With the development of polymer science and technology, people started using polymer as a material in various applications, both where other material cannot be used and as replacements for the conventional materials e.g. metals, ceramics, wood etc. Plastics are the class of polymers, characterized by high strength and load bearing capacity. Hence they are widely used in structural engineering applications.However, the poor fracture resistance of many commercial plastics restricts their use for such applications.Unlike the modification of thermoplastics, which often requires only the simple physical blending of a particular elastomeric modifier, the toughening of thermoset by rubbery secondary phase is achieved almost exclusively through chemistry. In this book, attempts have been made to discuss about the effectiveness of some new synthesized rubbery modifiers in the toughening of diglycidyl ether of bisphenol A (DGEBA) resin networks.Thus in this book every endeavor is made to retain the comprehensive character of the book, so as to ensure that it continues to be a one volume text for the research students. Hope they will be benefitted and enriched enough about the new findings.