Aging of GR-S Vulcanizates in Air, Oxygen, and Nitrogen

1945 ◽  
Vol 18 (1) ◽  
pp. 116-121
Author(s):  
J. Reid Shelton ◽  
Hugh Winn
Keyword(s):  
Tensile Strength ◽  
Chain Scission ◽  
Oxygen Bomb ◽  
Cross Linkage

Abstract The results of aging GR-S vulcanizates in air, oxygen, and nitrogen show: 1. The decrease in tensile strength observed in both bomb and oven aging is caused by the action of oxygen. 2. The modulus increase obtained in the oxygen bomb at 80° C is not caused by oxygen in the aging atmosphere. 3. At 100° C in air, more than half of the hardening, measured by the modulus increase obtained after five days, may be attributed to the action of oxygen. It therefore appears that oxygen acts on GR-S vulcanizates in two distinctly different ways: 1. A reaction leading to tensile breakdown, which no doubt involves chain scission. This reaction takes place at both 80° and 100° C, and is effectively retarded by the antioxidant, phenyl-β-naphthylamine. 2. A reaction producing a stiffening of the GR-S, as shown by the modulus increase. This stiffening suggests the formation of polymeric products—for example, by cross-linkage. This reaction was not observed at 80° C, but was a major factor in the aging at 100°, and was little affected by the antioxidant employed.

Volumetric Oxygen-Absorption Test for Rubber Aging

1951 ◽  
Vol 24 (4) ◽  
pp. 981-998
Author(s):  
J. Reid Shelton ◽  
William L. Cox
Keyword(s):  
Tensile Strength ◽  
Physical Properties ◽  
Chain Scission ◽  
Rate Of Change ◽  
Oxygen Absorption ◽  
Absorption Test ◽  
Absorption Data ◽  
Direct Function ◽  
Oxygen Bomb ◽  
Early Stages

Abstract A volumetric oxygen-absorption test for aging of rubber has been investigated from the point of view of the effect of cure and the effect of mercapto-benzimidazole on the aging behavior. The test has also been evaluated by comparison with conventional air oven and oxygen bomb aging. A compounded but uncured Hevea black stock is more resistant to oxidation than the vulcanized material, but after a reasonable cure is obtained, further heating produces only a small change in the rate of oxygen absorption. The change in physical properties corresponding to a given amount of oxygen absorbed varies somewhat with time of cure in the initial stages, but after the absorption of 4 or 5 cc. of oxygen per gram of rubber, the changes in most physical properties are a direct function of the amount of oxygen absorbed. Neither time of cure nor the presence or absence of inhibitor has any significant effect on the subsequent rate of change in such properties as tensile strength and ultimate elongation for a given amount of oxygen absorbed. Oven aging data on identical time cures confirm the reported superiority of a combination of mercaptobenzimidazole with a conventional type of anti-oxidant. Oxygen absorption data reveal, however, that mercaptobenzimidazole causes a significant decrease in the rate of oxidation of a Hevea black stock, and thus it clearly functions at least in part as an antioxidant in the usually accepted sense. The deterioration of properties is, in general, proportional to the oxygen absorbed, except in the early stages of oxidation where the mercaptobenzimidazole stocks change somewhat less than the controls for a given amount of oxygen absorbed. When the cures are selected to give comparable initial properties, however, the change in tensile strength of the mercaptobenzimidazole stocks with amount of oxygen absorbed is essentially the same as for the controls, even in the initial stages. These data suggest that the observed protection imparted by mercaptobenzimidazole results from a combination of two factors: (1) the normal antioxidant activity of mercaptobenzimidazole, which reduces the amount of oxygen absorbed; and (2) an effect on the nature of the cure attained when mercaptobenzimidazole is present, such that the absorption of a given amount of oxygen in the early stages is not accompanied by as great a change in properties. Thus, it appears that the deactivating effect may be the result of the effect of this material on the vulcanization process rather than a direct effect on the oxidation process. A comparison of the effect of oxygen absorption, air oven, and oxygen bomb aging methods on changes in physical properties of Hevea black stocks shows that the results obtained by oxygen absorption and air oven methods (both at 100° C) are similar, but that the higher oxygen concentration of the oxygen bomb test (70° C and 300 pounds per square inch) apparently results in a higher proportion of chain scission when compared to cross-linking of the polymer chains.

