Water Barrier Properties in Biaxially Drawn Poly(lactic acid) Films

Abstract

Crystallization is among the easiest ways to improve polymer barrier properties because of the tortuosity increase within the material and the strong coupling between amorphous and crystalline phases. In this work, poly(lactic acid) (PLA) films have undergone α' thermal crystallization or different drawing processes. Although no effect of α' thermal crystallization on water permeability is observed, the drawing processes lead to an enhancement of the PLA barrier properties. This work clearly shows that, in the case of PLA, the crystallinity degree is not the main parameter governing the barrier properties contrary to the crystalline and amorphous phase organizations which play a key role. X-ray analyses confirm that the macromolecular chain orientation in the amorphous phase is the main cause of the improvement of the drawn PLA water barrier property. This improvement is due to the orthotropic structure formation for sufficient draw ratios, particularly when using the Simultaneous Biaxial drawing mode. Moreover, independently of the draw conditions, the drawing process tends to reduce the plasticization coefficient. Consequently, the drawn material barrier properties are not much affected by the water passage.

Multi-scale analysis of the impact of polylactide morphology on gas barrier properties

“…In some cases, constancy or even an increase in the oxygen permeability with an increasing crystallinity degree of PLA was found [6,9]. A similar result was also observed in the case of the water vapour permeability of crystallized PLA [10,11]. Kanehashi et al [12] did an impressive review on approximately 300 studies concerning the relationship between gas permeability and crystallinity of various polymers.…”

“…The content of RAF in polylactide, X RA , depends on the conditions of crystallization and can vary from 0% to 35% [30]. Although this approach may look simplistic since it limits the description of the amorphous phase to its structure without considering its dynamics, the studies of Guinault et al [14], Drieskens et al [13], and Delpouve et al [11] proposed that an important amount of RAF is prejudicial for the barrier properties of PLA. The content of the RAF can be calculated after…”

Isothermal crystallization and structural characterization of poly(ethylene-2,5-furanoate)

“…The presence of this relatively stiff phase has an impact on material properties. For example, some previous studies showed that the rigid amorphous phase resulted especially in an increase of the elastic modulus [36e38] and had a strong influence on the barrier properties [39,40].…”

Structural Dependence of the Molecular Mobility in the Amorphous Fractions of Polylactide

“…11 The average interchain distance in the mesomorphic form is substantially reduced with regard to the most probable spacing of the amorphous chains. 10 The weight fraction of each phase has been calculated from the intensity profiles 6 and from the average heat flow curves (shown in a previous paper 21 ) obtained by means of TMDSC. Both techniques lead to similar results; TMDSC results are presented in Table 1.…”