Overview Of UV Curing In The Medical Industry
Overview of UV Curing inthe Medical IndustryManufacturers of a wide variety ofmedical products such as syringes,catheters, hearing aids, dialysismachines, medication patches,hydrogels, filters, test strips, etc. find UVcuring of coatings, inks and adhesivesspeeds production and reduces costs,while insuring high product quality. Thispaper provides an introduction to UV curing and its application in the medical market.BackgroundUV curing is a photochemical polymerization process. A UV-curable coating, ink, oradhesive has a photoinitiator, which when exposed to UV energy initiates thepolymerization (drying) process. So instead of using a solvent or waterborneformulation in which the solvent or water must evaporate, typically via thermal ovenprocessing, UV formulations cure very fast in a UV cure chamber. For more than fortyyears UV curing has been used in a wide variety of industrial processes. It is now thestandard processing method for many products including graphic arts printing, woodcoating, and smart phone displays to name a few. The medical industry has also beenusing UV curing for many years, but continues to find new and innovativeapplications, especially as new medical treatments and devices are developed.UV curing is a line-of-sight process. This means that every surface with the wet ink,coating or adhesive must see adequate UV energy to cure. UV energy cannotpenetrate opaque materials to cure in shadow areas. Obviously this can be achallenge for some three-dimensional parts. Although UV curing is a “cool” curingprocess, all UV systems generate heat, which can sometimes damage heat sensitivesubstrates. UV equipment suppliers use various techniques to adequately cure threedimensional parts and to reduce unwanted heat on substrates. Before ruling out yourapplication for UV curing, speak first with an equipment supplier. You may bepleasantly surprised what is possible with today’s technology.Marking/DecoratingWhether it’s a dialysis machine or adisposable test tube, UV inks and coatingsare used for product branding, measurementmarking, print-on-demand serial numbers,etc. UV formulations can be printed via pad,screen, inkjet or other commonly usedprinting methods onto a wide variety ofsubstrates including paper, glass, plastics,and metal. A good example of decorating isprinting a logo or other decorative elementonto a medical patch, bandage, or tape.1
Bonding/AssemblyPrimary applications for UV include curing of adhesives for assembly, sealing andalso pressure sensitive adhesives. UV curable adhesives are used for bondingsyringes, catheters and other medical devices. Because UV light of varied spectraloutput penetrates glass, polypropylene and many other plastics, both flat andcomplex 3D shaped parts are easily bonded instantaneously. By ensuring superiorbonding at higher speeds, UV curing produces quality assemblies faster and lessexpensively. UV-curable pressure sensitive adhesives find application on a variety ofmedical tapes and bandages. Most UV curing assembly processes are done via anindexing or continuous conveyor line, while most pressure sensitive adhesives areapplied on web type presses.CoatingsUV coatings include biocompatible andsterilizable seals, clear hard coats toimprove durability, and functional coatingsthat improve lubricity or healing, amongothers. Common applications include teststrips, hydrogels, catheters, medical filters,and medical instrument lenses. UV curingof coatings offers higher production ratesand standards of quality. Whether it’s aconverting operation on a wide web orthree-dimensional parts, UV curing integrates easily into coating productionprocesses.UV EquipmentTypically UV curing is either replacing an existing manual process or a thermal ovendrying process. Automated UV curing processes can dramatically improve mostmedical manufacturing processes where precision, consistency and quality are veryimportant. The following is a brief overview of UV curing equipment available in themarket and the advantages and disadvantages for most medical applications.Traditional UV curing systems consist of a lamp head, or irradiator, which contains thebulb and reflector. The lamp head is controlled by a power supply or ballast, which isconnected to the lamp head via electrical cables. For proper operation, the lamp headmust be cooled, so there is also some type of cooling mechanism such as a blower orcooling water to maintain bulb temperatures.More recently, UV LED curing systems are also available offering the added benefitsof long life and small form factor for easy integration into existing marking, decorating,and coating machines.The type of UV curing equipment (mercury arc, spot cure, microwave-powered, or UVLED), specific bulb type, and orientation to the part will depend on the chemistry,overall process design, and maintenance considerations. Many medical adhesivescure best with a long wavelength, iron or metal halide additive (350-430nm, oftenreferred to as “D” or “V”) type bulbs for efficient through cure. Some decorative inks2