Influence of Multifunctional Monomers on Gamma Irradiated Polylactic Acid

2015 ◽  
Vol 804 ◽  
pp. 59-62 ◽  
Author(s):  
Kantima Chaochanchaikul ◽  
Wanlop Harnnarongchai
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Polylactic Acid ◽  
Irradiation Dose ◽  
Crosslinking Agent ◽  
Chain Scission ◽  
Chain Extension ◽  
Molecular Characteristics ◽  
High Irradiation Dose ◽  
Gamma Irradiated

The aim of this work was to compare and discuss the influence of multifunctional monomers as crosslinking agent (Triallyl Isocyanurate; TAIC) and chain extender (Joncryl ADR4368) on the gamma irradiated Polylactic acid (PLA). The modified PLA samples with varying amount of TAIC and Joncryl were characterized by observing the molecular characteristics and mechanical properties. The results showed that irradiated PLA had lower average molar mass and mechanical properties compared to non-irradiated PLA due to irradiation induced chain scission. Gel content was observed and increased with increasing irradiation dose for the TAIC modified sample, indicating that the further crosslink of irradiated PLA was occurring. Crosslinking and chain extension were responsible for the improved modulus and tensile strength of irradiated PLA, however the decrease in tensile strength at high irradiation dose was observed for crosslinked PLA.

Influence of Exposing Vulcanized Rubber to Light on Its Subsequent Aging in the Dark

1944 ◽  
Vol 17 (1) ◽  
pp. 216-220
Author(s):  
J. R. Scott
Keyword(s):  
Tensile Strength ◽  
Accelerated Aging ◽  
Subsequent Aging ◽  
Oxygen Bomb ◽  
Vulcanized Rubber ◽  
Effect Of Light

Abstract The present experiments confirm the observations of Morgan and Naunton by showing that exposure of vulcanized rubber to light may affect the results of oxygen-bomb aging tests made some days, or perhaps even weeks, afterwards. They show also that a few days' exposure to even diffused daylight may noticeably lower the tensile strength of unaged rubber. With normal, i.e., not transparent, rubbers the effect of light on subsequent aging is small, and indeed does not seem to be noticeable at all in relatively slow aging tests, such as that in the Geer oven. Nevertheless, it is clearly advisable, as a precaution, to avoid unnecessary exposure to light of rubbers that are to be subjected to accelerated aging tests.

The Direct Determination of Oxygen in Rubber. The Adaptation of the Ter Meulen Method to Rubber and Its Application to the Study of Aging

1939 ◽  
Vol 12 (2) ◽  
pp. 269-282 ◽  
Author(s):  
H. I. Cramer ◽  
I. J. Sjothun ◽  
L. E. Oneacre
Keyword(s):  
Tensile Strength ◽  
Physical Properties ◽  
Direct Determination ◽  
Sulfur Poisoning ◽  
Oxidation Products ◽  
Oxygen Bomb ◽  
Vulcanized Rubber ◽  
Relationship Of ◽  
The Relationship

Abstract The ter Meulen method for the direct determination of oxygen has been adapted, with modifications, to the analysis of raw and vulcanized rubbers. Raney nickel has been found to be quite effective as the reducing catalyst and to be satisfactorily resistant to sulfur poisoning. The method has been applied to the study of the aging of vulcanized rubber in the Geer oven and oxygen bomb. From this study the following conclusions may be drawn: (1) The increase in combined oxygen is greater in the oxygen bomb than in the Geer oven. (2) Deterioration of rubber in the oxygen bomb involves oxidation primarily, whereas that occurring in the Geer oven involves not only oxidation but also thermal decomposition followed by volatilization of oxidation products. (3) The effectiveness of an antioxidant in retarding the absorption of oxygen in oxygen-bomb aging agrees well with its ability to maintain the physical properties of the stock in which it is present. (4) The deterioration in physical properties of a rubber stock in the oxygen bomb during the early stages of aging is a linear function of the increase in combined oxygen. For stocks containing antioxidants and diphenylguanidine as the accelerator, an increase in combined oxygen of approximately 1.2% corresponds to a decrease in tensile strength of 50%. (5) The relationship of increase in combined oxygen to decrease in tensile strength seems to be affected not only by antioxidants, but also by accelerators of vulcanization.

