An adhesive that passes a bench pull test can still fail in the field within months. The gap between the two is almost always chemical compatibility, locked-in stress, or an environment the bench never simulated. A durable thermoplastic bond accounts for all three before production starts. Substrate Compatibility Compatibility runs two directions. The adhesive has to wet and grip the plastic, and it must not attack it. Polycarbonate and some rigid PVC formulations are prone to stress cracking when exposed to aggressive solvent-based adhesives or to the solvents in some primers. An adhesive that bonds strongly but crazes the substrate has traded one failure mode for another. Verify compatibility by bonding stressed coupons, bending a bonded strip over a mandrel, holding it under load, and inspecting for surface crazing after 24 to 72 hours. Light-curable acrylics and well-chosen cyanoacrylates generally avoid this problem on sensitive resins, but confirm it on your specific grade. Cure Shrinkage and Locked-In Stress Every adhesive that cures by polymerization shrinks as it does so. If the bond is rigid and the shrinkage is high, the interface carries that stress before the assembly sees any external load. Over time, combined with service stress, it drives delamination. Two levers reduce the problem. Choose a grade with low linear shrinkage, and keep the bondline thin so the absolute shrinkage displacement stays small. For joints between materials with different stiffness or expansion rates, the mechanism is the same one described in how CTE mismatch causes adhesive bond failure, and a slightly flexible adhesive relieves it. Environmental Resistance Match the adhesive to the real service conditions: Humidity. Absorbed water plasticizes many adhesive polymers and lowers shear strength. Specify low water absorption for outdoor or washdown service and confirm with damp-heat aging at 85 percent relative humidity. Temperature cycling. Repeated expansion and contraction fatigues the interface. Run at least 100 cycles across the full service range on sample parts. Chemical exposure. Fuels, oils, cleaning agents, and disinfectant sprays can swell or attack both adhesive and substrate. Test with the actual chemicals, at the actual concentration and dwell time. For help mapping your service environment to an adhesive spec, Email Us. Viscosity and Application Compatibility and durability mean nothing if the adhesive cannot be applied cleanly. Low-viscosity grades wick into tight pre-assembled joints; thixotropic grades hold position on vertical or overhead surfaces. The Uni-Weld plastic bonder line is arranged by viscosity and substrate so the working properties are part of the selection rather than an afterthought. Cure Method Light-curable adhesives cure in seconds where a lamp can reach, which favors clear parts and open joints. Delivered dose determines cure quality, so verify irradiance at the part with a radiometer and account for lamp aging. For a primer on choosing a light source, see selecting a UV lamp for resin curing. Two-part systems cure regardless of light path but require fixturing through the cure. Surface Energy and Wetting An adhesive grips a plastic only if it can wet the surface, and it wets…

On a production line, adhesive cure time is dead time. A joint that needs minutes to fixture forces either a long conveyor or a bank of holding jigs. Fast-setting adhesives for precision plastic bonding collapse that window to seconds, but only if the process around them is built to match. Where Cure Speed Comes From UV and visible-light-curable acrylics stay liquid indefinitely until a lamp of the right wavelength and intensity reaches the adhesive. Cure then begins immediately and reaches handling strength within a few seconds at adequate irradiance. Incure light-cure grades are formulated for this on-demand behavior, which decouples cure from assembly pace and lets an operator or robot position parts without racing a pot life. Cyanoacrylates set fast by a different route, polymerizing on trace surface moisture in seconds to minutes. They need no equipment but give up process control, since ambient humidity and surface chemistry drive the speed. Designing the Joint for Speed Fast cure is wasted if the geometry fights it. For precision plastic assembly: Keep the bondline thin and consistent, 0.05 to 0.15 mm, so the light penetrates fully and the adhesive volume stays small. Provide direct line of sight from the lamp to the entire bond area. A joint hidden behind an opaque wall will not cure with a surface-only light chemistry. Where shadow is unavoidable, specify a grade with a secondary moisture or heat cure to finish the hidden region. The Uni-Weld plastic bonder range includes