Sphärolithwachstum in Polymeren

Dietz, W.

doi:10.1007/bf01524878

Cited by 42 publications

(26 citation statements)

References 19 publications

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“…The mixture entropy per unit mass (36) can be reformulated using (23) under consideration of the calculation rules for the logarithmic function:…”

Section: Specific Gibbs Free Energymentioning

confidence: 99%

“…This is caused by differences in the volumetric material properties of the three individual phases. Inserting (75) into (23), the fractions of the three phases at θ eq can be determined: This result shows that all three phases coexist at the equilibrium melting temperature. The combination of (74) and (75) under consideration of (73) allows computing θ eq in dependence on the pressure and the material constants:…”

Section: Equilibrium Behaviourmentioning

confidence: 99%

“…If the difference in the densities between the amorphous and the crystalline phase is neglected (see [23] for a discussion), x (t) ≈ V c (t)/V 0 holds in a good approximation; V c (t) is the volume of the crystallised polymer and V 0 the total volume of the specimen. Based on this interpretation, the model developed by Avrami [24] is frequently applied to describe temporal changes in the crystallinity under isothermal conditions:…”

Section: Introductionmentioning

confidence: 99%

“…[23,25,26]). The derivation of (2) considers the creation of crystal nuclei as well as a linear time-dependent crystal growth.…”

Section: Introductionmentioning

confidence: 99%

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A thermodynamic approach to model the caloric properties of semicrystalline polymers

Lion

Johlitz

2015

Continuum Mech. Thermodyn.

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It is well known that the crystallisation and melting behaviour of semicrystalline polymers depends in a pronounced manner on the temperature history. If the polymer is in the liquid state above the melting point, and the temperature is reduced to a level below the glass transition, the final degree of crystallinity, the amount of the rigid amorphous phase and the configurational state of the mobile amorphous phase strongly depend on the cooling rate. If the temperature is increased afterwards, the extents of cold crystallisation and melting are functions of the heating rate. Since crystalline and amorphous phases exhibit different densities, the specific volume depends also on the temperature history. In this article, a thermodynamically based phenomenological approach is developed which allows for the constitutive representation of these phenomena in the time domain. The degree of crystallinity and the configuration of the amorphous phase are represented by two internal state variables whose evolution equations are formulated under consideration of the second law of thermodynamics. The model for the specific Gibbs free energy takes the chemical potentials of the different phases and the mixture entropy into account. For simplification, it is assumed that the amount of the rigid amorphous phase is proportional to the degree of crystallinity. An essential outcome of the model is an equation in closed form for the equilibrium degree of crystallinity in dependence on pressure and temperature. Numerical simulations demonstrate that the process dependences of crystallisation and melting under consideration of the glass transition are represented.

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“…The mixture entropy per unit mass (36) can be reformulated using (23) under consideration of the calculation rules for the logarithmic function:…”

Section: Specific Gibbs Free Energymentioning

confidence: 99%

Section: Equilibrium Behaviourmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…[23,25,26]). The derivation of (2) considers the creation of crystal nuclei as well as a linear time-dependent crystal growth.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A thermodynamic approach to model the caloric properties of semicrystalline polymers

Lion

Johlitz

2015

Continuum Mech. Thermodyn.

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“…The transcrystalline 1 0 X t Å I ϱ 0 I t /I ϱ 0 I 0 Å exp(0kt n ) (1) where X t is the fraction of material crystallized can be obtained from the double logarithmic form and spherulitic growth lead to an Avrami exponent of 3, whereas thermal nucleation and spherof the Avrami equation ulitic growth, to a value of 4. 25 Based on the experimental results as tabulated in the above tables, log[0ln(1 0 X t )] Å log k / n log t (2) it is obvious that both the PP homopolymer and m-PP copolymer exhibit an Avrami exponent of 4. Figure 7 shows the plots of log[0ln(1 0 X t )] vs.…”

Section: General Behaviormentioning

confidence: 99%

Crystallization kinetics of compatibilized blends of a liquid crystalline polymer with polypropylene

Tjong

Chen

1997

J. Appl. Polym. Sci.

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Blends of a maleic anhydride-grafted polypropylene (m-PP) and a liquid crystalline polymer (LCP) based on a copolyester of hydroxynapthoic acid and hydroxybenzoic acid were fabricated. The morphology and isothermal and nonisothermal crystallization kinetics behavior of the m-PP copolymer and m-PP/LCP blends were investigated using polarizing optical microscopy, depolarized light intensity, and differential scanning calorimetry. A polarizing optical micrograph revealed that the m-PP is very effective to promote a finer dispersion of the LCP phase in the PP matrix. Consequently, the LCP domains or fibrils acted as potential sites for the spherulite nucleation. The isothermal kinetics measurements also indicated that the rate of crystallization is enhanced in the maleated PP/LCP blends which exhibit transcrystallinity. In general, the nonisothermal kinetics results were in good agreement with those obtained from the isothermal kinetics measurements.

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Rates of Crystallization of Polymers

Magill

1999

The Wiley Database of Polymer Properties

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Sphärolithwachstum in Polymeren

Cited by 42 publications

References 19 publications

A thermodynamic approach to model the caloric properties of semicrystalline polymers

A thermodynamic approach to model the caloric properties of semicrystalline polymers

Crystallization kinetics of compatibilized blends of a liquid crystalline polymer with polypropylene

Rates of Crystallization of Polymers

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