Aging of GR-S Vulcanizates. IV. Influence of the Vulcanizing Ingredients, Antioxidant, and Softener

1950 ◽  
Vol 23 (2) ◽  
pp. 397-403 ◽  
Author(s):  
J. R. Scott
Keyword(s):  
Tensile Strength ◽  
Aging Behavior ◽  
Tetramethylthiuram Disulfide ◽  
Oxygen Bomb ◽  
Acetone Extraction ◽  
Low Sulfur ◽  
Tension Strength

Abstract The results of air aging at temperatures from 25° to 100° C and of oxygen-bomb aging are discussed in relation to the composition of the mix; notes are given also on the relation of composition to the properties before aging. The main conclusions are: (1) a low proportion of sulfur or (still better) vulcanization by tetramethylthiuram disulfide (TMT) improves the maintenance of tensile strength and elongation under all conditions examined; a low-sulfur mix containing selenium gives results intermediate between the normal low-sulfur and TMT-vulcanized mixes; (2) when judged by the stiffening and hardening during aging, the relative merits of these alternative vulcanizing agents are different, age-stiffening being generally least with low sulfur plus selenium and greatest with TMT vulcanization; (3) on the whole, mercapto-benzothiazole (MBT) gave better results than TMT as an accelerator in mixes with the same proportion of sulfur; (4) acetone extraction of raw GR-S did not lead to the bad aging expected from the removal of antioxidant, but this point needs further study in view of contrary conclusions by other workers; (5) a large proportion of softener somewhat improves maintenance of strength but increases age-stiffening; (6) in general the formulation giving the best maintenance of tension strength and elongation does not give the least age-stiffening, and vice-versa; for the former, TMT vulcanization (possibly plus softener) appears best; for the latter an MBT-accelerated low-sulfur mix, possibly plus selenium, and (7) the 100° C air and the oxygen-bomb aging tests may give misleading indications of aging behavior in air at lower temperatures.

The Influence of Loading Rate on the Ultimate Properties and Fracture Mechanism of Styrenic Thermoplastic Elastomers

2008 ◽  
Vol 41-42 ◽  
pp. 91-97
Author(s):  
Qiu Mei Zeng ◽  
Jeremy W. Leggoe
Keyword(s):  
Tensile Strength ◽  
Fracture Surface ◽  
Strain Rate ◽  
Loading Rate ◽  
Chain Scission ◽  
Thermoplastic Elastomers ◽  
Tensile Fracture ◽  
Void Coalescence ◽  
Pull Out ◽  
Poly Ethylene

The influence of loading rate on the tensile fracture of polystyrene-polyisoprenepolystyrene (SIS) and polystyrene-poly(ethylene-co-butylene)-polystyrene (SEBS) has been investigated. The tensile strength of SIS initially increased with increasing strain rate, eventually reaching a plateau at elevated strain rates. In contrast, the tensile strength of SEBS was relatively unaffected by strain rate. The fracture surfaces of the tensile test specimens were examined by scanning electron microscopy. The fracture surface morphologies indicated that fracture initiated via cavitation, followed subsequently by void coalescence and catastrophic fracture. For both materials there was no qualitatively obvious change in fracture surface morphology with increasing strain rate. The results indicate that the ultimate strength of styrenic thermoplastic elastomers is governed by the nature of the dominant failure mechanism at the molecular scale; when chain scission dominates, the tensile strength is independent of the strain rate, but when chain pull-out dominates, the tensile strength increases with increasing strain rate.

Oxygen Absorption of Vulcanizates. A Means of Evaluating Aging Resistance

1950 ◽  
Vol 23 (2) ◽  
pp. 425-439
Author(s):  
Louis R. Pollack ◽  
Robert E. McElwain ◽  
Paul T. Wagner
Keyword(s):  
Tensile Strength ◽  
Physical Properties ◽  
Absorption Measurement ◽  
Oxygen Absorption ◽  
Oxygen Bomb ◽  
Ultimate Elongation ◽  
Synthetic Rubber ◽  
Standard Procedures ◽  
Aging Resistance

Abstract The rates of oxygen absorption of two natural and six synthetic-rubber stocks have been measured. In addition, the course of aging in the oxygen bomb and air oven was followed by means of changes in tensile strength and in ultimate elongation of the same eight stocks. Correlation between rates of oxygen absorption and deterioration of physical properties is close enough to justify substitution of a rapid oxygen absorption measurement for longer standard procedures in evaluating the aging characteristics of rubber stocks.

