Abstract: A process for forming thermoplastic composite materials that have improved properties wherein the process is an in-line compounding process that feeds a thermoplastic resin and a filler to a compounder to form a thermoplastic composite material that is then injected into a mold to form an article that includes the thermoplastic composite material. Since the thermoplastic composite material is not pelletized or otherwise processed between formation of the thermoplastic composite material and the injection-molded article, less damage and/or degradation of the filler occurs during processing such that the resultant thermoplastic composite material and/or article has improved properties at the same or even at lower filler loadings than prior art materials.