Sub-Tg annealing studies of rubber-modified and unmodified epoxy systems

Zohar H. Ophir; Garth L. Wilkes

doi:10.1063/1.324437

Sub-T_g annealing studies of rubber-modified and unmodified epoxy systems

Research output: Contribution to journal › Article › peer-review

Abstract

Epoxy network systems based on DGEBA (bisphenol-A-diglycidyl ether) and NMA (nadic methyl anhydride) systems modified with the low molecular weight CTBN (carboxyl-terminated butudiene-acrylonitrile copolymer) rubbers were prepared and studied. It was found that below the glass transition of the epoxy matrix these materials displayed time-dependent changes in their mechanical properties; specifically, the strain to break as well as the rate of stress relaxation were observed to decrease in a near-linear behavior with the logarithm of time at sub-T_g annealing. Calorimetric methods clearly showed a simultaneous decrease in enthalpy with time that behaved in a similar fashion as the time-dependent mechanical properties. All the calorimetric and mechanical data are qualitatively related. The importance of this phenomena is considered in view of the widespread use of epoxys. Similar behavior is expected for other network glasses thermally quenched into a nonequilibrium state.

Original language	American English
Pages (from-to)	5032-5038
Number of pages	7
Journal	Journal of Applied Physics
Volume	49
Issue number	10
DOIs	https://doi.org/10.1063/1.324437
State	Published - 1978
Externally published	Yes

ASJC Scopus subject areas

General Physics and Astronomy

Access to Document

10.1063/1.324437

Cite this

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title = "Sub-Tg annealing studies of rubber-modified and unmodified epoxy systems",

abstract = "Epoxy network systems based on DGEBA (bisphenol-A-diglycidyl ether) and NMA (nadic methyl anhydride) systems modified with the low molecular weight CTBN (carboxyl-terminated butudiene-acrylonitrile copolymer) rubbers were prepared and studied. It was found that below the glass transition of the epoxy matrix these materials displayed time-dependent changes in their mechanical properties; specifically, the strain to break as well as the rate of stress relaxation were observed to decrease in a near-linear behavior with the logarithm of time at sub-Tg annealing. Calorimetric methods clearly showed a simultaneous decrease in enthalpy with time that behaved in a similar fashion as the time-dependent mechanical properties. All the calorimetric and mechanical data are qualitatively related. The importance of this phenomena is considered in view of the widespread use of epoxys. Similar behavior is expected for other network glasses thermally quenched into a nonequilibrium state.",

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T1 - Sub-Tg annealing studies of rubber-modified and unmodified epoxy systems

AU - Ophir, Zohar H.

AU - Wilkes, Garth L.

PY - 1978

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N2 - Epoxy network systems based on DGEBA (bisphenol-A-diglycidyl ether) and NMA (nadic methyl anhydride) systems modified with the low molecular weight CTBN (carboxyl-terminated butudiene-acrylonitrile copolymer) rubbers were prepared and studied. It was found that below the glass transition of the epoxy matrix these materials displayed time-dependent changes in their mechanical properties; specifically, the strain to break as well as the rate of stress relaxation were observed to decrease in a near-linear behavior with the logarithm of time at sub-Tg annealing. Calorimetric methods clearly showed a simultaneous decrease in enthalpy with time that behaved in a similar fashion as the time-dependent mechanical properties. All the calorimetric and mechanical data are qualitatively related. The importance of this phenomena is considered in view of the widespread use of epoxys. Similar behavior is expected for other network glasses thermally quenched into a nonequilibrium state.

AB - Epoxy network systems based on DGEBA (bisphenol-A-diglycidyl ether) and NMA (nadic methyl anhydride) systems modified with the low molecular weight CTBN (carboxyl-terminated butudiene-acrylonitrile copolymer) rubbers were prepared and studied. It was found that below the glass transition of the epoxy matrix these materials displayed time-dependent changes in their mechanical properties; specifically, the strain to break as well as the rate of stress relaxation were observed to decrease in a near-linear behavior with the logarithm of time at sub-Tg annealing. Calorimetric methods clearly showed a simultaneous decrease in enthalpy with time that behaved in a similar fashion as the time-dependent mechanical properties. All the calorimetric and mechanical data are qualitatively related. The importance of this phenomena is considered in view of the widespread use of epoxys. Similar behavior is expected for other network glasses thermally quenched into a nonequilibrium state.

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