2014 UV & EB Technical Conference Proceedings
Table of Contents
Additive Manufacturing / 3D Printing
The Benefits of UV Curable Materials in Additive Manufacturing
Additive Manufacturing (AM) is the process by which successive layers of material are laid down on top of one another and bonded together to form a three dimensional object. UV curable formulations are uniquely suited for use in AM due to their rapid cure, range of properties, and dimensional accuracy. This paper will describe the physical properties of liquid and cured UV formulations, where they are being used today and the areas for potential use in the future.
Advanced Applications of Thiol-Ene Formulations
Thiol-Ene polymerization has gained tremendously increasing interest during the last decade thanks to the work of Charlie Hoyle and Chris Bowman. Advantages such as low oxygen inhibition and shrinkage, uniform networks with significantly improved mechanical properties are accompanied by up to now unsolved disadvantages such as unpleasant odour and poor storage stability. A new concept in thiol-ene stabilization gives excellent storage stability with nearly no increase in viscosity within one year. The main part of the presentation will focus on advanced applications in the field of 3D printing. Examples are the modification of gelatin and hyaluronic acid with low irritant polymerizable groups for the preparation of hydrogels.
Three Decades of UV Technology Innovation ― Stereolithography
Since the first patent application officially filled in 1984, stereolithography (SL) has advanced and become one of the most fascinating UV technology innovations over the past three decades. This technology creates complex three dimensional structures from digital data by successively curing a liquid resin layer by layer using a UV-laser. The fabricated SL parts have been widely applied for model verification, functional testing, and direct manufacture parts due to its accuracy, speed and process versatility. It serves many industries including service bureaus, consumer products, automotive, medical/dental, business machines, motorsports, aerospace, architectural, as well as academic and government/military. The tremendous success of stereolithography significantly benefits from the innovation of photocurable materials, UV laser technology and three dimensional computer imaging. This presentation will review UV technology innovation and application for stereolithography.
Made Strong: Product Development and Additive Manufacturing
Adhesives
High Performance Materials for Laminating Adhesives
The market demand for laminating adhesives in electronics or solar industry has been ramping up during the recent years. Key performance requirements include excellent adhesion properties on a variety of substrates such as PET, PC or glass, high adhesive reliability and good moisture resistance. In many applications, such as touch screen or solar panels, low-k dielectric property is also required. In this paper, several innovative materials that can meet all these requirements will be discussed.
A Formulator's Guide to Energy Curable Laminating Adhesives
Radiation curable liquid laminating adhesives (LA's) are continuously making inroads into conventional adhesive applications. With VOC (volatile organic compound) emissions and operating costs coming under constant and increasing pressure, formulators are increasingly turning to 100% solids energy curable adhesives as an environmentally acceptable high speed alternative. This study examines basic energy curable laminating adhesive formulations for specific low viscosity applications and delves into the respective differences between them. We would also like to introduce our Updated Laminating Adhesives Lab Report.
UV-triggered Thermosetting Film Adhesives
UV-triggered thermosetting film adhesives which balance shelf life with rapid cure at low temperatures have been developed. The adhesives exhibit greater than six months of ambient shelf-life and thermally cure in minutes at temperatures in the range of 80-120 °C. The film adhesives are chemically latent until irradiated with UV light, after which they possess a worklife/open time on the order of an hour prior to final thermal bonding and cure.
Light Curable Adhesives for Automotive and Electronic Applications and the Benefits of Surface Treatment
Advanced Applications
1K UV-A Hard Coats for Polycarbonate Head Light Refinishing
Over the last decade the automotive refinish industry has been forced to look at new technologies which reduce volatile organic content (VOCs) and hazardous air pollutants (HAPs) while providing a rapid return to service of the consumer's vehicles. UV A cured 1 K auto refinish primers were first introduced in the middle 1990's. UV A Clear Coats were subsequently introduced in the late 1990's. Materials have continued to be developed and pushed to mimic the classic 2K solvent based polyurethanes (PURs). However, slow acceptance by the auto refinish market over the last decade is indicative of a market that is difficult to change. RADTECH in conjunction I-CAR, an industrial training organization for the collision repair professional, developed a web based training module for UV A Cure 1 K auto refinishing. Since 2008 this paid web training module from I-CAR has had over 900 courses purchased by the collision repair professional. This paper will review the past history of the UV A cured 1K auto refinish market and formulations for primers and clear coats. It will also attempt to look at current UV A cured 1K auto refinish primers and clear coats in the NAFTA market as well as new formulations and new developments in UVA equipment.
Surface Modifying Additive for UV Curable Hardcoat
Hardcoats improve the durability and scratch resistance of plastics. Hardcoats are, however, susceptible to fingerprint smudge, stains and graffiti. The addition of a UV curable perfluoropolyether additive into existing hardcoat systems can alleviate these issues. This additive is optically clear, oleophobic, hydrophobic, and provides easy-to-clean properties. Using optical and contact angle measurements, we demonstrate that UV hardcoats that incorporate the perfluoropolyether additive have better fingerprint mitigation, easy-to-clean properties, and stain resistance than UV hardcoats without the additive.
New Developments in Initiators for Two-photon Polymerization
Two-photon induced polymerization allows greatly improved spatial resolution relative to traditional one-photon polymerization. The main limiting factors of the technology are the high cost of pulsed lasers, slow writing speeds, and poor reactivity of traditional initiators. We address the third issue by synthesizing a series of quadrupolar aryl ketones with both high two-photon absorbance and good initiating efficiency. As a result, sub-micrometer structures are produced both faster and with lower required laser intensity.
