Relationship between biaxial orientation and oxygen permeability of polypropylene film

Biaxially oriented poly(propylene-g-maleic anhydride)/phosphate glass composite films for high gas barrier applications

“…If the particles are platelet-shaped with aspect ratio a and oriented parallel to the polymer film surface, i.e., perpendicular to the permeation direction as in the biaxially stretched films, appropriate permeability models include those of Nielson [24] P P m ¼ The oxygen permeability data are summarized in Table 3. The decrease in P of PPgMA with increasing area draw ratio was consistent with previous reports for biaxially stretched isotactic PP [28]. The presence of spherical Pglass particles in the unstretched composite decreased the permeability somewhat.…”

“…This possibility was tested with density measurements, Table 4. In this case, the stretched samples were compared with an unstretched control that was annealed at the stretch temperature for 60 s. The decrease in density of PPgMA with increasing draw ratio was observed previously with biaxially stretched isotactic PP and was attributed to reduced crystallinity [28]. It should be recalled that the films were partially melted during the preheat period and they remained partially melted during the stretching process.…”

“…The results are given in Table 5. For the 94/6 and 90/10 v/v composites, the calculated density of the PPgMA phase decreased systematically with increasing glass content and with increasing draw ratio, but in all cases was substantially higher than the amorphous phase density of PP (r a ¼ 0.853 g cm À3 [28]). This was consistent with the hypothesis that the glass phase constrained crystallization of the PPgMA.…”

Mechanical Behavior of Filled Thermoplastic Polymers

“…Hence, rolling effectively suppresses brittle fracture of filled polymers. Particularly, PP behaviour is ductile and crazes do not appear even at temperature -40 o C [21,22]. 26 shows engineering yield stress, draw stress and strength of PP plotted against the rolling ratio .…”

Three dimensional molecular orientation of isotactic polypropylene films under biaxial deformation at higher temperatures

“…There are typically two types of stretching methods used to create such films: inflation molding, in which films are blown in a tubular shape, and tenter molding, in which films are elongated in the machine direction and/or the transverse direction by tenter clips [2,3]. Thus, oriented iPP films can be produced by a variety of stretching techniques based on sequential as well as simultaneous drawing processes using various balanced draw ratios at high temperatures near the melting point and at extremely high elongation speeds [4]. Elucidation of the deformation mechanism under biaxial stretching on the molecular scale would undoubtedly be indispensable for designing and controlling various physical properties of biaxially oriented iPP films.…”