Effect of orientation on the free volume and oxygen transport of a polypropylene copolymer

Abstract

The effect of uniaxial orientation on the free‐volume and oxygen‐transport properties of a propylene copolymer with 4.5 wt % ethylene was examined. The free‐volume hole size and hole density were measured with positron annihilation lifetime spectroscopy. Subsequently, the free‐volume characteristics were correlated with the oxygen‐transport properties. Orientation had only a small effect on the total amount of free volume: a small increase in the hole density was offset by a small decrease in the hole size. As a result, the oxygen solubility and amorphous‐phase density were unchanged by orientation. However, a pronounced decrease in the oxygen diffusivity when the draw ratio exceeded 6 indicated a change in the dynamic free volume. This was attributed to an increasing number of taut tie chains, which retarded oxygen diffusion. The reduced amorphous chain mobility was also manifest in the increased glass‐transition temperature, decreased bulk thermal expansivity, and decreased expansivity of free‐volume holes. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1230–1243, 2005

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. ]…”

Influence of incorporation of ZnO nanoparticles and biaxial orientation on mechanical and oxygen barrier properties of polypropylene films for food packaging applications

“…The biaxial stretching of the material either in one single step or sequentially is a fundamental step in the production of polypropylene films for packaging applications. Orientation of polypropylene involves a morphological transformation of spherulites into a network of microfibrils and reduces the gas permeability of polypropylene 13–15…”

The influence of orientation on the radiation-induced crosslinking/oxidative behavior of different PEs

“…Oriented polymers with high modulus are of particular relevance to applied sciences [1][2][3][4][5][6][7]. The drawing of isotropic semicrystalline polymer usually produces a fibrous material with a high degree of anisotropy in its physical properties due to molecular orientation.…”