Ignazio Blanco

Effects of novel reactive toughening agent on thermal stability of epoxy resin

A reactive amino-ended toughener was blended with different commercial epoxy resins namely, diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, diglycidyl p-aminophenol and 1,5-naphthalenediamine as curing agent. The toughener was an aromatic amino-ended copolyethersulphone (coPES):poly(ether-sulphone)–poly(etherether-sulphone). The effect of the toughener on the thermal decomposition and char oxidation behaviour of the epoxy resins was studied by the simultaneous differential thermal analysis and thermogravimetric techniques. The glass transition temperature (Tg) as well as characteristic parameters of decomposition, initial decomposition temperature (Ti) and temperature at maximum degradation rate (Tm), in both inert and oxidative environments, were determined in order to verify the influence of toughener on the thermal degradation of the different epoxy systems. It was observed that the presence of coPES maintains the high level thermal stability of the resin and that the glass transition temperature increase with the toughener percentage.

Evaluation of the influence of various (ether, ketone and sulfone) groups on the apparent activation energy values of polymer degradation

Abstract The kinetics of degradation of four model polymers containing ether, carbonyl and sulfone groups was studied in both N 2 flow and static air atmosphere, with the aim of evaluating the influence of various groups on the apparent activation energy values ( E a ) of degradation. The initial temperatures of decomposition ( T i ) and the temperatures of half decomposition ( T 1/2 ), were also determined. The degradation of all polymers was carried out in the scanning mode and the Kissinger equation used to evaluate the E a values of the first degradation stage. The results allowed us to make a kinetic stability classification among various groups (sulfone>ketone>ether) which could be explained on the basis of the double-bond character of the polymer chain links. The E a values showed a trend analogous to the glass transition temperatures ( T g ), in agreement with literature reports. By contrast, the characteristic temperatures of decomposition showed a different trend which could not be interpreted on the basis of the experiments until now performed.

A Kinetic Study of the Thermal and Oxidative Degradations of a New Poly(arylene)ether Copolymer

The degradation of a new thermoplastic poly(arylene)ether copolymer was carried out in both dynamic and isothermal heating conditions, under nitrogen flow and in a static air atmosphere. The measurements showed that the copolymer degraded through two stages in both investigated environments with the formation of a stable residue in N2 and complete mass loss in air. The apparent activation energy values associated with the degradation processes were evaluated. The obtained results suggested different degradation mechanisms between N2and air. Results were discussed and compared with those obtained for several polymers previously investigated.

End-life prediction of commercial PLA used for food packaging through short term TGA experiments: Real chance or low reliability?

A long-term (about nine months) isothermal degradation experiment of two different commercial polylactide (PLA) samples used for food packaging was carried out at a relatively low temperature (423 K). Thermooxidative degradations of the same polymers were carried out in a thermogravimetric (TG) analyser, at higher temperatures (453 K ≤ T ≤ 523 K), under isothermal heating conditions. The obtained set of experimental TG data was used to determine the apparent activation energy (Ea) of degradation through two isothermal kinetic methods. The results from long-term experiment evidenced considerable mass loss for both PLA samples in the investigated period, but the experimental data were not in agreement with those from the short-term degradations at higher temperatures, thus suggesting a different degradation kinetics, and, then a low reliability of the lifetime predictions for polymers in service or degradation forecasts for the end of their life based on experiments at higher temperatures.

Thermal and thermo-oxidative degradations of poly(2,6-dimethyl- 1,4-phenylene oxide) (PPO)/copoly(aryl ether sulfone) P(ESES-co-EES) block copolymers: a kinetic study

The thermal degradation of a series of three novel ABA block copolymers of different molar mass (Mn), were the block A is a poly(2,6-dimethyl-1,4-phenylene oxide) (PPO), while the block B is a random copoly(aryl ether sulfone) P(ESES-co-EES), was studied in both inert (flowing nitrogen) and oxidative (static air) atmospheres, to investigate the effects of Mn of the central block on the thermal stability. Copolymers were synthesized with a two step method: in the first stage, a linking molecule is selectively attached as end group to the P(ESES-co-EES) which reacts in the second step with the phenolic hydroxyl group of PPO. Degradations were carried out into a thermobalance, in the scanning mode, at various heating rates, and the characteristic parameters of thermal stability, namely initial decomposition temperature (Ti) and the activation energy (Ea) of degradation, of the various copolymers were determined. Both Ti and degradation Ea values increased exponentially as a function of Mn of copolymers. The results were discussed and interpreted.

