Amide-based oligomers for low-viscosity composites of polyamide 66

Melt viscosity control of polyamides is an important issue concerning polymer processing and quality composites which are directly influenced by the melt viscosity in extrusion and injection molding processes. In this work, a series of linear and cyclic PA6 (nylon6), PA46 (nylon46), and PA66 (nylon66)-based amide oligomers consisting of < 10 repeat units are prepared. The melt viscosities of the composites of each oligomer in a PA66 matrix are investigated. The linear oligomers have a larger viscosity-decreasing effect than cyclic oligomers containing the same repeat unit. Linear PA6 and PA46-based oligomers show a greater melt viscosity reduction than PA66-based ones, especially in PA6-based linear oligomer (A6-L), which shows a reduction of > 30%. This result suggests that proper hydrogen bonding mismatching in the polymer chain network plays an important role for lowering viscosity. A6-L/PA66 composites impregnated with 40 wt% glass fiber show a twofold increase in the melt flow index while maintaining their mechanical strengths.