Studies on the stretching of polypropylene film. I. Two‐step biaxial stretching

Abstract

synopsisA polypropylene film was stretched a t 1O&16O0C., quenched to room temperature, and then restretched a t the same temperature perpendicularly to the first stretching. The reorientation behavior was investigated by using optical and x-ray methods. During the restretching the monoaxiaI orientation caused by the stretching is converted into a new monoaxial orientation through a balanced state, where npp = npi > ns.. The more or less parallel orientation to the film surface of the polypropylene molecules, brought about by the first stretching, proceeds further on restretching. nss is a h e a r function of the degree of stretching in area VA. The inclination of this line is independent of the type of deformation, stretching, or restretching, provided the temperature is kept constant. At 160OC. the plot of nss versus thickness is less steep than it is a t 100 or 130OC. The overall reorientation apparently proceeds according to Kratky's first deformation law. The x-ray pattern of a restretched film is a four-point diagram which indicates the existence of a pair of reorientation axes inclined symmetrically against the stretching axis. The inclination grows larger with restretching, and the axes merge into the restretching axis at extreme restretching. This phenomenon is less pronounced when the restretching is carried out a t higher temperatures. The density of the restretched film is determined mainly by the stretching temperature, but extreme restretching has a tendency to lower it very slightly.

Influence of biaxial stretching mode on the crystalline texture in polylactic acid films

“…15 illustrates that the poles of these planes are primarily oriented in the ND. This is typical of SB stretching of many polymers [23][24][25][26]38,[48][49][50][51][52]57,58].…”

Crystalline structure at surfaces of uniaxially drawn polypropene films

“…The process of drawing reduces the large-scale molecular organization and this can lead to the changes in the crystallite size and the deformation of the crystal unit cell [16][17][18] . It is interesting whether the reorganization of lamellar crystals in the surface layer induced by drawing occurs or not.…”

Fabrication and characterization of orientation in skew stretched polyethylene terephthalate films

“…The distribution of refractive indices in the fdm was determined by the method of Okajima [4,5,34]. The distribution of refractive indices in the fdm was determined by the method of Okajima [4,5,34].…”

“…There has been a long history of investigations of stretching of (cast) polymer films to produce uniaxial and biaxial states of orientation [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. However, little attention has been given to processes in which films are created using skew (i. e., non perpendicular) stretches.…”