title: Processing, annealing and sterilisation of poly-L-lactide.
abstract: Poly-L-lactide (PLLA) is one of the most significant members of a group of polymers regarded as bioabsorbable. Degradation of PLLA proceeds through hydrolysis of the ester bonds in the polymer chains and is influenced significantly by the polymer's molecular weight and crystallinity. To evaluate the effects of processing and sterilisation on these properties, PLLA pellets were either compression moulded or extruded, subjected to annealing at 120 degrees C for 4h and sterilised by ethylene oxide (EtO) gas. Procedures were used to evaluate the mechanical properties, molecular weight and crystallinity. Upon processing, the crystallinity of the material fell from 61% for the PLLA pellets to 12% and 20% for the compressed and extruded components, respectively. After annealing, crystallinity increased to 43% for the compression-moulded material and 40% for the extruded material. Crystallinity further increased upon EtO sterilisation. A slight decrease in molecular weight was observed for the extruded material through processing, annealing and sterilisation. Young's modulus generally increased with increasing crystallinity, and extension at break and tensile strength decreased. The results from this investigation suggest that PLLA is sensitive to processing and sterilisation, altering properties critical to its degradation rate.
authors.affiliation: School of Mechanical and Manufacturing Engineering, Queen's University Belfast, Ashby Building, Stranmillis Road, Belfast BT9 5AH, UK. n.weir@qub.ac.uk
authors.forename: N A
authors.initials: NA
authors.lastname: Weir
authors.forename: F J
authors.initials: FJ
authors.lastname: Buchanan
authors.forename: J F
authors.initials: JF
authors.lastname: Orr
authors.forename: D F
authors.initials: DF
authors.lastname: Farrar
authors.forename: A
authors.initials: A
authors.lastname: Boyd
mesh_terms: D020341:Absorbable Implants; D001672:Biocompatible Materials / Q000138:chemical synthesis / Q000737:chemistry*; D003460:Crystallization / Q000379:methods*; D004548:Elasticity; D006358:Hot Temperature; D008420:Manufactured Materials / Q000032:analysis; D008422:Materials Testing; D008968:Molecular Conformation; D011091:Polyesters / Q000138:chemical synthesis / Q000737:chemistry*; D033081:Shear Strength; D013242:Sterilization / Q000379:methods*; D013499:Surface Properties; D013718:Tensile Strength
chemical_list: D001672:Biocompatible Materials; D011091:Polyesters; C033616:poly(lactide)