The direct long-fiber reinforced thermoplastic (D-LFT) process offers a streamlined material processing technique and decreases the degradation of the material. To ensure product consistency and process optimization, it is imperative to understand how the process sequence affects degradation and thermal properties of the material during the D-LFT process. This study investigates variation in molecular weight and thermal properties of the glass fiber reinforced polyamide 6 (PA6) composites throughout the D-LFT process. Viscosity number (VN) measurements, thermogravimetric analyses (TGA), and differential scanning calorimetry (DSC) analyses were performed on samples taken from different locations along the D-LFT process. It was found that VN, which is a measure of molecular weight of the PA6 base resin, decreased throughout the processes. In contrast, TGA results suggested that apparent activation energy for decomposition increased during consecutive process stages. Non-isothermal DSC results showed that there were no significant changes to the degree of crystallization; however, isothermal DSC results indicated that later stages of the process showed a decrease in crystallization half-time, and the largest changes were observed in areas after the two extrusion portions of the process. (c) 2017 Society of Plastics Engineers