X‐ray diffraction orientation studies on blown polyethylene films. III. High‐stress crystallization orientation

Abstract

SynopsisX-Ray diffraction orientation measurements have been made on a wide range of films blown from three high-density polyethylenes, to determine more precisely the conditions which lead to the high-stress crystallization type of orientation. The most extensive measurements relate to films from Hostalen GM 9955F; the results show that there is a very wide range of orientational behavior.Under very low-stress conditions there is almost pure a-axis orientation; with very high stress there is substantial c-axis orientation, both with reference to the machine direction. Commercial blowing conditions give rather high stress and the a axis is inclined a t 60" to 70" to the machine direction in the sheet-normal-machine-direction plane. Calcium stearate, used to improve the surface finish, increases the stress for a given set of machine conditions and, of these, a high draw ratio and a low extrusion temperature are most effective in promoting high-stress crystallization. The less extensive results for an experimental Rigidex grade and Shell LPPE 040 fit into this overall pattern; for a given set of blowing conditions they have lower stress than the Hostalen polymer. Commercial blowing conditions give an a-axis inclination of about 45".

Improving Barrier Through Orientation in Processing

“…However, the process by which this orientation is achieved is complicated and depends heavily on the processing conditions. One definitive study by Maddams and Preedy [9][10][11] described the morphology of the films using x-ray diffraction. The use of infrared was added by McRae and Maddams [12] to further delineate the orientation.…”

“…The effect of various processing methods on the morphology of polyethylene has been extensively studied by several authors [3][4][5][6][7][8][9][10][11][12][13]. The earliest work on polyethylene was that of Peterlin and co-workers [3][4][5][6][7] which produced the basis for his microfibrillar model of the morphology of highly oriented films.…”

X-ray Pole Figure and Small Angle Scattering Measurements on Tubular Blown Low-Density Poly(ethylene) Films

“…[4][5][6][7][8][9][10][11]13,15 Other researchers have observed this and the combined intermediate morphology equally in LDPE and HDPE films. 4,[8][9][10][11][12][13][14] To our knowledge, the Keller/Machin 2 morphology has been induced only in blown HDPE films. 11,12 In the present study, we analyze the crystalline molecular orientation induced in blown LDPE film by measuring the (200) and (020) pole figures.…”

“…4,[8][9][10][11][12][13][14] To our knowledge, the Keller/Machin 2 morphology has been induced only in blown HDPE films. 11,12 In the present study, we analyze the crystalline molecular orientation induced in blown LDPE film by measuring the (200) and (020) pole figures. SAXS measurements will be used to ascertain the type of morphology induced in the films.…”

X-Ray Diffraction Orientation Studies on Blown Polyethylene Films

“…The second stage of the work consisted of a general survey of the orientation present in a range of films blown from various high density polyethylenes (3)(4)(5). So far as was possible, the various machine variables, such as the melt temperature, the blow-up ratio, the draw ratio and the freeze line height, were varied independently over the usable range.…”