Calcined Kaolin And Its Complexes As Catalyst For The Polymerization Of L-lactide And ?-Caprolactone

Biodegradable materials are widely used in environmental protection and medical fields,due to its excellent biocompatibility and biodegradability.The most common biodegradable material is poly-lactic acid?PLA?,but its drawbacks limit its use that it is hard and brittle.While it can be copolymerized with caprolactone adjusted to achieve performance enhancement in toughness.Tin and rare earth compounds with high activity and catalytic effect are frequently used as catalyst currently,however,they are high cost and with a substantial residual toxicity.The study of this paper selected calcined kaolin as catalyst for the copolymerization of L-lactide and ?-caprolactone,for its low-cost and non-toxic.The results show that the calcined kaolin having catalytic activity which can catalyze the copolymerized of L-lactide and ?-caprolactone.The optimal reaction conditions were as follows:?-caprolactone and L-lactide monomers in the molar ratio is 90/10?0.02 mol total mol?,the amount of calcined kaolin 5mg,copolymerizing for 24h at 140 ?.In this case the copolymerization product was dark white powder and the yield was 72%,To improve the efficiency of polymerization,SnCl2·2H₂O and calcined kaolin form a complex to catalyze the copolymerized of L-lactide and ?-caprolactone.The results show that the characters of the product are better as it's white instead of dark white,and the yield of copolymer use of complex was higher than calcined kaolin or SnCl2·2H₂O was used alone as catalyst.In 8h,16h,24h of the three reaction time,we could get the highest yield at the reaction time of 16h with the composite catalyst.Compared with SnCl2·2H₂O alone used as the catalyst,higher molecular weight can be obtained with the composite catalyst of SnCl2·2H₂O and calcined kaolin,and the longer the reaction time,the lower the molecular weight.In summary,the study of low-cost and non-toxic calcined kaolin used as catalyst of the copolymerized of L-lactide and ?-caprolactone copolymer is significant,and composite catalyst of SnCl2·2H₂O and calcined kaolin can improve the efficiency and qualitis of the polymerization product comprehensively.