Effect of ozone on creep of vulcanizates

Metherell, C.

doi:10.1002/pol.1978.180160506

Cited by 4 publications

(5 citation statements)

References 6 publications

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“…(where log t = 3.3). The detailed experimental values are plotted in figure 5 together with all similar data reported for corresponding values of B and log ta in the papers by Gent [2] and Metherell [15]. One concludes from figure 5 that the criterion defining ta in eq.…”

Section: Appearance Time and Linearity Limitmentioning

confidence: 68%

“…In fact a plot of B against the reciprocal of the thickness was found in at least one instance [15] to have an intercept of zero. This means that B would vanish for a specimen of infinite thickness.…”

Section: Significance Of Bmentioning

confidence: 99%

“…The term" appearance time" used by Metherell [15] for the boundary might give a misleading implication that a new process begins at this point However, we shall continue to use it since the alternatives "induction time" or .. incubation time" used by Aben [16,17] are even more open to the same objection. Neither of these authors made quantitative definition of the term.…”

Section: Appearance Time and Linearity Limitmentioning

confidence: 99%

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Representation of long-time creep in a pure-gum rubber vulcanizate

Wood

1980

J. RES. NATL. BUR. STAN.

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Creep may be expressed as AEI E, = A log t + B(t-I) where AE is the increas e of elongation above E, the one-minute value, during the time t. The initial slope of a plot of AEI E, against log t is A, a measure of physical creep. The limit of the final slope of a plot of AEI E, against (t-I) is B, a measure of chemical creep. The validity of the equation is determined by the linearity of a plot of (AEI E, -A log t) against (t-I) after A has been determined by the first plot. B is obtained as the slope. The equation is almost always valid and simultaneous equations can be used to determine A and B from only three observations, if desired. A, usually between I and 10 per cent/unit log t, is strongly dependent on cross-linking and nearly independent of temperature. B, ranging from 0.1 X 10-' to 10,000 X 10-' per cent/ min is nearly independent of cross-linking and strongly dependent on temperature and specimen thickness. With an activation energy of 84-12SkJ (molt' (20-30 kcal (molt') it probably reflects oxidative degradation of the network, often initiated by ozone. The appearance time at which the creep is first observed to exceed A log t can be taken as equal to B-'. At high temperatures B is drastically increased with a corresponding strong reduction in appearance time. Creep in excess of that given by the equation is sometimes observed during a period immediately before rupture.

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Section: Appearance Time and Linearity Limitmentioning

confidence: 68%

Section: Significance Of Bmentioning

confidence: 99%

Section: Appearance Time and Linearity Limitmentioning

confidence: 99%

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Representation of long-time creep in a pure-gum rubber vulcanizate

Wood

1980

J. RES. NATL. BUR. STAN.

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“…Although the evaluation of B is useful as a means of comparing different rubbers in relation to each other it can not be regarded as a genuine characteristic property of a rub-ber since it depends on the thickness of the specimen. In fact a plot of B against the reciprocal of the thickness was found in at least one instance [15] to have an intercept of zero. This means that B would vanish for a specimen of infinite thickness.…”

Section: Significance Of Bmentioning

confidence: 99%

“…It is clear from figures 1, 2, and 3 that there is a region (short times) where flEIE, appears to be linear with log t. It is of interest to examine the upper boundary of this region where it first becomes apparent that flEIE, is greater than A log t. The time at which one can be sure that this is true will depend on the sensitivity of the method of measurement This boundary has been considered by several previous authors, but often the concept has been rather vague and has lacked a rigorous definition. The term" appearance time" used by Metherell [15] for the boundary might give a misleading implication that a new process begins at this point However, we shall continue to use it since the alternatives "induction time" or .. incubation time" used by Aben [16,17] are even more open to the same objection. Neither of these authors made quantitative definition of the term.…”

Section: Appearance Time and Linearity Limitmentioning

confidence: 99%

Representation of Long-Time Creep in a Pure-Gum Rubber Vulcanizate

Wood

1981

Rubber Chemistry and Technology

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Creep may be expressed as AEI E, = A log t + B(t-I) where AE is the increas e of elongation above E, the one-minute value, during the time t. The initial slope of a plot of AEI E, against log t is A, a measure of physical creep. The limit of the final slope of a plot of AEI E, against (t-I) is B, a measure of chemical creep. The validity of the equation is determined by the linearity of a plot of (AEI E,-A log t) against (t-I) after A has been determined by the first plot. B is obtained as the slope. The equation is almost always valid and simultaneous equations can be used to determine A and B from only three observations, if desired. A, usually between I and 10 per cent/unit log t, is strongly dependent on cross-linking and nearly independent of temperature. B, ranging from 0.1 X 10-' to 10,000 X 10-' per cent/ min is nearly independent of cross-linking and strongly dependent on temperature and specimen thickness. With an activation energy of 84-12SkJ (molt' (20-30 kcal (molt') it probably reflects oxidative degradation of the network, often initiated by ozone. The appearance time at which the creep is first observed to exceed A log t can be taken as equal to B-'. At high temperatures B is drastically increased with a corresponding strong reduction in appearance time. Creep in excess of that given by the equation is sometimes observed during a period immediately before rupture.

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Effect of an oxidative environment on the creep compliance of poly(ether urethane urea)

Sletten

Topolkaraev

et al. 1994

J of Applied Polymer Sci

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SYNOPSISSecondary creep of unstabilized poly( ether urethane urea) (PEUU) in an oxidative environment appears as a linear time-dependent component superimposed on the logarithmic, viscoelastic response. The surfaces of unstabilized PEUU crept in H202/CoC12 have been characterized by scanning electron microscopy and ATR-FTIR. By examining PEUU crept for various periods of time, it is found that surface damage proceeds at gradually increasing size scales, culminating in large voids. It is hypothesized that the initial chain scission creates a flaw that grows in size under the influence of the applied load into a "nano-pit," which grows further by coalescence into a pit and, finally, a void. The initial stages of voiding occur during an induction period when there is no measurable effect on the creep response. It is possible to estimate the average compliance of the damaged PEUU by assuming a composite model with an undamaged center layer' sandwiched between damaged surface layers. When the contribution of the surface layers to the creep compliance is estimated from the creep curves, the average compliance of the damaged layer is found to be about 1.6 times higher than that of the undamaged PEUU. Independent calculations of the damaged layer compliance from the void fraction indicate that the damaged layer behaves as a flexible foam in the early stages, then as a more rigid foam at longer creep times.

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Effect of ozone on creep of vulcanizates

Cited by 4 publications

References 6 publications

Representation of long-time creep in a pure-gum rubber vulcanizate

Representation of long-time creep in a pure-gum rubber vulcanizate

Representation of Long-Time Creep in a Pure-Gum Rubber Vulcanizate

Effect of an oxidative environment on the creep compliance of poly(ether urethane urea)

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