Positron lifetime study of PAN‐based carbon fiber‐reinforced polymer composites

Microstructural characterization of polyacrylonitrile‐based carbon fiber (PAN‐CF) reinforced polybutylene terephthalate (PBT) and polyethersulfone (PES) polymer composites have been performed. The positron lifetime parameters viz., o‐Ps lifetime (τ₃), o‐Ps intensity (I₃) and fractional free volume (F_v) of PAN‐CF reinforced PBT (PBT/PAN‐CF) and PAN‐CF reinforced PES (PES/PAN‐CF) composites are correlated with the mechanical properties. The fractional free volume obtained experimentally show negative deviation from the linear additivity relation in PBT/PAN‐CF composites for lower wt% of PAN‐CF loading. This indicates the improved adhesion between PAN‐CF and polymeric chains of PBT matrix in PBT/PAN‐CF composites. The positive deviation of fractional free volume (F_v) in PES/PAN‐CF composites suggests the formation of interface between PAN‐CF and polymeric chains of PES matrix. The increased glass transition temperature (T_g) of PBT/PAN‐CF composites suggests the reduced main chain and segmental mobility of PBT polymeric matrix by the presence of PAN‐CFs. The decreased glass transition temperature (T_g) in PES/PAN‐CF composites indicates the reduced molecular packing due to interface formation. The increased crystallinity and improved mechanical properties of PBT/PAN‐CF and PES/PAN‐CF polymer composites are attributed to the increased nucleation density of carbon fibers in the composites. The FTIR results suggest the improved chemical interaction between the functional groups of PAN‐CF and PBT matrix. The hydrodynamic interaction is also high in PBT/PAN‐CF than PES/PAN‐CF composites. POLYM. COMPOS., 40:E939–E952, 2019. © 2018 Society of Plastics Engineers