LETBOND® Moisture-Cure Silicone & Polymers
Description
The LETBOND® Moisture-Cure Adhesive Series consists of single-component, room-temperature vulcanizing (RTV) elastic bonding materials. These are formulated from silicone rubber, specialized silyl polymers, modified silicones (non-tin catalyst), polyurethanes (PU), or modified silyl esters. The products cure by reacting with ambient moisture to form an elastic bond layer resistant to impact and vibration, making them ideal for bonding rigid materials with differing coefficients of thermal expansion.
Once cured, these materials offer high flexibility and low contamination (with select models being RoHS compliant). They require no mixing and are easy to use, featuring a wide viscosity range (2,400 to 900,000 cps), tack-free times of 2 to 30 minutes, hardness levels from Shore A 18 to 78, and temperature resistance from -60°C to +149°C.
Features
- Single-Component Design: No mixing required; easy and safe to operate; solvent-free and environmentally friendly (select models are free of isocyanate toxicity and acid odors).
- Rapid Curing: Short tack-free times (2–30 minutes) with high initial bond strength. High thixotropy in specific models prevents sagging, often eliminating the need for fixtures.
- Elasticity & Durability: Elongation at break ranges from 135% to 350%, providing excellent impact/vibration resistance and energy absorption. Stable performance across a wide temperature range (-60°C to +149°C) with superior weather and thermal cycle resistance.
- Broad Adhesion: Excellent adhesion to various substrates, including metals (aluminum, stainless steel), plastics (PC, ABS, PMMA, PVC), glass, and wood.
- Specialized Functions: Select models offer thermal conductivity (0.22–1.53 W/m·K), high specific gravity (up to 4.50), or neutral alcohol-curing reactions.
Applications
- Structural & Assembly Bonding: The silyl-based high initial tack series (e.g., 29230C, 29231, 29253) is recommended for rapid positioning and thermal cycling applications involving dissimilar materials like metal-to-plastic, rubber, and ceramics.
- Sealing & Caulking (Construction & Glass): 29238B (Black) and 29238C (Clear) are oxime-curing silicone sealants suitable for glass-to-glass, glass-to-metal, and interior construction sealing.
- 3C/Electronics Potting & Light Shielding: PU moisture-cure models (29243) offer superior adhesion to ABS/PC compared to standard silicone. They are ideal for touch panel light shielding, 3C potting, and structural bonding in waterproof cameras or batteries.
- Weighting/Balancing: 29143 is a high-density (S.G. 4.5), high-hardness (Shore A 78) single-component PU adhesive. With a 3-minute tack-free time, it is specifically designed for cooling fan balancing.
- Thermal Fixation & Reinforcement: 29300W (modified silyl ester) features a 1.53 W/m·K thermal conductivity, suitable for fixing and reinforcing heat sinks onto PCBs.
Selection Specifications
A : Structural & Assembly Bonding (Bonding of dissimilar materials, high initial tack, and high-strength bonding.)
| Model | Color | Viscosity (cps) |
Tack-free Time (min) |
Hardness (Shore) |
Temp. Range (°C) |
|---|---|---|---|---|---|
|
29021B |
Black Paste |
50,000 ~ 100,000 (10 rpm) |
2 ~ 5 |
A 50 |
-20~120 |
|
29021C |
Clear Paste |
25,000 ~ 50,000 (10 rpm) |
2 ~ 5 |
A 50 |
-20~120 |
|
29021W |
White Paste |
50,000 ~ 100,000 (10 rpm) |
2 ~ 5 |
A 50 |
-20~120 |
|
29022BL |
Black Paste |
15,000 ~ 30,000 (10 rpm) |
4 ~ 9 |
A 48 |
-20~120 |
|
29022B |
Black Paste |
90,000 ~ 200,000 (10 rpm) |
6 ~ 15 |
A 50 |
-20~120 |
|
29230C |
Clear Paste |
80,000 ~ 120,000 |
7 |
A 55 |
-40~120 |
|
29231BL |
Black Liquid |
16,000 ~ 24,000 (5 rpm) |
11 |
A 35 |
-60~120 |
|
29231B |
Black Paste |
64,000 ~ 96,000 (5 rpm) |
10 |
A 51 |
-60~120 |
|
29231C |
Yellowish Translucent |
66,000 ~ 99,200 (5 rpm) |
8.5 |
A 50 |
-60~120 |
|
29231W |
White Paste |
65,600 ~ 98,400 (5 rpm) |
10 |
A 50 |
-60~120 |
|
29253BL |
Black Paste |
16,000 ~ 24,000 (5 rpm) |
11 |
A 35 |
-60~120 |
|
29253B |
Black Paste |
64,000 ~ 96,000 (5 rpm) |
10 |
A 51 |
-60~120 |
|
29253C |
Yellowish Translucent |
58,400 ~ 87,600 (5 rpm) |
8 |
A 50 |
-60~120 |
B : Sealing & Caulking (Sealing for construction and general industrial purposes.)
| Model | Color | Viscosity (cps) |
Tack-free Time (min) |
Hardness (Shore) |
Temp. Range (°C) |
|---|---|---|---|---|---|
|
29238B |
Black Paste |
Paste |
10 |
A 26 |
-48~149 |
|
29238C |
Clear Paste |
Paste |
10 |
A 26 |
-48~149 |
C : 3C/Electronics, Light Shielding & Potting
| Model | Color | Viscosity (cps) |
Tack-free Time (min) |
Hardness (Shore) |
Temp. Range (°C) |
|---|---|---|---|---|---|
|
29243BL |
Black Liquid |
2,400 ~ 4,400 (100 rpm) |
30 |
A 18 |
-40~120 |
|
29243B |
Black Paste |
32,500 ~ 48,800 (10 rpm) |
30 |
A 30 ± 5 |
-40~120 |
|
29243C |
Mist Translucent Liquid |
9,600 ~ 14,400 (10 rpm) |
30 |
A 36 |
-40~120 |
|
29244BL |
Black Liquid |
5,000 ~ 12,000 (100 rpm) |
16 ~ 20 |
A 42 |
-40~120 |
|
29244B |
Black Paste |
40,000 ~ 80,000 (10 rpm) |
7 |
A 42 |
-40~120 |
|
29244C |
Mist Translucent Liquid |
5,000 ~ 12,000 (100 rpm) |
9 ~ 14 |
A 65 |
-40~120 |
D : Balancing & High Specific Gravity Materials
| Model | Color | Viscosity (cps) |
Tack-free Time (min) |
Hardness (Shore) |
Temp. Range (°C) |
|---|---|---|---|---|---|
|
29143 |
Brick Red Paste |
600,000 ~ 900,000 (1 rpm) |
3 |
A 78 |
-20~120 |
E : Thermal Fixation & Reinforcement
| Model | Color | Viscosity (cps) |
Tack-free Time (min) |
Hardness (Shore) |
Temp. Range (°C) |
|---|---|---|---|---|---|
|
29300W |
White Paste |
180,000 ~ 270,000 (10 rpm) |
5 |
– |
-20~120 |
Notes:
- The values above are for reference only; actual values are based on the Certificate of Analysis (COA) of the shipped batch.