TY - JOUR
T1 - Model for Anomalous Moisture Diffusion through a Polymer-Clay Nanocomposite
AU - Drozdov, Aleksey D.
AU - Christiansen, Jesper de Claville
AU - Gupta, R.K.
AU - Shah, A.P.
PY - 2003
Y1 - 2003
N2 - Experimental data are reported on moisture diffusion and the elastoplasticresponse of an intercalated nanocomposite with vinyl ester resin matrix and montmorilloniteclay filler at room temperature. Observations in diffusion tests showed thatwater transport in the neat resin is Fickian, whereas it becomes anomalous (nonFickian)with the growth of the clay content. This transition is attributed to immobilizationof penetrant molecules on the surfaces of hydrophilic clay layers. Observationsin uniaxial tensile tests demonstrate that the response of vinyl ester resin is stronglyelastoplastic, whereas an increase in the clay content results in a severe decrease ofplastic strains observed as a noticeable reduction in the curvatures of the stress-straindiagrams. This is explained by slowing down the molecular mobility in the host matrixdriven by confinement of chains in galleries between platelets. Constitutive equationsare developed for moisture diffusion through and the elastoplastic behavior of a nanocomposite.Adjustable parameters in these relations are found by fitting the experimentaldata. Fair agreement is demonstrated between the observations and the resultsof numerical simulation. A striking similarity is revealed among changes in diffusivity,ultimate water uptake, and the rate of plastic flow with an increased clay content.
AB - Experimental data are reported on moisture diffusion and the elastoplasticresponse of an intercalated nanocomposite with vinyl ester resin matrix and montmorilloniteclay filler at room temperature. Observations in diffusion tests showed thatwater transport in the neat resin is Fickian, whereas it becomes anomalous (nonFickian)with the growth of the clay content. This transition is attributed to immobilizationof penetrant molecules on the surfaces of hydrophilic clay layers. Observationsin uniaxial tensile tests demonstrate that the response of vinyl ester resin is stronglyelastoplastic, whereas an increase in the clay content results in a severe decrease ofplastic strains observed as a noticeable reduction in the curvatures of the stress-straindiagrams. This is explained by slowing down the molecular mobility in the host matrixdriven by confinement of chains in galleries between platelets. Constitutive equationsare developed for moisture diffusion through and the elastoplastic behavior of a nanocomposite.Adjustable parameters in these relations are found by fitting the experimentaldata. Fair agreement is demonstrated between the observations and the resultsof numerical simulation. A striking similarity is revealed among changes in diffusivity,ultimate water uptake, and the rate of plastic flow with an increased clay content.
KW - diffusion
KW - mechanicalproperties
KW - nanocomposites
M3 - Journal article
SN - 0887-6266
VL - 41
SP - 476
EP - 492
JO - Journal of Polymer Science. Part B, Polymer Physics
JF - Journal of Polymer Science. Part B, Polymer Physics
IS - 5
ER -