Self-Wrinkling to Bioinspired Patterned Surface of Photo-Curing Coating
We here demonstrate a facile approach of one step to obtain the complex wrinkling patterned surface of the photocuring coating by using thiol and fluorocarbon chains containing POSS (F2-POSS-SH6) as reactive nanoadditive. F2-POSS-SH6 can self-assemble into the top layer of the UVcuring liquid resin. As a result, the mismatch of shrinkage caused by the different types of photo-cross-linking reaction between the top layer and bulk layer leads to formation of the wrinkling pattern. The resulting surface exhibits superlow surface energy (4.1 mN/m) when the concentration of F2-POSS-SH6 is only 1%. The feasibility and generality of this approach for the excellent hydrophobic and oleophobic surface will undoubtedlyfind practical application in photocuring coating with functions such as self-cleaning.
Advanced Materials
1K UV-A Hard Coats for Polycarbonate Head Light Refinishing
Over the last decade the automotive refinish industry has been forced to look at new technologies which reduce volatile organic content (VOCs) and hazardous air pollutants (HAPs) while providing a rapid return to service of the consumer's vehicles. UV A cured 1 K auto refinish primers were first introduced in the middle 1990's. UV A Clear Coats were subsequently introduced in the late 1990's. Materials have continued to be developed and pushed to mimic the classic 2K solvent based polyurethanes (PURs). However, slow acceptance by the auto refinish market over the last decade is indicative of a market that is difficult to change. RADTECH in conjunction I-CAR, an industrial training organization for the collision repair professional, developed a web based training module for UV A Cure 1 K auto refinishing. Since 2008 this paid web training module from I-CAR has had over 900 courses purchased by the collision repair professional. This paper will review the past history of the UV A cured 1K auto refinish market and formulations for primers and clear coats. It will also attempt to look at current UV A cured 1K auto refinish primers and clear coats in the NAFTA market as well as new formulations and new developments in UVA equipment.
Nanostructured Polymer Networks obtained by Photopolymerization in a LLC Template
Surfactants may self-assemble and form lyotropic liquid crystalline (LLC) mesophases (micellar cubic, bicontinuous cubic, hexagonal, lamellar) depending on their concentration in water. This self-assembly was used as a template for photopolymerization to obtain nanostructured polymer networks with enhanced transport, mechanical, and stimuli-responsive properties. In this work, we used reactive amphiphilic block copolymer in concert with photopolymerization to improve structure retention and enhance the overall mechanical stability of the templated material.
Fluoro-Silicones in UV Cured Coatings Films
A series of our non-PFOS fluoroalkyl silicones will be examined in UV cured coatings films for their impact on coatings properties such as COF reduction, tape release and stain release. Both reactive and non-reactive fluoroalkyl silicones will be examined. Earlier results of reactive silicones in films have shown interesting results on stain release and the hope is that the fluoroalkyl group will enhance these properties in particular.
Bio-based Materials
Next Generation of UV-curable Cellulose Esters
New generation of UV-curable cellulose ester additives and binders provide improved surface hardness and solvent resistance in hard coating and ink applications. UV-curable cellulose ester additives do not disturb clarity and therefore they are excellent additives for clear, very low haze coatings and glossy inks. Their effect in rheology, adhesion, and chemical resistance will be discussed.
Bio-based building blocks for advanced photo-cure coating systems
Photo-curing, more specifically UV-curing technology is among the fastest growing advanced coating technologies and is rapidly expanding into a host of new application areas. Their growing acceptance is primarily driven by their environmentally friendly features, performance of these coatings, potential for enabling new products and economy. Despite these benefits, the materials used in the current photo-cure systems are predominantly derived from petrochemical sources making them unsustainable over the long term. Development of renewable resource-based alternate materials tailored for photo-cure applications is, therefore, very critical to future sustainable development of photo-cure coating technology. This presentation highlights our research efforts in developing a platform of soybean oil-based value-added building blocks and demonstration of their suitability as alternative raw materials in advanced UV-curing coating compositions. A hyper-branched soy-polyol has been developed and used as primary component of UV-curable polyurethane dispersions (UV-PUDs). Coatings based on UV-PUDs with varying acrylate content and bio-based content > 45% have been characterized and compared. Due to hyperbranched structure and –OH functionality of slightly greater than 2, coupled with hydrophobic nature of this oil-derived polyol, these UV-PUDs show interesting properties for many potential industrial applications. Another group of soy-based derivatives, low viscosity and high-functionality acrylate monomers, have been designed and used as reactive diluent in conventional UV-cure formulation. The study demonstrates potential of these low odor and bio-based reactive diluents as partial or full replacement of conventional reactive diluents.
High Performance UV-Curable PUDs with High Renewable Carbon Content
UV curable polyurethane dispersions (UV-PUDs) have became a well established and commercially successful class of products because of their combination of low environmental impact, range of achievable properties and ease of use. Important end use applications for UV-PUDs include factory applied wood coatings, field applied coatings on concrete, wood or vinyl flooring and protective coatings on plastics. All of these applications require high degrees of hardness plus scratch and abrasion resistance. PUDs made from renewable raw materials are also well known (including some UV curable varieties), but are generally based on vegetable oil derivatives and even after UV curing are too soft for the applications mentioned above. This paper will discuss unique new UV-PUDs containing a high percentage of renewable carbon that have properties suitable for use in high performance coatings.
Cardanol-based branched UV-cured acrylic oligomers
A series of novel biobased UV-curable resins, mult-arms acrylates were synthesized from renewable cardanol and bio-polyols, such as glycerol, xylitolum, tripolyglycerol and sucrose. The resulting UV-curable resins, containing about 55wt % biorenewable content, have varying arms of cardanol from 3 to 6 by changing the kind of biobased polyol core. This work provides a new way of utilizing renewable resources to prepare environmentally friendly photosensitive resins with high bio-based content and high performance for coating applications.
