Multiple molecular relaxations of hot‐drawn and quenched polymers above their glass transition temperatures

Kato, Takahiro A.; Yanagihara, Naohisa

doi:10.1002/app.1981.070260702

Cited by 10 publications

(3 citation statements)

References 19 publications

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“…Both plots gave straight lines and the apparent activation energies of the molecular process accompanied with the thermal shrinkage around Tg of this polymer were estimated as 520 kJ/mol from the slope of the straight line (a) and as 500 kJ/mol from that of the straight line (b). These values correspond well to the reported one of this polymer, 480 • 20 kJ/mol by Krum and Muller [13] and 430-460 kJ/mol by Matz et al [15,16]. Fig.…”

Section: Methodssupporting

confidence: 90%

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A simple method for estimating activation energy from derivative thermoanalytical curves and its application to thermal shrinkage of polycarbonate

Ozawa

Koto

1991

Journal of Thermal Analysis

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Activation energy can be estimated by a new simple method, in which logarithm of maximum rate of conversion observed at different heating rates is plotted against reciprocal absolute temperature, because the conversion at the maximum rate is approximately independent of the heating rate. The method is applied to thermal shrinkage of polycarbonate, and the estimated activation energy is in good agreement with those obtained by conventional methods.For estimating activation energy from thermoanalytical curves, numerous methods have been proposed. Most of them are based on particular kinetic equations, and their applicability is, therefore, limited, because they can not be applied to processes other than those following the particular kinetic equations. When the methods are applied to these processes, they tend to lead false and wrong kinetic parameters and mechanism.A few methods, such as proposed by Flynn and Wall [1], Friedman [2, 3] and one of the present authors [3][4][5][6][7], were derived from a general form of the kinetic equation and their applicability is not limited to particular kinetic models, but they have wide applicability to processes of single elementary process following Arrhenius type temperature dependence of activation energy. One example is application to physical processes, such as John lr~ley & Sons, Limited, Chichester AkndOniai Kiad6, Budapest

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Section: Methodssupporting

confidence: 90%

“…But almost all of strain seems to be recovered by thermal treatment up to above the glass transition temperature. the authors (TK) [13]. The instrument was equipped with a programmed temperature controller so that the sample temperature could be varied linearly with time at several heating rates.…”

Section: Methodsmentioning

confidence: 99%

A simple method for estimating activation energy from derivative thermoanalytical curves and its application to thermal shrinkage of polycarbonate

Ozawa

Koto

1991

Journal of Thermal Analysis

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“…Previous studies on thermomechanical analysis (TMA) of oriented polymers generally have fallen into two categories: measurement of retractive force [12][13][14] and measurement of dimensional change. [15][16][17] Both methods have been applied to rigid PVC, 12,15 showing that significant changes in the oriented samples only occurred as the glass-transition temperature (T g ) of the material under test was approached. For example, a biaxially oriented sheet of rigid PVC with a T g of 74°C began to shrink at 64°C.…”

Section: Introductionmentioning

confidence: 99%

Dimensional stability of oriented, rigid poly(vinyl chloride)

Hitt

Gilbert

2003

J of Applied Polymer Sci

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ABSTRACT:Oriented PVC has enhanced properties, but on heating it begins to shrink and eventually reverts to its original dimensions. Thermomechanical analysis was used to study the effects of orientation variables and subsequent annealing or aging on the shrinkage of rigid PVC. The thermal history of the oriented PVC affected its crystallinity and the free volume in the oriented structure. These changes modified the temperature at which the oriented samples began to shrink (i.e., their dimensional stability.) Higher draw and annealing temperatures can be used to improve dimensional stability; however, their effective use is limited because PVC has a peak elongation at 90°C. Increased annealing time also increases dimensional stability. Aging greatly improves the dimensional stability of the material; this process can be accelerated at temperatures up to 60°C. The shrinkage onset temperature can be increased without compromising the enhancement of mechanical properties achieved by orientation.

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Die Relaxationsprozesse im nichtkristallinen Ethylen‐Propylen‐Copolymer nach Daten der Relaxationsspektrometrie und der Massenspektrometrie

Бартенев¹,

Boturov²

1984

Acta Polymerica

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Multiple molecular relaxations of hot‐drawn and quenched polymers above their glass transition temperatures

Cited by 10 publications

References 19 publications

A simple method for estimating activation energy from derivative thermoanalytical curves and its application to thermal shrinkage of polycarbonate

A simple method for estimating activation energy from derivative thermoanalytical curves and its application to thermal shrinkage of polycarbonate

Dimensional stability of oriented, rigid poly(vinyl chloride)

Die Relaxationsprozesse im nichtkristallinen Ethylen‐Propylen‐Copolymer nach Daten der Relaxationsspektrometrie und der Massenspektrometrie

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