Thermal characterization of a series of lignin-based polypropylene blends

Polypropylene (PP), due to its chemical stability, is considered one of the main responsible of the increasing amount of plastic wastes on earth. To overcome this problem and to reduce the dependence of oil feedstocks, the use of lignocellulosics as fillers or reinforcements in thermoplastic materials has been increasing enormously in the last decades. In the present work, Liquid Wood (a mixture of cellulose, hemp, fax and lignin) was used to prepare, by mechanical mixing followed by thermal extrusion, blends of various PP/Liquid Wood ratios. Differential scanning calorimetry and thermogravimetric analysis experiments were performed in order to verify whether and how much the composition of the blends affects the thermal properties of the obtained compounds. Both calorimetric and thermogravimetric results indicate that the application of PP as a matrix does not limit the processing temperature of Liquid Wood, which may lead to a perfect marketable composite from these components. The addition of Liquid Wood also resulted in enhanced mechanical properties for the PP/Liquid Wood blends.

Thermomechanical properties and morphology of blends of a novel thermoplastic copolymer and epoxy-resin

The present paper is about a study on the effects on thermomechanical properties of an epoxy resin system blended with an amine ended PES:PEES (polyethersulphone-polyetherethersulphone) copolymer. Four different epoxy systems, each containing different amounts of toughening agent, were fully characterised in terms of morphology, viscoelastic properties and fracture resistance. Moisture resistance of the systems was investigated. Morphologies varying from particulate, for low thermoplastic content, to phase inverted, for higher thermoplastic content, were obtained. The effect of observed morphologies on viscoelastic properties in the solid state was studied by means of D.M.T.A. (Dynamic Mechanic Thermal Analysis) in a bend mode configuration. An increase in toughness with an increase of thermoplastic amount was observed.

Dumbbell-shaped polyhedral oligomeric silsesquioxanes/polystyrene nanocomposites: The influence of the bridge rigidity on the resistance to thermal degradation

A comparative study concerning the resistance to the thermal degradation of polystyrene-based nanocomposites loaded with five novel aromatic dumbbell-shaped polyhedral oligomeric silsesquioxanes was carried out in dynamic heating conditions. The fillers were formed by two identical silicon cages R7(SiO1.5)8 (R = isobutyl) linked to several aromatic bridges (Ar, Ar–Ar, Ar–O–Ar, Ar–S–Ar and Ar–SO2–Ar) where Ar = p-C6H4. Nanocomposites were prepared by in situ polymerization of styrene in the presence of 5% of appropriate polyhedral oligomeric silsesquioxanes. The actual filler content in the products obtained, which was checked by 1H NMR spectroscopy, resulted in all cases slightly higher than that in starting mixtures. Glass transition temperature (Tg) was determined by differential scanning calorimetry. Thermogravimetric (TG) and differential thermogravimetric (DTG) analysis were carried out in both flowing nitrogen and static air atmosphere, and temperatures at 5% mass loss (T5%) were determined to investigate the resistance to the thermal degradation. The results obtained were compared with each other and discussed. The resistance to the thermal degradation showed modest increments in respect to neat polystyrene, differently from analogous nanocomposites containing as fillers aliphatic bridged polyhedral oligomeric silsesquioxanes, as supported by scanning electron microscopy measurements which evidenced polyhedral oligomeric silsesquioxanes auto-aggregation phenomena. This behaviour was interpreted as due to the rigidity of polyhedral oligomeric silsesquioxanes aromatic bridges, which leads to low miscibility between filler and polymeric matrix.

Photoactivity of hierarchically nanostructured ZnO–PES fibre mats for water treatments

A brush-like ZnO nanorods shell is grown by Chemical Bath Deposition on electrospun Zn(Ac)2 doped polyethersulfone fibres. The obtained mats are water resistant and photocatalytically active, thus resulting suitable for applications in water purification. The used procedure is simple, cost-effective and scalable to large volumes. The use of supported ZnO nanostructures onto fibrous mats paves the way to easily reusable photocatalyst that benefits the high surface area of nanostructures and limits the drawbacks associated to the use of nanoparticles and nanopowders (i.e. water turbidity, irradiation efficiency and photocatalyst recover), thus resulting suitable for use in membrane technology.

Green Composites Based on Blends of Polypropylene with Liquid Wood Reinforced with Hemp Fibers: Thermomechanical Properties and the Effect of Recycling Cycles

Green composites from polypropylene and lignin-based natural material were manufactured using a melt extrusion process. The lignin-based material used was the so called “liquid wood”. The PP/“Liquid Wood” blends were extruded with “liquid wood” content varying from 20 wt % to 80 wt %. The blends were thoroughly characterized by flexural, impact, and dynamic mechanical testing. The addition of the Liquid Wood resulted in a great improvement in terms of both the flexural modulus and strength but, on the other hand, a reduction of the impact strength was observed. For one blend composition, the composites reinforced with hemp fibers were also studied. The addition of hemp allowed us to further improve the mechanical properties. The composite with 20 wt % of hemp, subjected to up to three recycling cycles, showed good mechanical property retention and thermal stability after recycling.