low-viscosity grades that wick into close-fitting precision joints and cure once exposed. Dispensing Precision A fast line needs repeatable dose. Time-pressure valves suit low-viscosity adhesives at moderate rate; positive-displacement valves hold volume tighter across a shift and handle thicker grades. Keep the adhesive temperature stable, since viscosity and therefore dispensed volume shift with a few degrees of change. Under-dose starves the bond; over-dose squeezes out and contaminates adjacent surfaces. For help specifying a dispense and cure setup for your cycle time, Email Us. Curing Hardware and Line Integration Match the cure source to the part flow. A stationary flood lamp over an indexing table works for discrete stations. For continuous flow, an inline conveyor system carries parts under the lamp at a set speed, as described in matching a UV conveyor lamp head to line speed and part width. Size the lamp so the delivered dose at the fastest planned line speed still exceeds the adhesive's cure requirement, with margin for lamp aging. Spot systems using a light guide suit small, localized joints where a flood pattern would waste energy or heat nearby components. Fixture Strategy Even a two-second cure needs the parts held in position while the lamp fires. The fixture has to locate the parts repeatably, leave the bond area exposed to the light, and release without stressing a fresh bond. Practical points: Use hard tooling datums, not operator judgment, to set alignment. Keep clamp contact away from the bondline so the fixture does not shadow it. For clear parts, cure through the part where…

Not all thermoplastics bond the same way. Polycarbonate accepts adhesive readily; polypropylene fights it at every step. Knowing where a given resin sits on that spectrum is the fastest route to a reliable bond and the most common thing skipped before a joint fails. The Bondability Spectrum Thermoplastics divide roughly into three groups by how easily they accept an adhesive: Bond readily: polycarbonate (PC), acrylic (PMMA), ABS, PET, rigid PVC. Surface energies above 40 mN/m let most adhesives wet and grip with only a solvent wipe. Bond with preparation: nylon (PA), acetal (POM), PBT. These need abrasion, plasma, or a primer to reach dependable strength. Resist bonding: polyethylene (PE), polypropylene (PP), fluoropolymers, many thermoplastic elastomers. Surface energies near or below 30 mN/m demand plasma treatment or a specialty adhesion promoter. Confirm the resin before choosing anything. A part marked "plastic" on a drawing could be any of these, and the bonding approach changes completely between groups. Matching Adhesive Chemistry UV and visible-light-curable acrylics suit clear and pigmented parts that can see a lamp. They cure in seconds, hold clarity, and skip mixing entirely. Incure light-cure grades span low-viscosity wicking fluids for tight joints through gel consistencies that stay put on a vertical surface. Cyanoacrylates bond fast on small joints across most rigid thermoplastics, though they remain brittle and sensitive to humidity in service. Two-part epoxies and acrylics deliver the highest structural strength and gap fill, at the cost of pot life and fixture time. Solvent and solvent-free cements chemically fuse compatible amorphous plastics such as acrylic and rigid PVC, producing a bond as strong as the parent material. For clear assemblies specifically, compare the tradeoffs in UV glue versus epoxy for transparent bonding. Viscosity and Joint Geometry Match viscosity to the gap: 5 to 50 cP: capillary wicking into pre-assembled joints with gaps under 0.1 mm. 300 to 3,000 cP: general assembly with gaps of 0.1 to 0.5 mm. Thixotropic gels: vertical surfaces, overhead joints, and gaps beyond 0.5 mm. The Uni-Weld plastic bonder line is organized this way, with grades sorted by viscosity and target substrate so the selection follows the joint. For help matching a grade to your resin and gap, Email Us. Cure Method Tradeoffs Light cure is fast but needs line of sight; a shadowed joint stays liquid. Some adhesives add a secondary moisture or heat cure to reach into shadow zones. Two-part systems cure everywhere but tie up fixtures. Cyanoacrylate cures on trace surface moisture, which makes it quick but humidity-dependent. For light-cure work, cure quality depends on delivered dose. Verify irradiance at the part surface with a radiometer and account for output decline as lamps age, a pattern covered in what causes UV light guide degradation over time. Surface Preparation by Resin Group Preparation scales with how hard the plastic is to bond: Readily bonded resins (PC, PMMA, ABS, PET): a wipe with isopropyl alcohol to remove mold release and handling oils is usually enough. Avoid aggressive solvents on PC, which can craze it.…

