Influence of carbon nanotubes on the properties of films of polypropylene prepared by film blowing

The influence of carbon nanotubes on mechanical and bielongational properties of films of polypropylene prepared with film blowing technique were studied. The carbon nanotubes (CNTs) adopted as fillers were contained in a polypropylene pre-compounded with 20 wt% of carbon nanotubes (masterbatches). To investigate on the effect of moelecular and/or carbon nanotube orientation on the mechanical properties of PP, the tensile test were performed eiher on suitable composite sample plates, obtained by pressing the granulated melt- mixed composites, either on film samples. Furhermore, blown film samples were tested either in the blow-up direction (BD) either the take -up one (TD). Different response to the tensile tests were displayed by the blown films samples in the two directions of testing as a consequence of the biaxial orientation of molecules (and/or the carbon nanotubes) during the film blowing. Excellent improvement of the mechanical properties (Young's modulus and strength) for certain weight fractions of CNT of the blown composite films compared to the neat PP were revealed. Furthermore, the bubble formation and stability in the film blowing process of PP nanocomposites were correlated to their underlying rheology, structure, and crystallization behavior.