UV Radiation Curing Research Articles

Effects of microgravity and reduced atmospheric pressure on manufacturing photopolymer specimens

In-space manufacturing especially for external satellite structures has a huge potential to increase the packaging density of a satellite in launch configuration and enables large structures for advanced mission requirements. However, the processes and materials do have to withstand the harsh environmental conditions in space. These conditions have immediate effects on the manufacturing process as well as long-term effects on the structure manufactured in orbit. The experiments presented here are based on a photopolymer extrusion process by UV-radiation curing that is intended to be used as an in-space manufacturing technology. In order to understand the influence of reduced atmospheric pressure and microgravity on the process, we demonstrated the successful extrusion and curing of rod-shaped elements during a sounding rocket flight. Simultaneously, the same experiment was performed on the ground under normal gravity and ambient pressure. By comparing both groups of specimens, it was shown that the morphological artifacts and geometric deviations are more significant for the specimens manufactured during flight. This evaluation was performed by visual inspection, by comparison of the laser-scanned specimens with a reference model and by measuring and comparing the mass, length and diameter of the specimens. On a microscopic level, conducted by computer tomography, no influence of the reduced atmospheric pressure on the extrusion of the liquid photopolymer can be recognized as this was probably not low enough at the altitude reached by the rocket. As a result of this article, measures are proposed to avoid the morphological artifacts observed during the experiments and thus achieve higher accuracy and a resilient in-space manufacturing process.

Composite Materials from Renewable Resources as Sustainable Corrosion Protection Coatings.

Epoxidized linseed oil (ELO) and kraft lignin (LnK) were used to obtain new sustainable composites as corrosion protection layers through a double-curing procedure involving UV radiation and thermal curing to ensure homogeneous distribution of the filler. The crosslinked structures were confirmed by Fourier-transform infrared spectrometry (FTIR), by comparative monitorization of the absorption band at 825 cm−1, attributed to the stretching vibration of epoxy rings. Thermal degradation behavior under N2 gas indicates that the higher LnK content, the better thermal stability of the composites (over 30 °C of Td10% for ELO + 15% LnK), while for the experiment under air-oxidant atmosphere, the lower LnK content (5%) conducted to the more thermo-stable material. Dynamic-mechanic behavior and water affinity of the new materials were also investigated. The increase of the Tg values with the increase of the LnK content (20 °C for the composite with 15% LnK) denote the reinforcement effect of the LnK, while the surface and bulk water affinity were not dramatically affected. All the obtained composites were tested as carbon steel corrosion protection coatings, resulting in significant increase of corrosion inhibition efficiency (IE) of 140–380%, highlighting the great potential of the bio-based ELO-LnK composites as a future perspective for industrial application.

Preparation of UV‐thermal dual curable environmentally friendly polyacrylate pressure‐sensitive adhesives by bulk polymerization

AbstractThree different acrylate monomers containing butyl acrylate, 2‐hydroxyethyl acrylate, and acrylic acid were designed to synthesize polyacrylate pressure‐sensitive adhesives (PSAs) by bulk polymerization process initiated via radical photo‐initiators under UV irradiation and UV‐thermal dual curing. Thermal crosslinker, KL‐1202, with trifunctional isocyanate groups was introduced into the prepolymer to form an intermolecular crosslinking network structure. An emphasis was placed on the effect of the KL‐1202 content on the microstructure and adhesive properties of PSAs. The viscosity and composition of prepolymer synthesized by UV initiation were tested by a rotational viscometer and Fourier transform infrared spectroscopy, respectively. The degree of crosslinking of the final PSA was evaluated by the gel content value obtained via Soxhlet extraction, while the molecular weights of the soluble parts of PSA polymers were measured by gel permeation chromatography. Dynamic mechanical analysis was used to characterize the viscoelastic performance of PSAs. Moreover, the adhesive properties of PSAs were determined through a series of tests including loop tack force, peel force, and shear resistance. It was found that the C=C double bond and the isocyanate group disappeared after UV radiation and thermal curing process. Dual‐cure acrylate PSAs compensate for limitations in UV‐induced cure of thick coatings. The Tg value, storage modulus (G′), and shear resistance of PSAs were improved while the loop tack force and peel force of PSAs decreased as the KL‐1202 content increased.

