Reactive coupling between immiscible polymer chains: Acceleration by compressive flow

Abstract

It is demonstrated that processing flow affects the kinetics of the interfacial coupling reaction between functional groups that are grafted to polymer chains. At melt temperatures the amine group on the end of nylon 6 chains reacts with maleic anhydride grafted polyethylene (PE‐MA) and forms graft copolymers. Bilayers were made by lamination and coextrusion and adhesion was measured using asymmetric dual cantilever beam (ADCB). The amount of graft copolymer in the interface was quantified by X‐ray photon spectroscopy (XPS). With quiescent lamination, adhesion increased with temperature and the concentration of PE‐MA. The adhesion metric, Gc (critical energy release rate), plotted as a function of Σ (interfacial copolymer density) fell on the same master curve, unifying reaction process, temperature and time. Gc was a linear function of Σ for low‐copolymer coverage and weak adhesion. For relatively high coverage and strong adhesion, Gc scaled with Σ. Coextrusion with compressive flow resulted in a reaction rate strikingly two‐orders of magnitude faster than that without compressive flow. The rate in the noncompressive die was close to quiescent lamination. Even for lamination, when compressive flow was applied normal to the interface, the coupling reaction rate was also greatly accelerated. Several mechanisms are speculated for this remarkable acceleration in polymer chain coupling. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3391–3402, 2013

Fundamental understanding and modeling of diffuse interphase properties and its role in interfacial flow stability of multilayer polymers

“…Recently, basing on incompatible functional polymers, Song et al demonstrated that the extensional and compressive flow in coextrusion overcomes the diffusion barriers by decreasing the diffusion length scale, thus enhances diffusive flux of local reactive functions and eventually contributes to the accelerated reaction rate during coextrusion. Change of the diffusion lengthscale or diffusion layer after being subjected to the external flow could be appraised from a theoretical viewpoint.…”

Interfacial tension of reactive, liquid interfaces and its consequences

“…Zhang et al [111] showed experimentally that the presence of an external flow accelerates interfacial reactions. Song et al [112] also showed an acceleration of the reaction under a compressive flow, and state that this explains the remarkable ability of co-extrusive processes to build multilayer products with little residence times. These more realistic experimental conditions are still missing in the theories of kinetic evolution of copolymer coverage of the interface.…”

Bonding dissimilar polymer networks in various manufacturing processes

“…The silane coupling agents condensate after manufacturing and generate bonding across the interface. The idea is similar to placing a reactive inside different thermoplastics to improve adhesion 25 – 27 . Our approach improves adhesion independent of the sequence of forming the networks, and enables various manufacturing processes difficult or impossible to achieve using existing approaches.…”