cure best with a short wavelength mercury bulb (250-300nm, often referred to as “H”).Typically the chemistry formulator will specify which wavelengths to use. Arc lamps (also referred to as electrode type) have electrodes at either end ofa quartz tube and emit broad spectrum UV energy.Spot cure systems are available with either mercury arc or UV LED technologytypically with a light guide or wand to direct the energy to a small cure area ofan inch diameter or less. Some UV LED systems do not use a light guide,rather the LED chip is located at the point of cure. Spot cure systems may behand-held in manual processes or incorporated into high-speed automatedsystems for micro assembly bonding applications. The advantage is the energycan be directed precisely where it is needed, without damaging other sensitivecomponents.Microwave-powered lamps (also referred to as electrodeless type) are simply atotally enclosed quartz tube. Instead of striking an arc between two electrodesto excite the gasses in the bulb, microwave energy penetrates the quartz toexcite the gasses. They also emit broad spectrum UV energy.UV LED curing systems, commercial since the mid 2000’s, use light emittingdiode technology to emit essentially monochromatic UV energy at 365, 385,395 or 405 nm wavelengths. Individual LEDs are packed into arrays behind anemission window of a UV LED curing system. For efficient operation and longlife the LEDs must be cooled, but it’s significantly less compared to traditionaltechnologies and often self-contained inside the small form factor and lightweight lamp heads.The choice between mercury arc, spot cure, microwave-powered, or UV LED curingtechnology depends on several factors. Spot cure systems are ideal for precise curingof small areas. Arc lamp systems are generally less costly, but do not last as long orhave stable output over their short life as illustrated in the chart below. This isespecially true for thelonger wavelength,RADIANT OUTPUT STABILITYadditive bulbs where theMicrowave Lamp Compared to Arc Lampelectrodeless bulbs are100Fusion Microwave-PoweredBulbguaranteed for typically sixto ten times the life of anPercentarc type bulb and a UVof InitialArc LampRadiantLED system operatesOutputHigh Power or20,000 plus hours.many starts & stopsArc lamps generally useshutters when a process100020003000 8000requires lamps to shut off0for short periods, such asHours of Operationsome type of indexingconveyor line or when an automated line stops intermittently or unexpectedly.Microwave-powered lamps restart in seconds and UV LED lamps are instant on/off,so shutters are not required. Shutters can require additional maintenance.3
Microwave-powered and UV LED systems are available in modular units that fit easilyinto marking, decorating, bonding and coating machines. UV LED systems offer thesmallest form factor without the need for bulky cooling systems and are the mostenergy efficient, but they can be more expensive and are not very effective at workingdistances greater than about 50mm or more. UV LEDs offer long wavelength outputwhich is ideal for many bonding putStable EnergyOutputUV Curing Technology ComparisonsMercury ArcSpot CureMicrowave-powered500-2,000See arc or3,000-8,000 hourshoursUV LEDUV LED20k NoSee arc orUV LEDYesYesNoYesYesYesNoNoSee arc orUV LED1 inchdiameter orlessShuttersYesCure Area6 inch area ormoreCoolingAir or waterTypically airTypically airForm FactorLargestSmallestSmall, Modular6 inch area or moreCan becustomized toprocessAir, selfcontainedSmaller, ModularFormulationsUV curable formulations are available from a wide variety of suppliers. Somesuppliers specialize in custom formulators designed to meet your specificrequirements. Other larger formulators may offer a wide variety of standard productsand may or may not be able to customize them to meet your specific needs.Formulators typically specialize in adhesives, inks, or coatings and sometimes forspecific applications or substrates, although there are always exceptions.UV chemistries are typically very high solids, low or no VOC formulations. Some UVchemistries, especially for adhesive or sealing applications, may be formulated fordual cure in which the UV exposure sets or holds parts in place, while an oven orambient cure completes the cure.The important thing is to work with a formulator who is familiar with your applicationand has available approved medical grade adhesives and coatings. Especially fornew processes, it’s also important that the UV equipment supplier be involved asearly as possible because a successful project requires design input from both aformulating and curing perspective from the start. A complete list of UV formulatorswith approved medical grade materials is available from Heraeus Noblelight.4
Cost/Benefit AnalysisAny time you are considering a new process it’s important to ensure it will have anacceptable return on investment. When analyzing costs and benefits for a UV curingproject you’ll typically find that the UV formulations cost more per volume thantraditional formulations. However, you’ll also find that reduced labor costs, scrap,VOC emissions, along with increased production rates and other benefits more thanoffset the increase in costs of UV formulations.Below are two examples highlighting different cost benefits associated with a UVcuring process. The first focuses on a reduction in work-in-process (WIP) and thesecond focuses on UV-curable ink and adhesive costs. These two examples aretaken from a paper titled, Some Economic Factors of UV Curing, by Dick Stowe.Example 1: Reduction of WIPA manufacturer of complex electro-optical devices assembles a finished product witha value of approximately 50,000 and produces 50 assemblies per month. Eachsubassembly requires ten to fifteen adhesive bonds to make the complete product, fora total of about 100 bonds. When using both RTV and epoxies for these bonds, eachbond or seal required two to three days to set up before being tested and thenassembled. The total cycle time of the product was four months.The use of UV curable