Rheology‐processing‐property relationships in tubular blown film extrusion. II. Low‐pressure low‐density polyethylene

Abstract

SynopsisAn experimental investigation was undertaken to establish rheology-processing-property relationships in the tubular blown film extrusion of low-pressure low-density polyethylene (LP-LDPE). For the study, three commercial LP-LDPE resins, each from a different resin manufacturer, were used in producing tubular films, by employing the apparatus described in Paper I of this series. Both molecular and rheological characterizations of the resins were conducted, enabling us to interpret the tubular film blowing characteristics of the resins. Correlations were obtained between the processing variables (namely, blowup and takeup ratios) and the tensile properties of the films. The tubular film blowing characteristics of LP-LDPE and HP-LDPE resins are compared. Differences in the rbeological properties (namely, elongational viscosity) of the two types of resin are used in explaining the experimentally observed differences in their tubular film blowability.

Structure–Property–Process Relationship for Blown Films of Bimodal HDPE and Its LLDPE Blend

“…In film processing, the film‐blowing process has been a dominating technology due to the high‐production rate and flexibility in controlling film properties by modulating processing parameters. However, in spite of the fact that the relationships among structure, property, and varying processing of PE have been extensively studied for decades, the detailed correlation of structure‐property and film‐blowing processing have not been completely established, which is the objective of the current study.…”

Application of variational principles in modeling of the film blowing process for high stalk bubbles

“…During the biaxial orientation of the film, the bubble is cooled by air flowing along the film. The height at which the solidification starts is referred to as the freezeline and the stresses frozen at this area are inextricably related to the final mechanical and optical properties of the film [1][2][3]. With the aim to understand more deeply the stability of the film blowing process and the relationship between machine design, processing parameters, materials and final film properties, intensive experimental as well as theoretical [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45] effort has been done in past 40 years.…”

Modeling of the film blowing process by using variational principles

“…Therefore, the polymer is molten between the annular die and the freeze-line, above which it is solidified completely. The crucial factor, which determines physical and mechanical properties of the film, including the tensile strength, tear resistance, heat seal and optical characteristics, has been found to be the amount of frozen-in stresses in the film at the freeze-line [1][2][3]. Moreover, the occurrence of the wide range of bubble instabilities during film blowing process significantly reduces the processing window [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20].…”