Used thermoplastics and tires are a major environmental intricate problem worldwide. Post-consumed polymeric materials are those that have ended their functional life. Until recently, commingled of these wastes were either buried in landfill sites or stockpiled in huge dumps, vitally threatening the human health and ecosystem. Considering the economic and environmental advantages, recycling is one of the best options. Composite materials date from the use of straw-reinforced clay in Egypt about three thousand years ago. Various forms of spent polymers in a broad discipline found in blend and composite formulations not only development of new materials but also practical recycling in cost- effective polymer industry. This book demonstrates, in an unambiguous language, he prominent contributing role of radiation-induced crosslinking and degradation processing in improving physico-mechanical and thermal parameters of recycled polymeric blends and composites.