Frequently Asked Questions - Sign Adhesives - Assembly & Protection Solutions Division | Parker US

Although a premium sign adhesive is the basis of a quality bond, it’s only the beginning. Proper application is essential for best results. This resource is intended to provide an application guide for many of your sign-bonding questions.

Q: What is the best way to prepare the adhesive cartridges before use?

A: Below are best practices for preparing two-part adhesive and adhesive/sealant cartridges for optimum bonding results (refer to Figures 1-6).

  • Insert the cartridge into the dispensing gun with the proper mix ratio setup.
  • Remove any caps and plugs.
  • Level the plungers by applying pressure to the gun until both sides of the material flow through the openings in the cartridge.
  • Attach the mix tip.
    • Apply pressure to the gun forcing the material through the mix tip.
    • Run out a mixer's length of adhesive on scrap material to ensure a complete mix.
  • Position and Dispense adhesive

images showing how to dispense adhesive

 

Q: How do you store partially used cartridges of adhesives or sealers?

A: Store the cartridge with the mix tip on. The Mix tip will serve as a cap to keep material fresh. Replace the mix tip prior to the next use.

Q: Where can I buy LORD adhesives for signs?

A: Ask for LORD products at your local sign warehouse distributor. We have a network of authorized distributors in the US and Canada. Call our Customer Support Center (US & Canada) 877-275-5673 or contact us for more information on where to buy our sign adhesives.

Q: Does the adhesive have a shelf life or expiration date?

A: Yes. All LORD adhesives in cartridges carry a 'Use by' date printed on the label and should be considered the final word for the shelf life of these products. Bulk containers "Use by" date is listed on the product certificate.

Q: The LORD 400-series Acrylic Adhesive I dispensed is still tacky on the exposed adhesive. Is it cured?

A: Yes. Surface tack is normal for LORD 400-series acrylic adhesives. Wipe the surface with alcohol or organic solvent after full cure to remove the tacky layer. Surface tack is only on the surface; properly bonded joints are fully cured.

Q: How do I prepare my surfaces before bonding?

A: Surface Preparation
All surfaces should be clean and free from oil, grease and dirt. As a minimum, wipe the surface with a clean, dry rag or blow off the surface with clean air.
Solvent wipes all surfaces with isopropyl alcohol. Do not use lacquer thinners, mineral spirits, gasoline, toluene or xylene as they may leave a residue that may cause bonding problems. Do not use commercial cleaners. These often leave a residue that may cause bonding problems.

  • Steel/Aluminum - solvent wipe with isopropyl alcohol.
  • Stainless Steel - Solvent wipe with isopropyl alcohol. Then, mechanically abrade with 80-grit paper or grinder. Wipe with isopropyl alcohol to remove any sanding dust.
  • Pre-finished metal - Factory-painted metal with baked polyester finish can be solvent wiped. Shop-painted or other finishes must be removed by sanding prior to bonding.
  • Acrylic - Scuff with a scuff pad or 120-grit paper. Solvent wipe with isopropyl alcohol.
  • Polycarbonate - Solvent wipe with isopropyl alcohol.
  • PETG - solvent wipe with isopropyl alcohol.
  • Trimcap - Wipe with a clean, dry cloth.
  • Urethane Foam Board - Blow off the surface with clean air or wipe with a clean, dry cloth.
  • Sintra® - Scuff with scuff pad or 120-grit paper. Solvent wipe with isopropyl alcohol.
  • Ceramic and Stone - Porous: No primer required. Non-porous (smooth/polished): Lord AP-134 primer required.
  • Wood - Wipe with a clean, dry cloth.
  • Glass - LORD AP-134 primer required.

Note: Each substrate and adhesive should be tested for the specific use in which it will be expected to perform. The information reported here is from laboratory studies and is intended only to provide general information regarding the ability of material to be bonded with LORD® Engineered Adhesives.

Q: What are the recommended guidelines for Adhesive Bonded Joint Design?

A: Joint configuration should be designed so that the basic stress is primarily shear, tensile or compressive with cleavage and peel stresses minimized on the bondline. Joints should be designed so that all of the bonded area equally shares the load. Illustrations provided depict both recommended joint design alternatives and joint design to be avoided.

illustration showing do and don'ts of adhesive testing

 

  • Lap Joints - Lap joints are the most practical design and applicable in bonding thin materials. Lap joints are used to enhance joint strength by reducing its potential to peel stress.
  • Butt Joints - In tension, the straight butt joint is impractical for load-bearing assemblies. To minimize this stress, the angle design applies compression. Compressive loading will not affect the joint unless bucking of the vertical component occurs. Butt joints are not recommended.

