Sealants
Types and Durability
|
Description Sealants (Solvent based) |
Expected Lifespan (Years) |
Adjustment Factors
|
|
External
| ||
| Oil / solvent based
Oil based mastic, Butyl or bitumen rubber, Plastic but no elastic properties. |
5
| 1st stage adjustment factor:
In industrial areas (heavy polluted): -15% years In urban areas: -10% years In suburban areas: -0% years 2nd stage adjustment factor: West or south orientation: -10% years Applied to reseal existing joint: -15% years. Test certificate from approved local testing authority (as specified in SS 212:2000 for glazing material) : +15% years For sealant protected from UV in lap joints: +15% years |
| Acrylic
Acrylic (solvent type). Plastic and elastic properties. |
15
| |
| 1 or 2 part polysulphide
2 part polysulphide to BS 4254 (mainly elastic properties). 1 part polysulphide to BS 5215 (mainly elastic properties). |
20
| |
| Uninsured,i.e. 1 or 2 part polysulphide not to BS 5215 or BS 4254 |
< 20
| |
| 1 or 2 part polyurethane
2 part polyurethane (mainly elastic properties).1 part polyurethane (mainly elastic properties). |
20
| |
| Silicone
1 part low modulus silicone to BS 5889 Type A; elastic properties. |
20
| |
| Uninsured, i.e. silicone sealant not to BS 5889 Type A. Also Type B to BS 5889. |
< 20
|
Combination of adjustment factors (1st stage and 2nd stage) should be added to obtain the durability values. Refer to durability calculator.
Under favourable condition, the expected life quoted may be exceeded (see BS 6213)
Durability under the effects of weathering:
The basic property of the sealant must not change significantly with age. For example, the effect of long term exposure to heat on hardness can radically affect the sealant’s performance. Sealant must also have high resistance to the synergistic effect of the sunlight, temperature and rain acting together.
Notes:
- Water based sealant, such as Acrylic emulsion sealant (instead of acrylic-solvent based) is commonly used in Singapore. However, it can only be used indoor or any place not in contact with water.
- Two part sealant dependant on thorough mixing and constraints of ‘pot life’. (Polyurethane and Polysulphide only)
- One part sealant slow to cure with consequent depth limitations. (Polyurethane and Polysulphide only)
- High modulus silicone Type B is not suitable for this application (because it accommodates much less movement). (Silicone only)
- Contact with organic solvents and other petroleum-based products can lead to degradation of some sealants.
- The use of a suitable primer will increase adhesion and weatherproofing, particularly on porous joint surfaces.
- Refer to the manufacturer for guidance on compatibility with paints/applied finishes and with other sealant materials.
- Closed cell foam strips are not suitable for use in exposed/unprotected locations. Wax/resin impregnated foam strips are susceptible to UV degradation and are intended primarily for internal use.
Sealant Selection
Each sealant type, depending on the formulation, may have its own characteristic and certain relative merits or limitations. The particular manufacturer should be consulted for specific sealant. However, BS 6213 offers comprehensive details on sealant selection.
| Generic type/ curing process | MAF (%) | Application | Characteristic |
| One-part polysulphide/ atmospheric | 20-25 | Slow moving construction joints | Elastoplastic and elastic. No mixing but slow curre and unsuitable for wide joints. |
| Two-part polysulphide/ chemical | 25-30 | Movement joint in maintenance free application | Elastoplastic and elastic. Sealant with rapid cure characteristic and good durability, but high initial cost. |
| One-part polyurethane/ atmosphoric moisture | 10-30 | Slow moving construction joint | Elastoplastic and elastic. No mixing but relatively fast cure. |
| Two-part polyurethane/ chemical | 20-30 | All movement joints | Elastic |
| Low modulus silicone/ atmospheric moisture | 50-70 | All movement joints and for pointing | Elastic and elastoplastic. Fast cure and suitable for most porous surfaces. |
| High modulus silicone/ atmospheric moisture | 20-30 | All movement joints and for pointing | Elastic. Fast cure but some unsuitable for use on sanitary ware/ concrete/ porous surfaces. Some contain fungicide. |
MAF(%)= Movement accomodation factor.