A thermoplastic elastomer bond fails at the interface far more often than in the adhesive itself. The reason is almost always a mismatch between what the joint demands and what the adhesive chemistry can deliver. Getting the match right starts with defining the joint, not the product. Define the Joint First Before comparing adhesives, characterize four things about the assembly: Substrate pair. TPE to TPE behaves differently than TPE bonded to a rigid polymer, metal, or glass. Service movement. Estimate the strain the bondline sees during handling, assembly, and use. Environment. Operating temperature range, humidity, and any solvent or oil exposure. Optical and inspection needs. Whether the bond must stay clear and whether an automated system needs to verify it. Each of these narrows the field. A joint that flexes rules out rigid chemistries; a joint exposed to fuel or cleaning solvents rules out others. Light-Curable Acrylics UV and visible-light-curable acrylic adhesives dominate TPE assembly for one reason: cure on demand. The adhesive stays liquid until a lamp triggers it, which removes the pot-life and clamping constraints that slow two-part systems. Incure light-cure grades reach handling strength in seconds and full cure within a minute under adequate irradiance. For elastomer work, the key property is elongation. A grade with 250 to 350 percent elongation at break stretches with the substrate instead of splitting at the bond edge. Look also for low linear shrinkage, since shrinkage during cure pre-loads the interface before the part ever sees service. Many grades carry a fluorescing additive so a machine-vision station can confirm coverage and position before the part advances. For guidance on curing equipment for these adhesives, see how to match a UV LED flood lamp to your curing area. Bonding TPE to Rigid Plastics Wearable consumer electronics, automotive interior trim, and appliance controls all bond a soft TPE overmold or gasket to a rigid polycarbonate or ABS body. The modulus difference between the two materials can exceed two orders of magnitude, so the adhesive must absorb that gradient. Two strategies help. First, use a toughened, flexible adhesive rather than a high-modulus one, so the bondline yields slightly under strain. Second, design a transition zone rather than a hard edge. The physics here mirror how CTE mismatch causes adhesive bond failure: a stiff bond between materials that move at different rates concentrates stress until the interface separates. The rigid side of the joint has its own requirements. The Uni-Weld plastic bonder range is formulated for PC, ABS, and PMMA, and pairs well with a flexible grade on the elastomer face. For help selecting a chemistry for a dissimilar-substrate joint, Email Us. Environmental and Optical Considerations TPE assemblies often live in humid or thermally cycled environments. Choose an adhesive with documented resistance to damp heat and repeated thermal cycling, and verify it on aged samples rather than trusting a datasheet figure. Low water absorption matters because absorbed moisture plasticizes the bondline and drops shear strength. When the bond sits behind a clear lens or window,…

Thermoplastic elastomers combine the feel of rubber with the processing ease of plastic, which is exactly why they resist most adhesives. Their low surface energy, flexible backbone, and plasticizer content defeat bonds that hold on rigid plastics. Choosing the right TPE glue means understanding why the failure happens first. Why TPE Is Difficult to Bond Most thermoplastic elastomers have a surface energy between 28 and 34 mN/m. Adhesives wet a surface reliably only when their own surface tension sits below that of the substrate, so a standard acrylic or epoxy beads up instead of spreading. The result is a weak interfacial bond that peels cleanly under load. Two other factors work against adhesion. TPE grades often contain processing oils or plasticizers that migrate to the surface over weeks, forming a slip layer under any adhesive already in place. And because the elastomer stretches while a rigid bondline does not, every flex cycle concentrates stress at the bond edge. Surface Preparation Options Preparation does more for TPE bonding than adhesive selection. Effective methods include: Atmospheric plasma or corona treatment, which raises surface energy above 40 mN/m for a working window of several hours. Abrasion with a fine non-woven pad to create mechanical tooth, followed by a solvent wipe to remove loose particles. Adhesion promoters formulated for polyolefin and elastomer surfaces, applied as a thin primer coat and flashed off before bonding. Always bond within