Role of Plasticizers in Film Formation and Deformation-Induced Bonding of Glassy Polymers of Bidisperse Blends

Bonding between polymers below the glass transition temperature through molecular-scale dilatation (or densification)-based interdiffusion of macromolecules has recently been introduced. In this mechanism, plastic deformation enables polymer chains to interdiffuse and form entanglements at the interface, facilitating rapid bonding below the glass transition temperature (Tg). Here, we are addressing the role of low molecular weight plasticizer in bonding polymer interfaces of bidisperse blends through deformation-induced bonding (DIB) at temperatures well below the surface and bulk glass transition temperatures, Tgˢ and Tgᵇ, respectively, by using molecular simulations. These simulations reveal that addition of plasticizer (φ≤20%) drastically enhances the number of chain-ends at the interfacial region compared to a pure glass sample (φ=0%) during deformation below Tgˢ, which improves the possibility of opposite side entanglement formation. The changes in stress-strain response of debonded samples correlate with the normalized entanglement density. Likewise, the maximum interfacial fracture energy GI,max of debonded samples is correlated with the plasticizer concentration (φ), below Tgˢ. Furthermore, the optimization of material and process conditions for DIB has yielded a notable advancement: achieving a higher bonding strength, approximately one-third of the bulk, all while remaining below Tg.