Bio-engineering
Photopolymerized Micropatterned Platforms with Varied Mechanical Properties for Contact Guidance
Micropatterned substrates are formed in a rapid, single-step reaction by selectively blocking light with glass-chrome, ronchi rule photomasks which have parallel line-space gratings with a pitch of 10-100µm in width. The resultant pattern is a continuous series of parallel ridges and grooves at regular intervals and of various amplitudes that can be used for cellular contact guidance studies. Substrate rigidity is controlled by manipulating co-polymer crosslink density.
High Performance Hybrid UV Curing Soy-Bean Systems
In this Study, Soy Bean Epoxide was modified to prepare two different resins with acrylate and Vinyl ethers end groups, which homo-polymerization and thiol-ene/ homo-polymerization hybrid curing mechanisms were studied by blending modified soy bean resins with mercaptopropyl polyhedral oligomeric silsequioxane. The conversion of double bonds was obviously increased from 60% to 90% with hybrid curing mechanism. As a result, the system’s physical properties were also improved significantly.
Physical Properties of Photopolymers in Ocular Regenerative Scaffolds
Control of stem cell scaffold structure is crucial for their development as transplantable supports for photoreceptor regeneration. Photopolymerization allows manipulation of pore size, spacing, geometry, and other physical properties of these scaffolds to meet the needs of photoreceptor regeneration applications. In particular, observed changes in diffusion and growth and differentiation of cells will be discussed. The optimized materials were shown to support the stem cell differentiation to mature retinal cell types.
Chemistry
Directed Oligomer Structure By Controlled Radical Polymerization For Use In Photocurable Thin Films
Controlled Radical Polymerization (CRP) techniques may allow specific monomer unit placement to modulate photopolymer physical properties. Controlled Radical Polymerization techniques were utilized to synthesize functionalized oligomers with specific end group placement for use in photopolymerizable thin film systems. Comparison of end and randomly functionalized oligomer species revealed the impact of altering reactive group placement. Significant differences in modulus and creep behavior based on placement of functional groups along the oligomer backbone.
Study on “Core-shell Particles” as New Resin Technology for UV Curable Formulations
The Nano-sized “Core-Shell Particle Resins” are studied as potential new resin technology by incorporating them into a variety of UV curable formulations. Improved physical properties such as crack resistance and reduced shrinkage when curing can be achieved. Scratch resistance can be achieved from materials that typically do not exhibit these properties, along with clear & smooth appearance. The particles are designed properly to be consistent and discrete dispersion in UV formulations even after cured.
Interaction and Biodegradation of UV/EB Cured Print Inks Applied to a Compostable Polymer Blend
The use of compostable polymers has largely increased in short lifetime product applications, and most of these products contain printed information, which are mostly produced by ultraviolet/electron beam radiation (UV/EB) curable printing inks. However, when compostable polymers are used, they are printed with non-biodegradable UV/EB inks raising a question if the final printed structure is still compostable or not. It is important to understand the impact of these different coatings on the compostable polymeric substrates and their overall impact on the degradation of the whole system. The objective of this project was to assess the compostability of poly(butylene adipate-co-terephthalate) (PBAT)/ thermoplastic starch (TPS) blend films coated with different UV/EB radiation curable inks. This work also explores how the incorporation of degradation-promoting additives affects the chemical changes on the compostable polymer substrates and their effect on the overall quality of the compost used during the biodegradation process. In summary, biodegradation of the polymer substrate was reduced up to 35% as assessed by evolution of CO2. EB-cured samples presented lower biodegradation rate than the UV-cured samples, reflecting that the compostable substrate was crosslinked by the relatively higher penetration of the ionizing radiation. The incorporation of transition-metal salt based pro-degrading additive caused alterations on the initiation biodegradation step (during the 21 days) for the samples with lower curing degree.
Interaction Of Photoexcited Photoinitiators With Nitroxyl Radicals
Formulations which undergo photopolymerization have in the most case photoinitiators like Darocur, Irgacure (PI). These formulations may have nitroxyl radicals which are added for prevent of degradation of cured coatings. Nitroxyls are also formed during oxidation of HALS stabilizers. Thus, there is an opportunity of interaction photoexcited PI with nitroxyl. This process was studied ns laser flash photolysis and by time-resolved ESR. The pattern of TR ESR spectra provides valuable information on the interaction of one or another excited state with nitroxyl.
Electron Beam Polymerization
Depth/Dose Characterization of Electron-beam Polymerization
Monte Carlo simulations are often used to predict depth/dose profiles for various voltages (electron accelerations). Voltage was varied while keeping dose, dose rate, and sample thickness constant. Confocal Raman microscopy was used to determine polymer conversion as a function of depth. Low voltages result in low conversion near the sample bottom. This inadequate energy penetration is consistent with Monte Carlo simulations.
Modification of Polymer Surfaces using Electron Beam Induced Graft Copolymerization
Electron beam (EB) irradiation may be used to modify the surface properties of polymer substrates. The irradiation produces radical sites on or near the surface of the polymer substrate. Monomer solutions react with these radicals to produce covalently bonded copolymer chains. EB irradiation may occur in the presence of the monomer solution or the substrate may be treated with the solution immediately after irradiation. A wide variety of polymer substrates may be used. The substrates may be in the form of films, fabrics, membranes, beads, or gels. The goal of the grafting is to alter the surface characteristics of the polymer substrate. This could include rendering the surface hydrophilic, hydrophobic, acidic, basic, etc. EB induced grafting may be used to create unique media for absorption, purification, separation, and controlled release processes. The media may be used for industrial, medical, and food product applications. Several examples of EB induced graft copolymerization are provided from published literature.