adhesives reduced the cycle time of a subassembly to 2 hoursand the total product cycle time to 4 days. The WIP product value (assuming astraight-line value rate) of 4 months was:Using 2-part adhesive - 2.5 millionUsing UV adhesive - 18,750This example shows how a significant amount of capital can be tied up in WIP and thedramatic reduction possible with UV curing. This customer also significantly reducedscrap because they were able to rework faulty UV bonds on subassemblies, whichwas not possible with the 2-part adhesives.Example 2: Costs of Inks and AdhesivesGenerally UV curable inks are comparable in cost on anapplied basis to traditional solvent-based inks. Theprinciple differences in cost per unit volume relate to thepercent solids in the as-purchased form. Consequently,comparison of cost per unit area or per product unit ofdry film by weight or by coverage is a more meaningfulcomparison.For a meaningful comparison ofsolvent-based versus UV-curableink costs, compare the cost perunit area or cost per productunit of dry film by weight or bycoverage.For example, a conventional pad printing ink can bepurchased in concentrated form for 45 to 60 per liter,to which thinner, retarder, etc. is added. Mixing labor and loss will add to its net cost.The attention to the ink and re-adjustment during printing increases the effective costof its use. When these costs are considered, it may compare to a UV-curable ink at 120 per liter, which needs no adjustment or stabilizing, requires little attention andgives higher solids coverage.5
A typical assembly adhesive may cost 32.00 per liter (not including catalyst),compared to 53.00 for a one-part UV curable. One bond may use 0.15 in UVcurable material compared to 0.10. Multiplied by number of total bonds, a costdifferential is easily calculated. Interestingly, it is in adhesive applications that some ofthe most dramatic savings are achieved in process-related costs that completelyovershadow the direct material cost difference.Future TrendsDrug delivery systems including transdermal patches and medicated stents are beingcured with UV and UV light emitting diodes (LEDS) are now available for adhesivecuring applications. UV has been used for many years to purify water, but morerecently found application for sterilization of medical parts. 3D printing/additivemanufacturing of medical products is yet another area where UV curing is finding raeus Noblelight GmbHHeraeusstraße 12-1463450 HanauPhone 49 6181 35 4499Fax 49 6181 35 164499hng-uv@heraeus.comUSAHeraeus Noblelight America LLC910 Clopper RoadGaithersburg, MD 20878Phone 1 301 527 2660Fax 1 301 527 2661info.hna.uvp@heraeus.com6Technical data is subject to modification.HNG UVP140E/03.19The medical market continues to see strong growth and should remain strong as thebaby boomers age. There will be an increased need for more home medical devicesas a means to reduce health care costs. As medical research leads to new therapies,UV curing will certainly be a part of the many new medical devices and products tocome. Whether it’s curing an ink, coating or adhesive, UV curing can increaseproductivity and product quality, which is so vital to the medical market.
The medical industry has also been using UV curing for many years, but continues to find new and innovative applications, especially as new medical treatments and devices are developed. UV curing is a line-of-sight process. This means that every surface with the wet ink, coating or adhes
3.13.3 Curing Formed Surfaces 3.13.4 Curing Unformed Surfaces 3.13.5 Temperature of Concrete During Curing 3.13.6 Protection from Mechanical Injury 3.13.7 Protection After Curing 3.14 FIELD QUALITY CONTROL 3.14.1 Sampling 3.14.2 Testing 3.14.2.1 Slump Tests 3.14.2.2 Temperature Tests 3.14.2.3 Compressive Strength Tests
The Flexographic Process Flexography (Flexo) is a process in which the printing image stands up in relief. A liquid ink (generic term for low viscosity inks) is applied, whereby solvent- or water-based inks or UV curing can be used. UV-cured systems have seen rapid growth in certain segme
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A.J.D. ol. 20, No. 4 EFFECT OF DIFFERENT LIGHT CURING TECHNIQUES ON COLOR 397 Fig. (1) Composan Micro-hybrid resin composite Fig. (3) Halogen light curing unit* Fig. (5) custom-made split circular Teflon mold Fig. (2) Z250 nanohybrid composite Fig. (4) LED light curing unit (D-2000) Fig. (6) Spectrophotometer
Proof. A partition of nvertices into n 1 subsets necessarily consists of n 2 singletons and one pair of vertices fu;vg.This is a colour-partition if and only if uv̸ E.Hence an 1(G) n 2) m, where mis the number of pairs of adjacent vertices, equal to the number of edges of Gwhen there are no parallel edges.Then [zn 1]P(G;z) (1 2 n 1)an(G) an 1(G) m: The join G1 G2 of two graphs G1 .
the temperature of the adhesive curing reaction with a thermocouple inserted into standard mass (25 grams) of mixed adhesive. The maximum temperature found during the adhesive curing process was considered to be the exothermic peak. The peak exotherm test, where mass is 25-50 g, is often pres
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The dynamics of group size is an important component of group work. A small group is often considered to consist of three or more people (Beebe & Masterson, 2003). Groups of two are called dyads and are not encouraged for group work because there are not a sufficient number of individuals to generate creativity and a diversity of ideas (Csernica et al., 2002). In general, it is suggested that .
