Dielectric studies of water absorption and desorption in epoxy resins: influence of cure process on behaviour

McConnell, B.K.; Pethrick, Richard A.

doi:10.1002/pi.2324

Cited by 15 publications

(10 citation statements)

References 24 publications

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“…The increases in ɛ ′(ω) and ɛ ″(ω) observed below 10 Hz is attributed to ion conduction processes associated with blocking electrode effects and generally described by Maxwell Wagner Sillars polarization . The small feature observed in these systems is similar to that observed in other similar epoxy resins .…”

Section: Resultssupporting

confidence: 71%

“…Positron annihilation lifetime spectroscopy indicate that depending on the cure system voids are ∼5 to 6 Å in diameter compared with 3‐Å kinetic diameter of a water moleculeWater molecules diffuse initially as distinct entities rather than as clusters . The formation of “water droplets” is evident in nmr, infrared and dielectric measurements and is ascribed to “free water.” Bound water is associated with isolated water molecules interacting with OH, O, NH and in some cases quaternary sites in the matrix. Detailed analysis of the FTIR and nmr spectra have identified singly and doubly hydrogen bonded forms of water which is consistent with the breadth of the dielectric relaxation and the observed values of the Kirkwood “Ng” factor, Table .…”

Section: Resultsmentioning

confidence: 99%

“…Swelling of the matrix depends on the degree of crosslinking of the resin but is usually associated with aging at T g . Rehydration after initial exposure to moistureDehydration of a resin can change the topography as “water droplets” leave the nano‐voids and allow them to collapse. The level of subsequent moisture uptake will not necessarily follow that observed during the initial exposure of the resin to moisture . These irreversible changes reflect plasticization releasing stresses frozen into the matrix during the cure process modifying the void structure and in certain cases allow matrix densification.…”

Section: Resultsmentioning

confidence: 99%

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A dielectric study of water uptake in epoxy resin systems

Garden¹,

Pethrick²

2017

J of Applied Polymer Sci

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The influence of epoxy resin formulation on the nature and extent of moisture is studied using dielectric and gravimetric analysis for samples cured at 40, 50, 60, and 70 8C and aged at 50 8C and 70 8C. The equilibrium moisture uptake depends on the difference between the glass transition and aging temperature. Dielectric relaxation data measured from 1 to 3 3 10 10 Hz indicates the presence of water in at least two different environments. The high frequency relaxation ca. 1 3 10 10 Hz is associated with water clustered in nano-voids, whereas the relaxation at 10 5 Hz arises from a combination of OH pendant group reorientation motion coupled with that of molecularly dispersed water molecules. A correlation exist between the dielectric permittivity and the amount of moisture absorbed. Water initially resident in voids is re-dispersed with aging into the resin matrix aiding plasticization and allowing densification of the matrix. The extent to which changes occur depends on the chemical functions forming the matrix and densification leads to a drop in the amount of water absorbed. In the complex resin systems, water interacts with both OH groups and polyether of the amine curing agent which is not possible with the aliphatic diamine in the simple system.] V C 2017 Wiley Periodicals, Inc. J. Appl. Polym.Sci. 2017, 134, 44717.

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Section: Resultssupporting

confidence: 71%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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A dielectric study of water uptake in epoxy resin systems

Garden¹,

Pethrick²

2017

J of Applied Polymer Sci

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“…This shoulder was also observed on DMA spectra for DGEBA/TETA network cured with similar conditions to protocol 1 in other studies34, 37 where no information was given. It can be noted that the splitting of tan(δ) peak was noted41–44 for epoxy resins after water absorption. Since at this point no water had been in contact with the films, the presence of this shoulder can be explained by the curing conditions.…”

Section: Resultsmentioning

confidence: 95%

Effects of curing program on mechanical behavior and water absorption of DGEBA/TETa epoxy network

Dang

Cohendoz

Mallarino

et al. 2013

J of Applied Polymer Sci

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Water uptake in organic coatings remains an interesting challenge for fundamental and applied researches because chemical, physical, and mechanical properties are concerned. The polymer network, which is affected by the curing program, is a key factor for water absorption. In this work, an epoxy network based on diglycidyl ether of bisphenol A and a hardener triethylentetramine was cured at different temperatures: below T g (protocol 1) and above T g (protocol 2). DMA, Differential Scanning Calorimetry (DSC), and FT-IR measurements showed that both protocols allow to obtain totally cured networks. However, DSC and DMA results revealed that both cured networks present different levels of homogeneity, depending on the different curing conditions, which affect the free volume and the activation volume associated with visco-elastic properties. The mechanical properties of free films and water sorption behaviors were investigated as function of cured conditions. It was found that protocol 1-cured networks present higher mechanical properties and was less affected by water ingress than protocol 2-cured systems, leading to better barrier properties. These results highlight the influence of the curing program onto the heterogeneous distribution of the epoxy network.

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“…The diffusion behaviour of moisture into adhesives has been extensively investigated. 70–77 The effect of absorption followed by desorption is illustrated in Figure 17(b). The first sample A (-•-) was exposed to water for 140 h and then dried in an oven and then re-exposed to water.…”

Section: Mechanisms Of Ageing In Various Environmentsmentioning

confidence: 99%

Design and ageing of adhesives for structural adhesive bonding – A review

Pethrick

2014

Proceedings of the Institution of Mechanical Engineers, Part L:

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This review outlines some of the issues which have to be addressed when selecting an adhesive for a particular structural adhesive bonding application. The designer may find that a number of adhesives provide the required load bearing properties and the selection may require a more detailed consideration of the processes involved in the fabrication of the joint, the temperature over which it is to work and the environment in which it will have to operate. The article attempts to provide the reader with an insight into the effects of factors such as time and temperature used in the cure process, details of the components in the mixture and the effects of various additives on the physical properties of the adhesives which are created. The performance of an adhesive may vary with time as a consequence of stress-induced changes which are triggered by thermal effects or by hygrothermal factors. The review considers joints created using metal substrates and carbon fibre composites. The performance and durability of an adhesive bond is critically dependent on the stability of the interface between the adhesive and adherend and is sensitive to the pre-treatment processes used in the creation of the bond. The review outlines how broadband dielectric measurements can be used to non-destructively monitor the cure of adhesive bonds and the processes involved in ageing of joint. The dielectric method gives an insight into the fundamental processes which are giving rise to the changes in the mechanical properties of the joint as they age.

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Dielectric studies of water absorption and desorption in epoxy resins: influence of cure process on behaviour

Cited by 15 publications

References 24 publications

A dielectric study of water uptake in epoxy resin systems

A dielectric study of water uptake in epoxy resin systems

Effects of curing program on mechanical behavior and water absorption of DGEBA/TETa epoxy network

Design and ageing of adhesives for structural adhesive bonding – A review

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