A. Recca

An oxygen index evaluation of flammability on modified epoxy/polyester systems

Abstract This article describes a study on flame retardancy conducted on a dual cure thermosetting system consisting of an epoxy resin, blended with an unsaturated polyester. Neat resin panels and glass-fibre reinforced composites were prepared utilising several structurally different flame-retardant (FR) additives. These materials were tested in order to determine the Limiting Oxygen Index (LOI), which is a measure of the fire performance properties of a given material. Particular attention was paid to the FR properties of compounds, which are free of halogen such as bromine, in the absence of antimony oxide. These compounds are based on phosphorous containing molecules.

High resolution XPS investigation of photocured films containing perfluoropolyether acrylates

Abstract The paper reports an XPS investigation on films obtained by photopolymerising new perfluoropolyether methacrylates as pure products or added in low amounts to a typical UV-curable resin (Bisphenol A bis-ethylether diacrylate). The structure of the fluorinated monomers is Rf–Rh type, where Rh=–CH 2 O–CO–NH–CH 2 –CH 2 –OCOC(CH 3 ) CH 2 while Rf=CF 3 –CF 2 O–(CF 2 O) n (CF 2 –CF 2 O) m –CF 2 – for monomer 1 (PM 890, m / n =1.68), and Rf=Cl–CF 2 –CF(CF 3 )–O–(CF 2 CF(CF 3 )–O) 2 –CF 2 – for monomer 2 . Quantitative evaluation of the different atomic ratios was performed using take-off angles of 45 and 10° (very surface region) on both film sides, the one in contact with the glass substrate and the one exposed to air. The results obtained indicate strong fluorine enrichment on the air side of the films and a concentration gradient at the surface, while the glass side has a composition similar to the bulk.

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.

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.

Determination of degradation apparent activation energy values of polymers

The isothermal degradation of three aromatic polyetherketones was studied in an inert environment at various temperatures in the range 683-803 K. In the first degradation stage (mass loss D£20%) a linear increase of D as a function of heating time (t) was observed and the corresponding kinetic D=Do+bt equations at various temperatures were directly drawn by smoothing the experimental TG data. The b values, which represent the mass loss rates during degradation, increased as a function of temperature according to Arrhenius-type equations, from which degradation Ea values were determined, which appear in agreement with those from literature methods. Some differences observed were discussed and interpreted.

Synthesis and characterization of pendantly amine functionalized poly(arylene ether sulfone)

Abstract The synthesis of new pendantly functionalized polyaromatic thermoplastics using pre-functionalized monomers is reported. These will have potential applications as either toughening agents in thermosetting resins or, with the incorporation of crosslinking moieties, as matrices in their own right.

The surface photo-oxidation of polystyrene: Part I—The application of ToF-SIMS to monitor changes in polymer chain length

Abstract ToF-SIMS has been employed to monitor the changes in molecular weight which occur on UV irradiation in a polystyrene standard (MW 1700) as a thin film on silver. The ToF-SIMS spectrum of unirradiated polystyrene is also described. Polysiloxane contamination was present in some of the polystyrene samples studied; no effort was made to remove this contamination as it was considered to be part of the system under analysis and proved useful in confirming the role of the phenyl substituent in the photodegradation of polystyrene. Implications of this study, the possible development of the technique described and its application to real polymer surfaces are discussed.

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.

Surface photo-oxidation of phenoxy resin and polyetheretherketone

Abstract The changes in surface chemistry of phenoxy resin and polyetheretherketone during photo-oxidation were monitored by ESCA. Extensive oxygen uptake was observed for both materials and the data showed that oxidation of the phenyl rings had occurred. Comparison of phenoxy resin with its acetylated derivative indicated that the changes in surface chemistry of the former during the initial stages of exposure were not due to the hydroxyl group.

Metal selectivity properties of polymeric Schiff bases

Abstract The selectivity properties of polymeric Schiff bases derived from 5,5′-methylene-bis-salicylaldehyde in complexing with different metal ions have been investigated.