Benarbia Adel, Sobotka Vincent, Boyard Nicolas, Roua Christophe
Laboratoire de Thermique et Energie de Nantes (LTEN), Centre National de la Recherche Scientifique (CNRS), Nantes Université, UMR 6607, 44000 Nantes, France.
Cogit Composites Company, 9117 Rue des Vignerons, 18390 Saint-Germain-du-Puy, France.
Polymers (Basel). 2024 May 8;16(10):1319. doi: 10.3390/polym16101319.
Recent techniques for forming thermoplastics, such as welding, automated fibre placement or additive manufacturing, generate successive rapid heating and cooling cycles that cause the partial melting of crystals during the process. The melting of an interface is essential to guarantee a good molecular diffusion across the welded parts. Nevertheless, no model can correctly predict the melting kinetics and consequently the evolution of the crystalline degree during the layers' deposition process. The purpose of this paper was to define the melting kinetics depending on the crystallization conditions for polyetheretherketone (PEEK). Firstly, a non-isothermal crystallization model was proposed over a wide range of cooling rates from 0.1 K.s to 150 K.s. Experimental results have highlighted a dual-mode behaviour of melting and demonstrated the dependence of melting temperatures on crystallization conditions. Based on these observations, a model was developed to predict the melting behaviour after non-isothermal crystallization. The melting model revealed that after high cooling rates, primary and secondary crystals melt separately at low temperatures, while after slow cooling rates, both structures melt simultaneously at higher temperatures. Finally, the melting model was applied to the FFF thermal cycle to illustrate the influence of process parameters on the melting kinetics during deposition.
近期用于成型热塑性塑料的技术，如焊接、自动纤维铺放或增材制造，会产生连续的快速加热和冷却循环，这会导致过程中晶体部分熔化。界面的熔化对于确保焊接部件之间良好的分子扩散至关重要。然而，没有模型能够正确预测熔化动力学，因此也无法预测层沉积过程中结晶度的变化。本文的目的是确定聚醚醚酮（PEEK）在不同结晶条件下的熔化动力学。首先，提出了一个在0.1 K·s至150 K·s的宽冷却速率范围内的非等温结晶模型。实验结果突出了熔化的双模式行为，并证明了熔化温度对结晶条件的依赖性。基于这些观察结果，开发了一个模型来预测非等温结晶后的熔化行为。熔化模型表明，在高冷却速率后，初级和次级晶体在低温下分别熔化，而在慢冷却速率后，两种结构在较高温度下同时熔化。最后，将熔化模型应用于熔融沉积成型（FFF）热循环，以说明工艺参数对沉积过程中熔化动力学的影响。