Electron Beam Treatment of Wood Thermoplastic Composites
Wood thermoplastic composites are a building material that is a nontoxic alternative to pressure treated lumber, and a stronger, sustainable alternative to plastic lumber. Durability and weight have been expressed as primary performance issues. Past research has focused on coupling agents and nanoparticles as additives to increase strength properties of the composites. The focus of this study was to examine the potential benefits of radiation crosslinked thermoset composites. Wood fiber reinforcement in a polyethylene matrix was irradiated at five different dose levels, post extrusion, with an electron beam. The composite materials were evaluated using flexural and hardness tests and scanning electron microscopy. The mechanical properties were enhanced and scanning electron microscopy showed very little evidence of wood fiber degradation. Creep resistance, impact and fire performance are among other properties that should be examined. A cost analysis of incorporating an electron beam into an extrusion line would also be of interest.
Radiation Initiated Polymerization of Wood Impregnants
High energy electrons and X-rays, derived from a high energy, high-current electron beam (EB), initiated in-situ polymerization of a unique class of monomers that were found to penetrate the cell walls of wood. Ionizing radiation initiated an auto-catalytic acrylic polymerization. The final cured product having the polymerizate, a polymer, both in the wood cell lumens and in the cell walls is called wood impregnated with a wood-polymer penetrant (WPP). Controlled lower dose rate of X-rays overcame disproportionation encountered when using higher dose-rate electron beam initiation. With X-rays, the in-situ polymerization took place in one exposure of modest dose. With EB, multiple passes were needed to avoid excessive heat build-up and monomer volatilization. Having entered the cell walls of the wood and then being polymerized within the cell walls, these radiation-cured unique monomers imparted outstanding dimensional stability upon exposure of the impregnated wood to humidity cycling. The preferred monomer system was also chemically modified prior to impregnation with agents that would remain in the wood and prevent the growth of fungi and other microbials. This technique differs from historic uses of monomers that merely filled the lumens of the wood (historic wood-polymer composites), which are only suitable for indoor use. The WPP impregnated wood that was either X-ray cured or EB cured demonstrated enhanced structural properties, dimensional stability, and decay resistance.
Electronics
Graphene Based UV-Curable Materials
It is reported a new approach for the preparation of a graphene-epoxy flexible transparent capacitor obtained by graphene-polymer transfer and UV-induced bonding. The obtained material showed a stable and clear capacitive behavior. This is an elegant and an easy-to process strategy to obtain transparent and flexible organic capacitors. A route to obtain inkjet printable, environmentally friendly inks based on graphene/acrylic nanocomposites is also presented. The excellent rheological characteristics of the formulations warranted printability with good repeatability. Suggested applications for the so-prepared inks are devoted to flexible and organic electronics.
Develop a Hybrid Conductive Film With Primer
The ideal transparent electrode; conductive polymer coated film, and conductive silver nano-particle coated film, for flexible displays has been produced at lower cost, lower resistivity, higher transmittance and with improved flexibility property at the KTI (Kimoto tech Inc) by using roll-to-roll process. Furthermore, KTI has developed a hybrid conductive film by using a simple and effective method, and achieved highly conductive AgNP's (silver nano-particle) composite meshes with excellent optical transparency and mechanical properties. This is achieved via applying PEDOT:PSS solutions sequentially to treat AgNP's films, resulting in AgNP / PEDOT:PSS composites. Thin films coated from this composite possess excellent mechanical, electric, and optical properties. The strong adhesion between AgNPs and the substrate is critical to obtain stable and robust AgNP films for wide application. The coated film's network, transparence, and conductivity was increased when polyethylene oxide functional acrylic monomers as primer which bound AgNP and substrate. Kimoto's coating technology improves flexible conductive films by supplementing with consistent glossy/anti-glare surface, hard coated/scratch resistant surface, and attractive appearance. KTI adds value and functionality by applying a variety of proprietary coatings to plastic substrates on one or both sides. KTI has developed hard-coated polyester, polycarbonate material offering excellent impact resistance, optical clarity, excellent abrasion resistance, and weather ability.
Production of Stratified Films Utilizing Photopolymerization and Monomer Reactivity
The temporal and spatial control of photopolymerization may allow independent control of surface and bulk properties of a polymer in a single reaction step. Using this premise, films were produced from co-photopolymerization in a light gradient of monomers with inherently different reactivities. Monomer systems and driving forces that facilitate stratification include inherent reactivity ratio, mono/diene combinations and oxygen inhibition. Parameters that influence the production of stratified films and resulting properties from stratification will be presented.
Introduction Of UV/EB Curable High Refractive Index Monomers And Oligomers For Optical Films
The back light unit (BLU) is a core component of liquid crystal displays (LCDs) that are used in notebook computers, mobile phones, navigation devices, flat screen TVs, and public information display (PID) devices, among many others. To enhance the optical efficiency of LCDs, optical films with a high refractive index have been used in the BLU. In particular, high refractive materials have been the subject of recent investigations to enhance the optical efficiency of BLUs. We studied and will present the effect of various monomers and oligomers with high refractive index on optical film prism sheets.
Equipment
Photocuring in Areas Where You Typically Cannot Get Light
This paper describes a technique for photo-curing and/or performing photochemistry in areas where it is difficult, if not impossible to get actinic radiation by normal, conventional means. The technique involves the use of a Light Diffusing Fiber (LDF) to deliver the actinic radiation. In most cases of photo-curing, the actinic radiation (usually UV or visible light) is delivered to the photo-curable material by direct exposure to a light source or exposure to reflected light from a light source. The light may be focused, de-focused, collimated, or otherwise manipulated with lenses, reflectors, prisms, gratings, etc. The light sources typically are lamps, LEDs, excimers, lasers, etc. The light can even be directed down a fiber or waveguide such that the light emits out the opposite end of the fiber and is available for photo-curing and/or performing photochemistry. However, there are cases where it is desirable to photo-cure or perform photochemistry on a material when the material is in an area where it would be impossible to direct light. The light might be blocked by any opaque, absorbing or highly scattering material or object. An example would be trying to photocure a material that is between two pieces of metal, curing inside an opaque tube or pipe, curing under an opaque paint or highly absorbing coated layer, etc. Using LDF is a means to deliver light and allows for the facile photo-curing of materials in these hard-to-get-light-to areas due to the small diameter and flexibility of the LDF.
