Commingled yarns of surface nanostructured glass and polypropylene filaments for effective composite properties

Developing commingled yarn technologies and understanding the fundamental interface nanostructures of reinforcement and thermoplastic filaments are of significant current interest. Previous research on commingled yarns was mainly focused on the air-jet texturing process, while the mechanical properties of the composites are strongly influenced by the impregnation homogeneity, the polymer sizing properties and consolidation process. Here, we report a unique melt spinning equipment for E-glass fiber which is compatibly combined with a melt spinning extruder to manufacture commingled yarns. The in-situ commingling enables to combine homogeneously both glass and polypropylene filament arrays in one processing step and without fiber damage compared to commingling by air texturing. Variation of processing conditions are investigated, i.e. sizings, diameter ratios, and arrangements of sizing/finish application related to intermingling of filament arrays. A rapid processing is achieved because of good intermingling and the low flow paths. We found that the sizing enables a good strand integrity with the polypropylene yarn. The interfacial adhesion can be improved with a sizing for glass fibers consisting of aminosilane and maleic anhydride grafted polypropylene film former, which results in both improved transverse tensile strength and compression shear strength. We also found that a very small amount of single-wall carbon nanotubes (SWNTs) in the sizing provides significantly improved interfacial adhesion strength. This is attributed to the change in fracture behavior of the nano-structured interface and morphology of the model single-fiber composites.