Studies on the biaxial stretching of polypropylene film. XI. Type II orientation during [2‐2FI]‐type stretching and its change by subsequent thermal contraction

Abstract

SynopsisIn order to study the deformation mechanism of type I1 stretching, the change in orientation during the restretching and subsequent thermal contraction was investigated by x-ray daraction method. When a uniaxially oriented film is restretched, the lamellae which are stacked in the stretching direction by the stretching rotate as a whole toward the restretching axis. They rotate backward nearly reversibly during the thermal contraction, unless the restretching exceeds a balancing state, where the orientation in the film plane are equal in all directions. However, when the restretching degree is so high and the film orientation exceeds the balancing state, the lamellar rotation is accompanied by a complex phenomenon. It is considered from the wide-angle and small-angle x-ray diffraction patterns that the lamellar surface becomes indented because of slippage between microfibrils composing the lamellae, and the microfibrils themselves bend a t the boundary between the amorphous and crystalline regions within which the tilting of Caxis also occurs. Upon contracting of the film; these changes recover, but even in the last stage of contraction the orientation approaches the symmetrical biaxial orientation but not the uniaxial orientation from which the biaxial orientation is started. These orientation and disorientation behaviors are not affected basically by a slight change in the restretching temperature and the degree of stretching.Ia-' and type IIIIJJ were reported in the previous papers; hence, the orientation during type 11' stretching and its change due to subsequent thermal contraction are the subject of the present paper. It has been described' that [2-2FI]-type stretching, namely, stretching of a film with width unrestrained at temperature TI followed by restretching at temperature TZ perpendicularly to the stretching direction with insertion of a cooling pro-

Effect of environmental factors on the mechanical properties of grafted casein films: Influence of humidity and biaxial orientation

“…[31][32][33][34][35][36] In this present study, the effect of relative humidity and biaxial testing on the stress-strain behavior of grafted caseins was studied in detail. '~-~~ During biaxial stretching, the orientation of the material takes place in the sample.…”

Structural Transformations during the Low-Temperature Annealing of Biaxially Oriented Polypropylene Film

“…The crystalline structure of BOPP has been investigated in a relatively small number of studies (for example, references [10] to [13]). In reference [13], a model is proposed for BOPP that comprises further development of the "shish kebab" structure.…”

Effect of environmental factors on the mechanical properties of grafted casein films: Influence of humidity and biaxial orientation

“…'~-~~ During biaxial stretching, the orientation of the material takes place in the sample. [31][32][33][34][35][36] In this present study, the effect of relative humidity and biaxial testing on the stress-strain behavior of grafted caseins was studied in detail.…”