Synthesis of amidoxime polymer gel to extract uranium compound from seawater by UV radiation curing

ABSTRACT A new amidoxime polymer gel for uranium extraction from seawater was successfully prepared by photoinitiated crosslinking polymerization. It involves UV-induced radical polymerization of acrylonitrile (AN) and methacrylic acid (MAA) monomers with crosslinking agent and photoinitiator: an alternative synthesis pathway to gamma radiation. Characteristic peaks of Fourier transform infrared spectroscopy (FTIR) indicated that nitrile group was completely converted into amidoxime group. Eight hours of 60 W UV curing was enough for polymer gel formation. For the 4 to 1 ratio of AN to MAA, crosslinking agent concentration of 1 g/100 mL-monomers and photoinitiator content of 60 mL/100 mL-monomer, maximum uranium adsorption capacity of 17.02 mg/g adsorbent in seawater was achieved for sample spiked with 10 ppm uranium. For seawater sample spiked with 2,245 ppm uranium, the adsorption capacity reached 432.41 mg/g adsorbent. The amidoxime polymer gel could be regenerated for at least eight cycles while retaining about 50% of the uranium uptake capacity. Thus, the present amidoxime polymer adsorbent is a high-efficiency seawater uranium recovery agent for both high and low uranium concentrations.

Preparation and characterization of thermally conductive polymer composites containing silanized nanodiamonds

ABSTRACTRecent advances in light emitting diode (LED) technology have produced products with much higher power and brightness, creating the need for effectively thermal management. Therefore, there is a growing interest in thermally conductive composite materials for the development of excellent heat dissipation materials. Thermal conducting polymer composites were produced utilizing UV-curable monomer mixtures and methacrylate-functionalized nanodiamond (ND). Although UV-radiation curing process in the presence of ND was found to limit to some extent on the synthesis of ND/polymer composites, the surface-modified ND showed more effectiveness in controlling mechanical properties of ND/polymer composites than non-modified ND, due to chemical grafting to polymer matrix. In addition, improved thermal conductivity of polymer composites was accomplished with the use of methacrylate-functionalized ND.

Nonisotropic experimental characterization of the relaxation modulus for PolyJet manufactured parts

Abstract

Enhanced performance of a novel gel polymer electrolyte by dual plasticizers

In this contribution, polyethylene glycol dilaurate (PEGDL) is synthesized and adopted as the physical cross-linking agent to enhance the performance, especially the mechanical property of the gel polymer electrolytes (GPEs). With polyethylene glycol dimethyl ether (PEGDME) as the main plasticizer and PEGDL as the secondary plasticizer, several gel polymer electrolytes based on a copolymer of methoxy-poly(ethylene glycol) methacrylate (MPEGM) and hexadecal-poly(ethylene glycol) methacrylate (HPEGM) are prepared by UV radiation curing. The relationship between the composition of the GPE and the physical properties, e.g., thermal property, mechanical property and ionic conductivity, is investigated. The lithium ion transference number, lithium/GPE interfacial property and charge–discharge performance of the lithium polymer cell based on the physically cross-linked GPE are studied. The gel polymer electrolyte prepared with the optimum composition exhibits excellent mechanical properties and a relatively high ionic conductivity (8.2 × 10−4 S cm−1 at 30 °C). A coin cell Li/GPE/LiFePO4, shows a discharge capacity 152 mAh g−1 and 163 mAh g−1 when cycled at 30 °C and 50 °C, respectively, under a current density of 0.1 C.

UV-radiation curing of simultaneous interpenetrating polymer network hydrogels for enhanced heavy metal ion removal

Abstract Simultaneous interpenetrating polymer network (IPN) hydrogels have been prepared by UV-initiated polymerization of a mixture of acrylamide (AM) and triethylene glycol divinyl ether (DVE-3). The consumption of each monomer upon UV-irradiation was monitored in situ by real-time infrared (RTIR) spectroscopy. The acrylamide monomer AM was shown to polymerize faster and more extensively than the vinyl ether monomer DVE-3, which was further consumed upon storage of the sample in the dark, due to the living character of the cationic polymerization. The IPN hydrogels were used to remove heavy metal ions from aqueous solution under the non-competitive condition. The effects of pH values of the feed solution and the DVE-3 content in the formulation on the adsorption capacity were investigated. The results indicated that the adsorption capacity of the IPN hydrogels increased with the pH values and DVE-3 content in the formulation. Furthermore, the synergistic complexation of metal ions with two polymer networks in the IPN was found in the adsorption studies. Adsorption kinetics and regeneration studies suggested that the IPN hydrogels could be used as fast-responsive and renewable sorbent materials in heavy metal removing processes.

