This book includes three main sections. The First Chapter (Introduction); is concerned with the concepts of with some types of polymers like: - thermosetting polymers, such as: 1- phenolic resins [novolac phenol formaldehyde and resole phenol formaldehyde], their properties, modifications and applications, 2- epoxy resins, their history, synthesis of different types (epoxy resin based on bisphenol A, epoxy novolac resins, halogenated epoxy, hydrogenated bisphenol A, and epoxy resins from per acids). Curing and cross-linking reactions of epoxy resins, types of curing agents [alkaline curing agent (Lewis's base, primary and secondary aliphatic amines), acidic curing agent (Lewis's acids) and phenolic resins]. Modifications, properties, and applications of cured epoxy resins were also mentioned. II- thermoplastic polymers such as 1- poly (vinyl acetate), their polymerization, properties and applications, 2- poly (vinyl alcohol), their properties and applications, 3- poly (vinyl acetals) such as poly (vinyl formal) and poly (vinyl butyral), and their applications. Introduction also deals with providing some relevant researches that published in scientific journals are also included.