H.B. Fuller 1521

H.B. Fuller 1521 is a two-component, room-temperature-cure silicone system. It has very low ionic content and can be used for electronic component applications and electronics potting. Its applications include appliance sealing, connector sealing, and junction box potting. Additionally, it has good thermal conductivity and flame retardancy.

Chemical Family: Silicones

Product Type: 2K (2 component) Adhesive, Encapsulant, Potting Compound, Reactive Adhesive

Application Area: Batteries, Blades, Edge Gluing, Electronic Components, Energy Storage, Frame Sealing, HVAC Applications, Ingot Bonding, Junction Boxes, Lithium-Ion Battery, Module Installation, PV Modules, Rail Bonding, Solar Panel, Turbines

Compatible Substrates & Surfaces: Glass

Features: Enhanced Damp Proofing, Excellent Sealing Capability, Fast Cure, Good Adhesion, Good Electrical Properties, Good Thick Section Cure, Rapid Cure Response, Room Temperature Curing

Technical Data Sheet

Enhanced TDS

Identification & Functionality

Chemical Family

Features & Benefits

Applications & Uses

Compatible Substrates & Surfaces
Curing Conditions

Cure speed will vary with temperature, relative humidity, depth of material and presence of moisture. Some applications may require special surface preparation.

General Instructions
  • For best performance bond surfaces should be clean, dry and free of any contaminants and oils.
  • Part A should be blended thoroughly before mixing with Part B in order disperse filler material evenly.
  • Mix Parts A and B evenly according to the applicable mix ratio.
  • Apply the mixture to the sealing or potting application. Automated dispensing equipment is recommended for electronics sealing and potting applications.


Physical Form
Component A
ValueUnitsTest Method / Conditions
Component B
ValueUnitsTest Method / Conditions
Electrical Properties
ValueUnitsTest Method / Conditions
Volume Resistivity1.0 x 10¹⁵Ω.cmIEC60093, GB/T1692
Breakdown Voltage23.0kV/mmIEC 60243-1, GB/T1695
Cured Properties
ValueUnitsTest Method / Conditions
Elongation at Break (50% RH)110.0%ISO37, GB/528
Hardness40.0ISO7619, GB/T531, Shore A
Tensile Strength (50% RH)1.2MPaISO37, GB/528
Thermal Service Range- 50 - 150°C
Uncured Properties
ValueUnitsTest Method / Conditions
Fixture Time45.0min
Cure Schedule (50% RH)7.0days
Weight Mix Ratio6:1
Working Time8.0min
Specific Gravity1.4
Volume Mix Ratio4:1

Packaging & Availability

Regional Availability
  • Africa
  • Asia Pacific (Excluding Russia)
  • Europe (Excluding Russia)
  • India
  • Latin America
  • Middle East
  • North America
Packaging Information


Storage & Handling

Shelf Life
6 Months
Storage Condition

Product shall be ideally store in a cool, dry area in unopened containers. Material should be stored at a temperature of 8 - 25ºC for a maximum. In the original unopened container. Do not return unused material back into the container.