Heat capacity, enthalpy and crystallinity of polymers from DSC measurements and determination of the DSC peak base line

Mathot, Vincent; Pijpers, M. F. J.

doi:10.1016/0040-6031(89)85354-7

Cited by 52 publications

(21 citation statements)

References 11 publications

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“…1 [1, 2 the copolymers were used to calculate the enthalpy values, which, together with the enthalpy reference values for purely amorphous and purely crystalline LPE [69,76] made it possible to calculate the crystallinity values. In addition, the baseline and excess heat capacities were determined [72,75]. The excess values are crucial if the heat capacity measurements are to be used as input into a crystallization model.…”

Section: Discussionmentioning

confidence: 99%

“…Nor should this line be confused with the line which is obtained by extrapolating the part of the measured curve in the melt; in the case of the heating curve this is the part above the melting end temperature and in the case of the cooling curve it is the part above the onset of crystallization. As described earlier [72,75] this line can be used to calculate the value of the numerator in (3). From this and Ah(T), the denominator in (3), the crystallinity curve can be calculated.…”

Section: Co(t)mentioning

confidence: 99%

“…Since it is not strictly necessary to carry out a heat capacity measurement in order to be able to extrapolate from the melt, this is also a practical method for quantitatively calculating the crystallinity curve from ordinary (but quantitative, due to correction for the empty-pan signal) DSC curves. It is even possible to calculate the excess cp(T) in this way without having to carry out a real heat capacity measurement [72,75].…”

Section: Co(t)mentioning

confidence: 99%

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Dynamic DSC, SAXS and WAXS on homogeneous ethylene-propylene and ethylene-octene copolymers with high comonomer contents

Mathot

Scherrenberg

Pijpers

et al. 1996

Journal of Thermal Analysis

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Ethylene-propylene (EP) and ethylene-octene (EO) copolymers polymerized with the aid of homogeneous vanadium and metallocene catalysts were compared by DSC and time-resolved simultaneous SAXS-WAXS-DSC at scanning rates of 10 and 20~ rain -1 using synchrotron radiation. An EP eopolymer with a density of 896 kg m -3 (about 89 mol% ethylene) after compression moulding gave orthorhombic WAXS reflections. The crystallinity as a function of temperature [wC(7)] calculated from these reflections using the two-phase model was in good agreement with we(T) calculated from Cp measurements using DSC. The Cp measurements also enabled calculation of the baseline Cp and the excess Cp. The SAXS measurements revealed a strong change in the long period in cooling and in heating. The SAXS invariant as a function of temperature showed a maximum in both cooling and heating, which could be explained from the opposing influences of the crystallinity and the electron density difference between the two phases. Two EO eopolymers with densities of about 871 kg m -3 (about 87 mol% ethylene) no longer showed any clear WAXS reflections, although DSC and SAXS measurements showed that these eopolymers did crystallize. The similarity between the results led to the conclusion that the copolymers, though based on different catalyst systems -vanadium and metallocene -did not have strongly different sets of propagation probabilities of chain growth during polymerization. On the basis of a Monte Carlo simulation model of crystallization and morphology, based on detailed knowledge of the mierochain structure, the difference between WAXS on the one hand and DSC and SAXS on the other could be explained as being due to loosely packed cryz,tallized ethylene sequences in clusters. These do cause the density and the electron density of the cluster to increase (which is measurable by SAXS) and the enthalpy to decrease (which is measurable by DSC) but the clusters are too small and/or too imperfect to give constructive interference in the case of WAXS. Of an EP copolymer with an even lower ethylene content (about 69 mol%), the crystallization and melting processes could still be readily measured by DSC and SAXS, which proves that these techniques are eminently suitable for investigating the crystallization and melting behaviour of the copolymers studied.

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Section: Discussionmentioning

confidence: 99%

Section: Co(t)mentioning

confidence: 99%

Section: Co(t)mentioning

confidence: 99%

See 1 more Smart Citation

Dynamic DSC, SAXS and WAXS on homogeneous ethylene-propylene and ethylene-octene copolymers with high comonomer contents

Mathot

Scherrenberg

Pijpers

et al. 1996

Journal of Thermal Analysis

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“…when there is insignificant change in heat capacity during the transition [8]; if this is not the case, the proper heat of transition can be obtained by using a step function baseline [9]. This can easily be done by linear extrapolation of the baselines before and after the 1st order DSC transition, when the extrapolations meet to form a straight line, i.e.…”

Section: Resultsmentioning

confidence: 99%

Thermoplastic polymers quality control

Castelli

Deplano

Rota

1996

Journal of Thermal Analysis

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“…Standard DSC was employed for analysis of the RAF, and the determination of the enthalpy-based crystallinity of samples. Details about the calculation of the RAF and of the crystallinity as a function of temperature are described elsewhere [8,40,41]. For the crystallinity-calculation, a bulk heat of fusion of the PHB crystal of 146 J g À1 was used [35].…”

Section: Standard Differential Scanning Calorimetry (Dsc)mentioning

confidence: 99%

Surface structure of folded-chain crystals of poly(R-3-hydroxybutyrate) of different chain length

Androsch

2008

Polymer

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Heat capacity, enthalpy and crystallinity of polymers from DSC measurements and determination of the DSC peak base line

Cited by 52 publications

References 11 publications

Dynamic DSC, SAXS and WAXS on homogeneous ethylene-propylene and ethylene-octene copolymers with high comonomer contents

Dynamic DSC, SAXS and WAXS on homogeneous ethylene-propylene and ethylene-octene copolymers with high comonomer contents

Thermoplastic polymers quality control

Surface structure of folded-chain crystals of poly(R-3-hydroxybutyrate) of different chain length

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