An aqueous dispersion of gold nanoparticles was added to an acrylic resin and UV‐cured. The photopolymerization process was followed by means of real‐time FT‐IR spectroscopy. Nanostructured coatings containing a homogeneous dispersion of gold nanoparticles with an average size range of 20–25 nm were achieved. Macroscopic aggregation during polymerization was avoided due to the rapid initiation and kinetic associated with the photopolymerization technique, which allowed the medium to quickly solidify around the dispersion particles.
Surface properties of epoxy coatings are modified by PDMS additives in cationic UV curing of a cycloaliphatic epoxy resin. The cured films show a very high hydrophobicity that does not depend on PDMS concentration, indicating that a threshold is reached even at 0.3 wt% additive. A slight increase of the water contact angle as a function of PDMS molecular weight is observed. The additive selectively modified the air‐side of the film, while the glass‐side retains the surface properties of the pure resin. This segregation phenomenon permits to obtain highly hydrophobic films with still good adhesion properties on polar substrates, which is an important advantage over common surface‐modified resins.
Iron‐oxide nanoparticles were functionalized with epoxy groups and were dispersed into a dicyclo‐aliphatic epoxy resin to obtain organic‐inorganic hybrid coatings via cationic ring‐opening photopolymerization. TEM investigations confirmed that the filler has a size‐distribution range between 5 to 20 nm, without the formation of aggregates. The influence of the presence of Fe2O3 on the rate of polymerization was investigated by real time FT‐IR spectroscopy. Increasing the iron‐oxide nanofiller in the photocurable resin induced an increase in the Tg values. By controlling the phase separation it was possible to obtain transparent iron‐oxide nanostructured coatings, characterized by improved hardness.
Glass fiber biobased composites have been prepared by ROMP of a commercially available vegetable oil derivative possessing an unsaturated bicyclic moiety, and DCPD. The resins and the corresponding composites have been characterized thermophysically and mechanically. Higher DCPD content yields materials with higher glass transition temperatures. Glass fibers significantly improve the tensile modulus of the resin from 28.7 to 168 MPa. These biobased composites utilize only a limited amount of a petroleum‐based monomer, while employing substantial amounts of a renewable resource.
UV‐cured polysiloxane epoxy coatings containing titanium dioxide were prepared by means of a cationic photopolymerization process. A good distribution of the inorganic filler was achieved within the polymeric network with an average size dimension of around 500 nm. UV‐vis analysis performed on organic dye (methylene blue) stained coatings showed a high efficiency of the titania photocatalytic activity: a complete degradation of the dye on the coating surface is reached after 60 min of UV irradiation without affecting the matrix photo‐degradation.
Nanocomposite UV coatings with adjustable properties for use on wood substrates in outdoor conditions were developed. Nanoscale ZnO was shown to be an efficient light absorber. Coatings were characterized in terms of elongation at brake, residual PI and double bond conversion, universal hardness, transparency, hydrophobicity, and yellowing. Coated samples were artificially weathered and studied with regard to their optical and mechanical properties, as well as to changes in brightness, transparency, hydrophobicity, and water permeability. The prepared wood coatings showed an increased weather fastness and improved optical properties. The suitability for use in outdoor conditions was assured by optimizing the elasticity of the coating and decreasing its water permeability.
The design and synthesis of new fouling‐resistant coating materials, specifically PC‐substituted polyolefins, and their application to water purification membranes is described. Greatly improved fouling resistance is found for coated membranes subjected to environmentally relevant emulsified oil foulants. The coating method proves effective for reducing fouling on both UF and RO membranes, and for maintaining high rejection of organic material and salt. Providing membranes of various types with a coating that simultaneously gives high flux, fouling resistance, and foulant rejection represents a significant advance in membrane materials, and a promising route to extend membrane applications beyond what has been possible using conventional, known materials.
Acrylic‐epoxy interpenetrating polymer networks were prepared by means of UV curing. The photopolymerization process was investigated via real‐time FTIR spectroscopy. The hybrid, cured films showed a broad tan δ peak in DMTA demonstrating the high damping properties of the hybrid, cured formulations. A decrease on shrinkage was achieved by increasing the epoxy‐resin content in the photocurable formulation, with a consequent increase in adhesion properties.
High‐strength conductive pristine graphene/epoxy composites are prepared by two simple processing methods – freeze dry/mixing and solution processing. PVP‐stabilized graphene is aggregation‐resistant and allows for excellent dispersion in both the resin and final composite, as confirmed by optical microscopy and SEM images. The superior dispersion quality results in excellent nanofiller/matrix load transfer, with a 38% increase in strength and a 37% improvement in modulus for 0.46 vol% graphene loading. The composites have a very low electrical percolation threshold of 0.088 vol%. Despite the effectiveness of both methods, the freeze‐drying method is more promising and versatile enough to be used for graphene dispersion in a wide range of other composite precursors.
