Poly(vinyl alcohol)/graphene nanoplatelet nanocomposites: Elucidation of the nanofiller, dispersing agent, and interphase effects on thermomechanical properties

Abstract

Poly(vinyl alcohol) (PVA)/graphene nanoplatelet (GnP) nanocomposite films were fabricated by a solution casting method. High loadings (30–40 wt.%) of two GnP grades, that is, xGnP C300 (low surface area/large size) and C750 (high surface area/small size), were utilized in combination with three commercial dispersing agents, that is, DISPERBYK‐161, DISPERBYK‐162 TF, and DISPERBYK‐2014, to yield films with desirable stiffness and energy dissipation characteristics (dynamic mechanical analysis, DMA), as well as thermal properties (thermogravimetric analysis, TGA) for potential impact resistance applications. The addition of GnPs and dispersing agents to PVA leads to a maximum six‐fold increase in its Young's modulus for the PVA sample containing 40 wt.% C300 GnPs and DISPERBYK‐162 TF. However, the modulus of resilience drops dramatically for the same sample (about 18‐fold decrease), as expected. Also, C300 GnPs yield nanocomposites with higher Young's moduli that those obtained using C750 GnPs. The atomic force microscopy stiffness maps illustrate that C300 GnPs disperse better in the PVA matrix. Furthermore, the average interphase thickness in the PVA‐C300 nanocomposites (~300 nm) is almost double that of PVA‐C750 nanocomposites. Based on the TGA results, the addition of GnPs and dispersing agent to the PVA matrix leads to a moderate increase (an average of 3.5%) in the value of the neat PVA, while its char yield increases by an average 8.5‐fold. Specifically, the PVA/GnP nanocomposites containing DISPERBYK‐162 TF yield the largest and char yield values than the other systems. The insights gained in this work can guide the design of coatings for impact resistance applications.