Molecular Weight and Thermal Properties of Fiber Reinforced Polyamide-Based Composites Throughout the Direct Long-Fiber Reinforced Thermoplastic Process

The D-LFT process is an efficient and cost-effective process and includes two twin-screwextruders, a conveyer, and a compression molding machine. It is imperative to understand how the process sequence affects molecular weight and thermal properties of composite materials during the D-LFT process. The main objective of this study was to characterize variation in molecular weight and thermal properties of two types of polyamide (PA)-based composite materials (glass fiber reinforced PA6 composites and carbon fiber reinforced PA66 composites) through the D-LFT process. Samples were taken from different locations along the D-LFT process and characterized using triple detection gel permeation chromatography (GPC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), andfourier-transform infrared spectroscopy (FTIR). It was found thatmolecular weightof both PA-based composites increased after the second extruderby branching of PA molecules. Therefore, process conditions after the secondextruderneed to be carefully adjusted to design PA-based D-LFT products