LORD 7545-A/B Structural Urethane Adhesive

LORD 7545-A/B structural urethane adhesive is the general purpose workhorse of the LORD 7545 series, mixed 1:1 by volume and offered in off-white and black across 50ml, 200ml and 400ml cartridges. It bonds FRP, SMC and other plastics with little surface preparation, and it also bonds primed metals and dissimilar substrate combinations. The 3 to 5 minute work time is long enough to run a real bond line and short enough to clear a fixture in half an hour, which is why this is the grade most shops standardize on. Mixed, it is a non-sag paste that holds position on vertical and overhead surfaces. Made in the USA.

Key Product Details

Cured Properties

Parker publishes the following cured properties for the LORD 7545 system. The technical data sheet does not break them out by individual curative, so treat them as series-level and test your own joint before production.

Bond Performance by Substrate

Lap shear in psi, with failure mode in parentheses. SF is stock failure, meaning the substrate broke before the bond did. COH is cohesive failure, the adhesive itself split. ADH is adhesive failure, the bond released from the surface. Stock failure across most of the CFRP and ABS conditions is the number that matters most here, because it says the joint outlasted the part. Parker publishes this data for the LORD 7545 system without breaking it out by curative.

Test specimens: CFRP was 2×2 twill in an epoxy resin matrix, 3 mm thick. ABS and PC/ABS were both 5 mm thick. E-coated steel was 1008 steel, 8 mm thick, coated with PPG E6060C. Your substrate, joint geometry and surface prep will move these numbers, so run your own bond trial.

Performance in Production

• Stock failure on CFRP at 2900 psi and on ABS across nearly every aged condition means the part gives up before the joint does. On those substrates the adhesive stops being the limiting factor in the design.
• Cold performance goes the opposite way on plastic and metal. CFRP and ABS lose shear at -40°F while e-coated steel climbs to 3300 psi, so a cross-bonded plastic-to-metal joint gets stiffer and less forgiving in winter service. Design the joint for the plastic side.
• Shear drops roughly 60% at 150°F, which is expected for a urethane and is the reason the service ceiling sits at 212°F. Sustained heat above that belongs on an epoxy.
• 3 to 5 minutes of work time is enough to run a full bead and set a part without rushing, and 30 minutes to handling strength turns a fixture roughly twice an hour.
• At 230,000 to 650,000 cP the curative is a heavy paste. The mixed bead stays put on vertical and overhead work instead of slumping out of the joint.
• 70% elongation and a 22,200 psi modulus give the bond line room to move when two substrates expand at different rates, which is what kills a rigid adhesive on a plastic-to-metal seam.
• Flash point over 200°F on both components exceeds U.S. DOT non-flammability requirements, so no explosion-proof dispensing equipment is needed.
• 7545-A resin is moisture sensitive. Keep cartridges in the Mylar bag with the desiccant, and leave the used mixer in place on a partial as a plug, or the next bead cures short.

Common Applications

• Structural bonding of FRP and SMC panels, covers and enclosures
• Truck cap, tonneau cover, running board and toolbox assembly
• Service body and work truck panel, roof and door closure bonding
• Cross bonding plastics and composites to primed, painted or e-coated metal
• Sign fabrication, channel letters and dimensional signage
• Bonding ribs, bosses, stiffeners, brackets and inserts to molded parts
• Marine and recreational vehicle composite panel bonding
• Vertical and overhead bonding where the bead has to hold position

How to Dispense LORD 7545-A/B

Three to five minutes is a comfortable window, but it is still a window. Have the joint dry-fit and the clamps staged before the mixer goes on. Parker’s instruction is to discard the part if working time is exceeded, because a bead that has begun to skin will not wet the mating surface and the bond strength drops.

• Prep both surfaces. Plastics and composites get a dry rag wipe or a solvent-dampened rag to pull loose debris and processing fluids. Metals get primed, painted or grit blasted, then solvent washed.
• Load the cartridge in a 1:1 gun sized for that cartridge and pull the end caps. Level the plungers by expelling a little material with no mixer installed, until both sides dispense evenly.
• Fit the right static mixer for the size. Parker calls for at least 20 elements on a 50ml cartridge and at least 24 elements on a 200ml or 400ml cartridge. Purge a mixer’s length to waste before the first bead.
• Lay the bead, mate the parts and clamp inside the 3 to 5 minute work time. Target a 0.010 to 0.040 in bondline. Larger gaps can be filled where mating surfaces are irregular.
• Hold the part fixtured 30 minutes at 75°F, then handle. Full strength is 24 hours. Cure can be accelerated with modest heat, up to 250°F (121°C).
• Clean tools with acetone or MEK before cure. Do not use alcohol. Cured adhesive softens at 300°F (149°C) and above if parts have to come apart.

Substrates the process runs on: FRP, GRP, SMC, carbon fiber, ABS, polycarbonate, PC/ABS blends, other engineered plastics, HDU urethane foam, wood, and primed, painted, powder-coated or e-coated metals. Glass, non-porous ceramic and stone need LORD AP-134 first. Vulcanized rubber and elastomers need LORD 7701. TPE and TPO need LORD 459X. Bare aluminum and bare steel are not urethane substrates, so prime them or move to an acrylic.

