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Poly(glycolic acid) (PGA) is derived from glycolide obtained by fermenting pineapples or sugarcane, which has excellent gas barrier properties and a small carbon footprint. PGA is a potential substitute for the current aluminum-plastic composite films used in high barrier packaging applications. However, its poor ductility and narrow processing window limit its application in food packaging. Herein, poly(butylene succinate-co-butylene adipate) (PBSA) was used to fabricate PGA/PBSA blend films through an in situ fibrillation technique and blown film extrusion. Under the elongational flow field used during the extrusion process, a unique hierarchical structure based on the PBSA nanofibrils and interfacially oriented PGA crystals was obtained. This structure enhances the strength, ductility and gas barrier properties of the PGA/PBSA blend film. In addition, an epoxy chain extender (ADR4468) was used as a compatibilizer to further enhance the interfacial adhesion between PGA and PBSA. 70PGA/0.7ADR exhibited a very low oxygen permeability (2.34×10−4 Barrer) with significantly high elongating at break (604.4%), tensile strength (47.4 MPa), and transparency, which were superior to those of petroleum-based polymers. Thus, the 70PGA/0.7ADR blown films could satisfy the requirements for most instant foods such as coffee, peanuts, and fresh meat. [ABSTRACT FROM AUTHOR]

Used poly(lactic acid) (PLA) films as the research object, the degradation kinetics equation was established through the degradation experiments of samples in artificial seawater at 60, 70, 80 and 90 °C, and then the degradation performances of PLA films in artificial seawater at 90 °C were explored. The surface morphology, chemical structure and thermal properties of PLA films after degradation in artificial seawater at 90 °C were studied by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, gel permeation chromatography, differential scanning calorimetry and nuclear magnetic resonance spectroscopy, and the composition of degradation products was also analyzed. The results showed that the degradation of PLA films in artificial seawater conformed to the first-order reaction characteristics. The half-life period of degradation is 12 or 468 days under 90 or 60 °C. With the increase in degradation time, the surface of PLA films became roughness, the characteristic functional groups of the solid degradation products were basically unchanged, the crystallinity increased first and then decreased, while the relative molecular weight and Tm decreased gradually. The oxygen content of the surface of the material and lactic acid content in the degradation filtrate increased gradually. The degradation kinetics of poly(lactic acid) (PLA) films in artificial seawater was studied. The results showed that the degradation of PLA films in artificial seawater conformed to the first-order reaction characteristics, which provides theoretical guidance for the practical application of polylactic acid-based materials in the marine environment. [ABSTRACT FROM AUTHOR]

In this work, hydroxyl-terminated oxalamide compounds N1,N2-bis(2-hydroxyethyl)oxalamide (OXA1) and N1, N1′-(ethane-1,2-diyl)bis(N2-(2-hydroxyethyl)oxalamide (OXA2) were synthesized to initiate the ring-opening polymerization of L-lactide for preparation of oxalamide-hybridized poly(L-lactide) (PLAOXA), i.e., PLAOXA1 and PLAOXA2. The crystallization properties of PLA were improved by the self-assembly of the oxalamide segments in PLAOXA which served as the initial heterogeneous nuclei. The crystal growth kinetics was studied by Hoffman-Lauritzen theory and it revealed that the nucleation energy barrier of PLAOXA1 and PLAOXA2 was lower than that of PLA. Consequently, PLAOXA could crystallize much faster than PLA, accompanied with a decrease in spherulite size and half-life crystallization time by 74.8% and 86.5% (T = 125 °C), respectively. In addition, the final crystallinity of PLAOXA1 and PLAOXA2 was 6 and 8 times higher, respectively, in comparison with that of neat PLA under a controlled cooling rate of 10 °C/min. The results demonstrate that the hybridization of oxalamide segments in PLA backbone will serve as the self-heteronucleation for promoting the crystallization rate. The higher the content of oxalamide segments (PLAOXA2 compared with PLAOXA1) is, the stronger the promotion effect will be. Therefore, this study may provide a universal approach by hybridizing macromolecular structure to facilitate the crystallization of semi-crystalline polymer materials. [ABSTRACT FROM AUTHOR]

In this study, an eco-friendly superhydrophobic cotton fabric (CF) with water contact angle of 155° was fabricated via a facile two-step approach: imparting surface roughness through hydrothermal growth of ZnO particles, and using stearic acid to create a low-energy surface. ZnO prepared by hydrothermal reaction was in a rod-like shape and had nano- or micro-scale sizes. It was located on the surface in loose aggregates. After modification with stearic acid, the aggregate structure of ZnO particles was changed from loose packing to compact packing. The superhydrophobic CF could be wetted by oil but could not be wetted by water, showing excellent oil/water separation performance. The superhydrophobic CF was able to absorb oils selectively from their mixtures with water and could be used as a filtering membrane to separate oil/water mixtures directly with separation efficiency and oil flux of 96–99% and 2000–9000 L m−2 h−1, respectively, depending on the intrinsic property of the oils. In addition, the superhydrophobic CF showed excellent mechanical robustness and environmental durability with water contact angle almost remaining unchanged after exposure to sandpaper abrasion, ultrasonication, boiling water treatment and organic solvents erosion. With excellent robustness and durability, the superhydrophobic CF exhibits great potential in oil/water separation even under some harsh conditions. [ABSTRACT FROM AUTHOR]

Different proportions of polyamidoamine (PAMAM) dendrimer were blended with poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) resin in chloroform for film casting. Differential scanning calorimetry and scanning electron microscopy were employed to characterize the PHBV/PAMAM composite films upon stretching and tangential breaking. The results indicated that with the addition of PAMAM dendrimer, the glass transition temperature of the PHBV/PAMAM composite films became more distinct, indicating that the blends had a greater toughness than pure PHBV. The calculated crystallinity values indicated that the crystallinity of the PHBV/PAMAM blends was lower than that of PHBV (0.09-56.18 % vs. 73.18 %, respectively). Moreover, the mechanical performance tests indicated that the addition of PAMAM dendrimer considerably increased the tangential breaking strength of PHBV from 24.08 kN/m to as high as 62.03 kN/m, whereas the tensile strength remained basically unchanged. The optimal toughening effect was observed with a PAMAM dendrimer content of 3.0 phr. [ABSTRACT FROM AUTHOR]

In order to understand the relationship between enzymatic degradation and the structure of PBS-based copolyesters PBS-co-DEGS and PBS-co-BDGA modified with monomers (diethylene glycol and diglycolic acid) were synthesized and the enzymatic degradation property was studied. Pseudomonas cepacia lipase was selected as the catalyst, while the chloroform was used as solvent. The results indicated that both PBS-co-DEGS and PBS-co-BDGA can be catalytically degraded by PC lipase but they were different. The hydrolysis of PBS-co-BDGA improved greatly and the degree of hydrolysis of PBS-co-BDGA was almost consistent with the degree of degradation due to the introduction of DGA. Similarly, thermal property changes were also observed with a decrease of the decomposition temperature of 5 and 50% sample in most cases. The enzymatic degradation of PBS-based copolymers produced not only linear segments, but also cyclic oligomers. Furthermore, PBS-co-BDGA generated more oligomers than PBS-co-DEGS. According to the results of molecular docking, the free energy of binding between PCL and the substrate in chloroform was in the order BDGAB > DEGSDEG > BSB. That is, the docking of the substrate containing BDGA in the active site of PCL was more stable than any other ones. [ABSTRACT FROM AUTHOR]