UV Measurements of MP Lamps and LEDs for Process Design and Control
Accurate UV Measurements of spectral irradiance and exposure are essential to optimized design and production control of the UV curing process. Methods of measurement as well as some sources of error are presented. Radiometers and dosimeters are discussed, along with several techniques of using them for process specification and troubleshooting for both medium-preesure and LED systems.
Development in Low Voltage EB Curing for High Product Throughput Applications
Sustainable Packaging, lowest carbon foot print, are some of the mandates being required by brand managers and end users. Recent developments in EB curing equipment provides the required dose to cure at highest product speeds and at lowest input power. These developments have resulted in further reduction of the size of the equipment and the cost. Details of these developments will be presented.
High Efficiency LED Lighting Circuit by Series Regulator System
Most of LED lighting circuits are driven by switching regulator system in resent years. However, it is difficult to use the system in medical field, because switching regulator system generates electromagnetic noise. Therefore, we focus on series regulator system that doesn’t generate electromagnetic noise. The purpose of our research is to overcome disadvantages of series regulator system (power efficiency, inrush current and luminous flux stability, when compared to switching regulator system).
Formulating for Printing & Packaging
Developing Formable Properties in Energy Curable Flexo Inks
This paper will investigate a growing interest in the printing market for energy curable flexo inks that can be formed post cure. Factors such as: backbone chemistry, crosslink density, molecular weight, and ink properties will be the basis of the evaluations to determine the optimum chemistry selection. Testing will focus on a white ink formulation and correlations in performance will be drawn between physical property testing and vacuum forming and heat shrinking tests.
Self-Curing Acrylate Resin for UV Consumer Product Printing and Coating Applications
The continuous tightening of direct and indirect food contact regulations in the EU and elsewhere has forced the food packaging value chain to consider migration from packaging components more thoroughly. For UV curable inks and coatings, the focus has been on the migration of photoinitiators since in the past migration of low molecular photoinitiators into food have caused issues. Although polymeric photoinitators have been developed for low migration UV inks and coatings said photoinitiators suffer from poor solubility in acrylates, resulting in poor ink flowability and low reactivity which is problematic for high speed offset and Flexo printing processesF. This paper discusses Allnex's latest development in acrylated resin binder technology for UV printing and coating applications which does not require the addition of photoinitiators.
Mitigating Chemicals of Concern Through the Usage of Novel Energy Curable Acrylate Technology
Epoxy acrylates are one of the most widely used resins in energy cured inks, coatings and overprint varnishes for consumer product packaging and graphic arts. In addition to outstanding scratch and impact resistance, epoxy acrylates are known for their cost effectiveness. Bisphenol-A (BPA) is a building block for acrylated epoxy resins and in certain studies has been identified as a chemical of concern. The purpose of this presentation is to review what new chemistries are either currently commercially available or in development as resin system replacements for standard Bisphenol-A epoxy acrylates that would be appropriate for usage in consumer product packaging and graphic art applications. This presentation will take into consideration both conventional and bio-renewable approaches based on performance vs. cost criteria.
Novel Dual Function Photoinitiators for Low Migration and Low Odor Packaging Applications
UV curable systems for packaging applications require low migration photoinitiators. To meet this need a new approach was taken for the design of the photoinitiator. In this paper we will describe a dual function photoinitiator, in which both acrylates and photoinitiators are chemically part of a high molecular weight polymer. We will show how this results in good cure speed, low odor, very low migration and ease of use for inks and coatings.
Formulation
A Study for Enhancing Through Cure
There is an increasing number of requests requiring placement of more or new light/UV blocking additives into UV coatings. Each of these additives then has the potential to affect the cure of the coating. An initial survey of ways to fortify cure has been made.
Formulation and Performance Advances in (Meth)acrylate Based Sealants :A Dual Cure Feasibility Study
UV curable sealants offer both processing and performance advantages in a variety of applications. Sealants based on (meth)acrylate functional monomers/oligomers can be formulated for zero VOC, fast cure and rapid property development but have limitations in use for substrate geometries that have shadows or dark spots and formulations that are optically dense. This paper will explore the effect of co-free radical initiator to overcome these limitations and enhance sealant performance properties such as heat stability and creep resistance.
Shrinkage of UV Oligomers and Monomers
Volume shrinkage is one of the main drawbacks of UV-cured coatings and can lead to premature coating failures. Shrinkage occurs during polymerization and is due to the replacement of relatively weak long distance intermolecular Van der Waals bonds by strong, shorter, covalent bonds between the carbon atoms of different monomer units. In our study we investigated the shrinkage behavior of a wide range of monomers and oligomers, including the main chemistries for UV oligomers Epoxy, Polyester/Polyether and Urethane Acrylates and Methacrylates. Comparisons of theoretical calculations versus practical measurements of shrinkage were addressed as well as the influence of parameters like Double Bond Conversion, Glass Transition Temperature (Tg) and UV intensity. With a better understanding of why acrylates shrink, and with awareness of how to mitigate that shrinkage, end users are better able to choose raw materials that perform as needed and as expected.
