Superhydrophobic fabrics have gained a huge interest in the industries recently. New legislation pushes the industries to eliminate the use of fluorinated materials in the production of these type of fabrics. Hydrophobic and self-cleaning garments textiles can deliver stable water repellent properties without the need for fluorinated chemicals and reduce the consumption of detergents. New methods that could be implemented in current textile industry processes without major changes in instruments or materials is essential to move this industry to the next level. Filament development with the hydrophobic structure without coating could be strategic on one side and tricky on the other side. It has been proved that a stable hydrophobic self cleaning surface needs a hierarchical micro-nano structure to present sustainable properties. In this thesis, we used common materials in the textile industry for filament production which are polyethylene terephthalate (PET) and high molecular weight polystyrene (PS) and low molecular weight polystyrene (LMPS) to shape the microstructures on the surface of filaments. By adding the common compatibilizer polystyrene-co-maleic anhydride (PSMA) to the blend, PS in the matrix of PET could migrate to the surface. Even 1% wt. of PSMA boosted the migration of PS polymer droplets to the surface. The blend including compatibilizer was compounded, melt-spun into the monofilament, drawn, and annealed for various time durations in the furnace. Next, the filaments were immersed in tetrahydrofuran(THF) to remove the PS component obtaining the rough surface. We investigated the effect of mixture components content and different process parameters such as draw ratio and annealing time on hydrophobicity by the aid of statistical design. Applying the Wilhelmy method for contact angle measurement, we could achieve an advancing contact angle (ACA)of 114º and the average ACA of 96º by making micro-size structure on raw PET with an average ACA of 80º and the intrinsic contact angle of around 70º.