LOCTITE 5240
Harmonization Code : 3208.20.90 | Paints and varnishes that are dispersed or dissolved in a non aqueous medium
Main features
- Light-and-Moisture Dual Cure
- Shear-Thinning Cavity Filling
- Flexible Electrically Insulating Rubber
Product Description
LOCTITE SI 5240 is a clear, flowable one-component alkoxy silicone for bonding, potting, coating, and sealing. UV or visible light rapidly cures exposed material, while atmospheric moisture provides secondary cure in shadowed regions. The shear-thinning liquid supports controlled dispensing and uniform cavity filling before forming a flexible silicone rubber. Typical cured properties include Shore A hardness of at least 40, tensile strength of at least 3 N/mm^2, and elongation from 250% to 450% at the specified cure condition. Full ambient property development occurs over approximately 72 hours.
Key features
- Light-and-moisture dual cure: Exposed material cures with UV or visible light, while atmospheric moisture supports shadowed regions.
- Shear-thinning cavity flow: The 15,000 to 35,000 mPa s liquid supports controlled dispensing and uniform filling.
- Flexible insulating silicone: The cured rubber combines high elongation with measured dielectric and mechanical properties.
Applications / Suitable for
- Bonding and sealing components
- Potting and cavity filling
- Protective coating of assemblies
TDS, SDS & Technical Documents
Technical Specifications
General Properties
Chemistry Type
Alkoxy silicone
Color
Clear liquid with yellow to green tint slight haze permissible
The color
Component System
One component
Describes the number of components that must be supplied, mixed, or activated before application or cure.
Specific Gravity
1.06
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.
Physical Properties
Depth of Cure
≥10 mm
Tack-Free Time
50 to 55 minutes
Viscosity
15,000 to 35,000 mPa.s
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
Mechanical Properties
Elongation
250 to 450 %
Elongation is the process of lengthening something.
It is a percentage that measures the initial, unstressed, length compared to the length of the material right before it breaks.
It is commonly referred to as Ultimate Elongation or Tensile Elongation at break.
Electrical Properties
Dielectric Strength
21 kV/mm
Dielectric strength is measured in kV per mm and is calculated by the Breakdown voltage divided by the thickness of the tested material.
Those two properties go hand in hand and while Breakdown voltage is always thickness dependent, dielectric strength is a general material property.
As an example, the dielectric strength of Polyimide is 236 kV/mm. If we place 1mm of Polyimide between two electrodes, it will act as an insulator until the voltage between the electrodes reaches 236 kV. At this point it will start acting as a good conductor, causing sparks, potential punctures and current flow.
Surface Resistivity
5.15×10^15 Ohms/sq
Volume Resistivity
1.2×10^15 Ohms⋅cm
Volume resistivity, also called volume resistance, bulk resistance or bulk resistivity is a thickness dependent measurement of the resistivity of a material perpendicular to the plane of the surface.
Curing Conditions
Fixture Time
5 to 10 seconds
Additional Information
Technical properties
As-supplied / before-processing properties
Typical values and characteristics for the product before cure, application, or assembly.
| Property | Value | Unit | Method / condition |
|---|---|---|---|
| Appearance | Clear with yellow-green tint | - | As supplied |
| Chemical type | Alkoxy silicone | - | One-component material |
| Specific gravity | 1.06 | - | 23 deg C |
| Viscosity | 15,000 to 35,000 | mPa s | Brookfield RVT, spindle 5, 10 rpm, 25 deg C |
| Flow behavior | Shear thinning | - | Thixotropic as supplied |
| Primary cure mechanism | UV / visible light | - | Exposed material |
| Secondary cure mechanism | Atmospheric moisture | - | Shadowed regions |
Technical properties
After-processing / final-state properties
Typical values for the cured, bonded, treated, or in-service product under the listed conditions.
| Property | Value | Unit | Method / condition |
|---|---|---|---|
| Shore hardness | >=40 | Shore A | 70 mW/cm^2 at 365 nm for 60 s per side, then 7 d at 22 deg C |
| Elongation at break | 250 to 450 | % | 70 mW/cm^2 at 365 nm for 60 s per side, then 7 d at 22 deg C |
| Tensile strength | >=3 | N/mm^2 | 70 mW/cm^2 at 365 nm for 60 s per side, then 7 d at 22 deg C |
| Tensile modulus at 100% strain | 1 | N/mm^2 | 70 mW/cm^2 at 365 nm for 60 s per side, then 7 d at 22 deg C |
| Tear strength | 12.6 | N/mm | 70 mW/cm^2 at 365 nm for 60 s per side, then 7 d at 22 deg C |
| Volume shrinkage | 0.8 | % | Cured material |
| Dielectric breakdown strength | 21 | kV/mm | Cured material |
| Volume resistivity | 1.2 x 10^15 | ohm cm | Cured material |
