Advanced avrami formula and its application to describing the isothermal crystallisation of polymers

IF 3.5 2区化学 Q2 CHEMISTRY, ANALYTICAL Thermochimica Acta Pub Date : 2025-02-04 DOI:10.1016/j.tca.2025.179950

László Mihály Vas , Emese Slezák , Kolos Molnár , Ferenc Ronkay

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Abstract

The classic Avrami formula has widely been used to describe and characterize the crystallisation process of polymers. We showed that the Avrami formula is not correct for the random nucleation. To eliminate this and some problems of fitting the Avrami formula with integer exponent revealed in the literature, we modified the Avrami equation and derived a new extended formula that can describe instantaneous and random (time-dependent) nucleation simultaneously. This formula may give information on the crystalline structure of both types of nuclei; moreover, it makes it possible to determine the crystalline fraction developed from the instantaneous nuclei. The latter enables us to estimate, for example, the effect of nucleating agents numerically on the crystallisation process and the ultimate crystallinity. The applicability of the new formula was validated by performing isothermal crystallisation tests on poly(ethylene-terephthalate) (PET), polypropylene (PP), low- and high-density polyethylene (LDPE and HDPE) samples at various temperatures, which resulted in a better fit characterized by the much smaller relative maximum absolute error (0.4–2.9 %) related to that for the Avrami equation (1.9–15.9 %).

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先进的avrami公式及其在描述聚合物等温结晶中的应用

经典的阿夫拉米公式已被广泛用于描述和表征聚合物的结晶过程。我们证明了Avrami公式对于随机成核是不正确的。为了消除这一问题以及文献中发现的用整数指数拟合Avrami公式时存在的一些问题，我们对Avrami方程进行了修正，导出了一个新的扩展公式，该公式可以同时描述瞬时成核和随机成核。这个公式可以给出两种核的晶体结构的信息；此外，它还可以测定瞬时原子核形成的结晶分数。后者使我们能够估计，例如，成核剂对结晶过程和最终结晶度的数值影响。通过在不同温度下对聚对苯二甲酸乙二醇酯（PET）、聚丙烯（PP）、低聚乙烯和高密度聚乙烯（LDPE和HDPE）样品进行等温结晶测试，验证了新公式的适用性，结果表明，与Avrami方程（1.9 - 15.9%）相比，新公式的相对最大绝对误差（0.4 - 2.9%）要小得多。

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来源期刊

Thermochimica Acta 化学-分析化学

CiteScore

6.50

自引率

8.60%

发文量

210

审稿时长

40 days

期刊介绍： Thermochimica Acta publishes original research contributions covering all aspects of thermoanalytical and calorimetric methods and their application to experimental chemistry, physics, biology and engineering. The journal aims to span the whole range from fundamental research to practical application. The journal focuses on the research that advances physical and analytical science of thermal phenomena. Therefore, the manuscripts are expected to provide important insights into the thermal phenomena studied or to propose significant improvements of analytical or computational techniques employed in thermal studies. Manuscripts that report the results of routine thermal measurements are not suitable for publication in Thermochimica Acta. The journal particularly welcomes papers from newly emerging areas as well as from the traditional strength areas: - New and improved instrumentation and methods - Thermal properties and behavior of materials - Kinetics of thermally stimulated processes