The effects of the crystallinity and polymorphism of PLLA and PDLA–PLLA 50:50 blends on the free volume and transport properties have been studied. In the case of PDLA–PLLA 50:50 the increase on crystallinity promotes a process of densification and a reduction in free volume fraction and rigid amorphous fraction (RAF), contrary to PLLA in which the enlargement of a rigid amorphous fraction led to a dedensification. This result offers a unique opportunity to analyze separately the opposite influence in the transport properties of the crystallization and free volume associated with RAF. Overall, these findings provide a better understanding on the relationship between crystallinity and transport properties and would explain also the controversial data reported in the literature.

The effectiveness of tributyl citrate (TbC) as a plasticizer for polylactide and polyhydroxybutyrate was analysed in order to improve the ductility of these polymers and make them good candidates for food packaging applications. Although the thermal and mechanical properties have been widely studied in the literature, the effect of the plasticizer on free volume and transport properties has not been deeply analysed. The free volume was characterized using positron annihilation lifetime spectroscopy observing its linear increase with TbC content. The permeability to water vapour, oxygen and carbon dioxide was determined and the obtained results were related to the changes in glass transition temperature, level of crystallinity of the samples and free volume. This work would allow a better understanding of the effect of the plasticizer on the barrier and mechanical properties of polymers allowing the development of competitive materials for packaging applications. © 2018 Society of Chemical Industry

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In order to make poly(lactide) (PLA) suitable for food packaging applications, its toughness must be improved. In this work, the plasticization effectiveness of a low-molecular-weight plasticizer and a triblock copolymer are analyzed. For this purpose, PLA is blended with poly(ethylene glycol) (PEG) and poly(lactide-ethylene glycol-lactide) (LA-EG-LA) triblock copolymer. The obtained results show that copolymers are more effective, reducing the glass transition temperature of PLA. Although PLA/PEG blends have been widely studied in the literature, the barrier character has not been analyzed, which is of paramount importance for packaging applications. Therefore, the permeability to carbon dioxide, oxygen, and water vapor of PLA/PEG blends has been characterized observing an increase with the incorporation of PEG, which is the expected behavior. However, the incorporation of LA-EG-LA copolymers leads to permeability values that are slightly higher, similar, or even lower than PLA. Furthermore, the free volume of the samples has been analyzed in order to gain a deeper insight on the factors affecting the transport properties. Overall, this works aims to provide a better understanding towards the design of biodegradable packaging with improved properties that could be also extended to other biodegradable polymers.PLA blends containing PEG have been widely analyzed in the literature. [9][10][11][12][13][14][15] Younes and Cohn 9 studied PLA blends containing PEG of different molecular weights (1500-35 000 g/mol range) at different composition observing a microphase separation. Hu et al. observed that PLA containing more than 15% PEG were not stable over time and phase separation occurs forming PLA rich and PEG rich domains. [10][11][12] The phase separation of PLA and PEG has been Additional Supporting Information may be found in the online version of this article.

The improvement of the barrier character of polylactide by the addition of poly(hydroxy ether) of bisphenol A (Phenoxy) and poly(lactide-co-E-caprolactone) copolymer that acts as a compatibilizer is studied. First, differential scanning calorimetry, Fourier transformed infrared spectroscopy, and scanning electron microscopy show that the addition of the copolymer allows to obtain a miscible ternary system. The permeability of polylactide to water vapor, oxygen, and carbon dioxide is enhanced with the addition of phenoxy but better improvement in its barrier character is obtained with the addition of the compatibilizer. The effects of different factors such as miscibility, glass transition temperature, and crystallinity on the transport properties are analyzed. Several permeability prediction models for heterogeneous systems have been applied obtaining quite good results for water vapor and oxygen permeability.

Summary: The addition of Phenoxy to Polylactide causes a decrease of the permeability coefficients proportional to the amount of Phenoxy, even in spite of the lack of miscibility between both polymers. The effect of a Poly(caprolactone-blactide) multiblock copolymer as a compatibilizer of a Poly(lactide)/Phenoxy blend was analyzed, [1] achieving miscibility and providing an improvement in the barrier properties of the blend.

Gaur egun plastikoen hondakinek sortarazten duten arazoari aurre egiteko aukera bat polimero biodegradagarriak erabiltzea da. Hauen artean polilaktidak interes handia piztu du baina elikagaien ontziratzean erabilgarria izan dadin bere deformakortasuna hobetu egin behar da. Helburu horrekin lan honetan polilaktidari polietilenglikol plastifikatzailea gehitu zaio. Zehazki hiru polietilenglikol desberdin erabili dira eta pisu molekularrak propietate fisikoetan daukan eragina aztertu da. Plastifikatzailea gehitutakoan beira-trantsizio tenperatura jaitsi egiten da, bereziki pisu molekular altuena duen polietilenglikola gehitutakoan, eta kristalinitate-maila handiagoa egiten da. Bolumen askean aldaketak txikiak badira ere, plastifikatzaile kantitatea handitu ahala, bolumen askea nabarmen handiagoa egiten da. Hesi ezaugarriei dagokienez, oxigenoaren kasuan iragazkortasuna murriztu edo bere horretan mantentzen da; karbono dioxidoaren eta uraren kasuan ordea, iragazkortasuna handiagoa egiten da plastifikatzaile kopuruarekin. Aipatzekoa da plastifikatzaile nahaste desberdinen artean pisu molekular baxueneko plastifikatzailea duen sistemak azaltzen dituela iragazkortasun balio altuenak. PEG 1500 eta PEG 4600 sistemen kasuan aldaketak ez dira hain nabariak eta pisu molekularraz gain beste faktore batzuek, hala nola, beira-trantsizio tenperatura, kristalinitate-maila eta bolumen askeak, ere eragina daukate.