Kinetic study of UV radiation curing of the mixtures based on oxetane and epoxide by real time FT-IR

Kinetic study of UV radiation curing of the mixtures based on oxetane and epoxide by real time FT-IR

Study of Thermal Properties on UV-Curable Coatings Derived from Oleochemical Polyols

Over the last few years, UV radiation curing has become a well established coating technology used for several different applications. Polymeric component based on renewable resource is another area for getting low VOC coatings. In the present study cellulose and soya fatty acid were used to prepare oleochemical polyols which in turn reacted with diisocyanates to get PU which is further reacted with hydroxyl terminated acrylates to get oligomeric urethane acrylates. These polymeric compounds are used without any organic solvent for UV-coating formulation and cured by UV light on the metal surfaces. Thus effect of different types of polyols were used to prepared UV coatings studied on thermal properties like dynamic mechanical properties (DMA) and thermogravimetric analysis (TGA)

Photo-Catalytic Activity of Quencher Impurity Doped ZnS Nanocrystals

Intrinsic and extrinsic semiconductor nanocrystals seem to be good candidates for modern era optoelectronic and photo-catalytic applications due to their size tunable photo-physical and photo-chemical properties. In the present investigation, polyvinyl pyrrolidone (PVP) capped quencher impurity (Ni) doped ZnS nanocrystals have been synthesized using facile bottom-up synthesis technique; colloidal chemical co-precipitation method. Crystallographic and morphological characterization of synthesized nanomaterials have been carried out using X-ray diffraction (XRD) and transmission electron microscope (TEM), respectively. Photo-catalytic activity of the synthesized nanomaterials has been studied using methylene blue (MB) dye as a test contaminant. Photo-catalytic behavior dependence on dopant concentration, UV radiation curing and annealing of synthesized semiconductor nanomaterials have been studied in detail under sun light exposure.

Preparation and evaluation of epoxy methacrylate UV‐curable coatings containing phthalazinone

AbstractEpoxy methacrylate resin (EMA) UV‐curable coatings exhibit high reactivity, low viscosity and excellent chemical resistance in environmentally friendly coatings. A novel EMA containing phthalazinone moieties for high temperature resistant UV‐curable coatings was synthesized. The formulations were cured with hexanediol diacrylate (HDDA) and trimethylol propane triacrylate (TMPTA) as reactive diluents promoted by a photoinitiator, and then interpenetrating polymer networks were generated. The mechanical, chemical and thermal properties of the clear coatings were characterized using Chinese National Standard methods (GB). EMA was used with UV radiation curing in combination with 6.7 wt% of HDDA and 13.4 wt% of TMPTA, and the properties of the cured films were as follows: pencil hardness of 5 H, 30% NaOH resistance for 30 days, 15% HCl resistance for 10 days, 3% NaCl resistance for 30 days and 5% weight loss temperature of 300.5 °C. EMA UV‐curable coatings containing phthalazinone exhibit excellent chemical and thermal stability, and could be potential candidates for UV‐curable zero volatile organic compound coatings applied in the fields of salt spray corrosion, strong radiation and high‐temperature resistance. Copyright © 2009 Society of Chemical Industry

Generation and Self‐Replication of Monolithic, Dual‐Scale Polymer Structures by Two‐Step Capillary‐Force Lithography

Inhibition effects in UV radiation curing caused by oxygen are used for fabricating monolithic, micro/nanoscale hierarchical polymer structures via a two-step UV-assisted capillary molding technique (see image). Using this approach, various dual-scale polymer structures are created within a few minutes with precise control over geometrical parameters. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Effects of UV cure on glass structure and fracture properties of nanoporous carbon-doped oxide thin films

The effects of UV radiation curing on the glass structure and fracture properties were examined for a class of nanoporous organosilicate low dielectric constant films. A detailed characterization by nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy showed significant changes in the glass structure with increasing curing time, marked by the removal of terminal organic groups and increased network-forming bonds following the initial removal of porogen material. The higher degree of film connectivity brought about by an increased cure duration is demonstrated to significantly enhance adhesive fracture properties and to moderately improve cohesive fracture resistance. Explanations for the enhanced fracture behavior are considered in terms of the glass structure. The important role of crack path selection during adhesive and cohesive fracture processes is used to rationalize the observed behavior.

