Temperature effect in quasiharmonic infrared bands of stressed polymers

Bretzlaff, R. S.; Wool, Richard P.

doi:10.1063/1.328527

Cited by 23 publications

(11 citation statements)

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“…If during heating these stresses are reduced, the bands should shift to higher frequencies. The analysis of the data (Bretzlaff, 1981(Bretzlaff, , 1983Vettegren, 1992Vettegren, , 2009Bronnikov, 1996) shows that the "red" shift of the absorption bands under external mechanical stresses in highly oriented polypropylene is less than 3 cm -1 even at scission strain (Bretzlaff, 1981(Bretzlaff, , 1983. In our case the observed bands shift is several times higher ( Figure 10).…”

Section: Journal Of Materials Science Researchsupporting

confidence: 49%

“…Let's investigate frequency position temperature dependences. It is known that the Δν T frequency shift during temperature increase from T 1 to T 2 , in other polymers, (Bretzlaff, 1981(Bretzlaff, , 1983Vettegren, 1992Vettegren, , 2009Bronnikov, 1996) can be written as follows:…”

Section: Discussionmentioning

confidence: 99%

“…This can influence the absorption bands frequency position. Indeed, the application of σ m mechanical stress to the polymer films under isothermal conditions result in a Δν σ shift of the characteristic frequencies of the vibration spectrum as per the following equation (Bretzlaff, 1981(Bretzlaff, , 1983Vettegren, 1992Vettegren, , 2009Bronnikov, 1996)…”

Section: Journal Of Materials Science Researchmentioning

confidence: 99%

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Structural Aspects at Phase Transitions in Ferroelectric Copolymers of Vinylidenefluoride and Tetrafluoroethylene

Kochervinskiĭ¹,

Kozlova²,

Бессонова³

et al. 2014

JMSR

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Permittivity and conductivity low-voltage temperature dependences of a ferroelectric copolymer of vinylidenefluoride VDF with tetrafluoroethylene TFE in the ferroelectric to paraelectric phase transition range were investigated. The as received films obtained by crystallization from a solution had the metastable structure shown in particular in coexistence of ferroelectric and paraelectric phases below a Curie point. Temperature dependences of electrical characteristics in the first and second cycles of heating differ. Low glass transition (−40 ºC) facilitate intensive micro-Brownian chains mobility in the amorphous phase at ambient temperatures and above. As per the x-ray and spectroscopic data, the first heating cycle will result in a recrystallization process for molecular structure improvement. Asymmetry of temperature dependence of a dielectric susceptibility in a vicinity of "order-disorder" phase change is found out. For the first time paid attention to the fact that for crystalline polymer ferroelectrics interpretation of the parameters of the temperature dependences of the dielectric susceptibility in the cycle of heating near the phase transition point should take into account the possibility of the premelt processes. First the method of IR spectroscopy shows that the melting of ordered structures, emerging secondary crystallization is accompanied by a change of the basic parameters (frequency position, the integral intensity and half-width) component of the doublet of valence vibrations of С-Н groups. Such structural changes lead to the emergence of "anomalies" on the temperature dependences of conductivity.The phase transition ferroelectric to paraelectric mechanism research is usually done on copolymers P(VDF-TrFE), in which Curie point T c and melting point T m considerably differ (Wang, 1988; Nalva, 1995;Kochervinskii, 1999) more often. In this paper, the order-disorder transition is investigated on copolymer VDF-TFE of composition 71/29 for which both a chain chemical microstructure , and crystallographic parameters (Kochervinskii, 2010) had being studied earlier. It was shown, that in the copolymer isotropic films been crystallized from a low-boiling solvent at room temperature, T c and T m temperate values differ slightly. It was founded out, that the order-disorder transition having the first kind phase transition type. The electric parameter anomalies in the close proximity to a ferroelectric-paraelectric transition are depends on www.ccsenet.org/jmsr

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Section: Journal Of Materials Science Researchsupporting

confidence: 49%

Section: Discussionmentioning

confidence: 99%

Section: Journal Of Materials Science Researchmentioning

confidence: 99%

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Structural Aspects at Phase Transitions in Ferroelectric Copolymers of Vinylidenefluoride and Tetrafluoroethylene

Kochervinskiĭ¹,

Kozlova²,

Бессонова³

et al. 2014

JMSR

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“…The average stress application rates for Figure 4 I. An interpretation of these shifts in terms of their "mixing" and "anharmonic" contributions is given in ref 16.…”

Section: Resultsmentioning

confidence: 98%

Frequency shifting and asymmetry in infrared bands of stressed polymers

Bretzlaff¹,

Wool²

1983

Macromolecules

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The effect of stress and temperature on infrared frequency shifting and band asymmetry in polymers is investigated. Valence coordinate deformation of individual polypropylene chains accounts for the observed frequency shifting in samples of oriented isotactic polypropylene. Each chain may be modeled as a one-dimensional enharmonic system, whose wave functions and energies are obtained in the quasi-harmonic approximation. The theoretical stress-induced frequency shifting coefficient is related to the Gmneisen parameter and is expressed by ac = -a0 -CTosc, where a0 and C are positive constants and Toer is the temperature of the oscillators in equilibrium with the radiation field. Two mechanisms of band broadening are considered: The first is due to the presence of an average interchain perturbing force. The second is due to the existence of anisotropic crystal field forces. Each description predicts symmetric broadening. Therefore, the development of an observable asymmetry in a stressed infrared band may be associated with a nonuniform molecular stress distribution. Only the crystal field broadening mechanism, however, is consistent with the assumptions required for calculation of the linear ac(T) relation, which agrees well with experiments on oriented polypropylene. The anisotropic broadening mechanism is also investigated for oriented polyethylene.

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“…This is because semicrystalline polymers such as polyethylene exhibit a marked deviation from linear viscoelastic behavior even at small strains [1][2][3][4][5] . It has been identified that plastic deformation, such as dislocation, microvoid formation, and the slippage of crystallites, can arise from any applied deformation [6][7][8] and that anharmonic elastic response can be caused by mechanical and thermal excitations 9,10) . To fully describe the stressrelaxation behavior of semicrystalline polymer solids, it is necessary to consider both contributions from plastic deformation and anharmonic response.…”

Section: Introductionmentioning

confidence: 99%

Prediction of stress-relaxation behavior in high density polyethylene solids

Nitta¹,

Suzuki

1999

Macromol. Theory Simul.

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SUMMARY: The stress-relaxation behavior of a high density polyethylene solid was investigated using a nonlinear viscoelastic model in which two nonlinear parameters such as the anharmonicity in elastic response and the plastic deformation are introduced into a generalized Maxwell model. The determination of the nonlinear parameters demands the transient modulus data under a constant rate of deformation. The nonlinear viscoelastic model developed from the tensile behavior was found to predict the stress-relaxation behavior in the nonlinear region.

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Temperature effect in quasiharmonic infrared bands of stressed polymers

Cited by 23 publications

References 7 publications

Structural Aspects at Phase Transitions in Ferroelectric Copolymers of Vinylidenefluoride and Tetrafluoroethylene

Structural Aspects at Phase Transitions in Ferroelectric Copolymers of Vinylidenefluoride and Tetrafluoroethylene

Frequency shifting and asymmetry in infrared bands of stressed polymers

Prediction of stress-relaxation behavior in high density polyethylene solids

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