[show abstract][hide abstract] ABSTRACT: We report here a simple, cheap and scale up process for obtaining a multifunctional coating with both, IR reflective and hydrophobic properties. These coatings can be applied on solar devices in order to limit their overheating under operating conditions. The system is based on UV-curable epoxy coating containing IR-reflective fillers and a silicone additive to modify the surface properties with a good hydrophobicity enhancement. The filler dispersion into the epoxy UV-curable resin did not significantly influence the photocuring rate, while a slight decrease of the final epoxy group conversion was evidenced. The optical properties of the obtained coatings have been evaluated by UV–vis–NIR spectroscopy showing that the films act as good “filters” in the NIR region, giving rise to a reduction of the absorbed heat and of the working temperature of the cells. A pronounced increase of hydrophobicity for the films containing the silicone additive was observed. The optical properties were not affected by the addition of the silicone additive.
Progress in Organic Coatings 01/2014; 77(2):458–462. · 1.85 Impact Factor
[show abstract][hide abstract] ABSTRACT: Epoxy resins, widely used in conservation, still remain controversial materials. Considering some of the drawbacks that currently limit the application of epoxy consolidants, we present the application of the cationic ring opening polymerization as a novel method to cure the epoxy monomer in the restoration field. The cationic polymerization was carried out through a redox system based on the reduction of the iodonium salt in the presence of ascorbic acid catalyzed by a copper salt. The use of this initiator system for carrying out a suitable consolidant for lime plaster is considered. First, the film properties of the cured films were investigated. Then, the formulation was applied on a sample of plaster and its compatibility was verified. Its effectiveness as a consolidant product is explored through the evaluation of chromatic changes, mechanical strength, morphology of the re-aggregated material, and changes of the surface properties.
[show abstract][hide abstract] ABSTRACT: A new approach is reported for the preparation of a graphene-epoxy flexible transparent capacitor obtained by graphene-polymer transfer and UV-induced bonding. SU8 resin is employed for realizing a well-adherent, transparent, and flexible supporting layer. The achieved transparent graphene/SU8 membrane presents two distinct surfaces: one homogeneous conductive surface containing a graphene layer and one dielectric surface typical of the epoxy polymer. Two graphene/SU8 layers are bonded together by using an epoxy photocurable formulation based on epoxy resin. The obtained material showed a stable and clear capacitive behavior.
[show abstract][hide abstract] ABSTRACT: A procedure is proposed to prepare electrically conductive epoxy resin composites exploiting in situ reduction of graphene oxide (GOx) during the epoxy thermal curing in presence of amine. The optimum curing conditions are evaluated, and the efficiency of the reduction process of GOx induced by amine is confirmed by XPS analyses. The composites electrical resistivity show a decrease by increasing filler amount, and this can only be due to the partial restoration of the conductive sp2 structure occurred during thermal curing. This is a simple, easy-to-scale, one-step process to obtain electrically conductive epoxy cured materials by mixing the resin components and the well dispersible insulating GOx.
Macromolecular Materials and Engineering 12/2013; · 2.34 Impact Factor
[show abstract][hide abstract] ABSTRACT: Epoxy–ZnO composites are prepared via UV-induced cationic polymerization. Complete unsoluble materials are achieved after 10 min of irradiation. Thermal analyses shows an increase of Tg in the presence of the ZnO attributable to a strong hindrance effect of the polymer chain mobility. Electrical characterization of the cured materials shows the decrease of the real part of permittivity with frequency. Both permittivity and AC conductivity values increase with nanofiller content, especially for the highest contents. This is described as typical behavior of nanocomposites made from polymers and fillers with higher permittivity and conductivity values, in accordance with previous data reported in literature for similar composites.
Macromolecular Materials and Engineering 07/2013; · 2.34 Impact Factor
[show abstract][hide abstract] ABSTRACT: 2012): Synthesis of the fluorene spiroorthocarbonate and the evaluation of its antishrinking activity in the cationic photopolymerization of an epoxy resin, Designed Monomers and Polymers, In this work, the spiroorthocarbonate FSOC derived from fluorene was prepared. After characterization by FTIR and NMR spectroscopy, the synthesized FSOC was evaluated as antishrinkage additive in the cationic photopolymerization of bis-glycidil ether of Bisphenol-A (DGEBA). The FSOC was mixed at 2.5–10 mol% with DGEBA. It was found that shrinkage decreased with increased concentration of FSOC. At 10 mol% of FSOC not only shrinkage was eliminated, but a small level of volume expansion was also achieved. The presence of FSOC did not interfere with the photopolymerization of DGEBA.
