197 research outputs found
Effect of surfactant alkyl chain length on the dispersion, and thermal and dynamic mechanical properties of LDPE/organo-LDH composites
Low density polyethylene/layered double hydroxide (LDH) composites were prepared via melt compounding using different kinds of organo-LDHs and polyethylene-grafted maleic anhydride as the compatibilizer. The organo-LDHs were successfully prepared by converting a commercial MgAl-carbonate LDH into a MgAl-nitrate LDH, which was later modified by anion exchange with linear and branched sodium alkyl sulfates having different alkyl chain lengths (nc = 6, 12 and 20). It was observed that, depending on the size of the surfactant alkyl chain, different degrees of polymer chain inter- calation were achieved, which is a function of the interlayer distance of the organo-LDHs, of the packing level of the alkyl chains, and of the different interaction levels between the surfactant and the polymer chains. In particular, when the number of carbon atoms of the surfactant alkyl chain is larger than 12, the intercalation of polymer chains in the interlayer space and depression of the formation of large aggregates of organo-LDH platelets are favored. A remarkable improvement of the thermal-oxidative degradation was evidenced for all of the composites; whereas only a slight increase of the crystallization temperature and no significant changes of both melting temperature and degree of crystallinity were achieved. By thermo- dynamic mechanical analysis, it was evidenced that a softening of the matrix is may be due to the plasticizing effect of the surfactant
Antioxidant and UV-Blocking Functionalized Poly(Butylene Succinate) Films
The introduction of a limited number of functional groups on poly(butylene succinate) (PBS) chains by covalent bonding can impart new properties to the polymer without modifying its thermal and mechanical properties. In pursuit of a viable approach to obtain light- and heat-stabilized PBS samples, the nitroxide radical coupling (NRC) reaction between PBS macroradicals and the 3,5-di-tert-butyl-4-hydroxybenzoyl-2,2,6,6-tetramethylpiperidine-1-oxyl radical (BHB-TEMPO), a functionalizing agent bearing a sterically-hindered antioxidant phenol moiety, is here proposed. The reaction was initiated by peroxide and carried out in solution and in a melt. The functionalized materials were characterized by UV-visible spectroscopy (UV-Vis), proton nuclear magnetic resonance (1H-NMR), and size exclusion chromatography (SEC) analysis to gain structural information and by thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) to investigate the thermal properties. In addition, films of the samples were subjected to thermal and photo-oxidative aging to assess their resistance to degradative processes. Finally, the PBS film with the highest degree of functionalization showed the ability to protect β-carotene, a molecule found in food and drugs and that is very sensitive to UV light, from degradation. This result suggests the use of this material (either alone or blended with other biopolyesters) for biodegradable and compostable active packaging
Binary green blends of poly(Lactic acid) with poly(butylene adipate-co-butylene terephthalate) and poly(butylene succinate-co-butylene adipate) and their nanocomposites
Poly(lactic acid) (PLA) is the most widely produced biobased, biodegradable and biocompatible polyester. Despite many of its properties are similar to those of common petroleum-based polymers, some drawbacks limit its utilization, especially high brittleness and low toughness. To overcome these problems and improve the ductility and the impact resistance, PLA is often blended with other biobased and biodegradable polymers. For this purpose, poly(butylene adipate-co-butylene terephthalate) (PBAT) and poly(butylene succinate-co-butylene adipate) (PBSA) are very advantageous copolymers, because their toughness and elongation at break are complementary to those of PLA. Similar to PLA, both these copolymers are biodegradable and can be produced from annual renewable resources. This literature review aims to collect results on the mechanical, thermal and morphological properties of PLA/PBAT and PLA/PBSA blends, as binary blends with and without addition of coupling agents. The effect of different compatibilizers on the PLA/PBAT and PLA/PBSA blends properties is here elucidated, to highlight how the PLA toughness and ductility can be improved and tuned by using appropriate additives. In addition, the incorporation of solid nanoparticles to the PLA/PBAT and PLA/PBSA blends is discussed in detail, to demonstrate how the nanofillers can act as morphology stabilizers, and so improve the properties of these PLA-based formulations, especially mechanical performance, thermal stability and gas/vapor barrier properties. Key points about the biodegradation of the blends and the nanocomposites are presented, together with current applications of these novel green materials
A Perspective on Recent Advances in Phosphorene Functionalization and its Application in Devices
Phosphorene, the 2D material derived from black phosphorus, has recently
attracted a lot of interest for its properties, suitable for applications in
material science. In particular, the physical features and the prominent
chemical reactivity on its surface render this nanolayered substrate
particularly promising for electrical and optoelectronic applications. In
addition, being a new potential ligand for metals, it opens the way for a new
role of the inorganic chemistry in the 2D world, with special reference to the
field of catalysis. The aim of this review is to summarize the state of the art
in this subject and to present our most recent results in preparation,
functionalization and use of phosphorene and its decorated derivatives. In
particular, we discuss several key points, which are currently under
investigation: the synthesis, the characterization by theoretical calculations,
the high pressure behaviour of black phosphorus, as well as decoration with
nanoparticles and encapsulation in polymers. Finally, device fabrication and
electrical transport measurements are overviewed on the basis of recent