A new and convenient route to polyacrylate/silver nanocomposites by light-induced cross-linking polymerization

A new method for the preparation of silver nanoparticles/polymer nanocomposite materials by UV-radiation curing of multifunctional acrylate monomers has been developed. Silver nanoparticles possessing an average diameter of 6.6 nm were first prepared by chemical reduction of silver nitrate with t-BuONa-activated sodium hydride in THF. Transmission electron microscopy (TEM) and size distribution analysis revealed that silver(0) nanoparticles remained well-dispersed in acrylic formulations composed of tetrahydrofurfuryl acrylate, polyurethane acrylate and polyethylene glycol 400 diacrylate. The curing process was followed quantitatively by infrared spectroscopy through the decrease of the IR bands characteristic of the functional groups upon UV exposure. The viscoelastic properties of the nanocomposite photopolymer were monitored by dynamic mechanical analysis (DMA). Silver nanoparticles were found to have no detrimental effect on the photopolymerization kinetics and the incorporation of metal nanoparticles allowed to reduce the gloss of UV-cured coatings. An increase of the diameter of silver nanoparticles to 20 nm was observed during the curing process.

Depth dependence of ultraviolet curing of organosilicate low-k thin films

UV radiation curing has emerged as a promising postdeposition curing treatment to strengthen organosilicate interlayer dielectric thin films. We provide the evidence of film depth dependent UV curing which has important effects on through thickness mechanical and fracture properties. Force modulation atomic force microscopy measurements of the elastic modulus through the thickness of the films revealed evidence of periodic modulations of the glass stiffness which increased in magnitude with UV curing time. Furthermore, while significant increases in fracture energy were observed with UV curing time at the top of the organosilicate film, much lower increases were observed at the bottom. The increase in fracture energy with UV curing was film thickness dependent. The cohesive fracture resistance was less sensitive to UV curing. Possible explanations for the stiffness modulations through the film thickness involving UV light interference or phase separation by spinodal decomposition during the cure process are described.

高度水添テルペンフェノール樹脂の電子材料用途への応用

This article presents about raw materials and characteristic of terpene resins, additionally introduces new type terpene resin.Terpene resins are synthesized from essential oil of pines and orange peels. These resins are used as tackifier of adhesives, such as pressure sensitive adhesives and hot melt adhesives. Also these resins are used for modifier of elastomers and plastics.The new type hydrogenated terpene resin has been developed for electoronic materials. This resin contains hydroxyl group and has weather resistance and light stability. Therefore it is used as a modifier of taransparent plastics and a tackfier of acrylic type adhesives including UV radiation curing adhesives.

Synthesis of metal/polymer nanocomposite by UV-radiation curing

Nanocomposite polymers containing bismuth nanoparticles (2 wt%) have been obtained by photopolymerization of acrylic resins. The bismuth nanoparticles have been synthesized by reduction of BiCl 3 with t-BuONa activated sodium hydride. In situ t-BuONa stabilization protects the metallic particles against aggregation. Transmission electron microscopy (TEM) analysis has shown that the bismuth nanoparticles are well dispersed in the acrylic resin. The curing process was followed quantitatively by infrared spectroscopy through the decrease upon UV exposure of the IR bands characteristic of the functional groups. The bismuth nanoparticles were found to have no detrimental effect on the photopolymerization kinetics. Dynamic mechanical analysis (DMA) has shown that the viscoelastic properties of the nanocomposite photopolymer are significantly modified in comparison with corresponding UV-cured polymer. The addition of metal nanoparticles was found to greatly reduce the gloss of UV-cured coatings.