the treated window. Surface energy decays as polymer chains reorient, and a treated part left overnight often bonds no better than an untreated one. For help matching a surface treatment and adhesive to your TPE grade, Email Us. Adhesive Families That Work on TPE UV and visible-light-curable acrylics cure in seconds under a lamp, which suits high-volume assembly. Incure formulates light-cure adhesives with elongation in the 200 to 350 percent range so the cured bond flexes with the substrate rather than cracking at the interface. A fluorescing tracer lets an automated vision system confirm adhesive presence before cure. Cyanoacrylates with rubber toughening bond many TPE grades quickly but stay brittle relative to the substrate, so they fit small static joints rather than parts under repeated flex. Silicone adhesives tolerate the movement well and resist heat, but cure slowly and bond with modest strength, making them a sealing choice more than a structural one. For bonding TPE to a rigid housing of polycarbonate or ABS, the Uni-Weld plastic bonder line covers the rigid side of the joint, while a flexible light-cure grade handles the elastomer interface. Joint Design for Flexible Substrates A butt joint on TPE almost always fails. Design the joint so the adhesive works in shear, not peel or cleavage. Practical measures: Increase overlap length to spread load across more bond area. Add a lead-in radius or flexible transition zone so stress does not step sharply from bonded to unbonded material. Keep the bondline thin and uniform, typically 0.05 to 0.15 mm, to limit internal stress. Because a modulus mismatch drives many of these failures, the…

Form-in-place gasketing dispenses a liquid sealant bead onto a flange and cures it into an elastomer gasket bonded to the part. With a UV-curable material the cure takes seconds, which is what makes the method viable for a production line. This guide walks through the process from surface prep to inspection. When to Use Form-in-Place Form-in-place gasketing pays off when you have medium-to-high volume, complex or non-planar flange paths, tight control requirements on gasket position, or a history of seam leaks with cut gaskets. It removes cut-gasket inventory and scrap, gives an exact fit to any 2D path, and delivers consistent bead volume from an automated dispenser. For very large flanges or very low volume, a cut gasket may still be simpler. Step 1: Surface Preparation The gasket has to adhere to the flange to stay positioned and to seal at the bead-to-flange interface. Clean the flange with isopropyl alcohol to remove machining oil, mold release, and handling residue. On low-energy plastic flanges, add plasma or corona treatment, or a compatible primer, and verify surface energy with a dyne pen. On metal flanges, a light abrasion improves durability for demanding service. Bond within the material's stated open time after preparation. Step 2: Bead Design Compression target: Size the dispensed bead so that at assembly it compresses 20 to 40 percent. Under-compression risks leaks; over-compression fatigues the gasket. Groove or hard stop: A retaining groove positions the bead and caps how far it compresses. On a flat flange, design a metal-to-metal hard stop so fastener torque cannot crush the gasket. Flange stiffness: Space fasteners closely enough that compression stays even. A flexible flange bows between bolts and opens the seal mid-span. Cross-section: A rounded bead compresses predictably. Avoid a tall, narrow bead that can roll or shadow its own base during cure. Step 3: Dispensing Use a programmable dispenser with volumetric or progressive-cavity metering for a repeatable bead. Program the path to follow the flange centerline with a controlled tie-in where the path closes on itself, so there is no thin spot or overlap lump. Keep the needle standoff and travel speed constant; changes in either alter bead width. Dispense at a stable material temperature, since viscosity drifts with temperature and changes the deposited volume. Incure's Uni-Seal form-in-place gasket line is 100 percent solids with no solvent, cures rapidly under low-energy LED lamps, and cures to a soft, resilient elastomer with good elastic memory, moisture and temperature resistance, and chemical resistance to oils and process fluids. For help matching a grade to your flange material and service conditions, Email Us with the enclosure drawing. Step 4: Curing Cure the dispensed bead under a UV source sized to the flange. A UV LED flood lamp covers a bench-scale part in one exposure; higher volume runs on a conveyor curing system. Verify the delivered dose at the bead with a radiometer against the data sheet. Expose a deep bead from more than one angle so the base cures. If the exposed bead surface…

