Microwave assisted in situ ring-opening polymerization of polylactide/clay nanocomposites: Effect of clay loading

• We synthesize PLA/clay nanocomposites in monomode microwave.
• We examine the effect of various clay loadings on polymerization yield in microwave.
• Increase in clay percentage shows decrease in polymerization yield for Cloisite® 15A.
• Cloisite® 30B had negligible effect on polymer yield & Cloisite® Na+ shows no yield.
• The exfoliation was confirmed by XRD and TEM and thermal stability was improved.

Poly (lactic acid)/clay nanocomposites were prepared through microwave-assisted in situ ring opening polymerization of lactide at various clay loadings. The polymerization rate was much faster with microwave heating compared to conventional heating. The synthesis of poly (lactic acid)/clay nanocomposites was catalyzed by stannous octoate (SnOct2) and dibutyltindimethoxide (DBTM). The monomer to initiator ratio was kept at 2500:1 and the temperature was maintained at 150 °C. Three types of commercially available clays (Cloisite® 30B, 15A, and Na+) were employed to study the effect of clay loadings on the polymerization of lactide and in situ formation of polymer–clay nanocomposites. The percentage yield decreased with increase in the clay loading from 0.1 to 5% for both Cloisite® 30B and Cloisite® 15A but no product was formed with Cloisite® Na+ clay. The characterization of nanocomposites was done by using XRD (X-ray diffraction), TGA (thermo-gravimetric analysis), SEM (scanning electron microscopy) and TEM (transmission electron microscopy) analyses. This is the first report on the marked effect of clay mineral on in situ polymerization of lactide using microwave irradiation.

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