LOCTITE 438
Harmonization Code : 3907.30.00.40 | Epoxy Mold Compounds containing by weight more than 70 % silicon dioxide
Main features
- Black Rubber-Toughened Bonding
- Enhanced Shock and Peel Resistance
- Low-Viscosity Multi-Material Assembly
Product Description
LOCTITE 438 is a black, one-part, low-viscosity, rubber-toughened ethyl cyanoacrylate instant adhesive for bonding metals, plastics, rubbers, and selected porous materials. Its black color makes adhesive placement visible, while the toughened formulation combines increased flexibility and peel strength with resistance to shock. A viscosity of 100 to 250 mPa s supports thin bondlines and rapid wetting. Fixture time ranges from under 5 seconds on nitrile rubber and balsa wood to 30 to 60 seconds on common metal substrates under the specified conditions.
Key features
- Black visible bondline: The black liquid provides clear visual contrast for adhesive placement and cured bond identification.
- Rubber-toughened performance: Increased flexibility and peel strength are combined with enhanced resistance to shock.
- Low-viscosity multi-material cure: A 100 to 250 mPa s viscosity supports rapid bonding across tested metals, plastics, rubbers, and porous materials.
Applications / Suitable for
- Visible black bonding of metals and plastics
- Shock- and peel-resistant rubber bonding
- Bonding selected wood, paper, leather, and fabric
TDS, SDS & Technical Documents
Technical Specifications
General Properties
Chemistry Type
Ethyl cyanoacrylate
Color
Black liquid
The color
Component System
One component
Describes the number of components that must be supplied, mixed, or activated before application or cure.
Specific Gravity
1.1
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.
Thermal Properties
Glass Transition Temperature (Tg)
130 °C
The glass transition temperature for organic adhesives is a temperature region where the polymers change from glassy and brittle to soft and rubbery. Increasing the temperature further continues the softening process as the viscosity drops too. Temperatures between the glass transition temperature and below the decomposition point of the adhesive are the best region for bonding.
The glass-transition temperature Tg of a material characterizes the range of temperatures over which this glass transition occurs.
Linear thermal expansion
80x10^-6 K -1
Thermal Conductivity
0.1 W/m.K
Thermal conductivity describes the ability of a material to conduct heat. It is required by power packages in order to dissipate heat and maintain stable electrical performance.
Thermal conductivity units are [W/(m K)] in the SI system and [Btu/(hr ft °F)] in the Imperial system.
Physical Properties
Viscosity
100 to 250 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
Peel Strength
4 N/mm
Electrical Properties
Dielectric Strength
25 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
10×10^15 Ohms Ohms/sq
Volume Resistivity
10×10^15 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
30 to 45 seconds
Additional Information
Technical properties
As-supplied / before-processing properties
Typical values for the product before cure, application, or assembly.
| Property | Value | Unit | Method / condition |
|---|---|---|---|
| Appearance | Black liquid | - | Uncured |
| Chemical type | Ethyl cyanoacrylate | - | As supplied |
| Components | One part | - | No mixing required |
| Specific gravity | 1.1 | - | 25 deg C |
| Viscosity | 100 to 250 | mPa s | Cone and plate, 25 deg C, shear rate 1,000 s^-1 |
| Cure mechanism | Humidity | - | Atmospheric moisture |
Technical properties
After-processing / final-state properties
Typical values for the cured or installed product under the listed conditions.
| Property | Value | Unit | Method / condition |
|---|---|---|---|
| Fixture time, nitrile rubber | <5 | s | 22 deg C, 50% RH; time to 0.1 N/mm^2 shear strength |
| Fixture time, ABS | 10 to 20 | s | 22 deg C, 50% RH; time to 0.1 N/mm^2 shear strength |
| Fixture time, aluminum | <=60 | s | Isopropanol-wiped aluminum, 22 deg C, 50% RH |
| Glass transition temperature | 130 | deg C | ISO 11359-2; cured 24 h at 22 deg C |
| Lap shear strength, grit-blasted steel | 19 | N/mm^2 | ISO 4587; cured 24 h at 22 deg C |
| 180-degree peel strength, grit-blasted steel | 4 | N/mm | ISO 8510-2; cured 48 h at 22 deg C |
| Side impact resistance, aluminum | >=4 | J | Cured 24 h at 22 deg C |
