Improving interfacial adhesion between immiscible polymers by carbon nanotubes

Although previous work has already shown that the presence of functionalized multiwalled carbon nanotubes (FMWCNTs) induced the great improvement of fracture toughness of an immiscible polymer blend, there is not exact evidence to show that the improvement of fracture toughness is only attributed to the improvement of interfacial adhesion resulting from the selectively distributed FMWCNTs at the interface of the immiscible polymer blend. In this work, we design several samples by compressing different polymer sheets to merge together and measure the peel adhesion strength between polymer sheets to evaluate the interfacial adhesion of different samples. The results show that with the presence of FMWCNTs in the high density polyethylene (HDPE) or in the maleic anhydride grafted HDPE (HDPE-g-MA), the peel adhesion strength between HDPE and polyamide 6 (PA6) or between HDPE-g-MA and PA6 is greatly improved, showing the positive effect of FMWCNTs in improving the interfacial adhesion between immiscible polymers. Further results obtained from scanning electron microscope (SEM) indicate that the presence of FMWCNTs induces the severe plastic deformation of sample during the peel adhesion test. The mechanisms for the improvement of interfacial adhesion are attributed to the enhancement of polarity of HDPE or HDPE-g-MA sample induced by FMWCNTs which facilitate the chain segments diffusion across the interface, and the bridge effect of FMWCNTs at the interface which prevents the propagation of crack along the interface.