MXD6 in film manufacturing: State of the art and recent advances in the synthesis and characterization of new copolyamides

Semiaromatic polyamides belong to a large family of polymers commonly utilized in demanding engineering applications due to a unique set of outstanding mechanical properties as well as in terms of thermal and chemical resistance. Somewhat less understood is the use of certain members of this family in packaging applications such as the manufacturing of films and sheets or thin-walled containers, as well as the motivations and limitations in designing film structures containing them. This article reviews how m-xylylene diamine (MXD)-based polyamides are used in packaging applications. Attention is also given to film manufacturing and criticalities in its processing. Recent developments in MXD-based polyamides for gas barrier applications are also reported, while examining future perspectives in speciality film manufacturing. The new described copolymers based on MXD6 were synthesized by introducing different co-units, like isophthalic acid, 2,6-naphthalenedicarboxylic acid, glutaric acid, oxalic acid or 1,6-hexamethylene diamine. The performed characterization analyses (DMTA, DSC, density and OTR) allowed the polymer structures and properties to be correlated. Introducing 2,6-naphthalenedicarboxylic acid along the MXD6 chain led to the highest Tg (101°C) and density (1.233 g/cm 3 ) and the lowest OTR (0.0035 cm 3 ·cm/m 2 ·day·atm, up to one order of magnitude lower).