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

Abstract

AbstractFilms of amorphous polystyrene (PS) with a weight‐average molecular weight (Mw) of 225 × 103 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 (th) and healing temperature (Th). G was found to develop with (th)1/2 at Th = Tg‐bulk − 33 °C (where Tg‐bulk is the glass‐transition temperature of the bulk sample), and log G was found to develop with 1/Th at Tg‐bulk − 43 °C ≤ Th ≤ Tg‐bulk − 23 °C. The smallest measured value of G = 1.4 J/m2 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 (<Tg‐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 Tg‐bulk. Close values of G = 8–9 J/m2 were measured for the symmetric interfaces of polydisperse PS [Mw = 225 × 103, weight‐average molecular weight/number‐average molecular weight (Mw/Mn) = 3] and monodisperse PS (Mw = 200 × 103, Mw/Mn = 1.04) after healing at Th = Tg‐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