Deformational history of LLDPE/LDPE blends on blown film equipment

Abstract

A video camera tracer technique (T. A. Huangand G. A. Campbell, paper Although literature results on film blowing deformation are available, '-I6 most of the work was conducted on a small line where throughput and cooling rates are limited. Recently, we initiated a research program aimed toward a fundamental understanding of the process. The effect of extrusion variables upon stretching and cooling histories for LDPE and LLDPE is discussed elsewhere. *' DEFORMATIONAL, HISTORY OF LLDPEILDPE BLENDSFor LLDPE/LDPE blends, data of deformational history on the blown film equipment are not available in the literature. Recently, it became a plastics industry practice to add small amounts of LDPE into LLDPE for stabilization of the bubble and for improvement of LLDPE film opticals. Also, the addition of small amounts of LLDPE into LDPE reduces bubble breaks and improves drawdown characteristics. The purpose of this work is to quantify the changes in strain and strain rate histories caused by these additions of resin types. INTRODUCTIONMATERIAL DATA Blown film technology has been practiced in industry for many years. It is generally recognized that stretching and cooling histories experienced by the fluid element between die and frost line have an important effect on determining final film properties.

Online measurements of crystallinity using Raman spectroscopy during blown film extrusion of a linear low‐density polyethylene

“…Although the profiles for crystallinity as a function of axial distance displayed slight differences for various TURs, the development of crystallinities was significantly different when plotted as a function of time. From the measured velocity profiles, the strain rates (velocity gradients) along the machine direction (e 1 ) were calculated (15) and are presented in Fig. 6.…”

“…Axial film velocity was calculated by the video camera tracer technique (15), and the diameter profiles were obtained from image analysis of the captured bubble pictures. Temperature measurements were obtained using an Ircon Infrared pyrometer (Modline 340, Niles, IL).…”

Influence of Processing Conditions On the Peel Behavior of Polyethylene/ Polybutene-1 Peel Systems

“…The exit speed of the melt out of the die gap, and also the TUS (being constant from FLH) is known. The velocity of the film bubble between die gap and FLH was approximated by a linear law, since a measure of this value by other scientists evidences a nearly linear dependence [6]. After production by blowing process, the films were sealed at a temperature of 1408C, for a period of 2 s at a pressure of 160 kPa using a seal device (Kopp, Germany); subsequently, the sealed films were cooled to ambient temperature.…”

Structure of blown films of polyethylene/polybutene‐1 blends

“…Reports about orientation of the a-axis or c-axis of the crystal lattice at an intermediate angle between MD and TD show that via the ratio k MD /k TD, the orientation can be tailored. This intermediate orientation was observed for high-density polyethylene (PE-HD) [5] in particular, and for linear lowdensity polyethylene (PE-LLD) [10,12,22].…”

“…The draw ratio k (¼ l/l 0 , with l and l 0 being the length of a volume element after and before drawing, respectively) in each direction is variable, and is controlled by the amount of air blown into the bubble, and by the take-up speed or by the screw speed. Final fixing of the bubble occurs at the frost-line by cooling with refrigerated air [5][6][7][8][9]. In general, the sequence and ratio of drawing the film in transverse and longitudinal directions, in combination with the superimposed field of temperature, i.e., the conditions of cooling, are major factors controlling the final physical structure of the blown films.…”