Confinement effect in PC/MXD6 multilayer films: Impact of the microlayered structure on water and gas barrier properties

Abstract

A B S T R A C TFilms of PC and MXD6 were prepared via multilayer coextrusion. Films presenting stretched nodules/lamellas of MXD6 in the PC matrix, and films with quasi-continuous thin MXD6 layers alternating with PC layers were obtained.The transport properties were specifically investigated from water and gas permeation kinetics, and the corresponding permeation parameters were determined. The confinement effect of MXD6 in the multilayer structure was highlighted by comparing the permeability predicted from the series model equation with the experimental data. Although the MXD6 layers were not homogeneous and continuous for all membranes, water and gas permeabilities of the PC/MXD6 multilayer film were largely reduced. Such improvement of barrier properties was related to the change of the MXD6 structure, considering that the confinement of the MXD6 layers induced by PC layers allowed to bring chain orientation and to reduce the chain segment mobility in the MXD6 amorphous constrained zones. In addition, in the case of a PC/MXD6 multilayer structure well defined with continuous layers and relatively homogeneous thicknesses, the degree of crystallinity was slightly increased.

Multilayer packaging: Advances in preparation techniques and emerging food applications

“…A typical coextrusion process involves two or more polymeric materials usually in the form of granules or pellets being subjected to heat treatment and being molten separately (Ajitha et al., 2016). The polymeric melt streams are then combined together and extruded as a single unit with multiple layers (Messin et al., 2017) (Figure 2). Common methods employed in extruding multilayer films include cast extrusion/flat die extrusion, blow extrusion, and sheet extrusion (Neuman, Konieczny, & Garty, 2018).…”

“… Schematic representation of coextrusion process for multilayer film preparation (Source: Messin et al., 2017) …”

“…This can be increased even up to a thousand layers at a microscale thickness by employing microlayer coextrusion. The system utilizes a merging approach of processing in which two to five layered feed blocks are followed by sequential layer multiplication dies (Messin et al., 2017). Each of these multiplication dies double the layers by cutting/tearing, spreading, and stacking the layered melt stream.…”

Impact of water and thermal induced crystallizations in a PC/MXD6 multilayer film on barrier properties

“…In a previous paper on the elaboration of a polycarbonate (PC)/poly (m-xylene adipamide) (MXD6) multilayer film [13], an improvement of the MXD6 barrier performances was obtained due to a confinement effect induced by the PC under multilayer form. Even if the degree of crystallinity of MXD6 was close to only 8%, the barrier properties of the MXD6 were improved by a factor of 60% in the case of nitrogen and oxygen and 13% in the case of water as permeant molecules.…”

“…Therefore, two types of crystallization treatments have been applied on the PC/ MXD6 multilayer film. The first crystallization treatment consists in heating the multilayer film at the crystallization temperature of the MXD6 and the second one in immersing the sample into liquid water as MXD6 is able to crystallize in contact with water [13]. It has already been demonstrated that the water sorption into MXD6 produced a glassto-rubber transition, which facilitated the crystallization of the polyamide thanks to the rearrangement of the polymer chains [15].…”