Study of crystal structure of (Polyvinylidene fluoride/clay) nanocomposite films: Effect of process conditions and clay type

Abstract

Three Polyvinylidene flyoride (PVDF) different in molecular structure were used to produce nanocomposities films by cast extrusion with a particular emphasis on maximizing the β crystal phase content. The PVDF/clay compounding followed by cast film production was carried out throygh melt extrusion using a twin screw extruder equipped with a slit die. X-ray diffraction (XRD) resylts showed that clay melt intercalation is almost similar for all three PVDFs. The XRD resylts also revealed that nanocomposite films from PVDF with branched chain structure (PVDFB} generated the greatest amount of β phase. FTIR spectroscopy measurements confirmed the XRD resylts but also revealed that significant stretching of the melt films at the die or rapid cooling would adversely affect the formation of β phase. The amount of β phase obtained based on nanoclay compoynding was compared with that obtained from conventional method; stretching of molded PVDF film with initial α phase. Stretching of PVDF film at 60°C yielded pure β phase that means complete transformation of α to β. From mechanical properties, tensile tests were carried out on PVDF nanocomposite films to evaluate mechanical strength. PVDF with low molecylar weight exhibited a very low strain at break while branched PVDF and high molecular weight PVDF could sustain more strain. © 2008 Society of Plastics Engineers.