Evaluation of Wear Resistance of Cross-Linked Ultra-High Molecular Weight Polyethylene for Joint Prostheses in the Multi-Directional Pin-on-Plate Apparatus

2005 ◽  
Author(s):  
T. Sawano ◽  
T. Murakami ◽  
Y. Sawae
Keyword(s):  
Tensile Strength ◽  
Wear Resistance ◽  
Gamma Irradiation ◽  
Chain Scission ◽  
Optimum Dose ◽  
Gamma Irradiated ◽  
Joint Prostheses ◽  
Ultra High Molecular Weight ◽  
Plate Apparatus ◽  
Minimum Wear

Gamma irradiation is used as a sterilization method for joint prosthesis. For this procedure, gamma irradiation causes crosslinking of UHMWPE. Crosslinked UHMWPE molecules connect each other strongly. However gamma irradiation causes the reduction in mechanical properties such as tensile strength and elongation because primary chain scission occurrs. Therefore, excessive irradiation would cause some problems. We suggest the existence of the optimum dose for minimum wear and moderate reduction in tensile strength and elongation. Furthermore we indicate a mechanism of wear resistance of gamma irradiated UHMWPE.

Thermo- and Photo-Degradation of LDPE and PP Films Using Metal Oxides as Catalysts

2010 ◽  
Vol 93-94 ◽  
pp. 505-508 ◽  
Author(s):  
Sarinya Shawaphun ◽  
Thara Manangan ◽  
Sirirat Wacharawichanant
Keyword(s):  
Tensile Strength ◽  
Free Radicals ◽  
Metal Oxides ◽  
Carbonyl Compounds ◽  
Photo Degradation ◽  
Plastic Films ◽  
Carbonyl Index ◽  
Cross Linkage ◽  
Preliminary Study ◽  
Hexane Solution

Degradation of LDPE and PP films using the photo sensitive metal oxides or pro-oxidants (e.g. Fe2O3, CuxO, ZnO, and TiO2 at various particle sizes) as the catalysts in both thermo- and photo-oxidation of plastic films with oxygen followed by photolytic process to give free radicals has been studied. Our preliminary study in hexane solution found that the carbonyl index (CI) increased under the shortwave ultraviolet (254nm) significantly greater than under the longer wave (366nm) due to its greater energy and highly absorbed by the pro-oxidants generating more free radical concentration which could then be photolysed into carbonyl compounds. The pro-oxidant blended PE and PP films under ultraviolet (254nm) irradiation showed the carbonyl index elevation at the beginning and then reducing to a constant level similarly in most cases. This probably suggested that the carbonyl primarily formed and degraded into other free radicals. Under shortwave ultraviolet irradiation for 72 hours, the LDPE films containing nano-sized rutile-TiO2 and nano-sized anatase-TiO2 (1%w/w) were able to reduce the film tensile strength by 32% and 55%, respectively. The film containing micron-sized commercial TiO2 lower the film tensile strength only by 7-10%. However, the tensile strength of the TiO2 blended PP films tends to increase possibly because the rate of cross linkage exceeds the rate of scission.

A Manometric Test for Oxygen Absorption by Vulcanized Rubber

1942 ◽  
Vol 15 (1) ◽  
pp. 83-90
Author(s):  
Robert H. Johnson
Keyword(s):  
Tensile Strength ◽  
Oxygen Absorption ◽  
Aging Behavior ◽  
Strength Deterioration ◽  
Oxygen Bomb ◽  
Vulcanized Rubber ◽  
Rubber Compounds ◽  
Manometric Method ◽  
Set Up ◽  
Bomb Method

Abstract An apparatus can be set up in laboratory glassware that will confirm the results obtained by Dufraisse in his manometric test for oxygen absorption. It has been shown that different rubber compounds possess different tendencies to absorb oxygen. It has also been shown that the differences in the rate at which rubber compounds absorb oxygen are comparable with those differences found in the rate of tensile-strength deterioration of the same compounds aged in the oxygen bomb. This modified Dufraisse manometric method is convenient, efficient, accurate and, above all, a speedy method for measuring the relative aging behavior of vulcanized rubber compounds. Within two hours it is possible to have the results by this method, whereas it is necessary to wait from four days to two weeks for such information by the oxygen bomb method.

Sign in / Sign up

Export Citation Format

Share Document