Orientation Determination and Morphological Study of High Density Polyethylene (Hdpe) Extruded Tubular Films

Abstract

Fiber spinning and extrusion, which result in preferred molecular orientation for polyethylene, have been investigated for many years [1,2]. Particular effort has been undertaken to study the mechanism of molecular orientation on the structure and properties of polyethylene extruded blown films [3-5]. In 1994, Simpson and Harrison investigated the effect of processing parameters on the crystalline and amorphous morphologies in high density polyethylene (HDPE) blown films [3]. In their study, the crystalline structure in the polyethylene blown films was suggested to be a row nucleated structure. The development of the chain folded lamellae, which grow radially from the extended chain row nuclei, were found to be strongly dependent on the processing variables: take-up ratio, blow-up ratio and frostline height. Later, Fruitwala et al. examined the crystalline orientation and morphology for both HDPE and linear low density polyethylene (LLDPE) blown films [5]. The c-axis orientation in which the c-axis of the PE crystal unit cell mainly lies in the machine direction, was observed in the blown film HDPE systems. On the other hand, the LLDPE blown films were observed to possess preferential a-axis orientation with the a-axis of the PE crystal unit cell oriented toward the machine direction.