Choosing Color and Size

Color is a cosmetic decision, not a performance one. The off-white and black 7545-B curatives run the same 3 to 5 minute work time and the same 30 minute handling strength, so a black bond line costs you nothing on throughput. Pick black when the joint stays visible and unpainted against a dark part, off-white when it will be painted or hidden. Size is the decision that changes what is on your bench, because the three cartridges take different guns and different mixers.

Take the 50ml for repair work, small parts, bond trials and anything you run occasionally, because a 3 to 5 minute work time means an opened cartridge that sits is a cartridge you are going to scrap. Move to the 200ml once the same joint runs daily, since the purge waste per cartridge is about the same either way and you spread it across four times the material. The 400ml is for long continuous bond lines and panel work, and it is worth knowing it comes in black only, so a job that needs both an off-white bond line and 400ml of material has to run two 200ml cartridges instead.

LORD 7545 Series Grades Compared

Every grade runs the same 7545-A resin at the same 1:1 volume ratio. The curative letter changes speed, mixed color and cured elasticity, not the chemistry. Parker states the full range of work times all provide the same bond strength, so pick by how long your assembly actually takes.

Available Sizes and Part Numbers

Dispensing Equipment

Each cartridge size takes its own gun. The mixers below meet Parker’s element minimums for these sizes, 20 elements on the 50ml and 24 elements on the 200ml and 400ml.

Related Products

Surface modifiers, used when the substrate needs priming before bonding:

• LORD AP-134 adhesion enhancer for glass, non-porous ceramic, stone and concrete
• LORD 459X adhesion enhancer for TPE and TPO
• LORD 7701 surface treatment for vulcanized rubber and elastomers

Frequently Asked Questions

What is LORD 7545-A/B used for?

LORD 7545-A/B is a two-part structural urethane adhesive used to bond FRP, SMC and other plastics with minimal surface preparation, plus primed metals and dissimilar substrate combinations. It is the general purpose grade of the 7545 family, used across truck and trailer bodies, service vehicles, signage, marine and composite panel assembly. Urethane adhesive, polyurethane adhesive and PU adhesive all describe the same chemistry.

Does LORD 7545-A/B come in black?

Yes. The 7545-B curative is offered in off-white and in black, and both run identical work time and handling strength, so choosing black costs you nothing in the shop. Black is available in 50ml, 200ml and 400ml. Off-white is available in 50ml and 200ml only, so if you need 400ml of material in off-white you will be running two 200ml cartridges.

Which cartridge size should I order?

Take the 50ml for repairs, small parts and occasional use, the 200ml once you are running the same joint daily, and the 400ml for long continuous bond lines and panel work. The material is identical in all three. A 1/4 in bead gets you roughly 5 ft from the 50ml, 20.7 ft from the 200ml and 41.4 ft from the 400ml. Each size takes a different gun, so confirm what is on your bench before switching.

What gun and mixing tip does each cartridge need?

A 1:1 gun matched to the cartridge size, with a static mixer of at least 20 elements on the 50ml and at least 24 elements on the 200ml and 400ml. Those element counts are Parker’s minimums from the 7545 series application notes, and under-mixing is the most common cause of a bead that never fully cures. The dispensing equipment table above lists what we stock for each size.

What surface prep does LORD 7545-A/B need?

Plastics need a dry rag wipe or a solvent-dampened rag to remove loose debris and processing fluids. Metals should be primed or grit blasted and then solvent washed for optimum bond performance. Glass, non-porous ceramic and stone need LORD AP-134 first, vulcanized rubber needs LORD 7701, and TPE and TPO need LORD 459X. Parker notes plasma treatment can help on hard-to-bond materials in special cases.

How strong is a LORD 7545 bond?

Strong enough that the substrate usually fails first on composites and plastics. Parker’s testing shows stock failure on CFRP at 2900 psi lap shear at room temperature and on ABS across almost every aged condition, meaning the test coupon broke before the bond did. On e-coated steel the failure mode is cohesive at 2350 psi. The full table is above, including salt spray, humidity and water immersion aging.

What is the shelf life, and how should cartridges be stored?

8 months from date of manufacture in the original unopened container stored at 65 to 85°F (18 to 30°C). The resin is moisture sensitive, so keep cartridges in the Mylar bag with the desiccant until you need them, and protect a partial by leaving the used mixer in place as a seal. Run inventory first in, first out.

How does LORD 7545-A/B compare to the other LORD 7545 curatives?

A/B sits second fastest, at 3 to 5 minutes work time and 30 minutes to handling strength. A/G is quicker at 1.5 minutes but only comes in 50ml and only in black. C, D, E and F run progressively slower, out to 45 to 65 minutes on A/F. E and F also cure noticeably more elastic. The grade comparison table above lays out all six.

Questions on fit for your bonding application? Call (800) 220-1966 or email [email protected].