Surface Migration of Conductive PEBA in Ternary Polymer Blend Films with Different Wetting Morphologies

Abstract

It will be shown that ternary blends comprising a low-density polyethylene (LDPE) matrix and dispersed poly(etherblock-amide)/poly(butylene-adipate-co-terephthalate) (PEBA/PBAT) or PEBA/polyvinylidene fluoride (PVDF) can result in different wetting morphologies which can significantly enhance or fully restrain the surface migration of a conductive PEBA copolymer in the blend films. In the LDPE/PEBA/PBAT blends, the minor PEBA and PBAT phases combine to form a unique highly associated dispersed phase morphology demonstrating some weak partial wetting characteristics (i.e., three-phase contact), but neither PEBA nor PBAT can be regarded as the middle phase partially wetting the other component. This unique morphology is also a result of the particularly low interfacial tension between PEBA and PBAT. The use of a low-viscosity PBAT results in an increase in the surface composition of PEBA of up to 4 times as compared to that of the binary LDPE/PEBA blends. This is due to the enhancement of the combined PEBA/PBAT continuity, the low interfacial tension between PEBA and PBAT, and the high migration velocity of PBAT in the ternary blend. On the other hand, the LDPE/PEBA/PVDF blend system generates a completely wet morphology where PEBA is confined as a layer phase at the LDPE and PVDF interface. In this latter system, PEBA/PVDF also has a low interfacial tension, and even under conditions of similar viscosity and continuity to the partially wet LDPE/PEBA/PBAT system, the PEBA surface migration in LDPE/PEBA/PVDF can be fully suppressed. With these different PEBA surface migration characteristics in LDPE/PBAT/PEBA and LDPE/PEBA/PVDF, either a hydrophilic or a hydrophobic film surface can be generated at various surface resistivities.

Closely Packed Conductive Droplets with Polygon-Like Patterns Confined at the Interface in Ternary Polymer Blends

“…In the previous work, we investigated the surface migration behaviors of dispersed PEBA and PBAT in an LDPE matrix during film extrusion. 4 It was found that the minor PEBA and PBAT phases were closely associated and demonstrated the partial wetting characteristic of three-phase contact. These features in combination with the low viscosity of the components resulted in significant surface enrichment of PEBA and PBAT in the extruded film.…”

“…Note that the resistivity evolution and percolation phenomenon in various polymer blends with conductive PEBA have also been reported in previous publications. 3,4,14,37 Static annealing was further applied to highlight the stable phase structure. Figure 3 presents the morphology of the LDPE/PEBA/PBAT and LDPE/PEBA/PP blends after annealing at 200 °C for different periods of time.…”

“…16−23 Wang et al confined the conductive PEBA at the interface in both completely wetted and partially wetted systems for improved antistatic performance. 3,4,14 It was shown that assembling the conductive polymer at the continuous interface of multiphase polymer blends resulted in a significant reduction of percolation threshold from 9.7 to 0.37%. 14 Other studies have introduced conductive nanofillers into the completely wet middle phase to further increase the electrical conductivity for dielectric and electromagnetic interference (EMI) shielding applications.…”

“…The spreading of a liquid at the interface (e.g., gas/solid or liquid/liquid interface) is an important fundamental phenomenon for many applications, such as painting, inkjet printing, oil spill recovery, superhydrophobic materials, and multiphase polymer blends. − The equilibrium profile of a small droplet on a solid surface satisfies the Young equation where the contact angle is determined by the surface tensions of the liquid and the solid and the interfacial tension between them . If the droplet is placed on a deformable surface or interface, a lens-shape configuration will be developed as dictated by the Neuman triangle conditions (Figure a) …”

“…However, Wang et al recently demonstrated that in a ternary PE/poly­(ether- block -amide) (PEBA)/PS blend, PEBA can form connected droplets at the PE/PS interface after compatibilization and annealing . Some other studies have demonstrated that a transition from partial wetting to complete wetting is possible in some systems (i.e., weak partial wetting), either through composition variation or via annealing. ,, The difference between weak partial wetting and strong partial wetting is that the former usually has a negative spreading coefficient close to zero (eq ). Or equivalently, the Neumann angle of the middle phase (Figure b) in those systems is relatively small (e.g., < 100° as further discussed in Section ), and the droplets are extended along the interface.…”