Study On Polymerization And Degradation Performance Of Glycolic Acid

Biodegradable polymer materials are those could be completely decomposed by environmental microorganisms, even ultimately be mineralized to become a part of carbon cycle in nature. Polyglycolic acid is one of biodegradable materials, which has been widely used in the fields of medical sutures, fracture fixation, tissue repair and drug delivery.In this paper, the polycondensation technique of glycolic acid has been investigated firstly, from which the low molecular weight polyglycolic acid (PGA) was prepared. Furthermore, the solid polycondensation was carried out to increase the molecular weight of PGA, and the kinetics of solid polycondensation was also studied. Finally, the degradation of PGA was studied by investigate the PLGA blend fibers dipping in the simulated body fluid for various times. The main contents of this paper were listed as follows.(1)The optimal polycondensation techniques were determined by exploring process conditions of temperature of dewatering, temperature of reaction, the kind of catalysts and time of extreme vacuum. FTIR and NMR spectra proved the products should be. PGA. The melting point of obtained PGA reached220℃judged from DSC curves, while the inherent viscosity reached0.505dL/g.(2)Solid polycondensation was carried out to increase the molecular weight of PGA. The PGA oligomer was smashed to small particles, which were treated in vacuum under different temperatures of190,195,200℃for.20hours. During the solid polycondensation, the sampling has been done every2.5hours. It has been found from DSC testing that after treatment the melting point of PGA could reached221℃, and the corresponding inherent viscosity was0.613dL/g. Kinetics of solid polycondensation was studied by combining the results of inherent viscosity of the samples and the reaction equation. It was found that both polymerization and degradation processes were involved in the treatment. From calculation, it has been found the the reaction energy of polymerization Ea was18.489kJ·mol-1and preexpontial factor A was2.716*104, while Ea=25.548kJ-mol"1and A=2.492*104for the degradation.(3)PGA/PLA blend fibers were prepared and the degradation of PGA was studied by investigating the blend fibers dipping in the simulated body fluid for various times. In original, the tension strength of blend fiber was about0.8cN/dtex, and the tension strength and the elongation descends faster along with the degradation process. It was found from the DSC measurement that the melting point of blend fiber decreased with the degradation, and reached close to pure PLA after two weeks and lower than PLA after four weeks of degradation, indicating that the degradation period of PGA was about3weeks. Moreover, the surfaces of fibers were observed by SEM and the crystallizations of fibers were analyzed by XRD.