Q: When are adhesives not suitable?

A: Sometimes an adhesive is not appropriate. The rule of thumb is to use adhesives where the joint design is loaded in shear or compression, instead of peel or tension. Areas like butt joints or “T” joints do not always allow sufficient overlap for the adhesive to bond properly. Sometimes it is more appropriate to assemble these designs by welding, fastening, or with a combination of mechanical fasteners and structural adhesives.

Q: What are the advantages of LORD Structural Adhesives?

A: LORD Structural Adhesives offer advantages to Sign Designers over welding and mechanical fastening. They bond dissimilar materials, provide improved appearance, insulate against galvanic corrosion and offer excellent environmental resistance. Adhesive bonding provides cost savings due to reduced labor costs and assembly time.

Q: How do I select the right adhesive for my sign application?

A: Refer to our Sign Adhesives Selector Guide or contact us for adhesive product selection.

This page also contains considerations that may influence your choice of adhesive. Please remember that these are guidelines and that you should always test for acceptable performance with your application.

Q: What are Structural Adhesives?

A: Structural adhesives are thermoset polymers. They will not melt or change with environmental exposure, temperature or time. Acrylics and epoxies can withstand temperatures from -40°F to +400°F. Most urethanes are good up to 250°F with a low end slightly better than the other chemistries. Exposure to water, humidity, oil, gasoline, solvents, and other environmental factors won’t weaken bond strength in properly designed joints.

Q: What are some of the main differences between the adhesive chemistries?

A: Understanding the type of chemistry being used is important. In general, acrylics excel at bonding unprepared metals, composites, and thermoplastics. Epoxies give the highest strength when bonding prepared metals, composites, and natural substrates such as stone and wood. Urethanes offer resiliency and flexibility and are candidates for joining composites, thermoplastics, natural materials and prepared metals.

Q: Can I Powder Coat after bonding? With which adhesives?

A: Yes.
Note: Clamp or fixture the assembly prior to powder coating to avoid slippage during the powder coating process. The assembly should remain fixtured until the adhesive returns to room temperature and re-hardens.

LORD acrylic adhesives have excellent heat resistance characteristics up to 400°F, reducing the concern of possible degradation of the cured adhesive due to heat during the powder coating process. Allow the adhesive to fully cure before powder coating. Tested products include the Signlok Series, LORD 400 Series and LORD 800 Series adhesives.

However, it is important to keep in mind that at these higher temperatures, the hot tear strength is very low. At about 180°F, the adhesive will begin to soften. These lower strength values make it essential that the assembly is properly fixtured or placed to avoid slippage of the bonded pieces, especially if they are heavy. Mechanical or spot welds are frequently used in the industry to hold the assembly in place. Assemblies need to be fixtured to avoid any stresses during the time that the adhesives are soft and until adhesives return to room temperature and re-harden.

The integrity of the bond will remain unchanged, and in fact increase, once the assemblies have returned to room temperature.

For complete instructions, refer to Powder Coating after Bonding with LORD® Acrylic Adhesives.

Q: How do I cross-bond dissimilar materials?

A: When bonding larger assemblies involving dissimilar materials, such as aluminum or steel to polycarbonate or acrylic, attention should be placed on the expansion and contraction of the materials. Differences exist in the expansion coefficients of metal and plastic. Substrates will expand and contract at different rates with temperature changes. There are two factors to consider:

1) The design must be flexible enough to accommodate the expansion, and

2) The adhesive must be strong enough to tolerate the stresses that the thermal expansion produces.

LORD urethane adhesives (LORD 7542, LORD 7610DTM) provide flexibility and prevent stress fractures and/or bond failure of the plastic materials. Prime the bare metals, scuff the plastic, and bond with a LORD urethane structural adhesive.

LORD acrylic adhesives (SignlokTM 403, Signlok 406, LORD 400 Series, Signlok 810, Signlok 204) provide exceptional structural strength and are particularly formulated for assemblies with a bare metal substrate. However, they may not provide as much flexibility as needed for outdoor or large cross-bonded assemblies.

Q: Are there different considerations for bonding indoor and outdoor installations?

A: Outdoor metal installations will benefit from using LORD 400 or 200 Series because these adhesives provide excellent corrosion and environmental resistance.

Outdoor installations may require greater adhesive flexibility because the size of the assembly is large, if the metal is painted, or if the assembly will need to tolerate flexing. If these factors are present, consider bonding an outdoor assembly with LORD 7542 or 7610DTM adhesive. Prime bare metal surfaces when using LORD 7542 adhesive.