Cardanol, a well known natural resource, was used to produce a polymer resin in the presence of formaldehyde, catalyzed by H2SO4. Before reticulation, PAni · H2SO4 was blended with the resin. The blended material was cast into poly(propylene) cups and kept inside a desiccator under vacuum until complete water evaporation. The final in situ polymer blend was solid and could not be dissolved in ordinary solvents, indicating that a reticulated material had been obtained. Samples prepared similarly were then characterized, showing that the produced blends can be used as pressure sensing materials.
An easy and robust approach for the production of long‐term‐stable silver nanoparticle dispersions with narrow size distribution (mean diameter ≈3–5 nm) has been developed. Amphiphilic‐modified hyperbranched polyethyleneimines with core/shell architecture were used as macromolecular templates and carriers. We systematically investigated the antibacterial performance and morphology of thin silver‐loaded hyperbranched polymer coatings on poly(ethylene terephthalate) prepared by different wet coating techniques. Furthermore, the influence of the density of the hydrophobic shell, varied by the degree of amidation between 50 and 70%, was studied with respect to the silver release behavior, wetting properties and antibacterial activity of the silver/hbp hybrid surface coatings.
This review presents the state of the art regarding the improvement of scratch resistance of polymeric coatings. In particular, our attention is focused on the effect of inorganic nanometric fillers on the scratch resistance of organic coatings. Two main strategies are described for the achievement of such nanostructured hybrid organic/inorganic coatings: either a top‐down or a bottom‐up approach.
A recently developed electrohydrodynamic printing method is described that can be used to create ordered structures and complex patterns using coarse processing needles and two polymeric materials. The results highlight the method's potential for direct 3D writing of biomedical polymers and composites for a variety of biomedical applications.
Acrylamide dynamic viscosity has been measured in aqueous solutions. Separate rheological measurements were performed on neat resins devoid of the curing agent over a range of shear rates to yield the initial resin viscosity. The gels were also characterized by sub‐ambient DSC to determine the phase structure as a function of formulation. The dynamic viscosity shows a marked sigmoidal behavior with a plateau viscosity. Mathematical interpretations of the gel time both by sigmoidal and power law models were comparable. The power law model allowed a direct determination of the gel time while the sigmoidal model yielded parameters associated with the initial viscosity, one associated with the plateau viscosity of the gel, and two time constants controlling the sharpness of the transition.
This paper demonstrates how the electric‐field‐assisted thermal annealing of octadecylamine‐functionalized SWNT/PMMA films induces an increase in the composite transversal conductivity of several orders of magnitude and a decrease in the lateral conductivity. This difference has been rationalized in terms of the nanotube alignment into the polymer matrix along the electric field direction. This result provides an initial understanding of how electric fields can be used to control the bulk physical properties of such nanocomposites.
Electrically conductive, cationically UV‐cured composites were prepared using exfoliated graphite plates (EGP) with cycloaliphatic epoxy resin and polyalcohol binder system. Exfoliated graphite (EG) was obtained from natural flake graphite through chemical and thermal treatment. Sonication of EG in solvent produced EGP. Characterization of graphite samples by XRD showed structural similarity between original graphite and EGP. UV curing behavior was characterized using photoDSC. Electrical resistivity measurements of the composites as a function of EGP concentration showed that at low filler concentration the binder system can influence the electrical percolation behavior. Some formulations showed electrical percolation at less than 1 vol.‐% of EGP filler.
Nowadays, silicon represents the most important material used for microelectronic applications. In this paper, both H–Si (111) surfaces and H–Si powders are used to initiate a multifunctional acrylate photopolymerization. The polymers formed are characterized by IR spectroscopy. This should be the way to create either an acrylate polymer coating on a Si wafer or a polymer film containing covalently linked silicon particles.
Novel materials were prepared from dual photo and thermal polymerization of hybrid thiol‐ene/cationic systems. In the first stage, the thiol‐ene system proceeded to high conversions, while the cationic photopolymerization was inhibited. The formation of sulfides during this stage was the main factor for the inhibition of the cationic photopolymerization of the epoxy monomers. Once those sulfides were formed, they reacted with the oxonium‐terminated growing polyether chains to form trialkylsulfonium salts. These salts promoted the thermal polymerization of the epoxy monomers in the second stage. The viscoelastic properties of the resulting polymers were measured by DMA.
The scientific and industrial history of polyurethane wire enamels during the previous six decades is reviewed. Their main use is as coatings for wires in miniature electrical devices and in electronics, where fast solderability at low temperatures is crucial. Market trends for polyurethane enamels are discussed, and an outlook is provided as to how future developments might influence the industrial use of polyurethane wire enamels.
A fluorinated acrylic resin was synthesized for use as a co‐monomer with a commercially available epoxy resin for UV‐cured interpenetrating polymer network preparation. Hybrid IPN networks were achieved with morphology ranging from a co‐continuous IPN to complete phase separation simply by changing monomer ratios. Highly hydrophobic coatings with good adhesion properties on glass substrates were obtained.
