Microwave Assisted Polymerization of Lactide and In Situ Preparation of Poly Lactic Acid Clay Nanocomposites

Abstract

Poly(lactic acid), PLA is made from renewable agricultural products and is readily degradable. Since PLA can be synthesized from lactic acid, which is a product of fermented starch, and can be degraded into nontoxic end-products thus it is an environment friendly material. This thesis embodies the subject matter resulting out of this study and is arranged in five chapters. A brief introduction, historical background and applications of PLA have been described first. A brief account of the advantages of using microwave for the synthesis of PLA has been included. The mode of heating (conventional and microwave heating) for the synthesis of PLA has been compared. The importance of lactic acid, the starting material, used in the synthesis of polylactide has also been discussed. The important method of synthesizing PLA is the ring-opening polymerization technique which is more useful than polycondensation for the production of high molar mass PLA. Polymerization kinetics of microwave-assisted synthesis of PLA has also been discussed. Microwave heating has been used for the synthesis of PLA from l-lactide and the ring-opening polymerization method has been chosen for the present work. Relevant literature for the polycondensation method and ring-opening method used in microwave oven has been reviewed. In-situ preparation of PLA-clay nanocomposites under microwave irradiation has also been reviewed. Two types of microwave heating system: domestic microwave and monomode microwave have been used to synthesize PLA and its clay nanocomposites in the present work. Studies on the effects of different parameters: polymerization temperature, polymerization time, monomer to initiator ratio, nature of initiator, effect of clay etc. which affect the polymerization of l-lactide to give PLA and its clay nanocomposites have been studied and discussed.