Though the nanofibrillar composites (NFCs) concept has been developed more than a decade ago, the applied feasibility of NFCs in industrial scale has not been assessed yet. The present thesis contemplates the manufacturing process of NFCs specifically fibrillization step by designing and using industrial scale Spunbond Spinning System from two semi crystalline polymers Polypropylene (PP) and Polyethylene Terephthalate (PET). The PET domain adopts fibrillar structure as low as 40 nm with an average size of 92 nm. The research further develops the fundamental understanding of nanofiber formation by evaluating morphological study through employing SEM and polarized microscopy, thermal and viscoelastic properties by differential scanning calorimetry and rheological characterization method. In-situ visualization technique was utilized at the die exit to observe the matrix fiber formation and the well-known die swell phenomenon. Result shows that the final in-situ nanofibril size directly depends on the die swell and processing parameters such as airspeed and polymer flowrate.