Article: Effects of deformation and physical aging on nano-scale free volumes in polycarbonate studied by positron annihilation lifetime spectroscopy Journal: International Journal of Nano and Biomaterials (IJNBM) 2009 Vol.2 No.1/2/3/4/5 pp.279 - 288 Abstract: Positron annihilation lifetime spectroscopy (PALS) has been employed to measure the variation of free volume hole parameters in poly(carbonate) (PC) after plastic deformation below the glass transition temperature (Tg). Changes in nano-scale free volume holes (Vh) and in their fraction (%fv) due to plane-strain and uniaxial compression and aging time were investigated at temperatures below Tg. For both deformation modes, %Δfv showed weak variations up to 30% thickness reduction followed by significant decrease at higher thickness reduction. As would be expected, trends in the variation of Vh were discernibly different for plane-strain and uniaxial deformation owing to shape transformation in free volumes. Vh showed a decrease followed by an increase during physical aging for both modes of deformation indicating the possibility of an amorphous-amorphous transition. Δfv showed a decrease only under uniaxial compression. The corresponding Vh size distributions showed high dependency on the mode of plastic deformation. Inderscience Publishers - linking academia, business and industry through research

Title: Effects of deformation and physical aging on nano-scale free volumes in polycarbonate studied by positron annihilation lifetime spectroscopy

Authors: M. Mohsen, E. Gomaa, M.A. Sharaf, H. Salem, W. Gomaa

Addresses: Physics Department, Faculty of Science, A in Shams University, Abbassia 11566, Cairo, Egypt. ' Physics Department, Faculty of Science, A in Shams University, Abbassia 11566, Cairo, Egypt. ' Department of Chemistry, Helwan University, Cairo, 11795 Egypt. ' Department of Mechanical Engineering, The American University in Cairo, P.O. Box 74, New Cairo, 11835 Egypt. ' Egyptian Customs Authority, Naser City, Cairo, 11635 Egypt

Abstract: Positron annihilation lifetime spectroscopy (PALS) has been employed to measure the variation of free volume hole parameters in poly(carbonate) (PC) after plastic deformation below the glass transition temperature (T_g). Changes in nano-scale free volume holes (V_h) and in their fraction (%f_v) due to plane-strain and uniaxial compression and aging time were investigated at temperatures below T_g. For both deformation modes, %Δf_v showed weak variations up to 30% thickness reduction followed by significant decrease at higher thickness reduction. As would be expected, trends in the variation of V_h were discernibly different for plane-strain and uniaxial deformation owing to shape transformation in free volumes. V_h showed a decrease followed by an increase during physical aging for both modes of deformation indicating the possibility of an amorphous-amorphous transition. Δf_v showed a decrease only under uniaxial compression. The corresponding V_h size distributions showed high dependency on the mode of plastic deformation.

Keywords: nano free volumes; positron annihilation life time spectroscopy; PALS; polycarbonate; plastic deformation; physical aging; uniaxial compression; plane strain deformation; amorphous-amorphous transition; nanomaterials; nanotechnology.

DOI: 10.1504/IJNBM.2009.027723

International Journal of Nano and Biomaterials, 2009 Vol.2 No.1/2/3/4/5, pp.279 - 288

Published online: 08 Aug 2009 *

Full-text access for editors Full-text access for subscribers Purchase this article Comment on this article

Title: Effects of deformation and physical aging on nano-scale free volumes in polycarbonate studied by positron annihilation lifetime spectroscopy

Keep up-to-date