This book is about poly(ethylene terephthalate), usually referred as PET, chemical processoing particularly regarding to improve its hydrophilic characteristics. Hydrophilicity is mainly required in almost all the formal and casual textile garment wears, however original polyester is not having this important property. Therefore, in order to improve the hydrophilic properties, it is highly necessary to treat polyester textile substrates with some non harmful chemicals. Accordingly, here also PET was treated with Polyvinyl alcohol (PVA) in the alkaline medium. Due to this treatment, PET is getting improved from hydrophobic behaviour to hydrophilic behaviour. This PVA treated PET gave very good water absorbency, wicking character and thereby leading for the improvement of dyeing characteristics. Therefore, this PVA treated PET textile materials would be quite useful for the usage of many normal day-to-day garments and similar applications suitable for the end users.