Loctite AA 3321

Loctite AA 3321

Color:Clear
Key characteristics:Wavelength for cure: UV / VIS
Viscosity, Brookfield – RVT, @ 25.0 °C:3500.0 mPa·s (cP) – 7500.0 mPa·s (cP)

Product Overview

LOCTITE AA 3321 is a transparent, high-viscosity acrylic adhesive that cures rapidly upon exposure to UV/visible light, forming durable bonds especially suited to stress-sensitive plastics, metals, glass and ceramics. With a fixture time around 12 seconds, tack-free time over 30 seconds and a depth of cure of greater than 13 mm, this one-component system is ideal for applications requiring precise, on-demand bonding without mixing. 
Its high viscosity and thixotropic nature reduce migration or flow after application, making it well suited for vertical or irregular surfaces.

Key Features & Benefits

  • Very high viscosity / thixotropic formulation — holds its shape, avoids run-off on vertical or textured surfaces.

  • Rapid on-demand cure (~12 seconds fixture time) — enables fast production throughput and minimal fixturing delay.

  • One-component light-cure system — no mixing required, simplifying process control and reducing waste.

  • ISO-10993 qualified — suitable for medical device assembly applications requiring biocompatibility.

  • Excellent substrate compatibility — works with metals, many plastics (including stress-sensitive types), glass and ceramics.

Application

  1. Surface Preparation: Ensure bonding surfaces are clean, degreased and free of contaminants. For best results, use substrates compatible with UV/Vis irradiation.

  2. Application: Apply LOCTITE AA 3321 in the desired amount; because of its high viscosity it will stay where applied.

  3. Assembly: Position parts promptly after application, then expose to appropriate UV/visible light source until initial fixturing occurs (approx. 12 seconds in ideal conditions).

  4. Curing / Handling: After light exposure, allow sufficient time for full cure (depending on substrate, gap size and exposure level) before putting the assembly into service.

  5. Disassembly / Service: As this is designed for durable, permanent bonds, disassembly may require mechanical force or specialized methods; review TDS for details.

Tips:

  • Use appropriate light source and exposure time to ensure full cure through the bondline.

  • If bonding opaque or large parts where light cannot reach the full bond area, consider dual-cure adhesives or irradiate via edges.

  • Ensure good confinement and appropriate adhesive volume to avoid thick bond layers which may delay full cure.

FAQs

Q1: What substrates can LOCTITE AA 3321 bond?
A1: It bonds well to metals, glass, ceramics and many plastics including stress-sensitive types; however, for certain materials or specific conditions you should verify compatibility.
Q2: What is the expected fixture time?
A2: Generally about 12 seconds under specified UV/Vis conditions.
Q3: Does the adhesive require mixing?
A3: No — it is a one-part system. Simply apply and cure under proper light source.
Q4: Is this suitable for medical device assembly?
A4: Yes — LOCTITE AA 3321 is ISO-10993 qualified for biocompatibility.
Q5: What if the bond area is very thick or opaque?
A5: Because full cure depends on light penetration, very thick or opaque bondlines may cure more slowly or irregularly; in those cases consider using specialized light-assist techniques or alternative adhesive technologies.

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