Designed Monomers & Polymers 01/2013; · 0.88 Impact Factor
[show abstract][hide abstract] ABSTRACT: New photocatalytic materials prepared by dispersing graphene oxide (GO x ) into UV-curable epoxy resin can be classified as semiconductors and thanks to this behavior it can be used in order to activate photoxidative process in a similar way as it happens with the well-known TiO2. The activity of these new photocatalytic materials was evaluated in aqueous phase; photoactivity was determined by following the photodegradation of phenol during irradiation in the presence of epoxy crosslinked films containing GO x .
Journal of Materials Science 01/2013; 48(15):5204-5208. · 2.16 Impact Factor
[show abstract][hide abstract] ABSTRACT: This work reports the formulation of waterbased graphene oxide/acrylic nanocomposite inks, and the structural and electrical characterization of test patterns obtained by inkjet direct printing through a commercial piezoelectric micro-fabrication device. Due to the presence of heavily oxygenated functional groups, graphene oxide is strongly hydrophilic and can be readily dispersed in water. Through a process driven by UV irradiation, graphene oxide contained in the inks was reduced to graphene during photo-curing of the polymeric matrix. Printed samples of the nanocomposite material showed a decrease of resistivity
with respect to the polymeric matrix. The analysis of the influence of printed layer thickness on resistivity
showed that thin layers were less resistive than thick layers. This was explained by the reduced UV penetration depth in thick layers due to shielding effect, resulting in a less effective photo-reduction of graphene oxide.
Journal of Materials Science 01/2013; 48:1249-1255. · 2.16 Impact Factor
[show abstract][hide abstract] ABSTRACT: In this paper, we describe a novel methodology for fabricating conductive epoxy-polythiophene network
films by simultaneous photoinduced step-growth and cationic ring opening polymerization processes. For
this purpose, formulations containing a bifunctional epoxy monomer, namely 1,6-hexanediol diglycidyl
ether (HDGE) and different amount of thiophene ranged from 0 to 50 wt% in the presence of an iodonium
salt, namely (4-methylphenyl)[4-(2-methylpropyl) phenyl]-iodonium, hexafluorophosphate were irradiated
under UV light. In the process, while polythiophene was formed through electron transfer reaction
between photochemically formed phenyliodinium radical cations followed by proton release and coupling
reactions, cationic ring opening polymerization of HDGE initiated by the liberated protons resulted in the
formation of epoxy network. Conductivity of the obtained films was evaluated by surface resistivity
measurements by means of a standard two-point micro-contact method before and after iodine doping. It
was found that iodine doping provided a significant improvement in the surface conductivity. This work
conclusively provides a new approach for bonding conducting polymers with epoxy-based network films
via photoinduced electron transfer reactions in a simple, fast, and efficient approach of importance in
electronic and other applications.
[show abstract][hide abstract] ABSTRACT: We present a comprehensive study related to UV-curable nanocomposite (NC) materials, based on acrylic
matrix containing Ag nanoparticles (NPs) formed by in situ reduction and co-formulated with titania NPs.
Addition of titania produces a diffusion limited aggregation of in situ formed Ag NPs during photocuring
due to radical propagation, allowing to obtain electromechanical percolation at very low solid content.
Keeping low the solid content is important, considering the cost of raw materials. Compared to NCs based
on spherical fillers, where percolation is reached at very high solid contents (around 70%), by radical
engineering we could approach it by adding 5 to 30% of Ag precursor (Ag content 2 to 10%). These NCs
are characterized by a low viscosity at room temperature, allowing full processability by means of inkjet
printing (IjP), as well as good electrical properties after curing, ranging from metallic to dissipative, in their
annealed state. We present morphological, chemo-physical and electrical characterisation, as well as
outstanding piezoresistive properties of these materials in the thin film state and after direct patterning by
means of IjP. The goal was to realize low cost printed strain-gages featuring improved characteristics when
compared to available commercial products. We obtain diffusion-engineered unstructured materials
featuring gauge factors (GF) as high as 13.4, corresponding to a seven-fold increase with respect to
commercial metallic alloys. Measurements performed on structured NC IjP strain gauges produce GF up to
220, corresponding to a hundred-fold increase in comparison with commercial devices.