线型环型烷烃和高聚物的链段长度对热力学性能的影响(PerkinElmer)
2007-05-16 11:36
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资料摘要:
The specific heat capacity was measured with step-scan differential scanning calorimetry for linear
alkanes from pentane sC5H12d to nonadecane sC19H40d, for several cyclic alkanes, for linear and
cyclic polyethylenes, and for a linear and a cyclic polystyrene. For the linear alkanes, the specific
heat capacity in the equilibrium liquid state decreases as chain length increases; above a carbon
number N of 10 sdecaned the specific heat asymptotes to a constant value. For the cyclic alkanes, the
heat capacity in the equilibrium liquid state is lower than that of the corresponding linear chains and
increases with increasing chain length. At high enough molecular weights, the heat capacities of
cyclic and linear molecules are expected to be equal, and this is found to be the case for the
polyethylenes and polystyrenes studied. In addition, the thermal properties of the solid-liquid and
the solid-solid transitions are examined for the linear and cyclic alkanes; solid-solid transitions are
observed only in the odd-numbered alkanes. The thermal expansion coefficients and the specific
volumes of the linear and cyclic alkanes are also calculated from literature data and compared with
the trends in the specific heats.
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线型环型烷烃和高聚物的链段长度对热力学性能的影响
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