Encapsulating components on a circuit board is a balance. The coating has to seal against moisture and mechanical stress, but it cannot distort fine-pitch parts as it cures, and inspectors still need to confirm it went where it should. Incure Uni-Seal 3718F is formulated around those three constraints. What a Precision Encapsulant Has to Do Seal without stress. A board-level encapsulant sits directly on solder joints, wire bonds, and small passive components. If the material shrinks hard as it cures, it drags on those features. Over thermal cycling that residual stress becomes cracked joints and lifted pads. A low-stress, low-shrinkage formulation keeps the mechanical load on delicate features small. Cure fast, in line. Board assembly runs at a cadence. An encapsulant that needs an hour to gel forces work-in-process to pile up. UV cure in seconds keeps the encapsulation step in step with the rest of the line. Be inspectable. After application, quality control has to verify coverage: did the material reach every component that needed it, and did it stay off the ones that had to remain clear? A fluorescing additive makes that a fast visual check under blacklight instead of a slow manual trace. Incure Uni-Seal 3718F Properties Fast cure in seconds under UV or visible light, with an optional secondary heat cure for regions the light cannot fully reach, such as under a tall component or in a deep pocket. Low stress and low shrinkage, minimizing distortion of fine-pitch parts and the substrate during cure. Superior moisture barrier, protecting sensitive components from humidity-driven corrosion and dendrite growth. Fluorescing feature for rapid coverage inspection and quality control under blacklight. Good moisture and temperature resistance for the board's service life. 100 percent solids, no VOCs, so there is no solvent-loss shrinkage and no solvent handling requirement. Thermal cycling ready, suited to products that see repeated temperature swings. For a recommendation on application method and cure setup for a specific board, Email Us with the board layout and the components to be encapsulated. Applying It Board cleanliness. Remove flux residue and handling oils first. Contamination reduces adhesion and can let moisture track under the cured film. Dispense control. Use a programmable dispenser for repeatable bead volume and position. Selective application keeps the material on target components and off connectors and test points. Bond-line and fillet. A controlled film thickness cures more predictably than a thick, uneven pool. Where a fillet is needed around a component base, size it so light can still reach the fillet toe. Curing Cure under a UV LED flood lamp for bench and low-volume work, or run boards through a conveyor curing system at production rate. Verify the delivered dose at the board with a radiometer against the data sheet. Where a tall component shadows encapsulant at its base, follow the UV exposure with the optional heat cure to complete the shadowed region. Confirm full cure by hardness or solvent-rub check on a trial board. Inspection Under blacklight, the fluorescing encapsulant shows a clear outline of…

Potting protects electronics from moisture, vibration, and aggressive fluids by embedding them in a cured resin. The property that most often separates a reliable potting compound from a problem one is cure shrinkage. A resin that pulls in as it cures puts every embedded component under stress and can open a leak path at the pot wall. Why Shrinkage Matters All curing resins shrink to some degree as liquid monomer converts to a solid network. In a potted module that shrinkage acts in three damaging ways: Component stress. The resin grips leads, solder joints, and component bodies and pulls on them as it contracts. Fine wires, ceramic capacitors, and glass diode bodies are sensitive to this. Interface separation. Shrinkage away from the potting-shell wall or a connector face creates a gap that moisture and gas can enter, defeating the seal. Warpage. Uneven shrinkage through a thick pot bends the substrate or the housing. A low-shrinkage resin minimizes all three. UV-curable acrylic potting compounds formulated at 100 percent solids avoid the additional shrinkage that solvent-borne systems suffer as solvent leaves, and they cure fast enough for inline production. Incure Uni-Seal Potting and Sealing Line Incure's Uni-Seal potting grades are designed for encapsulation where dimensional stability and fast cure both matter: Rapid cure, with some grades reaching full cure in about 60 seconds under a UV source, versus hours for a two-part thermoset. Very low shrinkage and very low water absorption, so the cured resin stays