1. Gamma irradiation Gamma cell model 220, series 142 from Atomic Energy of Canada Limited. Doses of 25, 50, 75, 100 and 500 kGy (dose rate of 4.3 kGy/h ). Acknowledgements : P47 Gamma Radiation Effect on Structural Properties of PLLA/PCL Blends Yasko Kodama a,*, Luci D.B. Machado a, Claudia Giovedi b, Kazuo Nakayama c a Instituto de Pesquisas Energéticas e Nucleares – IPEN–CNEN/SP, São Paulo, Brazil b Centro Tecnológico da Marinha em São Paulo – CTMSP, São Paulo, Brazil c Nanotechnology Research Institute, National Institute of Advanced Industrial Science and Technology – AIST, Tsukuba, Ibaraki, Japan. www.polymerprocessing.com Films MATERIALS Poly(  -caprolactone) – PCL, Tm = 60 o C and Tg = -60 o C Poly(L-lactic acid) – PLLA Tm = 178 o C and Tg = 68 o C Scanning Electron Microscopy (SEM) DS-720 TOPCON Co., homopolymers and blends sheets cryogenic fractured and 4-5 min gold coating JXA-6400 (JEOL), irradiated homopolymers and blends sheets surfaces fractured samples Figure 1 – SEM micrographs of non irradiated as extruded a) PCL; b) PCL:PLLA 50:50 blend and c) PLLA. a b c Figure 2 - SEM micrographs of non irradiated annealed b) PCL:PLLA 50:50 blend and c) PLLA. b c Figure 3 - Temperature dependence of (a) dynamic storage modulus (E’) and (b) loss tangent (tan  ) for as extruded PLLA and PCL 1, 5, 10, 25, 50, 75 and 100%. a b a b c Figure 4 - SEM micrographs of as extruded samples after gamma irradiation up to 100 kGy: a) PCL; b) PCL:PLLA 50:50 and c) PLLA. Figure 5 - SEM micrographs of as extruded samples after gamma irradiation up to 500 kGy: a) PCL; b) PCL:PLLA 50:50 and c) PLLA. ab c CONCLUSION The SEM micrographs of the fractured homopolymers and blends show their immiscibility. The crystallization of PLLA can be observed on the annealed samples. Samples irradiated with 100 kGy presented few variation on the morphology. But in PCL homopolymer and PCL:PLLA 50:50 irradiated with 500 kGy samples it was possible to observe significant alteration. The ruptured sample surface of irradiated PCL with 500 kGy became full of scales maybe due to an increase of crosslinking density induced by the ionizing radiation, but no changes promoted by ionizing radiation is observed by SEM on the irradiated PLLA. If the main effect observed is degradation, the results could be an indication that the desirable degradability will be increased by gamma radiation. FTIR spectrum of A) PLLA and B) PCL homopolymers and C) PCL:PLLA 50:50 blend, non irradiated. FTIR spectrum of A’) PLLA and B’) PCL homopolymers and C’) PCL:PLLA 50:50 blend, gamma irradiated.. FTIR spectrum of A”) PLLA and B”) PCL homopolymers and C”) PCL:PLLA 50:50 blend, EB irradiated. ABSTRACT Poly(L-lactic acid) (PLLA) and poly(  -caprolactone) (PCL) extruded homopolymers and PLLA/PCL blends films were irradiated with gamma rays from Co-60 at doses in the range of 25 to 500 kGy to investigate the effect of the ionizing radiation on the morphological properties of the samples. The morphology of the homopolymers and the blends were observed by scanning electron microscope (SEM). The micrographs of the fractured homopolymers and have shown immiscibility of the blends. The crystallization of PLLA can be observed on the annealed samples. Samples irradiated with 100 kGy presented few variation on the morphology. But in PCL homopolymer and PCL:PLLA 50:50 irradiated with 500 kGy samples it was possible to observe significant alteration. If the main effect observed is degradation, the results could be an indication that the desirable degradability will be increased by gamma radiation. TG curves for irradiated and non irradiated PCL and PLLA homopolymers and PCL:PLLA 50:50 in air TG curves for irradiated and non irradiated PCL and PLLA homopolymers and PCL:PLLA 50:50 in N 2.