LOCTITE AA 3921

Harmonization Code : 3506.10.00.00 | Prepared glues and other prepared adhesives, not elsewhere specified or included; products suitable for use as glues or adhesives, put up for retail sale as glues or adhesives, not exceeding a net weight of 1 kg

LOCTITE AA 3921

Main features

  • 5-Second UV/Visible-Light Cure
  • Transparent Cured Bondline
  • High-Hardness Acrylic Adhesive

Product Description

LOCTITE® AA 3921™ is a one-component UV/visible light-curing acrylic adhesive engineered for high-speed bonding applications requiring flexibility, strong adhesion and sterilization resistance. The adhesive cures within seconds when exposed to appropriate UV or visible light sources and develops excellent adhesion to glass, plastics and metals. Its fluorescent response under UV light enables inspection of adhesive presence, making it particularly suitable for medical device assembly. LOCTITE AA 3921 was specifically developed for bonding stainless steel cannulas into hubs, syringes and lancets used in disposable needle assemblies and has been evaluated to ISO 10993-based biocompatibility protocols.

Key Features & Benefits

  • UV and visible light curing acrylic adhesive.
  • Rapid fixture times of approximately 5 seconds under UV/LED light.
  • Fluoresces under UV light for inspection and quality control.
  • Excellent adhesion to glass, plastics and metals.
  • Flexible cured bond line with high toughness.
  • Resistant to autoclave, ETO and gamma sterilization processes.
  • Designed for disposable medical device assembly.

Recommended Applications

  • Needle-to-hub bonding for syringes and cannula assemblies.
  • Disposable medical device manufacturing.
  • Glass-to-metal and glass-to-plastic bonding.
  • UV-curable industrial assembly operations.
  • Applications requiring adhesive inspection under UV light.
Product Family

LOCTITE AA 3921

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TDS, SDS & Technical Documents

Technical Specifications

General Properties
Appearance
Appearance at room temperature.
Transparent to hazy liquid and Free of undissolved solids
Specific Gravity
Specific gravity (SG) is the ratio of the density of a substance to the density of a reference substance; equivalently, it is the ratio of the mass of a substance to the mass of a reference substance for the same given volume. For liquids, the reference substance is almost always water (1), while for gases, it is air (1.18) at room temperature. Specific gravity is unitless.
1.03
Physical Properties
Viscosity
Viscosity is a measurement of a fluid’s resistance to flow. Viscosity is commonly measured in centiPoise (cP). One cP is defined as the viscosity of water and all other viscosities are derived from this base. MPa is another common unit with a 1:1 conversion to cP. A product like honey would have a much higher viscosity -around 10,000 cPs- compared to water. As a result, honey would flow much slower out of a tipped glass than water would. The viscosity of a material can be decreased with an increase in temperature in order to better suit an application
150 mPa.s

Additional Information

Technical Properties

As-Supplied / Before-Processing Properties

Property Value Unit Condition
Technology UV Acrylic — UV / Visible Light Cure
Appearance Transparent to Hazy Liquid — Uncured, free of undissolved solids
Fluorescence Positive Under UV Light — Inspection aid
Components One Part — No mixing required
Specific Gravity 1.03 — 25°C
Density 1.03 g/cm³ 20°C
Brookfield Viscosity 100 - 200 mPa·s (cP) RVT, Spindle 2, 20 rpm, 25°C
UV Fixture Time 5 seconds 100 mW/cm² LED at 365 or 405 nm
Technical Properties

After-Processing / Final-State Properties

Property Value Unit Condition / Method
Glass Transition Temperature (Tg) 89 °C ASTM E228
Shore Hardness 67 Shore D ISO 868
Tensile Strength 19.5 N/mm² ISO 527-3
Elongation at Break 32 % ISO 527-3
Coefficient of Thermal Expansion 108 × 10⁻⁶ K⁻¹ Below Tg, ISO 11359-2
Water Absorption 2.0 % ISO 62, boiling water
Block Shear Strength (Steel to Glass) 16.5 N/mm² ISO 13445
Block Shear Strength (Aluminum to Glass) 14.8 N/mm² ISO 13445
Block Shear Strength (Polycarbonate to Polycarbonate) 21.1 N/mm² ISO 13445
VOC Content <3.0 % 2010/75/EC
Environmental Classification Aquatic Acute 1 / Chronic 1 — H400 / H410

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