dimensionally stable and does not swell in humid service. Protection against mineral oils, gases, and common process chemicals, which suits utility metering, fluid-system electronics, and industrial sensor potting. Good adhesion to many metals and to glass, keeping the resin sealed to the housing and to feed-through pins. Color options, including opaque grades where the potted circuit must be hidden. Where an application references specific standards such as EN 16314 or EN 1359 for gas-metering equipment, confirm the exact grade's documented compliance against the current standard text. For a grade recommendation against your module and its environment, Email Us with the potting geometry and fluid exposure. Design and Process Pot depth and light path. UV cure needs light to reach the resin. A shallow pot cures top-down in one exposure. A deep pot, or one with components that shadow the resin below them, needs either a translucent resin that lets light propagate, a dual-cure grade with a secondary heat step, or staged filling with a cure between lifts. Fill technique. Dispense slowly along the pot wall to avoid entraining air. Vacuum degassing before cure removes trapped bubbles that would otherwise become moisture traps. Bond-line and wall adhesion. Clean the housing interior. Residual mold release or flux lets the resin debond from the wall as it shrinks, however slightly. Curing Cure under a UV LED flood lamp for bench work, or a conveyor system for volume, with a batch cure chamber an option for even exposure of many parts at once. Verify the delivered dose at the resin…

On a populated circuit board, some areas must stay sealed and some must stay coating-free. Connectors, test points, switches, and displays cannot be conformal coated, but they still need protection from the coating process and from moisture in service. A UV-curable gasket dispensed onto the board solves both problems in one fast step. The PCBA Sealing Problem Conformal coating protects a board from humidity, dust, and corrosion, but it must be kept off certain components. The traditional approach is hand-applied masking dots, tape, and boots, which are labor-intensive, inconsistent, and generate waste. They also do nothing for in-service sealing around a connector or a board-to-enclosure interface. A dispensed UV gasket replaces masking with a precise, automated bead. It defines a keep-out boundary the coating cannot cross, seals the perimeter of components that need it, and stays on the board as a permanent gasket where a board-to-housing or connector seal is required. Incure Uni-Seal 3393 Incure's Uni-Seal 3393 is a UV-curable form-in-place gasket and sealant developed with PCBA work in mind. Its characteristics: Fast LED cure for high-volume board assembly, cured before the board moves to the next station. Soft yet tough, balancing enough compliance to seal against uneven surfaces with enough toughness to resist tearing during handling. Ease of peel for rework, so a sealed area can be reopened to replace a component and re-gasketed, without damaging the board or pads. Air-tight sealing around connectors and enclosure interfaces. Moisture and temperature resistance for the board's service environment. Chemical resistance, consistent with the electronics and automotive use where the chemistry is common. Applied along a keep-out boundary before conformal coating, the cured gasket gives the coating a clean edge to stop against. Applied around a connector footprint, it provides the in-service seal. For guidance on bead placement and cure setup for a specific board, Email Us with the board layout and coating process details. Dispensing and Bead Design Bead width and height: Match the bead to the gap it has to seal and the compression the mating part applies. For a masking boundary with no compression, a low, wide bead that adheres firmly to the laminate is enough. Standoff from components: Program the path with enough clearance that the bead does not creep onto a pad or lead, while staying close enough to keep the coating out. Adhesion to the laminate: Boards should be clean and dry. Residual flux or handling oils reduce gasket adhesion and can let coating wick underneath. Automated dispense: A programmable dispenser gives repeatable bead volume and position, which manual masking cannot match. Curing Cure the dispensed bead under a UV LED flood lamp sized to the board, or run boards through a conveyor curing system for volume. Verify delivered dose at the board with a radiometer. Tall components can shadow a nearby bead, so check that beads next to connectors and headers get full exposure, or expose from a second angle. Cure the gasket fully before applying conformal coating so the coating solvent does not attack…