X‐ray diffraction orientation studies on blown polyethylene films. I. Preliminary measurements

Abstract

SynopsisX-Ray diffraction pole figure measurements have been made on six films blown from high-density polyethylene. Five were prepared on an experimental unit; the sixth, blown on commercial equipment, had a higher degree of overall orientation thus enabling more extensive results for the a-, b-, and c-axis distributions to he obtained. The results provide information on the orientation present, how it may be related to the stress crystallization process of Keller and Machin, and the dependence of the tear strengths in the machine and transverse directions on the orientation. The typical hehavior, with the a and c axes a t 90" and both a t an angle to the plane of the film, is shown to be the result of a composite process involving several types of stress during the blowing operation and a partial relaxation arising a t one or possibly two stages of the process. The predicted relative tear strengths, obtained from the concentration of c axes inclined towards the machine direction, are in line with the experimental values. There is some evidence that transcrystallization in the surface layers of the films may lead to a better balance of the tear strengths in the machine and transverse directions.

Morphological considerations on the mechanical properties of blown high-density polyethylene films

“…Some correlations shed light on our understanding of the mechanical were found between the anisotropy of the tear and properties of blown HDPE films. tensile properties of blown HDPE films and the state of orientation of the crystalline molecular chain axes [1][2][3][4][5] and lamellar stacks 6-9 at the film EXPERIMENTAL plane. Few studies have investigated the dart drop impact resistance of blown HDPE films.…”

Biaxial orientation in HDPE films: comparison of infrared spectroscopy, X-ray pole figures and birefringence techniques

“…For the particular case of PE, FTIR allows the determination of crystalline axes orientation as well. However, the accuracy and precise significance of the different orientation factors determined from these techniques is to be established, although some studies in the past addressed partially this issue as well as their correlations to structure and properties [7][8][9][10][11][12][13][14][15][16].…”

Correlations between processing parameters, morphology, and properties of blown films of LLDPE/LDPE blends, part 2: Crystalline and amorphous biaxial orientation by WAXD pole figures

“…2,[16][17][18] Details regarding the f B calculation from the IR absorbencies were documented previously. 2,3 It must be pointed out that the crystallinity indexes used to calculate f B were the ones measured by differential scanning calorimetry (DSC).…”