Self‐bonding in an amorphous polymer below the glass transition: A T‐peel test investigation

Abstract

Abstract Films of amorphous polystyrene (PS) with a weight‐average molecular weight ( M w ) of 225 × 10 3 g/mol were bonded in a T‐peel test geometry, and the fracture energy ( G ) of a PS/PS interface was measured at the ambient temperature as a function of the healing time ( t h ) and healing temperature ( T h ). G was found to develop with ( t h ) 1/2 at T h = T g‐bulk − 33 °C (where T g‐bulk is the glass‐transition temperature of the bulk sample), and log G was found to develop with 1/ T h at T g‐bulk − 43 °C ≤ T h ≤ T g‐bulk − 23 °C. The smallest measured value of G = 1.4 J/m 2 was at least one order of magnitude larger than the work of adhesion required to reversibly separate the PS surfaces. These three observations indicated that the development of G at the PS/PS interface in the temperature range investigated (< T g‐bulk ) was controlled by the diffusion of chain segments feasible above the glass‐transition temperature of the interfacial layer, in agreement with our previous findings for fracture stress development at several polymer/polymer interfaces well below T g‐bulk . Close values of G = 8–9 J/m 2 were measured for the symmetric interfaces of polydisperse PS [ M w = 225 × 10 3 , weight‐average molecular weight/number‐average molecular weight ( M w / M n ) = 3] and monodisperse PS ( M w = 200 × 10 3 , M w / M n = 1.04) after healing at T h = T g‐bulk − 33 °C for 24 h. This implies that the self‐bonding of high‐molecular‐weight PS at such relatively low temperatures is not governed by polydispersity. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1861–1867, 2004