A New Phenomenon: Sub-Tg, Solid-State, Plasticity-Induced Bonding in Polymers

Abstract

Polymer self-adhesion due to the interdiffusion of macromolecules has been an active area of research for several decades. Here, we report a new phenomenon of sub-Tg, solid-state, plasticity-induced bonding; where amorphous polymeric films were bonded together in a period of time on the order of a second in the solid-state at ambient temperatures, up to 60 K below their glass transition temperature (Tg), by subjecting them to active plastic deformation. Despite the glassy regime, the bulk plastic deformation triggered the requisite molecular mobility of the polymer chains, causing interpenetration across the interfaces held in contact. Quantitative levels of adhesion and the morphologies of the fractured interfaces validated the sub-Tg, plasticity-induced, molecular mobilization causing bonding. No-bonding outcomes (i) during the uniaxial compressive straining of films (a near-hydrostatic setting which strongly limits plastic flow) and (ii) between an ‘elastic’ and a ‘plastic’ film further established the explicit role of plastic deformation in this newly reported sub-Tg solid-state bonding.

Deformation‐induced bonding of polymer films below the glass transition temperature

“…The labels used for the present films match those adopted in a previous study. 22 These films demonstrated excellent adhesion characteristics when subjected to plastic deformation.…”

“…Roll-bonding and peel-tests were carried out on the polymer films using the experimental apparatuses described in previous studies. [22][23][24][25] The time duration for bonding during plastic deformation in rolling processes depends on the angular speed of the rollers and, the initial and final (after rolling) thicknesses of the film stack. A pair of 200-mm diameter rollers were driven at an angular speed of 0.5 rpm, leading to an exit speed of 5.23 mm/s.…”

“…A new phenomenon of bonding glassy polymers, taking place at ambient temperatures (well below the glass transition temperature), referred to as plasticity‐induced bonding, has been reported in recent studies 22–25 . The plasticity‐induced bonding is achieved by bulk plastic compression of polymeric films held in intimate contact; the plastic deformation has been shown to generate enhanced molecular mobility 26,27 .…”

“…A new phenomenon of bonding glassy polymers, taking place at ambient temperatures (well below the glass transition temperature), referred to as plasticity-induced bonding, has been reported in recent studies. [22][23][24][25] The plasticity-induced bonding is achieved by bulk plastic compression of polymeric films held in intimate contact; the plastic deformation has been shown to generate enhanced molecular mobility. 26,27 This type of bonding is in contrast with the conventional heat-based bonding of polymers, since heat-based methods require holding polymer pieces in contact under moderate pressures for minutes, hours, or even day(s), whereas plasticityinduced bonding occurs over fractions of a second.…”

“…In their original study of plasticityinduced bonding, the authors focused on the blends of a cellulose-based hydroxypropyl methylcellulose (HPMC) polymer and a small-molecule polyethylene glycol (PEG) plasticizer. [22][23][24][25] Bonding was achieved by imposing a plastic deformation in rolling experiments, and the strengths of the bonded interfaces were determined by estimating the interfacial fracture toughness through peel-tests. 28 Building on these previous studies, in this work we followed a similar methodology to investigate solid-state, deformation-induced bonding results in blends of organic polymers consisting of films of HPMC and polyvinyl alcohol (PVA) products.…”