Calorimetry of High Polymers. III. A New Type of Adiabatic Jacket and Calorimeter

Worthington, A. E.; Marx, Paul C.; Dole, Malcolm

doi:10.1063/1.1715290

Cited by 33 publications

(4 citation statements)

References 5 publications

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“…The apparatus was the same as that used in the previous specific heat measurements on polyethylene terephthalate. 2.' A recalibration of the calorimeter using aluminum oxide and a recalibration of the watt-hour meter were performed.…”

Section: Experimental Methods and Materialsmentioning

confidence: 99%

Specific heat of synthetic high polymers. VIII. Low pressure polyethylene

1957

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Specific heat measurements have been carried out on granular and annealed Marlex 50, a polyethylene polymerized at relatively low pressures, over the temperature range −25 to 150°C. Calculation of the crystallinity yields maximum values of 82.6 and 93.8% for the granular and annealed Marlex 50, respectively. The specific heat of crystalline Marlex 50 at room temperature is slightly less than that previously predicted for a crystalline paraffinic hydrocarbon of infinite chain length. The maximum melting temperature, 134.8°, is about 1.7° less than that of polymethylene and close to the predicted value for a long chain solid hydrocarbon. 90% of the solid Marlex 50 melts over a 15° range of temperature. The shape of the specific heat‐temperature curve can be well reproduced by application of Flory's theory of crystallization in copolymers by considering branch points and chain ends to be the noncrystallizing copolymer units. Negative temperature drifts just below the melting point and low specific heat values just above have not been explained.

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Section: Experimental Methods and Materialsmentioning

confidence: 99%

Specific heat of synthetic high polymers. VIII. Low pressure polyethylene

1957

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“…It was a sign of problems to come that this first paper dealt with the specific heat capacity and crystallinity of polyethylene. Much foresight and courage was needed then to devote a new adiabatic calorimeter [2] exclusively to the investigation of linear macromolecules. Not only was the field of macromolecules still new at that time, but one also had to venture into the field of thermodynamics of systems not in equilibrium.…”

Section: Introductionmentioning

confidence: 99%

The thermal properties of polypropylene

Grȩbowicz

Lau

Wunderlich

1984

J. polym. sci., C Polym. symp.

195

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The thermodynamic properties of isotactic polypropylene in the fully crystalline, glassy, and molten state are established from 0 to 500 K based on data bank heat capacities and the vibrational frequency spectrum. The seven skeletal vibrations are described by θ3 and θ1 of 91 and 714 K for crystalline polypropylene. For the calculation of Cp − Cv, a Lindemann A0 value of 1.5 × 10−3 K mol/J was found. Calculated and experimental heat capacity data show agreement within an average error of −0.3 ± 1.6%. Glassy polypropylene was similarly treated up to the glass transition temperature at 260 K (θ3 = 78 K, θ1 = 633 K, average heat capacity error −0.6 ± 2.8%). The residual 0 K entropy of glassy polypropylene is 1.9 J/K mol. Partially crystalline polypropylene is shown through high‐sensitivity DSC measurements to have a glass transition range from 260 to 380 K. Similarly, high‐sensitivity DSC has been used to characterize the condis phase of polypropylene (conformationally disordered polypropylene) which was prior called “smectic mesophase” or “paracrystalline.” Its heat of transformation to the stable crystal phase is 600 J/mol.

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“…The general shape of the large endothermic peak, according to data reported by a number of experimenters (8)(9)(10)(11), is represented by the solid black line in Figure 2. The foil calorimeter data obtained at various heating speeds show good agreement with this "standard" curve.…”

Section: Polytetrafluoroe Thylenementioning

confidence: 92%

High‐speed thin‐foil calorimetry

Hager

1973

J. polym. sci., C Polym. symp.

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A method is described for performing adiabatic scanning calorimetry on thin samples heated at high speeds. Sample sheets are inserted between layers of a folded metal foil heater to form a stacked array. A thin‐foil thermocouple is inserted near the median plane of the array. The sample assembly is heated by passing a current through the foil heater. There is a brief initial period during which the sample interior heats adiabatically. During this period, the thermocouple signal is traced as a function of time on a chart recorder. Analysis of the chart yields the sample heating rate dT̃/dt at selected values of the mean sample temperature T. Specific heat values are calculated from dT̃/dt, using an energy‐conservation equation. The sample thickness is kept small to permit attaining rapid heating rates without excessive temperature gradients. The overall thickness of the stacked array is designed to make the adiabatic period sufficient in duration, so that results are valid over the desired temperature range. Results are shown for polytetrafluoroethylene and polyethylene terephthalate at various heating rates up to 600 K/sec. At low speeds, results agree with previously published data, but at higher speeds radically different curves are obtained. Above the glass transition temperature of the polyethylene terephthalate, it is observed that the positions of inflections in the specific heat curve vary sharply with sample heating speed.

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Calorimetry of High Polymers. III. A New Type of Adiabatic Jacket and Calorimeter

Cited by 33 publications

References 5 publications

Specific heat of synthetic high polymers. VIII. Low pressure polyethylene

Specific heat of synthetic high polymers. VIII. Low pressure polyethylene

The thermal properties of polypropylene

High‐speed thin‐foil calorimetry

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