Laura Genovese

Gas permeability, mechanical behaviour and compostability of fully-aliphatic bio-based multiblock poly(ester urethane)s

A family of poly(ester urethane)s obtained by chain extending hydroxyl-terminated polyester prepolymers has been studied. Poly(butylene cyclohexanedicarboxylate) has been coupled in different mass ratios with two poly(butylene succinate)-based random copolymers containing ether linkages. So, five high molecular weight bio-based poly(ester urethane)s have been designed. The effect of the chemical structure and of the mass ratio of the two blocks in the final polymer has been evaluated by characterizing the materials from a molecular, thermal and mechanical point of view. In addition, envisioning a food packaging application, biodegradation in compost and measurement of the gas barrier properties have been carried out and correlated to the polymer chemical structure. The activation energy of the gas permeation process has been calculated, too. The results highlight that through the adopted strategy it is possible to prepare a new class of promising materials whose properties can be easily tailored by acting on two parameters: the mass ratio between the two prepolymers in the final material and the chemical structure of each block.

Poly(Neopentyl Glycol Furanoate): A Member of the Furan-Based Polyester Family with Smart Barrier Performances for Sustainable Food Packaging Applications

In the last decade, there has been an increased interest from the food packaging industry toward the development and application of bioplastics, to contribute to the sustainable economy and to reduce the huge environmental problem afflicting the planet. In the present work, we focus on a new furan-based polyester, poly(neopentyl glycol 2,5-furanoate) (PNF) to be used for sustainable food packaging applications. The aromatic polyester was successfully synthesized with high molecular weight, through a solvent-free process, starting directly from 2,5-furandicarboxylic acid. PNF was revealed to be a material with good thermal stability, characterized by a higher Tg and Tm and a lower RAF fraction compared to poly(propylene 2,5-furanoate) (PPF), ascribable to the two methyl side groups present in PNF glycol-sub-unit. PNF’s mechanical characteristics, i.e., very high elastic modulus and brittle fracture, were found to be similar to those of PPF and PEF. Barrier properties to different gases, temperatures and relative humidity were evaluated. From the results obtained, PNF was showed to be a material with very smart barrier performances, significantly superior with respect to PEF’s ones. Lastly, PNF’s permeability behavior did not appreciably change after contact with food simulants, whereas it got worse with increasing RH, due to the polar nature of furan ring.

Barrier Properties of Poly(Propylene Cyclohexanedicarboxylate) Random Eco-Friendly Copolyesters

Random copolymers of poly(propylene 1,4-cyclohexanedicarboxylate) containing different amounts of neopentyl glycol sub-unit were investigated from the gas barrier point of view at the standard temperature of analysis (23 °C) with respect to the three main gases used in food packaging field: N2, O2, and CO2. The effect of temperature was also evaluated, considering two temperatures close to the Tg sample (8 and 15 °C) and two above Tg (30 and 38 °C). Barrier performances were checked after food contact simulants and in different relative humidity (RH) environments obtained with two saturated saline solutions (Standard Atmosphere, 23 °C, 85% of RH, with saturated KCl solution; Tropical Climate, 38 °C, 90% RH, with saturated KNO3 solution). The results obtained were compared to those of untreated film, which was used as a reference. The relationships between the gas transmission rate, the diffusion coefficients, the solubility, and the copolymer composition were established. The results highlighted a correlation between barrier performance and copolymer composition and the applied treatment. In particular, copolymerization did not cause a worsening of the barrier properties, whereas the different treatments differently influenced the gas barrier behavior, depending on the chemical polymer structure. After treatment, Fourier transform infrared analysis confirmed the chemical stability of these copolymers. Films were transparent, with a light yellowish color, slightly more intense after all treatments.

Gas Barrier and Thermal Behavior of Long Chain Aliphatic Polyesters after Stressed Treatments

ABSTRACT Poly(hexane dodecanoate)-based random copolyesters containing ether linkages have been subjected to contact with food simulant liquids and thermal and photoageing. Gas permeability, thermal and mechanical properties have been analyzed after each treatment, and the results obtained have been compared with low-density polyethylene films. The results showed that the gas barrier behavior was highly influenced by the polymer chemical composition. The contact with simulant liquids and the ageing treatments induced an increase in the crystallinity degree, together with a decrease in the molecular weight. This caused an increment of the elastic modulus and a decrement of the elongation at break. GRAPHICAL ABSTRACT

How stress treatments influence the performance of biodegradable poly(butylene succinate)-based copolymers with thioether linkages for food packaging applications

Biodegradable poly(butylene succinate) (PBS)-based random copolymers containing thioether linkages (P(BSxTDGSy)) of various compositions have been investigated and characterized from the gas barrier, thermal, and mechanical point of view, after food contact simulants or thermal and photoaging processes. Each stress treatment was performed on thin films and the results obtained have been compared to the same untreated film, used as a standard. Barrier properties with different gases (O2 and CO2) were evaluated, showing that the polymer chemical composition strongly influenced the permeability behavior. The relationships between the diffusion coefficients (D) and solubility (S) with polymer composition were also investigated. The results highlighted a correlation between polymer chemical structure and treatment. Gas transmission rate (GTR) mainly depending on the performed treatment, as GTR increased with the increase of TDGS co-unit amount. Thermal and mechanical tests allowed for the recording of variations in the degree of crystallinity and in the tensile properties. An increase in the crystallinity degree was recorded after contact with simulant liquids and aging treatments, together with a molecular weight decrease, a slight enhancement of the elastic modulus and a decrement of the elongation at break, proportional to the TDGS co-unit content.