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This paper aims to investigate the optimal formulation of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx)/ZnO bionanocomposites for food packaging applications with respect to filler content ratio. Bionanocomposite samples prepared by melt-compounding at various ZnO-NPs contents (1.5, 3, and 6 wt%) were evaluated in terms of optical, thermal, viscoelastic, and mechanical properties. UV–Vis spectroscopy revealed a significant enhancement in the photochemical stability of PHBHHx/ZnO bionanocomposites compared with neat PHBHHx, which exhibits a strong absorption band at wavelengths below 380 nm, thus confirming the anti-UV activity of ZnO nanoparticles. Thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA) demonstrated improved thermal stability and increased stiffness/mechanical strength with increasing ZnO-NPs content. Notably, the bionanocomposite with 3 wt% of ZnO exhibited the most substantial improvements, with a 20% increase in thermal decomposition temperature and a 30% increase in storage's modulus at room temperature than the neat PHBHHx. Moreover, a decrease in loss modulus (E″) and tanδ indicated reduced energy dissipation and enhanced material elasticity. Overall, incorporating 3 wt% ZnO nanoparticles into PHBHHx resulted in a bionanocomposite with superior photochemical stability, thermal stability, and viscoelastic properties compared to both neat PHBHHx and other bionanocomposite samples, which makes it as a promising candidate for food packaging applications. [ABSTRACT FROM AUTHOR]

The effects of thermo-mechanical recycling through repeated extrusion cycles on morphology and properties of neat ethylene vinyl acetate copolymer (EVA) and EVA/olive husk flour (OHF) composites (70/30 w/w) with and without ethylene–butyl acrylate–glycidyl methacrylate (EBAGMA) compatibilizer were investigated in a single screw extruder machine up to five repeated cycles. The study showed that no significant modifications in the properties of the virgin EVA/OHF composite were observed along the recycling and this stability was further enhanced in the presence of EBAGMA. Indeed after five repeated extrusion cycles, the chemical structure and properties of both uncompatibilized and compatibilized composites remained unchanged compared to the neat polymer, which was subjected likely to cross-linking, in the fifth cycle. Furthermore, SEM analysis showed a better dispersion of OHF particles in EVA matrix and a good filler–polymer interfacial adhesion, being, however, more pronounced for the compatibilized composite. [ABSTRACT FROM AUTHOR]

The hydrothermal degradation at 90°C in distilled water of metallocene linear low density polyethylene films (mLLDPE) has been studied using low density polyethylene (LDPE) for comparison. FTIR spectroscopy, DSC and chemiluminescence techniques were used for investigation of the hydrothermal ageing-induced changes. The stabilization effect of a commercially available HALS, namely Sanduvor PR 31, able to graft on polyolefin structures has been also studied, as well. It was found that intense oxidation process occurs in the case of LDPE: hydroxyl, carbonyl and unsaturated groups were identified in FTIR spectra. mLLDPE reference films presented considerably higher stability as compared to LDPE ones, this behaviour being assigned to the structural peculiarities. Sanduvor PR 31 induced higher stability in LDPE, possibly by grafting mechanism, but it did not present a significant effect in the case of mLLDPE. Besides a possible antagonist interaction with the process stabilizer or a graft-hindering effect of the alkyl side groups, the intrinsic higher stability of the mLLDPE which offers less active sites for grafting could be supposed to explain this lower effectiveness. [ABSTRACT FROM AUTHOR]

The effects of recycling cycles (up to six repeated cycles) on the structure and properties of neat poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), neat polylactide (PLA) and PHBV/PLA: 50/50 (wt%) blends elaborated by melt molding process were investigated. The changes in the chemical structure, the morphology and the thermal, mechanical and rheological properties of the recycled materials were studied. The reduction of molecular weights of both PHBV and PLA showed the predominance of chain scission mechanism as a result of degradation inducing an enhancement of PHBV chain mobility, as also revealed by the increasing of the PHBV crystallinity measured using differential scanning calorimetry and wide angle X-ray scattering. Nevertheless, all these effects were significantly smaller for neat PLA and PHBV-PLA blends compared to those of neat PHBV. Contrary to PLA, PHBV seems to be relatively more sensitive to the thermomechanical degradation and the presence of PLA in the PHBV-PLA blend tends to partially prevent the degradation of PHBV. Mechanical results evidenced the great recyclability of PHBV/PLA blends, even after six reprocessing cycles, since the values of mechanical characteristics remain more or less constant compared to the initial ones revealing the preservation of the material mechanical properties. A stabilizing effect of PLA on the recyclability of PHBV-PLA blends was highlighted and it can be concluded that the incorporation of PLA in PHBV/PLA blends might be a promising route to extend the PHBV applications. [ABSTRACT FROM AUTHOR]

Blends of poly(3-hydroxybutyrate- co-3-hydroxyvalerate) (PHBV) and polylactide (PLA) with different PHBV/PLA weight ratios (100/0, 75/25, 50/50, 25/75, 0/100) were prepared by melt compounding. Their mutual contributions in terms of thermal stability, flammability resistance, mechanical properties and rheological behavior were investigated. The study showed that the increase in PLA content in PHBV/PLA blends leads to enhanced properties. Consequently, thermal stability and flammability resistance were improved. Further, the rheological measurements indicated an increase in storage modulus and loss modulus of PHBV matrix by addition of PLA. [ABSTRACT FROM AUTHOR]

Fast scanning chip calorimetry (FSC) has been used for analysis of the crystallization behavior of a polyamide 11/organo-modified montmorillonite (PA 11/OMMT) nanocomposite. The addition of OMMT leads to a significant increase of the crystallization temperature of the polymer matrix only on cooling faster than about 10 K s. In case of slow cooling at rates typically used in standard differential scanning calorimetry (DSC), the nucleating effect of OMMT on crystallization of PA 11 is negligible. The critical cooling rate to suppress crystallization of PA 11 and to completely vitrify the relaxed melt increases at least by one order of magnitude due to the addition of OMMT. Furthermore, the enthalpy of crystallization is nearly independent on the cooling conditions in the analyzed cooling rate range from 10 to 2 × 10 K s in PA 11/OMMT nanocomposites. Isothermal crystallization experiments confirmed that the nucleating effect of OMMT on the crystallization of PA 11 increases with supercooling, being therefore of particular importance at cooling conditions relevant in polymer processing. The evaluation of the kinetics of crystallization of the PA 11/OMMT nanocomposite by FSC and DSC in a wide range of cooling rates/supercooling has been completed by analysis of the effect of OMMT on the α/δ' polymorphism of PA 11 and the spherulitic superstructure. [ABSTRACT FROM AUTHOR]

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