Dual UV Curing System Using a Dimethacrylate Containing a Chalcone Moiety
We have designed and synthesized a dimethacrylate containing a chalcone moiety. A novel dual UV curing system using photo-radical polymerization of methacrylates and photodimerization of chalcone was devised using the monomer. The mixture of the monomer, 2-ethylhexyl methacrylate as a diluent, and photoinitiators was placed between two CaF2 plates to obtain a sample film. The film was irradiated at UV light (wavelength: 254, 365, 405 nm and 370 < λ < 400 nm). The effect of initiators or irradiation wavelength on the conversion of the methacryl unit and the chalcone unit was investigated using UV and FT-IR spectroscopy. We have found that the conversion of the methacryl unit and the chalcone unit was tunable by the irradiation wavelength and initiators added. The effect of atmosphere in the system was slightly observed. The mixture of the monomer and 2-ethylhexyl methacrylate was photopolymerized without an initiator. The result suggests the possibility of a novel photoinitiating system using a chalcone moiety.
Global Market Overview
High Performance Coatings
Heat-Resistant UV-Curable Clearcoat for Aircraft Exteriors
We are continuing the development of a heat-resistant UV-curable clearcoat for use on the aircraft exterior. The latest formulations tested show significantly improved resistance to discoloration experienced in service, compared to thermally-cured alternatives. This has resulted in improved appearance and engineering performance. These non-pigmented urethane-based coatings were tested to our requirements for finish quality and engineering performance. Pathways were identified for development and deployment of the clearcoat in production. Follow-on work will be focused on formulations that will protect underlying pigmented paint from discoloration.
Radiation Curable Components and Their use in Hard, Scratch Resistant Coating Applications
Hard, scratch resistant acrylated components are used on plastic substrates in a complex range of application segments ranging from electronics, communications, semiconductor and data storage to optics, automotive, aerospace, and medical industries. Just as the applications are wide and diverse the variety of plastics that are used increases and includes materials such as PET, PMMA and PC. This paper will describe a range of high functionality monomers and oligomers including some waterborne polyurethane dispersion (UV-PUD) examples. Data demonstrating excellent scratch and abrasion properties will be discussed along with accelerated weathering data supporting use for exterior coatings applications.
Effect of polymer particles on the light scattering properties of UV cured antigalre hard coating
Organic PMMA particles concentration, particle size, particle size distribution, refractive index difference with resin, coating thickness, and so on, which effect on the light scattering properties of UV cured antigalre hard coating were studied, respectively. And on the basis of the above study, the mechanism of light scattering in the coating was studied preliminarily.
Smart UV Bionic Coatings on Architecture Application
Inspired by the self- adjustment of focal distance of eyeballs behavior in nature, we developed several coatings that can facilitate the bionic creation of self–etching, patterning surfaces on various substrates, thus providing a feasible way of fabricating surfaces with photochromic properties for civil and industrial applications, especially on architecture application to lower Carbon emission.
LED Formulation
Pushing the Limits of LED Curing and Looking Forward to a Bright Future
In recent years, LED curing has become a viable and economical technology for offset printing. In order to maximize the full potential of the LED process, the industry needs to overcome certain technological barriers, such as lamp energy and the lack of suitable photo initiators. It is now possible to optimize the chemistry and process in order to produce inks for packaging and even low migration inks for primary food packaging.
A 100% Solids UV LED Curable Coating
A 100% solids UV LED curable coating and the machine for its application/cure has been developed. The machine is equipped with a 395 nm UV LED. The coating is suitable for different flooring applications: VCT, hard wood, laminate, marble, terrazzo, concrete. Some of the applications such as hard wood, concrete and terrazzo floors require a 100% solids UV LED curable primer that has been acquired as well. The resulting coating is scratch and impact resistant.
UV-LED Photoinitiators – The Right Tool for the Job
While there has been a rise in interest with UV-LED curing, it is recognized that simply transferring over materials and formulations from traditional UV curing will not work in most cases. There are challenges getting surface cure without significant yellowing in UV-LED curing. Pigmented systems reduce the impact but this is still a problem in clear coatings such as OPV's. In addition, the use of inefficient photoinitiator systems can cause poor performance as well as increasing a systems cost. The PL Industries division of Esstech, Inc. has been developing a series of new photoinitiators targeted specifically for use in UV-LED curing. These photoinitiators perform well in systems ranging from ultra-thin pigmented systems right through very high coat weight films. Examples will be presented in the 4 offset process colors as well as both thin and thick clear films.
Measurement & Analysis
Produce a temperature-sensitivity film coated on the glass via photopolymerization
In this study, a hydroxylated glass was coated by a poly(N-isopropylacrylamide) (pNIPAM) film via photopolymerization reaction. The pNIPAM film grafted on the glass was investigated by ATR-FTIR and XPS. UV-Vis spectrophotometric direct transmittance analysis was used to study the temperature-sensitivity property of the pNIPAM film. All the results indicated that the pNIPAM film, which was grafted on the surface of the glass, has a good adhesive strength and stability, and it has many potential applications due to the property of discoloration with different temperature.
Comparison a Blue Diode Laser with a Mercury Arc Lamp in the Curing of a Water-Soluble Resin by Pho
Photo-differential scanning calorimetry (Photo-DSC) and photo-dielectric analysis (Photo-DEA) are powerful analytical tools for examining the dependence of UV-curing kinetics on different light sources, resin formulations, and process conditions. In this presentation, the efficiencies of two different radiation sources, a Hg arc lamp with a broad band filter (320 nm to 500 nm) and a 447 nm blue laser will be compared in the curing of blue-curing adhesives used for stereolithography.
The Importance of Controlling Coating Temperature in UV Application Processes
In this presentation, we examine the temperature vs. viscosity characteristics of UV cure coatings and demonstrate how variations in viscosity caused by changes in coating temperature at the point of application produce significant variations in the outcome of the coating process. While directly applicable to the end-user, this information is also extremely important for the formulator to understand as they are trying to develop coatings for specific applications.
