Yasuo Saruyama

A new method of analysing transformation kinetics with temperature modulated differential scanning calorimetry: application to polymer crystal growth

Abstract A new method is presented to analyse endothermic or exothermic process with temperature modulated differential scanning calorimetry, utilizing the shift in phase lag between sample temperature and heat flow. It has been shown that the temperature coefficient of transformation rate, e.g. of crystal growth, is obtainable by the analysis. The method is applied to polymer crystallization and the validity has been examined with the experimental results of polyethylene crystallization.

A new analyzing method of temperature modulated DSC of exo- or endo-thermic process: Application to polyethylene crystallization

Abstract A new method is presented to analyse an exothermic or endothermic process with temperature modulated differential scanning calorimetry. The response of exo- or endo-thermic process against temperature modulation has been directly taken into account in an apparent heat capacity difference of complex quantity. Utilizing the shift in phase lag between sample temperature and heat flow, the specific heat during the transformation process and the temperature coefficient of the transformation rate, e.g. crystal growth rate, are obtainable by the analysis under a reasonable assumption. The applicability of the present method has been examined with the experimental results of polyethylene crystallization.

An application of temperature modulated differential scanning calorimetry to the exothermic process of poly(ethylene terephthalate) crystallization

Abstract We have examined the applicability of a new analysing method of temperature modulated differential scanning calorimetry to the exothermic process of poly(ethylene terephthalate) crystallization. The method utilizes the change in the phase lag between modulation components of sample temperature and of heat flow, to introduce an apparent heat capacity of complex quantity. The phase lag showed a peak and a dip during the isothermal crystallization, above and below the temperature at which the growth rate of crystals becomes a maximum, respectively. The present method incorporates the change, and predicts negative and positive temperature dependence of crystal growth rate, for the peak and dip in the phase lag, respectively. The temperature dependence of crystal growth rate agreed well with the literature values obtained from the direct measurements of growth rate of spherulites by optical microscopy.

Development of the light heating dynamic DSC

The dynamic DSC is a recently developed technique for simultaneous measurement of DSC and AC calorimetry (ACC). Thermal information which cannot be obtained by DSC or ACC alone can be obtained by comparing the results of DSC and ACC. Commercial apparatus are not always suitable for such comparison because of the low frequency and the large amplitude of the sinusoidal modulation. In this study the light heating technique used in ACC was employed to generate the sinusoidal modulation. The frequency and the amplitude achieved were, respectively, ten times and one-tenth those of the commercial apparatus. Results obtained from polyethylene by light heating dynamic DSC are presented.

Melting transition of polyethylene studied by light-modulated calorimetry

Abstract Melting transition of polyethylene crystals was studied by light-modulated calorimetry. The light-modulated calorimeter (or light-heating dynamic DSC) was constructed using heating through light to give heat-flow modulation to the sample. Frequency dependence of the complex heat capacity was measured in the (0.01 – 0.2) Hz range. It was found that, in the melting-temperatures range, the real part of the complex heat capacity at frequencies equal to or higher than 0.1 Hz reached limiting value at a sufficiently high frequency. Linearity between the cyclic temperature change of the sample and the modulation, and the difference between melting and crystallization from the viewpoint of the complex heat capacity were also investigated.

Temperature modulated d.s.c. study of poly(ethylene terephthalate) crystallization : 2. Applicability to non-isothermal process

The non-isothermal crystallization of poly(ethylene terephthalate) has been examined by temperature modulated differential scanning calorimetry (TMd.s.c.). A new analytical model of TMd.s.c. has been applied to the process, taking account of the response of exothermic heat flow to temperature modulation in an apparent heat capacity of complex quantity. By examining the frequency dependence of the apparent heat capacity, the applicability has been successfully examined for the non-isothermal process. The method is capable of determining the temperature dependence of crystal growth rate from TMd.s.c. data analysis. The results agree well with the dependence determined from literature values of spherulite growth rate measured by optical microscopy.

Quasi-isothermal measurement of frequency dependent heat capacity of semicrystalline polyethylene at the melting temperature using light heating modulated temperature DSC

Frequency dependence of the heat capacity of semicrystalline polyethylene was measured using light heating modulated temperature DSC (LMDSC). The quasi-isothermal measurement was carried out in the melting temperature range of the crystal. Two decades of the frequency, from 0.01 to 1 Hz, was covered by the LMDSC instrument constructed in the authors laboratory. It was found that in the melting temperature range polyethylene exhibited Debye relaxation with the relaxation time of 14 s and had excess heat capacity independent of the kinetics. The excess heat capacity and the relaxation strength could be attributed to the disordered crystals generated during rapid cooling from the molten state and/or its surrounding amorphous region instead of the stable crystals reorganized during the quasi-isothermal measurement.

A modeling of the irreversible melting kinetics of polymer crystals responding to temperature modulation with retardation of melting rate coefficient

Abstract An extension of the modeling proposed previously has been examined for the irreversible melting kinetics of polymer crystals on heating with response to temperature modulation. The previous modeling has been successful in the explanation of the frequency dependence of the apparent heat capacity obtained with temperature modulated DSC in the melting region of poly(ethylene terephthalate), polyethylene and poly(caprolactam). In the present work this modeling was extended to explain an unusual behavior reported by Schawe et al. for poly(ϵ-caprolactone) and syndiotactic polypropylene, in which the latent heat gave a substractive effect to the real part of the apparent heat capacity. A retardation of the melting rate coefficient in response to temperature change has been considered. The retardation implies an activation process in the melting kinetics of polymer crystals.

AC calorimetry at the first order phase transition point

A model is proposed for AC calorimetry (ACC) at the first order phase transition point. The model is compared with the results of ACC around the melting point of ann-paraffin (C20H42). The observed frequency dependence of ACC is consistent with the model. A harmonic component of the temperature modulation with a frequency equal to twice the heating frequency was observed at the phase transition point. It is shown that the harmonic component can be explained on the basis of the proposed model.ZusammenfassungEs wird ein Modell für die AC-Kalorimetrie (ACC) von Phasenumwandlungen erster Ordnung vorgeschlagen. Das Modell wird mit den Ergebnissen von ACC in Nähe des Schmelzpunktes des n-Paraffins C20H42 verglichen. Die beobachtete Frequenzabhängigkeit von ACC stimmt mit dem Modell überein. Im Phasenumwandlungspunkt kann eine harmonische Komponente der Temperaturmodulation mit einer Frequenz festgestellt werden, die doppelt so hoch wie die Heizfrequenz ist. Es wird gezeigt, daß die harmonische Komponente anhand des vorgeschlagenen Modelles erklärt werden kann.

Development of light heating dynamic DSC II: determination of complex calibration constants

Complex calibration constants of light heating dynamic DSC were determined experimentally. The complex calibration constants must be known to measure the phase and the amplitude of the cyclic temperature response in dynamic DSC although only real calibration constants have been estimated so far. A new mathematical equation appropriate for light heating dynamic DSC was derived and used to determine the complex calibration constants. The new equation gave results which agreed well with experimental data.