubber vulcanizates and to other synthetic-rubber types to locate the approximate limiting values at various temperatures for oxidation and aging studies which extend into the autocatalytic stage of rapid reaction. The constant-rate period of oxidation is more important from a practical point of view than the autocatalytic stage, since properties are so seriously degraded as to make the rubber of little value before it reaches the final stage of rapid oxidation. Somewhat thicker samples may be used for studies that are confined to the earlier stages of oxidation. A 0.075-inch sample is free of limitation by diffusion in the constant-rate stage in the following cases: GR-S black and gum stocks at 110° C; Hevea black with added antioxidant at 100° C; and uninhibited Hevea black and gum stocks at 60° C. A 0.040-inch sample is satisfactory in this range for: uninhibited Hevea black at 100° and gum at 80° C; Butaprene-NXM black at 100° and gum at 90° C; and Neoprene black and gum stocks at 100° C.

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.

Effect of Epoxidized Oil on Tensile and Tear Strength of NR Vulcanizate and its Comparison with Aromatic Oil NR Vulcanizates

2013 ◽  
Vol 812 ◽  
pp. 204-209 ◽  
Author(s):  
Mohamed Rahmah ◽  
Wan Zain Norazira ◽  
Ahmad Faiza Mohd ◽  
Mohd Nurazzi Norizan
Keyword(s):  
Tensile Strength ◽  
Natural Rubber ◽  
Rubber Compound ◽  
Tear Strength ◽  
Green Component ◽  
Strength Tests ◽  
Tearing Energy ◽  
Polymer Industry ◽  
Natural Rubber Vulcanizates

Epoxidized oil (EO) is a sustainable oil that can be obtained form edible or non-edible naturals oil. The incorporation of epoxidized oil can increase the green component in rubber compound. It can contributes to worldwide technology specially in green tyre manufacturing. Epoxidized oil has the potential to replace aromatic oil (AO) to rubber and polymer industry. The effect of incorporation of EO and AO into natural rubber vulcanizates (NR) was studied via tensile and tear strength tests according to ISO 31-1977 and ISO 6133, respectively. Tensile strength of AO value showed greather value compared to EO. Gradual increases of elongation were observed form both AO and EO. Both moduli at 100% and 300% elongation, showed reductions as oil loading were increased. The tear strength results showed that tearing energy insignificantly increased with oil loading. EO compound was found to possess higher tearing energy compared to AO compound for most composition except for 15 pphr EO.

Antioxidant Efficiency of p-Phenylenediamines in Natural Rubber Vulcanizates

1961 ◽  
Vol 34 (3) ◽  
pp. 816-833 ◽  
Author(s):  
O. Lorenz ◽  
C. R. Parks
Keyword(s):  
Antioxidant Activity ◽  
Natural Rubber ◽  
Oxidation Products ◽  
Oxygen Absorption ◽  
Fast Reaction ◽  
Alkyl Aryl ◽  
Antioxidant Efficiency ◽  
Rate Region ◽  
Constant Rate ◽  
Natural Rubber Vulcanizates

Abstract The consumption of various p-phenylenediamines during the oxidation of natural rubber vulcanizates has been investigated in the temperature range of 80–120° C. Oxygen absorption was used to follow the oxidation. Diaryl-p-phenylenediamines were consumed mainly in a termination reaction during the constant rate region of the oxygen absorption, where five to six molecules of oxygen were absorbed per molecule of diamine consumed. The constant rate stage of the oxygen uptake was found to be about twice as long as the time of the constant rate consumption of the diamine, indicating that the reaction product also possessed antioxidant activity. The effect of the nature of the curing system, carbon black, structure of the diamine, initial concentration of the diamine, and temperature of oxidation were studied. Dialkyl- and alkyl-aryl-p-phenylenediamines were consumed predominantly by a direct, relatively fast reaction with oxygen, the rate being dependent on the structure of the diamine and also on the nature of the curing system. The oxidation products formed exhibited antioxidant activity, those of N-isopropyl-N′-phenyl-p-phenylenediamine being particularly effective.

Measurement of Tensile Strength of Natural Rubber Vulcanizates at Elevated Temperature

1982 ◽  
Vol 55 (1) ◽  
pp. 66-75 ◽  
Author(s):  
C. L. M. Bell ◽  
D. Stinson ◽  
A. G. Thomas
Keyword(s):  
Tensile Strength ◽  
Elevated Temperature ◽  
Critical Temperature ◽  
Natural Rubber ◽  
Test Piece ◽  
Flaw Size ◽  
High Tensile Strength ◽  
Test Pieces ◽  
Naturally Occurring ◽  
Natural Rubber Vulcanizates

Abstract The tensile strength of test pieces made from natural rubber vulcanizates drops abruptly at a critical temperature which can vary from 40 to 130°C. This variation in critical temperature is shown here to be a result of the variation in critical cut length with temperature. When the naturally occurring flaws in the test piece are smaller than the critical cut length, high tensile strength values occur, but when the flaws are longer than the critical cut length, low tensile strength values occur. The critical cut length decreases as the temperature increases, and the abrupt drop in tensile strength occurs as the critical cut length reaches the natural flaw size in the test piece. The natural flaw size in tensile test pieces depends on the sharpness of the cutter, and for tensile strength measurements at elevated temperature, it is shown that even a slightly blunt cutter may give markedly different results from a sharp one.

Effect of Ingredient Loading and Temperature on Tensile Properties of Surfactant-Loaded Natural Rubber Vulcanizates

2019 ◽  
Vol 803 ◽  
pp. 356-360
Author(s):  
J. Arabit-Cruz ◽  
Bryan Pajarito
Keyword(s):  
Tensile Strength ◽  
Elastic Modulus ◽  
Natural Rubber ◽  
Tensile Properties ◽  
Tensile Strain ◽  
High Loading ◽  
Glycerol Monostearate ◽  
Taguchi Design Of Experiment ◽  
Used Oil ◽  
Natural Rubber Vulcanizates

Tensile properties are among the measures that give rubber products value. In this study, the effect of ingredient loading and temperature on the tensile properties of surfactant-loaded natural rubber vulcanizates (NRV) are investigated. Rubber dogbone samples are compounded using an L12 orthogonal array of Taguchi design of experiment, where ingredients are treated as factors varied at low and high loadings. Rubber specimens for each formulation are thermally aged for 20 days in ovens with temperatures of 40, 50, and 60 °C. Results show that zinc oxide (ZnO), paraffin wax, sulfur, mercaptobenzothiazole (MBT), and diphenylguanidine (DPG) significantly have the highest effect on increasing the elastic modulus while decreasing the tensile strength, tensile strain, and tensile set. Used oil has the highest effect on decreasing the elastic modulus but has the highest effect on increasing tensile strength, tensile strain, and tensile set. High loading of cocamide diethanolamide (coca DEA) significantly increases tensile strength at 60 °C. High loading of glycerol monostearate (GMS) significantly decreases tensile strength and strain at 40 °C. Highest elastic modulus, tensile strength, strain, and set are achieved when NRV are thermally aged at 50 °C.

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