A tale of two polyamides: Comparing the crystallization kinetics of a hot-melt adhesive and a PA 6/66 copolymer

In this work, the isothermal and non-isothermal crystallization kinetics of two polyamides, a polyamide-based hot melt adhesive with the trade name of Technomelt PA 6910 and a copolymer of PA 6 and PA 66, are studied using Fast Scanning Calorimetry (FSC) and Differential Scanning Calorimetry (DSC). 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 glass transition temperature encourages room temperature crystallization of Technomelt PA 6910. PA 6/66 is a random copolymer whose faster crystallization is attributed to a high density of hydrogen bonding accompanied by a sheet-like structure of the hydrogen bonding within the melt, which favors high-temperature crystallization. The kinetic results from this study enable coupling the crystallization kinetics of these materials with thermal models for processing techniques including material extrusion additive manufacturing.