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首页> 外文期刊>Journal of pharmaceutical sciences. >Dynamic heat capacity and relaxation time of ultraviscous melt and glassy acetaminophen.
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Dynamic heat capacity and relaxation time of ultraviscous melt and glassy acetaminophen.

机译：超粘熔体和玻璃状对乙酰氨基酚的动态热容和弛豫时间。

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摘要

The real and imaginary components, C'(p) and C''(p), of the complex heat capacity, C*(p)=C'(p)-iC"(p) of supercooled, ultraviscous melt of acetaminophen have been measured at different temperatures during cooling through its vitrification range and during heating through its glass-softening range by using a modulation frequency of 3.3 mHz. From these data, the distribution of relaxation time parameter, beta, and a characteristic (calorimetric or configurational) relaxation time, tau(cal), have been determined. A constant value of 0.65 for beta fits the data, and tau(cal) varies with the temperature according to the Vogel-Fulcher-Tammann equation, tau(cal) = 10(-12.95) exp[1813/(T - 240.5)]. This relation differs significantly from the one deduced by others in which the configurational entropy theory was used to deduce tau(cal). The C'(p) and C''(p) values measured during the cooling of its ultraviscous melt and during the heating of its glassy state show a small hysteresis only at low temperatures. These investigations also provide a comparison of calorimetric and dielectric relaxation times in ultraviscous acetaminophen and highlight the role of faster modes of relaxation at low temperatures in organic, molecular glasses that can help in a better understanding of the crystal nucleation process in glasses at T below their T(g).
机译：对乙酰氨基酚的过冷超粘熔体的复热容C *（p）= C'（p）-iC“（p）的实部和虚部C'（p）和C''（p）具有通过使用3.3 mHz的调制频率，在其玻璃化温度范围内的冷却过程中以及在玻璃软化范围内的加热过程中，通过使用3.3 mHz的调制频率在不同温度下测量这些数据，这些数据包括弛豫时间参数，β和特性（量热或构型）分布确定了弛豫时间tau（cal），β的恒定值为0.65，符合数据，并且tau（cal）根据Vogel-Fulcher-Tammann方程随温度变化，tau（cal）= 10（- 12.95）exp [1813 /（T-240.5）]。这种关系与其他人的推论有很大的不同，后者使用构型熵理论来推导tau（cal）。C'（p）和C''（p ）在其超粘熔体的冷却过程中以及在其玻璃态的加热过程中测得的值仅在较低温度下显示出较小的滞后性温度。这些研究还提供了超粘性对乙酰氨基酚的量热和介电弛豫时间的比较，并突出了有机分子玻璃在低温下更快的弛豫模式的作用，可以帮助更好地理解T低于其温度时玻璃的晶体成核过程。 T（克）。

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