Indoor applications generally do not need to accommodate temperature or environmental changes as much as outdoor applications and can be bonded with the adhesive recommended based on the materials.

Q: What adhesives do I use for installing studs in a sign assembly?

A: Depending on the materials and application, LORD has adhesive solutions for common stud bonding applications:

  • Metal studs and metal brackets - LORD 400 and 200 Series Adhesives
  • Plastic stud to Painted Metal - LORD 7542 and 7610DTM Adhesives
  • Stud Mount to brick or stone wall - LORD 320/322 Adhesive

Q: What should be considered when bonding large pieces or panels?

A: Large pieces or panels may need to accommodate movement in the assembly. LORD 7542 or 7610DTM adhesive may be more appropriate for bonding applications requiring greater flexibility. Prime bare metal surfaces when applying LORD two-part urethane adhesives, such as LORD 7542 adhesive, to metal.

Q: Why would I use a no-mix system for bonding?

A: Large assemblies with a tight tolerance, like mounting a sign face, may benefit from the LORD No-Mix Series that allows for an indefinite open time for bonding. No-mix adhesives components, also known as "honeymoon" adhesives, are applied on the opposite mating surfaces of the substrates to be bonded. Curing does not start until the parts are brought together. Recommended bondline thickness is 10 mils and can be no more than 20 mils. No-Mix options include LORD 201 and 204 used with LORD Accelerator 4.

Q: How do I laminate materials with no-mix systems?

A: Laminating is the process of bonding two or more layers of material together with an adhesive.

Sign designers can use LORD 201 or 204 adhesives in combination with LORD Accelerator 4 to laminate acrylic, bare metals, painted metals, aluminum composites, polycarbonate, vinyl and high-density urethane foams. No-Mix adhesive components are applied on the opposite mating surfaces of the substrates to be bonded. Curing does not start until the parts are mated.

The recommended bondline thickness of the LORD 201 or 204 adhesive is 10 mils. Estimate 2 oz. of Accelerator 4 per 1/10 gallon cartridge of LORD 201 or 204 adhesive. Coverage would be 16 sq. ft. per 1/10 gallon cartridge or 160 sq. ft. per gallon (ten 1/10 gallon cartridges).

LORD 201 adhesive has a thinner consistency and is best for brushing applications. LORD 204 adhesive is non-sag and best to spread with a notched trowel.

Q: How do I laminate foam board for a sign?

A: Sign Designers can use readily available grades and standard foam thicknesses to manufacture a variety of designs by layering the foam and laminating the layers. Laminating reduces the cost and the need for storage space and inventory of various grades and thicknesses of sign foam.
Brush or roll LORD 7650 with a recommended dry film thickness of 2-4 mils (.002-.004") or a wet film thickness of 3-6 mils (0.003-0.006"). LORD 7650 can also be applied by spray if done in a spray booth with proper ventilation.

Q: How do I estimate how much material I need to laminate the foam board?

A: To calculate coverage, one gallon of LORD 7650 will cover approximately:

  • 535 Sq. ft at a wet film thickness of 3 mils
  • 267 Sq. ft. at a wet film thickness of 6 mils

Once the adhesive has been applied, wait approximately 20-30 minutes for a good tack to develop as the solvent evaporates. Mate the substrates, slide to reposition, and apply uniform pressure with a board and/ or weights. The assembly should remain under pressure for 10-24 hours at 75°F (24°C) to reach handling strength. LORD 7650 will fully cure in 1 to 5 days depending on humidity. Once fully cured, the bonded area can be cut on a router to the desired shape. Finish with a primer or sanding.

Q: How do I estimate how much adhesive is needed for a job?

A:

  • Apply the adhesive to the part to ensure complete adhesive coverage to the bond area. The rule of thumb is to dispense a bead with a diameter of about 1/6th to 1/4th the width of the bond joint.
    For example, if the bond joint is 1" wide, the bead diameter should be approximately 0.17".
  • Allow for variation in bondline thickness around the periphery of the part. Increase the bead size dispensed in areas of “poor fit” to ensure adequate coverage.
    For example, if the bondline thickness is 0.030" rather than 0.010", the bead diameter should be approximately one-quarter of the bond width. In this case, a 0.25" bead diameter should be used when the bondline thickness is expected to be 0.030" on a 1" wide bond area.
  • Bead diameter is a measurement as seen in the figure on the right.

adhesive bead diameter illustration

table showing adhesive bead length estimator

Q: What is the best way to apply adhesive for metal bonding?

A: Apply the adhesive to the part in a manner that will ensure complete adhesive coverage to the bond area. (Refer to chart below). The rule of thumb is to dispense a bead about one-sixth the diameter of your bond joint.

