Pourali Masoumeh, Adisa Ahmed, Salunke Shalmali, Peterson Amy M
Department of Plastics Engineering, University of Massachusetts Lowell, 1 University Ave, Lowell, MA, 01854, USA.
Sci Rep. 2024 Nov 1;14(1):26297. doi: 10.1038/s41598-024-77635-9.
In this work, a heat transfer model is developed for thermally-driven material extrusion additive manufacturing of semicrystalline polymers that considers the heat generated during crystallization by coupling crystallization kinetics with heat transfer. The materials used in this work are Technomelt PA 6910, a semicrystalline hot melt adhesive with sub-ambient glass transition temperature (T) and slow crystallization, and PA 6/66, a traditional semicrystalline polyamide with a higher T and fast crystallization. The coupled model shows that the released heat during crystallization depends on material selection, with Technomelt PA 6910 and PA 6/66's temperatures increased by less than 1 °C and up to 6.3 °C, respectively, due to enthalpy of crystallization. Increasing the layer time decreases the layer temperature as well as the initial crystallinity. However, its effect on final crystallinity in Technomelt PA 6910 is negligible due to continued crystallization of the material after printing. Experimental validation shows good agreement for Technomelt PA 6910, but consistently underpredicts PA 6/66 crystallinity. Increasing modeled environmental temperature leads to better agreement with experimental results for PA 6/66, suggesting that higher temperatures may have been experienced. Shear-induced crystallization may also be contributing to crystallinity in this material. The results from this model highlight the importance of and interrelationships between material and processing parameter selection and can aid in achieving quality prints from semicrystalline thermoplastics.
在这项工作中，针对半结晶聚合物的热驱动材料挤出增材制造开发了一种传热模型，该模型通过将结晶动力学与传热相耦合来考虑结晶过程中产生的热量。本工作中使用的材料是Technomelt PA 6910，一种具有低于环境玻璃化转变温度（T）且结晶缓慢的半结晶热熔胶，以及PA 6/66，一种具有较高T且结晶快速的传统半结晶聚酰胺。耦合模型表明，结晶过程中释放的热量取决于材料的选择，由于结晶焓，Technomelt PA 6910和PA 6/66的温度分别升高不到1°C和高达6.3°C。增加层间时间会降低层间温度以及初始结晶度。然而，由于打印后材料的持续结晶，其对Technomelt PA 6910最终结晶度的影响可以忽略不计。实验验证表明，对于Technomelt PA 6910有良好的一致性，但始终低估了PA 6/66的结晶度。提高模拟环境温度会使与PA 6/66的实验结果更吻合，这表明可能经历了更高的温度。剪切诱导结晶也可能对该材料的结晶度有贡献。该模型的结果突出了材料和工艺参数选择的重要性及其相互关系，并有助于实现半结晶热塑性塑料的高质量打印。
