(74f) Crystallization Kinetics and Thermal Modeling of Material Extrusion Additive Manufacturing of Two Polyamides

Semicrystalline thermoplastics are interesting materials in engineering applications due to their high mechanical strength and excellent heat, chemical, and abrasion resistance. However, their crystallization during processing can result in significant shrinkage and warpage. In this work, we compare the kinetics of crystallization of two polyamides that are relevant to material extrusion additive manufacturing: a PA 6/66 copolymer and a polyamide-based hot melt adhesive with the trade name of Technomelt PA 6910. While both of these materials exhibit good performance as feedstocks for material extrusion additive manufacturing, their crystallization behavior and kinetics differ substantially. Technomelt PA 6910 crystallizes much slower than the PA 6/66 due to the lower density of hydrogen bonding within Technomelt PA 6910’s structure. The low T_g encourages room temperature crystallization of Technomelt PA 6910. PA 6/66 is a random copolymer whose faster crystallization is attributed to the high density of hydrogen bonding accompanied by a sheet-like structure of the hydrogen bonding within the melt, which favors high-temperature crystallization. We then coupled the crystallization kinetics of these materials with thermal models of material extrusion additive manufacturing in order to investigate how and where crystallization occurs and affects thermal profiles during additive manufacturing.