Allow for variations in bondline thickness around the periphery of the part. While a 0.010" (0.254 mm) bondline thickness is ideal, the fit of the parts to be bonded is not always ideal. Therefore, increase the bead size dispensed in areas of "poor fit" to assure adequate coverage.

A small amount of squeeze-out along the bondline may be desirable for use as a sealant and also as a visual assurance of adhesive presence. However, if this squeeze-out interferes with the aesthetic appearance of the final product, it should be removed before the adhesive completely cures. Refer to the product literature for product working time and remove the squeeze-out before the working time has elapsed.

The chart below provides a general guideline on what bead diameter to dispense to ensure complete coverage of the bond joint at various bondline thicknesses.

table showing adhesive bead size to dispense on overlap area and bondline thickness

Q: What is the best way to position and mate the parts?

A: Mate the materials carefully to properly align the pieces. If the materials need to be re-positioned after mating, SLIDE the pieces into position. Do not lift or separate the pieces as this can allow air into the bondline and cause voids, resulting in less than optimum coverage and strength.

A small amount of squeeze-out along the bondline may be desirable for use as a sealant and also as a visual assurance of adhesive presence. If the squeeze-out interferes with the aesthetic appearance of the final product, it should be removed before the adhesive completely cures. Refer to the product literature for product working time.

Q: What are the guidelines for non-structural applications with LORD 7550, optically clear adhesive for Trim Cap & Plastics?

A: For best results, follow these guidelines:

  • Scuff polycarbonate and plastics to be bonded lightly – the adhesive will fill in scuffed areas.
  • Let LORD 7550 adhesive flow easily into spaces and fill up voids.
  • Less adhesive is better than more – use only what covers the areas to be bonded.
  • Let assembly sit in place for a minimum of 24 hours (72 hours is best) at room temperature – do not torque during the cure process to allow the adhesive time to create a “bite” to the surfaces

Q: How can I clamp the parts after bonding?

A: Immediately after the parts are positioned correctly, they must be weighted with even pressure until handling strength is achieved. Some of the means typically used to accomplish this are clamps, boards/stiffeners, weights, mechanical fasteners or braces.

  •  Maintain even pressure across the sign assembly (Figure 9).
  •  Avoid applying pressure in areas that allow the assembly to "bow".
  •  Boards can be used to apply even pressure across the bondline on flat assemblies (Figure 10).
  •  Weight bonded signs with sandbags, bean bags or other formable materials to distribute weight evenly.
  •  Mechanical fasteners (screws, rivets, bolts) can be used to fixture particularly difficult-to-clamp areas and can be removed after handling strength is achieved (Figure 11).
  •  Braces can be used to hold odd-shaped signs in place while curing (Figure 12).

images show how to clamp parts after bonding them with adhesive

Q: How can I avoid Read-Through or ghosting?

A: Read-through is a condition where you can see the footprint of the adhesive through the material. This is caused by shrinkage that results in a pull on the bonded materials. Read-through can occur on surfaces that are high gloss, high polish, or have a mirrored finish. Thin gauge metals less than 0.030" are more susceptible to read-through.

Sandwich panel material, such as DiBond® or Alucobond®, which are aluminum composite panels that are typically 0.3 to 0.5 mm thick aluminum sheets covering a solid polyethylene core with a total thickness of 3 mm or more, or similar panels from any manufacturer, may also be susceptible to read through.

Following are some tips to avoid read through:

  •  Maintain a thin and consistent bondline of 0.010" (10 mils)
  •  Remove squeeze out
  •  Weight the bond line appropriately so that full surface contact results between the materials being bonded to avoid gaps in the bondline.

Q: What adhesives are used for thin substrates and to avoid Bond Line Read-Through (BLRT)?

A: Signlok 810 Low Read-Through (LRT) acrylic adhesive is a flexible adhesive system specifically designed for bonding metals, such as aluminum, galvanized steel and CRS, and engineered plastics, such as PC-ABS and ASA. Signlok 810 adhesive delivers fast cure speed and strong bonding with minimal read-through.

Q: What are UL Approved Adhesives for Sign and Electrical Enclosure Bonding?

A: LORD offers an extensive line of UL Approved Adhesives that bond various substrates.

Q: What are some general safety guidelines when using adhesives?

A: Because adhesives contain chemicals, you need to wear protective equipment and clothing. Safety glasses or goggles and gloves should be worn when applying adhesives. The area should be sufficiently ventilated to protect you from fumes and vapors. Always refer to the Safety Data Sheet (SDS) of the adhesive for safe use guidelines

 

 

 

 

 

 

 

 

 

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