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

Nikhil Padhye,David M Parks,Alexander H Slocum,Bernhardt L Trout

doi:10.1038/srep46405

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.

Highlights

IntroductionEvidence of enhanced molecular dynamics characteristic of rubbery-like behavior, taking place within a thin layer at the free surface of an otherwise glassy polymer, has been obtained from both experiments[32,33] and computer simulations[34]
The polymer remains in a rubbery state
We report that active plastic deformation of glassy polymeric films held in intimate contact can trigger requisite molecular-level rearrangement sufficient to cause interpenetration of polymer chains across the interface, which leads to bonding

Summary

Introduction

Evidence of enhanced molecular dynamics characteristic of rubbery-like behavior, taking place within a thin layer at the free surface of an otherwise glassy polymer, has been obtained from both experiments[32,33] and computer simulations[34]. The segregation of chain ends at the free surface can contribute to the depression of the glass transition temperature at the surface[35,36,37,38]. Such effects decay within distances from the free surface comparable to the bulk radius of gyration of the polymer.

Methods

Results

Conclusion