The preparation and physical properties of UP/montmorillonite nanocomposite by UV radiation curing

AbstractThis article describes the preparation and properties of unsaturated polyester (UP)/montmorillonite (MMT) nanocomposite by UV radiation. Benzildimethylketal and 1‐hydroxy cyclohexyl phenyl ketone (HCPK) as a photoinitiator in UP were photolyzed under nitrogen condition. Analysis of X‐ray diffraction patterns of the composites shows that the interlayer spacing of MMT is substantially increased. The type and amount of photoinitiator affects the level of improvement in mechanical properties, and our results suggest that HCPK is a more efficient photoinitiator of UP curing reaction. The interaction between photoinitiators and MMT should be considered to acquire the reinforcement effect of the dispersed MMT nanolayers. The properties of nanocomposite are dependent upon the amount of MMT. The effect of MMT concentration on thermal and dielectric properties is also investigated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3609–3615, 2006

A Facile Route to ZnS–Polymer Nanocomposite Optical Materials with High Nanophase Content via γ‐Ray Irradiation Initiated Bulk Polymerization

Studying the fabrication and composition of semiconductor nanoparticles in polymer matrices has attracted the interest of many scientists because nanoparticle–polymer composites may find applications in high-refractive-index materials, light-emitting diodes, photocatalysts, photovoltaic solar cells, and nonlinear optical devices. Control of the nanoparticle size and size distribution as well as the dispersion homogeneity in the polymer matrix are critical prerequisites for controlling the properties of the composites. However, nanoparticles are prone to aggregation in the polymer because of their high specific surface energies and inherently hydrophilic character. Therefore, it is still a technological challenge to incorporate inorganic nanoparticles into polymer matrices and thus to prepare transparent bulk nanocomposites with high nanoparticle content. Far fewer studies of nanoparticle–polymer bulk materials have been reported than of nanocomposite films. Semiconductor nanoparticles (PbS, CdSe, CdTe) have been introduced into bulk polymer matrices to prepare bulk nanocomposites, although the content of inorganic particles was low (< 5 wt %). In these studies, two main approaches have been developed: in situ formation of nanoparticles in a presynthesized polymer and bulk polymerization of an organic monomer in the presence of premade nanoparticles. The latter provides full synthetic control over both the nanoparticles and the matrices, and is a more effective and practical route for fabricating bulk polymer nanocomposites on a large scale. We have utilized UV radiation curing to prepare transparent ZnS–polymer nanocomposite films with high ZnS contents from a solution mixture of premade ZnS particles and acrylate macromers. This is an effective method for preparing nanocomposite films with nanoparticles dispersed homogeneously horizontally and vertically throughout the entire polymer matrix, but it is unsuitable for preparing thick bulk nanocomposites. In addition, the ZnS nanoparticles obtained by the usual method cannot be redispersed in monomer or solvent because of their incomplete surface modification with organic molecules. The application of c-ray irradiation in the preparation of bulk polymer nanocomposites has remarkable advantages, such as processing under ambient pressure at room temperature and quick polymerization of monomers. These valuable properties can be put to use in the fabrication of nanocomposites with homogeneously dispersed inorganic nanoparticles. In this communication, we report a novel, facile route for the preparation of transparent bulk nanocomposites with high ZnS content via c-ray irradiation initiated polymerization (Fig. 1). Our strategy involves the design and optimization of the nanoparticle surface and polymeric monomer as well as the selection of a suitable polymerization technology. First, we reasoned that the compatibility between nanoparticles and the polymer matrix is a prerequisite for synthesizing a bulk nanocomposite with high nanophase content. So, it is necessary to tailor the corresponding polymer matrix by the decoration of the nanoparticles with organic molecules. Furthermore, it is highly important that the monomer should act as both the ligand and solvent for the inorganic nanoparticles. It has been reported that polar organic solvent molecules, such as N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), co-ordinate to the surface of ZnS or CdS nanocrystallites and can effectively stabilize them. Thus, it is expected that a monomer with a similar structure to DMF can be selected as both the solvent and ligand for the nanoparticles. Here, we have selected N,N-dimethylacrylamide (DMAA), which can effectively disperse and stabilize ZnS particles, as the monomer. Finally, the c-ray irradiation technique is another crucial factor in the fabrication of a bulk polymer nanocomposite with high particle content. This polymerization method can induce a mild and rapid gelation process for the bulk polymeric system containing a high content of nanoparticles uniformly dispersed inside. We present a simple approach for the large-scale production of mercaptoethanol (ME)-capped ZnS nanoparticles in DMF from Zn(OAc)2 (Ac: acetate) and thiourea. The MEC O M M U N IC A TI O N S