loctite 403

Loctite 403

Technologies:Cyanoacrylate
Application method, Recommended:Dispense system; Manual
Applications, Recommended:Bonding close fitting parts
Color:Ultra clear
Fixture time, Steel:30.0 sec.
Gap fill:0.2 mm
Key characteristics, Recommended:Bloom: low bloom; Gap filling; Odor: low odor; Surface insensitive; Viscosity: medium viscosity
Operating temperature:-40.0 °C – 80.0 °C (-40.0 °F – 175.0 °F)
Shear strength, Mild Steel (grit blasted):20.3 N/mm² (2950.0 psi)
Viscosity:1200.0 mPa·s (cP)

Overview

Loctite 403 is a clear, one-part cyanoacrylate instant adhesive engineered for applications where smell and “whitening” (blooming) must be tightly controlled. It combines low odor and low bloom with a medium viscosity (~1200 mPa·s), giving you clean bond lines even in visible cosmetic areas.

The adhesive cures rapidly in the presence of surface moisture and delivers high shear strength on metals, plastics and elastomers, and also works very well on porous and absorbent materials such as wood, paper, leather and fabric.

Typical data:

  • Chemistry: Alkoxyethyl cyanoacrylate

  • Viscosity: ~900–1650 mPa·s (medium–high)

  • Fixture time (steel): ~30 seconds

  • Shear strength (mild steel): ~20 N/mm² (~2950 psi)

  • Gap fill: up to about 0.2 mm (0.008″)

  • Operating temperature: approx. –40 °C to +80 °C (–40 °F to 175 °F)

When used with a plastic primer such as Loctite SF 770, Loctite 403 can also bond difficult-to-bond plastics like PP, PE and PTFE.

Key Features & Benefits

  • Low odor
    Formulated to greatly reduce the strong cyanoacrylate smell, improving comfort in workcells and applications where vapor management is challenging.

  • Low bloom / low whitening
    Minimizes the white, frosty residue typical of many super glues, making it ideal for visible joints, clear parts and cosmetic assemblies.

  • Medium-to-high viscosity, gap filling
    Approx. 900–1650 mPa·s helps 403 stay where you put it, wetting the bond area without running and filling gaps up to around 0.2 mm.

  • Fast handling strength
    Typical fixture times around 30 seconds on steel, faster on some plastics and rubbers, keep assembly throughput high.

  • Wide substrate compatibility
    Bonds metals, many plastics, elastomers and porous substrates such as wood, leather, paper and fabric – good for mixed assemblies.

  • One-part, room-temperature cure
    No mixing required; cures with ambient humidity and reaches full strength typically within 24 hours, depending on gap and conditions.

Typical Applications

Loctite 403 is used in OEM assembly, repair and MRO where low odor and good appearance matter, for example:

  • Consumer & cosmetic assemblies

    • Bonding clear housings, covers and lenses

    • Joining decorative trim where blooming would be visible

  • Electronics & electrical devices

    • Fixing small plastic, rubber and metal parts around switches, connectors and housings

    • Bonding components where fumes need to be minimized near sensitive parts

  • General industrial & hobby use

    • Bonding rubber seals, gaskets and O-rings

    • Quick repair of plastic enclosures and fixtures

    • Assembly on porous materials (wood, fabric, leather) where standard CAs soak in too quickly

When primed, it can also be used for non-polar plastics that are normally hard to bond.

How to Use Loctite 403

Always follow the latest Henkel Technical Data Sheet (TDS) and your internal process instructions.

Step 1 – Surface preparation

  1. Ensure substrates are clean, dry and free from oils, dust and release agents.

  2. For metals, a light abrasion followed by solvent cleaning usually improves bond strength.

  3. For very low-energy plastics (PP, PE, PTFE), apply a suitable Loctite plastic primer and allow it to dry.

Step 2 – Application

  1. Apply a small, controlled drop or thin bead of Loctite 403 to one surface only.

  2. Use just enough to cover the bond area – cyanoacrylates work best in thin bondlines.

Step 3 – Assembly

  1. Quickly bring the parts together and press firmly to spread the adhesive into a thin film.

  2. Maintain light pressure until handling strength is achieved (typically seconds to tens of seconds, depending on material).

Step 4 – Cure

  1. Allow the joint to remain undisturbed until full cure – usually up to 24 hours at room temperature for maximum properties.

Step 5 – Cleanup

  1. Remove uncured squeeze-out immediately with a suitable solvent (check compatibility).

  2. Cured CA usually needs mechanical means (scraping, careful cutting) or specialized debonders.

Safety & Handling

From the SDS for Loctite 403:

  • Bonds skin and eyes in seconds – avoid contact with skin and especially eyes.

  • Vapors may cause irritation; use in a well-ventilated area.

  • Keep away from heat, sparks and open flames; some versions are classified as combustible or flammable liquids.

  • Wear safety glasses and suitable gloves; avoid prolonged or repeated skin contact.

  • Do not allow uncured adhesive to enter drains or water systems; dispose of waste per local regulations.

Always consult the current Safety Data Sheet (SDS) before large-scale or repetitive use.

FAQs

Q1: What is Loctite 403 mainly used for?
Loctite 403 is mainly used where you need a fast-curing cyanoacrylate but cannot tolerate strong odor or white blooming – for example cosmetic parts, clear plastics, small electronics and porous substrates.

Q2: How is it different from standard super glues?
Compared with typical CAs, 403 offers much lower odor and significantly reduced blooming, while maintaining high strength and fast cure. This makes it far better suited to visible or enclosed applications.

Q3: What materials does Loctite 403 bond?
It bonds metals, many plastics, elastomers and porous materials (wood, paper, leather, fabric). With the right primer, it can also bond difficult plastics such as PP, PE and PTFE.

Q4: Is it suitable for large gaps?
It is designed for close-fitting parts with gaps up to about 0.2 mm. For larger gaps or flexible joints, consider an epoxy, acrylic or modified CA formulated for gap filling.

Q5: What is the typical operating temperature range?
Loctite 403 is generally used between –40 °C and +80 °C (–40 °F to 175 °F). For continuous use above this, a high-temperature adhesive system is recommended.

Q6: How fast does it reach handling strength?
On active metals like steel, fixture can be achieved in ~30 seconds, often faster on some plastics and rubbers. Exact times depend on material, gap and humidity.

Q7: Can Loctite 403 be used on 3D-printed parts?
Yes, it’s often used on 3D-printed plastics because of its low bloom and low odor, especially where surface appearance matters. Always test on your specific material and print finish.

Q8: Is the bond removable?
Like most cyanoacrylates, 403 forms a rigid, high-strength bond that is not designed for easy removal. Rework usually needs mechanical methods or debonders and may damage one or both parts.

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