Thermal analysis of poly(butylene terephthalate) for heat capacity, rigid‐amorphous content, and transition behavior

Wiley - Tập 189 Số 10 - Trang 2443-2458 - 1988
Stephen Z. D. Cheng1,2, Robert Pan1,2, Bernhard Wunderlich1,2
1Chemistry Division, Oak Ridge National Laboratory, Oak Ridge, TN, U.S.A.
2Department of Chemistry, The University of Tennessee, Knoxville, TN 37996-1600, U.S.A.

Tóm tắt

AbstractThermal analysis was performed on poly(butylene terephthalate), PBT, between 210 and 560 K. By combination of experimental heat capacities with computations with an approximate frequency spectrum of 65 group and 19 skeletal vibrations, preliminary recommended ATHAS (1988) heat capacities are proposed for the solid state from 0 to 600 K. The Tarasov parameters used for the computation of the skeletal vibrations were θ1 = 542 K and θ3 = 80 K for crystalline PBT and θ3 = 40 K for amorphous PBT. The glass transition temperature of amorphous PBT was found on efficiently quenched samples to be 248 K, much lower than for semicrystalline PBT where a 310–325 K glass transition temperature is typical. The increase in heat capacity calculated for 100% amorphous samples is 107 J/(K · mol) at 248 K and 77 J/(K · mol) at 320 K. The equilibrium melting temperature is estimated to be 518 K. The unique existence of rigid‐amorphous fractions of the semicrystalline polymers is discussed with quantitative data for samples crystallized from the glass and from the melt between 275 and 490 K. The rigidamorphous fraction varies between above 0,9 for cold‐crystallized samples to 0,3 for samples crystallized at 490 K. The crystallinity varied from below 0,1 to 0,5. The crystallinity could be separated into four parts, melting at high, medium, and low temperatures, and a part crystallized on cooling after isothermal crystallization. The sequence of crystallization of differently melting crystals was established.

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Wiley

Tập 189 Số 10

2443-2458

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