Nanofiller-Polymer Interactions At and Above the Glass Transition Temperature

Zhu, Aijun; Sternstein, S. S.

doi:10.1557/proc-661-kk4.3

Cited by 8 publications

(10 citation statements)

References 14 publications

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“…While relatively small due to the high stiffness of the Dynastat, corrections were still made for the machine compliance. This correction was minimal for the above T g data reported here but significant for the glass transition data obtained using a symmetric simple-shear sandwich and reported elsewhere …”

Section: Methodssupporting

confidence: 46%

Reinforcement Mechanism of Nanofilled Polymer Melts As Elucidated by Nonlinear Viscoelastic Behavior

2002

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Nonlinear viscoelastic properties are reported for composites of fumed silica with various surface treatments and matrices of poly(vinyl acetate) of different molecular weights as well as a copolymer matrix of vinyl acetate and vinyl alcohol. Data above the glass transition temperature are reported here. The increase in the composite storage and loss moduli measured at low strains, and their relative rates of decrease with strain, are found to depend on filler surface treatment. The nonlinear behavior of the loss factor with strain is dramatically altered by filler treatment and quite revealing as to the likely mechanism causing the nonlinearity. In addition, the relative reinforcement and the degree of nonlinearity are found to be the highest for the lowest molecular weight matrices. The effect of copolymer substitution for the homopolymer matrix is equivalent to an increase in molecular weight. The primary underlying mechanism for reinforcement and nonlinear behavior appears to be the filler−matrix interactions, but not filler agglomeration or percolation. It is proposed that temporary (labile) bonding of chains to the filler surface results in trapped entanglements, having both near- and far-field effects on matrix chain motions. These trapped entanglements cause greatly enhanced non-Gaussian (Langevin) chain behavior that affects storage and loss moduli differently, resulting in very high reinforcement by nanofillers. Applied strain (stress) aids the release of the trapped entanglements, thereby leading to the reduction in dynamic moduli. The reinforcement and nonlinear viscoelastic properties of the nanofilled polymer melts bear striking similarity to what is observed in filled elastomers (the Payne effect), suggesting a common mechanism that is rooted in the macromolecular nature of the matrices.

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Section: Methodssupporting

confidence: 46%

Reinforcement Mechanism of Nanofilled Polymer Melts As Elucidated by Nonlinear Viscoelastic Behavior

2002

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“…During the past few years, intensive discussion on the origin of the reinforcement in polymer nanocomposites has been hold. As it has been shown by Sternstein et al1–3 and Kalfus et al,4, 5 rubbery nanocomposite reinforcement depends considerably on the external conditions (e.g., temperature, dynamic strain amplitude) and composite structure—the polymer matrix nature, filler surface treatment and mainly the filler‐matrix contact area. Direct filler agglomeration and filler particle shape seemed to be less important representing only a second‐order contribution to the viscoelastic response of a nanocomposite.…”

Section: Introductionmentioning

confidence: 92%

“…On the basis of the theoretical analyses as well as experimental data published in literature, there is sufficient background for more general understanding of the reinforcing mechanism in polymer nanocomposites 1–16. In this contribution we compared results from molecular model utilizing reptation concept with relaxation data obtained from modulus recovery measurements following the Payne effect published previously 5.…”

Section: Introductionmentioning

confidence: 99%

Relaxation processes in PVAc‐HA nanocomposites

Kalfus

Jančář

2007

J Polym Sci B Polym Phys

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Fundamental principles of polymer physics were used for description of relaxation behavior of polymer chain near solid surface. In a nanocomposite, considerable portion of polymer matrix is in contact with the filler surface even at very low filler loadings. In this study, nanocomposite was considered as a two component system consisting of (i) bulk polymer matrix and (ii) effective particles composed of adsorbed polymer shell and filler particle core. Both polymer phases, i.e., bulk and immobilized, are able to relax, however, each of them on a different time scale. Thus, above the neat matrix T g , these two phases undergo (i) free and (ii) retarded reptation dynamics due to the adsorption processes on the filler surface, respectively. Relaxation time was calculated for each phase using the reptation theory. To calculate the mixed response of the whole polymer nanocomposite, a simple rule of mixtures model and percolation model were used. Calculated composite relaxation times were correlated with experimental modulus recovery data measured after the Payne effect in poly(vinylacetate)-hydroxyapatite nanocomposite. Good agreement was found between theoretical predictions and experimental data.

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“…So far, serious attempts to investigate the reinforcing mechanism in polymer nanocomposites have been predominantly restricted to systems with amorphous matrices [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. In these matrices above their T g , the chains can undergo segmental immobilization induced even by weak interactions on the large filler-matrix internal interface.…”

Section: Introductionmentioning

confidence: 99%

Effect of weakly interacting nanofiller on the morphology and viscoelastic response of polyolefins

Kalfus

Jančář

Kučera

2008

Polymer Engineering & Sci

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Effect of silica nanofiller on the deformation response and morphology of low-and high-density polyethylene (HDPE, LDPE) and isotactic polypropylene (PP) modified with fumed silica was investigated. The dynamicmechanical thermal spectroscopy, differential scanning calorimetry, optical microscopy, and density measurements were carried out to determine the temperature dependence of storage and loss moduli as well as nanocomposite morphology. It was demonstrated that the degree of matrix reinforcement is considerably affected by the extent of matrix crystallinity, especially, in the temperature range from (T m -1308C) to T m . Based on experimental evidence and literature review, it is proposed that this phenomenon may be attributed to the alpha-mechanical relaxation process occurring above matrix T g . As a result of adding silica into the melted matrix, mobility of chains in contact with silica particles became reduced. This caused substantial changes in morphology of these semicrystalline nanocomposites.

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Nanofiller-Polymer Interactions At and Above the Glass Transition Temperature

Cited by 8 publications

References 14 publications

Reinforcement Mechanism of Nanofilled Polymer Melts As Elucidated by Nonlinear Viscoelastic Behavior

Reinforcement Mechanism of Nanofilled Polymer Melts As Elucidated by Nonlinear Viscoelastic Behavior

Relaxation processes in PVAc‐HA nanocomposites

Effect of weakly interacting nanofiller on the morphology and viscoelastic response of polyolefins

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