Aging, Physical

Simon, Sindee L.

doi:10.1002/0471440264.pst015

Cited by 11 publications

(7 citation statements)

References 125 publications

(147 reference statements)

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“…This is referred to as structural relaxation or physical aging. 13,14 A transition from ductile to brittle mode of failure is observed when a material physically ages. 14 Consequently, characterization of physical aging is of essential importance for polymer engineering.…”

Section: Introductionmentioning

confidence: 99%

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Physical Aging of Single Wall Carbon Nanotube Polymer Nanocomposites: Effect of Functionalization of the Nanotube on the Enthalpy Relaxation

2010

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The glass-transition temperature and enthalpy relaxation of nanocomposites synthesized with low loadings of single wall carbon nanotubes (1 wt %) in poly(methylmethacrylate) (PMMA) have been investigated using differential scanning calorimetry (DSC). The results are compared with pure PMMA, and the effect of carbon nanotubes on the mobility of the polymer chain is discussed. Composites have been synthesized with unmodified nanotubes (SWNT/PMMA) as well as with amino-functionalized nanotubes (a-SWNT/PMMA) to provide a better interaction between the nanotube and the host matrix material. It was found that the glass-transition temperature of the unmodified nanocomposite SWNT/PMMA is the same as the neat PMMA (T g =99°C). A significant increase of 17°C in the glass-transition temperature of the modified nanocomposite a-SWNT/PMMA is found when compared with the neat PMMA. Glass-transition results indicate that the presence of a-SWNT in PMMA restricts the segmental motion of the polymer chain. No significant change in activation energy of the enthalpy relaxation process or fragility index of PMMA is observed due to the addition of a-SWNT. However, a large broadening of the enthalpy peak is observed with the incorporation of SWNT in PMMA. This broadening leads to difficulty in the calculation of the activation energy and fragility index of SWNT/PMMA. Enthalpy relaxation behavior during isothermal aging is characterized at the same temperature with respect to the respective glass-transition temperatures of the three samples (at T g and T g -2°C (2°C lower than the glass-transition temperature of each system)). The equilibrium enthalpy is reached at a shorter aging time in pure PMMA compared with SWNT/PMMA and a-SWNT/PMMA. The results obtained for enthalpy recovery show the signature of the restrictive environment of a-SWNT and SWNT on polymer chain mobility.

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Section: Introductionmentioning

confidence: 99%

“…13,14 A transition from ductile to brittle mode of failure is observed when a material physically ages. 14 Consequently, characterization of physical aging is of essential importance for polymer engineering. To the best of our knowledge, only a few reports on physical aging of polymer nanocomposites have been published.…”

Section: Introductionmentioning

confidence: 99%

Physical Aging of Single Wall Carbon Nanotube Polymer Nanocomposites: Effect of Functionalization of the Nanotube on the Enthalpy Relaxation

2010

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“…F o r P e e r R e v i e w Introduction Physical aging refers to structural relaxation of the glassy state toward the metastable equilibrium amorphous state (Hodge 1995), and it is driven by the attempt to achieve equilibrium density through configurational rearrangements on a molecular scale (Simon 2001). Physical aging is accompanied by changes in almost all physical properties, at both the macrostructural (bulk) and microstructural (molecular) scale (Struik 1977;Hodge 1995;Hutchinson 1995).…”

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confidence: 99%

Characterization of physical aging by time-resolved rheometry: fundamentals and application to bituminous binders

2018

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Physical aging is a ubiquitous phenomenon in glassy materials and it is reflected, for example, in the time evolution of rheological properties under isothermal conditions. In this paper, time-resolved rheometry (TRR) is used to characterize this time-dependent rheological behavior. The fundamentals of TRR are briefly reviewed, and its advantages over the traditional Struik's physical aging test protocol are discussed. In the experimental section, the TRR technique is applied to study physical aging in bituminous binders. Small-diameter parallel plate (SDPP) rheometry is employed to perform cyclic frequency sweep (CFS) experiments over extended periods of time (from one to 8.6 days). The results verify that the mutation of rheological properties is relatively slow during physical aging (mutation number N'mu << 1), thus allowing rheological measurements on a quasi-stable sample. The effects of temperature, crystallinity and styrene-butadiene-styrene (SBS) polymer modification on the physical aging of bitumen are evaluated. The time-aging time superposition is found to be valid both for unmodified and for polymer modified bitumen. Vertical shifts are necessary, in addition to horizontal time-aging time shifts, to generate smooth master curves for highly SBS modified bitumen.

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“…TOFA (mix of oleic (46 wt%), linoleic (35 wt%), linolenic (12 wt%), palmitic (4 wt%), and stearic (3 wt%) acids) [34] were supplied by Colorquímica SA. P-toluenesulfonic acid, phenol, isopropanol, potassium hydroxide, tetrahydrofuran and xylene were supplied by Sigma-Aldrich.…”

Section: Methodsmentioning

confidence: 99%