Orientation in extruded polyethylene films

Abstract

A discussion of the methods for studying orientation of crystalline and amorphous regions in polyethylene films is given. Extruded polyethylene films and films after having been stretched approximately 200% were studied by the methods of x‐ray diffraction and absorption of polarized infrared radiation. It is shown that in extruded polyethylene films the a‐axes of the crystallites are oriented parallel to the extrusion direction. The amorphous regions in these are either not oriented or show only to a slight degree the orientation of chains perpendicular to the extrusion direction. When the polyethylene films are stretched, both the crystallites and the amorphous regions become oriented. In stretched films, the orientation of the crystallites is with c‐axis parallel to the stretching direction, and the chains in the amorphous regions are also oriented parallel to the stretching direction. Two mechanisms by which a‐axis orientation may arise during extrusion of polyethylene films, and a convenient method for determining the relative degree of a‐axis orientation in polyethylene films are given. The relative degrees of a‐axis orientation as determined by x‐ray diffraction and dichroism of absorption at 13.70 μ are compared for a number of film samples.

Structure of blown films of polyethylene/polybutene‐1 blends

“…Based on the WAXS data, we therefore intend to describe the orientation of crystals of PE-LD in blown films of blends of PE-LD and iPB-1, which were processed at the specific condition summarized in Table 1, as a uniaxial a-texture. This result is in accord with earlier observations [6,10,14,17], and shows that addition of iPB-1 does not qualitatively affect structure formation of PE-LD on film blowing from the crystal orientation angle. This is further demonstrated with the data of Fig.…”

“…The super-molecular structure, including the crystallinity, and the morphology and orientation of the crystals of blown films of polyethylene (PE) have been extensively studied [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. Typically, blown films of PE are semicrystalline with a maximum degree of crystallinity, which depends on the molecular architecture/branching-characteristics.…”

Computer simulation of the film blowing process incorporating crystallization and viscoelasticity

“…Because of the orientations of the a-and b-axes, the orientation of the chain axes in the crystalline region is mainly perpendicular to the machine direction [Aggarwal et al (1959)]. …”

“…In a study on orientation in polyethylene films made by film blowing and fiat casting, Aggarwal et al (1959) proposed two limiting cases of orientation, shown in Figure 54. Firstly, the a-axis is mainly oriented in the machine direction and the b-and c-axes are oriented perpendicular to the machine direction.…”

“…Consequently, the amorphous preferred orientation was in the direction perpendicular to the machine direction. Aggarwal et al (1959). Zhang et al (2004) studied different types of PE (HDPE, LDPE, LLDPE) blown films.…”