In-situ pultrusion of nylon 6 based profiles - Key parameters of the process

Pultruded profiles based on thermoplastic matrices are increasingly emerging as a material of choice for the industry due to their special advantages such as easy recyclability, opportunities to be functionalized with injection or compression overmolding, thermoforming, etc.. The production of these thermoplastic profiles can be done in several ways. The reactive processing of the monomer ε-caprolactam which polymerizes to polyamide 6 (the so-called "in-situ pultrusion"), makes it possible to achieve high fiber content and excellent mechanical properties at competitive raw material costs. The production of profiles with 73% FVC of glass and 74% FVC of carbon fibers at haul-off speeds up to 2 m/min has been proven successfully, as of now. For high quality of the profiles produced at high haul-off speeds, deep knowledge of material parameters, process parameters and conditions as well as their interactions is necessary. In this study, a statistical screening "Design of Experiment" (DoE) trial campaign with the seven most promising parameters was carried out to establish the ones that have a significant influence on profile quality and process robustness. The results show that four of the seven parameters are significant, comprising the amount of activator and catalyst, the temperature for fiber preheating, the fiber volume content and the haul-off speed.