Fully AliphaticCopolyesters Based on Poly(butylene1,4-cyclohexanedicarboxylate) with Promising Mechanical and BarrierProperties for Food Packaging Applications.

Poly(butylenecyclohexanedicarboxylate/diglycolate) random copolymers(P(BCEmBDGn)) of various compositionswere synthesized and characterized from the molecular, thermal, structural,and mechanical point of view. Barrier properties to different gases(oxygen and carbon dioxide) were also evaluated. All the polymersshowed good thermal stability and appeared as semicrystalline materialsat room temperature. The main effect of copolymerization was a loweringin the crystallinity and a decrease of Tmwith respect to homopolymers. The dependence of Tmon composition for copolymers with high butylene cyclohexanedicarboxylateunit content was well described by Baur’s equation. X-ray diffraction(XRD) measurements indicated that two different crystalline phasesare present, depending on composition: copolymers with high BCE unitcontent were characterized by PBCE crystal phase, whereas those richin BDG counits crystallized in PBDG lattice. The samples displayeddifferent surface hydrophilicity: the water contact angle regularlydecreased with the increasing mol % of BDG. The mechanical propertieswere found strictly related to crystallinity degree (χc); the copolymers containing 60–75 mol % of BDG showed thelowest elastic modulus and the highest elongation at break. Lastly,the chemical composition of the copolymer strongly influenced permeabilityto CO2and O2. Moreover, the selectivity ratiosfor the examined samples increased with the increasing of BDG mol%, confirming the existence of a correlation between the permeabilityand the chemical composition. Almost all copolymers showed improvedbarrier properties with respect to polylactide films tested underthe same conditions. [ABSTRACT FROM AUTHOR]