Spray coating of poly(acrylic acid)/ZnO tetrapod adhesion promoting nanocomposite films for polymer laminates

Zinc oxide tetrapods (ZnO TP) have reached a high level of interest in the last years due to their broad fields of applications. Here, the combination of the adhesion promoting properties of both ZnO TP and poly(acrylic acid) (PAA) is demonstrated. A very rapid spray coating of water-based dispersions has been used to deposit homogenous thin nanocomposite films on poly(propylene) (PP) foils considered as model system. The characterization of ZnO TPs has been carried out by field-emission scanning electron microscopy (FE-SEM), high-resolution X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The increased shear strength values exhibited by PP/PP laminates with interfacial ZnO TP/PAA films could be attributed to mechanical interlocking of ZnO TP and the macromolecular adhesion promotion by PAA. FE-SEM imaging after shear tests indicated a failure in the core of the ZnO TP. The fast application method via plasma activation of the PP foils and spray coating of the composite films with low concentrations of 0.085 mM PAA and 8 mg/ml ZnO TP makes this technique rather interesting for industrial applications.