Synthesis and Properties of UV-Curable Polyurethane Acrylates Based on Pcdl Diols
UV-curable polyurethane (UV-PUA) was synthesized based on polycarbonate diols (PCDL) with different molecular weight and end-capping groups. Methylacrylate-β-hydroxyethyl methacrylate (HEMA) and pentaerythritol triacrylate (PET3A) was used to impart mono-methacrylate, and tri-acrylate functionality to the end-capping group, respectively. FTIR, GPC, UV spectroscopy and tensile test were used to characterize the UV-PUA. The results showed that: with the increasing of the molecular weight of PCDL, the molecular weight and viscosity of the UV-PUA was increasing, Young's modulus of the UV-curable film becomes smaller but the elongation at break becomes larger in the tensile test; The molecular weight and viscosity of the UV-PUA end-capped by PET3A was larger than those end-capped by HEMA, Young's modulus of the UV-curable film of the former was larger than the latter, but the elongation at break was smaller. All the films of UV-PUA showed excellent chemical resistance.
Medical & Dental
Recent Advances In Monomers And Photoinitiators For Dental Restoratives
Mimicking and replacing the natural tooth hard substance is considerably the most challenging task in modern dental medicine. State of the art dental restoratives are often based on di(meth)acrylate photochemistry and have already replaced the use of potentially toxic and aesthetically unpleasing mercury alloys. However, di(meth)acrylate photochemistry has created a number of new challenges that need to be targeted in order to improve dental replacements. Two major problems are stress induced by photopolymerisation shrinkage and limited penetration of light leading to insufficient curing depths. Those drawbacks can be solved by proper modification of monomers, photoinitiators (e.g.: Ivocerin) and inorganic fillers.
An Overview on Low Cytotoxic Alternatives to (Meth)Acrylates: Vinyl Esters and Vinyl Carbonates
Vinyl esters and vinyl carbonates have been shown to be promising alternatives to (meth)acrylates due to significantly lower cytotoxicity. Their reactivity is lower than those of acrylates. By addition of thiols, the reactivity may exceed the acrylates. These materials are suitable for biomedical application as well as for coatings.
The Technical Challenges of Transitioning your UV Curing Process from Lamp to LED
The benefits of LED technology such as long lifetimes, lower energy costs and lower curing temperatures have driven interest in medical device manufacturers to transition existing curing processes from lamp systems to LED. However, there are a number of technical challenges, which must be considered to ensure a successful transition. Adhesive compatibility, radiometry and oxygen inhibition will be discussed, along with an overview of process limitations that may be encountered.
Metal
UV Technology for Protection of Surfaces
In addition to providing manufacturing efficiency and environmental benefits, UV technology provides excellent protection for surfaces, including UV protection and resistance to weathering from sunlight. UV technology also provides toughness, solvent resistance, abrasion resistance, and corrosion protection for metal surfaces, including steel and high strength aluminum aerospace alloys. When compared to conventional technology, high performance solvent-free UV curable coatings provide improved protection with dramatically faster cure and lower material usage.
Achieving Adhesion to Difficult Metal and Plastic Substrates
One of the most challenging tasks that a formulator for UV and EB cured systems has to face is that of getting good adhesion to difficult to adhere to substrates. Recent work at PL Industries has focused on the development of a range of UV and EB curable materials that can be used to enhance adhesion in a wide range of formulations. A comparison of the data in using these materials to improve adhesion on metals such as Stainless Steel, Tin Free Steel, and plastics such as PET, Polycarbonate and Polyethylene will be discussed.
Oxygen Inhibition
UV Curing in an Inerted Atmosphere Update
Displacing Oxygen within a curing chamber with Nitrogen has been an industry accepted practice for years providing improved cross linking of > UV inks and coatings. This paper provides an update in processes,applications and equipment for the UV Industry
Using con-focus RAMAN spectra to analysis double bond conversion at top 1 micron/1 micron far from
The difference of UVC Intensity (mW/cm2) and UVC energy (mJ/cm2) between Microwave Powered UV H Lamp (M.P.UV H Lamp) and Electrode Powered UV H Lamp(E.P. UV H Lamp) will be compared carefully. This investigation using con-focus RAMAN spectra will show that More UVC output and better spectra matching between the absorption spectra of Irg.184 and the emission spectra of E.P.UV H Lamp greatly reduce oxygen inhibition at surface of cured film, improve the surface curing efficiency and increase surface scratch resistance ability for optical functional hard coatings. There is a possibility of reducing required Nitrogen concentration when your system needs to be cured in inert atmosphere, and increasing lon-term light stability of Cured optical functional films. We can provide alternative solution for reducing Oxygen inhibition for hard coatings and improving surface curing. Both Double Bond Conversion and Scratch resistance for the optical functional hard coating will be presented in this paper.
Mitigation of Oxygen Inhibition in UV LED, UVA, and Low Intensity UV Cure
Oxygen inhibition is an age-old problem for coatings that cure via free-radical polymerization. Molecular oxygen can physically quench the triplet state of the photoinitiator/sensitizer, or it can scavenge the free radicals or active radical centers to produce unreactive peroxide radicals. The end results range from reduced coating properties to uncured, liquid surfaces on the coating. This issue is even more pronounced in low intensity cure processes, such as UV LED or UVA cure, which frequently result in tacky, uncured surfaces. There are known physical and chemical ways to reduce oxygen inhibition or improve surface cure. This paper will discuss these methods, provide starting point formulations that use the chemical solutions, and show the cured coating properties of these formulations.
Experimental comparison of various anti-oxygen inhibition strategies in LED curing
Photocuring of coatings with LEDs in air suffers from the detrimental effect of molecular oxygen causing low double bond conversion and poor properties of a cured coating. The objective of this study is to assess the performance of various anti-oxygen inhibition strategies by comparing double bond conversions at low light intensities.