literature and new results collected in our laboratories
Thermo-oxidative stabilization of poly(lactic acid) with antioxidant intercalated layered double hydroxides
Two antioxidant modified layered double hydroxides (AO-LDHs) were successfully prepared by theintercalation of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid (IrganoxCOOH) and 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox) in the layered structure of LDH. It was foundthat by anchoring the phenolic moieties to the LDH layers the antioxidant power is retained in the caseof Trolox, and even amplified in the case of IrganoxCOOH. A small amount of the two AO-LDHs wasincorporated into poly(lactic acid), PLA, by solution mixing and melt extrusion. The thermo-oxidativestability of the composites was compared with that of the neat PLA and PLA containing free AOs. SECanalysis indicates that, after a controlled period of ageing, both the AO-LDHs protect the PLA fromchain scission. The oxidation induction time (OIT, DSC) at 230 °C shows also the beneficial effects ofthe presence of the functional filler in the polymer matrix. Further, results from a preliminary migrationtest suggest that the AO species have a low tendency to migrate away from the AO-LDHs embedded inthe polymer matrix thus keeping the AO protected inside the nanofiller layers thereby remaining activefor a longer time
Polymer-based black phosphorus (bP) hybrid materials by in situ radical polymerization: an effective tool to exfoliate bP and stabilize bP nanoflakes
Black phosphorus (bP) has been recently investigated for next generation
nanoelectronic multifunctional devices. However, the intrinsic instability of
exfoliated bP (the bP nanoflakes) towards both moisture and air has so far
overshadowed its practical implementation. In order to contribute to fill this
gap, we report here the preparation of new hybrid polymer-based materials where
bP nanoflakes exhibit a significantly improved stability. The new materials
have been prepared by different synthetic paths including: i) the mixing of
conventionally liquid-phase exfoliated bP (in DMSO) with PMMA solution; ii) the
direct exfoliation of bP in a polymeric solution; iii) the in situ radical
polymerization after exfoliating bP in the liquid monomer (methyl methacrylate,
MMA). This last methodology concerns the preparation of stable suspensions of
bPn-MMA by sonication-assisted liquid phase exfoliation (LPE) of bP in the
presence of MMA followed by radical polymerization. The hybrids characteristics
have been compared in order to evaluate the bP dispersion and the effectiveness
of the bPn interfacial interactions with polymer chains aimed at their
long-term environmental stabilization. The passivation of bPn results
particularly effective when the hybrid material is prepared by in situ
polymerization. By using this synthetic methodology, the nanoflakes, even if
with a gradient of dispersion (size of aggregates), preserve their chemical
structure from oxidation (as proved by both Raman and 31P-Solid State NMR
studies) and are particularly stable to air and UV light exposure
Study of the compounding process parameters for morphology control of LDPE/layered silicate nanocomposites
AbstractA careful insight into melt compounding procedure is proposed in order to achieve a better understanding and control of the dispersion and orientation mechanisms of organo-clay platelets into LDPE nanocomposites. The method involved is the preparation of a maleic anhydride grafted polyethylene masterbatch containing 10 wt% organo-clay via twin-screw extrusion. A substantial nanodispersion and orientation of clay platelets was obtained as observed by X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses. Moreover, the nanocomposites prepared by diluting the master-batch through the blend mixing with additional LDPE preserved or improved the exfoliation and lamellae orientation. Finally, the thermo-gravimetric analysis (TGA) showed a significant improvement of the thermal stability while both differential scanning calorimetry (DSC) and XRD evidenced a slight increase of the LDPE crystallinity degree with respect to neat polymer matrices thus suggesting the occurrence of orientation also for the polymer
Zinc layered hydroxide salts: intercalation and incorporation into low-density polyethylene
Binary Green Blends of Poly(lactic acid) with Poly(butylene adipate-co-butylene terephthalate) and Poly(butylene succinate-co-butylene adipate) and Their Nanocomposites
Poly(lactic acid) (PLA) is the most widely produced biobased, biodegradable and biocompatible polyester. Despite many of its properties are similar to those of common petroleum-based polymers, some drawbacks limit its utilization, especially high brittleness and low toughness. To overcome these problems and improve the ductility and the impact resistance, PLA is often blended with other biobased and biodegradable polymers. For this purpose, poly(butylene adipate-co-butylene terephthalate) (PBAT) and poly(butylene succinate-co-butylene adipate) (PBSA) are very advantageous copolymers, because their toughness and elongation at break are complementary to those of PLA. Similar to PLA, both these copolymers are biodegradable and can be produced from annual renewable resources. This literature review aims to collect results on the mechanical, thermal and morphological properties of PLA/PBAT and PLA/PBSA blends, as binary blends with and without addition of coupling agents. The effect of different compatibilizers on the PLA/PBAT and PLA/PBSA blends properties is here elucidated, to highlight how the PLA toughness and ductility can be improved and tuned by using appropriate additives. In addition, the incorporation of solid nanoparticles to the PLA/PBAT and PLA/PBSA blends is discussed in detail, to demonstrate how the nanofillers can act as morphology stabilizers, and so improve the properties of these PLA-based formulations, especially mechanical performance, thermal stability and gas/vapor barrier properties. Key points about the biodegradation of the blends and the nanocomposites are presented, together with current applications of these novel green materials
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