Oxygen permeability of biaxially oriented polypropylene films

Abstract

The effect of thermal history on the oxygen permeability of biaxially oriented polypropylene (BOPP) films was investigated. Compression-molded sheets prepared with different cooling rates were biaxially oriented at several temperatures in the range between the onset of melting and the peak melting temperature and at a strain rate similar to that encountered in a commercial film process. The stress response during stretching was found to depend on the residual crystallinity in the same way regardless of the thermal history of the compression-molded sheet. Biaxial orientation reduced the oxygen permeability measured at 23°C; however, the reduction did not correlate with the amount of orientation as measured by birefringence or with the fraction of amorphous phase as determined by density. Rather, the decrease in permeability was attributed to reduced mobility of amorphous tie molecules. A single one-to-one correlation between the oxygen permeability and the intensity of the dynamic mechanical b-relaxation was demonstrated for all the films used in the study. POLYM. ENG. SCI., where DH m is heat of melting of the specimen and DH 0 m is the heat of fusion of 100% crystalline PP and is taken as 209 J g -1 [12].

Impact of oxygen transport properties on polypropylene thermal oxidation, part 1: Effect of oxygen solubility

“…It has been necessary to use a value of oxygen solubility six times higher for iPP3 than for iPP2 to report the experimental discrepancies. This variability on the oxygen solubility is in satisfactory agreement with the large scattering reported when compiling the data of various authors (see Figure ). All these results constitute a supporting evidence of the impact of oxygen solubility on the iPP thermal oxidation kinetics.…”

“…(A13) in Appendix A]. The values of oxygen solubility determined in the iPP amorphous phase in this study are compared with the data compiled from the literature in Figure . is of the same order of magnitude and almost temperature independent for all iPPs.…”

“… Comparison of the oxygen solubilities of iPPs measured in this study and compiled from the literature: iPP1 (this study). Lin et al; ○ Somlai et al; Villaluenga et al; Beltrame et al; Mani et al; Kiryushkin and coworkers; Denisov and Afanas'ev; Thorlaksen et al; Kurek et al [Color figure can be viewed in the online issue, which is available at http://wileyonlinelibrary.com. ]…”

“…Comparison of the oxygen solubilities of iPPs measured in this study and compiled from the literature: iPP1 (this study). Lin et al 45,46 ; ᭺ Somlai et al 47 ;…”

Impact of oxygen transport properties on the kinetic modeling of polypropylene thermal oxidation. II. Effect of oxygen diffusivity

“…It is thus relevant to position our experimental values among an exhaustive compilation of literature data, as performed for oxygen solubility in the first part of this study . It can be now fulfilled in the case of the oxygen permeability and diffusivity, of which the respective Arrhenius graphs have been depicted in Figures and .…”