Photoinitiator
Photopolymerization Using Photolatent Amine Catalysts
A novel series of photobase generators (PBG), in the form of quaternary ammonium salts of an absorbing carboxylic acid was synthesized. The photobases have the ability to generate highly reactive bases such as 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5-Diazabicyclo[4.3.0]non-5-ene (DBN) or 1,1,3,3-Tetramethylguanidine (TMG). The synthesis procedure is really simple and consists to complex an equivalent of phenylglyoxylic acid (PA) with an amount of desired amines. It is known that PA compound undergoes a photodecarboxylation process in highly quantum yield, allowing the release of the photolatent base. These photolatent bases were applied effectively to the crosslinking of an epoxide monomer without any post thermal treatment. By adding thiol in the photocatalyst system, an improvement of the polymerization performances was observed due to the production a very strong nucleophilic thiolate anion. Finally, these compounds were effectively applied as catalyst to induce the formation of polythiourethane polymer and interprenated epoxy-acrylate polymer network.
Photoinitiating Covalently Bound Organically-Modified Clay Additives
Organically-modified clays have been explored for years as property enhancing additives for composite materials. Much of the aforementioned research has focused on intercalated quaternary ammonium ionic compounds; however, herein the effects of covalently bound organically-modified (CBOM) clays are explored with particular emphasis on photoinitating CBOM clays. Compared to multiple controls, physical testing of the photoinitiating CBOM clay formulations was generally enhanced, as expected, while photo-differential scanning calorimetry (photo-DSC) indicated little to no rate depreciation via the photoinitiating CBOM clays.
Novel Phosphine Oxide Photoinitiators
This paper presents the work completed on the synthesis of a range of novel phosphine oxides which show enhanced surface curing of acrylate systems when exposed to both high pressure mercury lamps and LED's operating at 365/395nm, without the addition of other photoinitiators. The new phosphine oxides are much less prone to oxygen inhibition, this is shown by the analysis of cured films by RT-FTIR and Photo-DSC which have been used to study the double bond conversion at the surface and in the interior of the exposed samples. These results are backed up by standard curing tests, CIDNP and ESR spectroscopy that have also been performed on the cured films.
Waterborne
Waterborne UV Curable Coatings for Industrial Market Segments
UV cured waterborne PUDs have demonstrated their versatility in many industrial market segments. Today there are ever-increasing customer requests for film properties specific to more than one market. There is no general solution: each customer has his/her own list of coating requirements. To meet customer expectations, the formulator needs a general approach for formulation development. In this paper we discuss a formulating strategy for using blends of UV curable PUDs and non-UV curable PUDs to attain desired film properties.
Novel Robust Energy-Curable Polyurethane Dispersion With High Formulation Versatility
The furniture industry is under constant pressure to develop the next generation of coatings matching more stringent economical, regulatory and performance requirements. Water-based energy-curable compositions are increasingly selected as the environmental-friendly partner of choice – considering that their formulation versatility associated with their fast cure constitutes a strong technological asset. In order to support formulators on their endeavors to develop improved cost-conscious product formulations, Allnex has developed a robust & versatile radiation-curable polyurethane dispersion that can be used as the building block for wood coating formulations with a genuine value in use. This encompasses the excellent dispersion stability and the good aspect of the coating after forced drying. The new product can be easily formulated with additives and offers a wide compatibility with other waterborne polyacrylic & polyurethane resins to meet good final coating performance at an advantageous cost. A technical benchmarking is presented with supportive test results showing the appealing performances of the new prototype compared to the current market standards. An insight on the polymer architecture is also provided that places the new developments in perspective.
Wood
Waterborne UV Coatings for Industrial Wood Applications
Waterborne (WB) UV curable coatings have become popular choices for industrial wood applications. Kitchen cabinet and office furniture manufacturers choose these coatings because they have excellent resistance and mechanical properties, excellent application properties and very low VOCs. This paper will compare the performance of WB UV coatings to that of a traditional solvent-based acid catalyzed varnish. Test methods and formulating techniques will be discussed.
Comparing UV Cured Wood Floor Finishes to Conventional 2K Systems
UV Curable Water-based Polyurethane Dispersions (UV PUDs) are being used to coat wood floors in such areas as residential, sports, and commercial. This technology offers ease of application similar to a 1K and provides protection and durability equal to or better than the best 2K systems. Due to the instant cure chemistry of these coatings, a reduction in downtime is a valuable benefit to the end user due to the quicker return to service. Homeowners can return to live on the floor, a gym can be reopened sooner or a restaurant can be reopened the next morning. This water-based finish is more environmentally friendly with a near 0 VOC and extremely low odor. This talk will focus on the on-site application and curing of conventional 2K and UV cured systems on wood floors. Specifically, the strengths and weaknesses of the 2K and UV Cured systems will be discussed, using the Maple Flooring Manufactures Association (MFMA) specifications.
UV-Cured Powder Coating : The Development of a High Gloss Coating for MDF
Up until this year a single step high gloss UV-cured powder coating could not be produced. DVUV, working with its sister company Keyland Polymer, developed and successfully introduced in the spring of 2013 a single coat high gloss UV-cured powder coating for MDF. The development process required various resources in the R&D lab as well as on the application floor. This article will describe the challenges of developing a high gloss coating for MDF and the processes it took to overcome them.
Advancements in UV LED curing for wood coatings
Not only is UV LED curing for wood coatings possible today, UV LED lamp technology has progressed to the point where air-cooled lamps have the performance needed for these demanding applications. The combination of continuous high irradiance with uniform output and flexible scaling, now allows users to implement air-cooled LED curing into environments for wood coatings applications that were previously only attainable by water cooled solutions.