Sikalastic®-621 TC
High performance, one-component, liquid applied polyurethane top coat for SikaRoof® MTC roof waterproofing systems
Sikalastic®-621 TC is a cold-applied, one-component, seamless, highly elastic and UV-stable moisture-triggered polyurethane Top Coat (TC) designed to provide easy application and a durable solution as part of the SikaRoof® MTC systems, as well as for detailing on single ply membranes. Suitable for use in hot and tropical climatic conditions.
- Proven technology - over 25 year track record
- One component - no mixing, easy and ready to use
- UV resistant - Highly reflective (RAL9016) and resistant to yellowing
Usage
- Top Coat for SikaRoof® MTC 12, 15, 18, 22 in both new construction and refurbishment projects
- For roofs displaying complex detail areas and geometry, even when accessibility is limited
- For cost efficient life cycle extension of failing roofs
- Highly reflective top coat Sikalastic®-621 TC - SR (traffic white RAL 9016) as part of the Sika SolaRoof™ MTC systems for excellent cool roof characteristics and bi-facial photovoltaic panels.
- For detailing solutions on singly ply membranes
Packaging
5 L (~7.2 kg) metal pail
15 L (~21.6 kg) metal pail
Advantages
- Proven technology - over 25 year track record
- One component - no mixing, easy and ready to use
- UV resistant - Highly reflective (RAL9016) and resistant to yellowing
- Cold applied - requires no heat or flame
- Seamless roof waterproofing membrane
- Compatible with Sika® Reemat Premium - easy to detail
- Fast curing - free from resin damage almost immediately on application
- High elastic and crack-bridging - retains flexibility even at low temperatures
- High root resistance
- Easily re-coated when needed - no stripping required
- Good adhesion to most substrates - see primer chart
- Vapour permeable - allows substrate to breathe
- Strong resistance to common atmospheric chemicals
Colour
Slate grey (RAL 7015), shale grey (RAL 8500), traffic white (RAL 9016), other colours available upon request
Product Details
APPROVALS / CERTIFICATES
As part of SikaRoof® MTC Systems
- Liquid applied roof waterproofing kit according to ETAG 005, ETA – 09 / 0139 issued by technical assessment body British Board of Agrément (BBA) provided with the CE marking, Declaration of Performance
SikaRoof® MTC 12: 44125185
SikaRoof® MTC 15: 27265077
SikaRoof® MTC 18: 15813688
SikaRoof® MTC 22: 75346978
- Root resistance approval according FLL (Institute of Horticulture)
- Reaction to fire according to EN 13501-1: Euroclass E
- External fire performance according to EN 13501-5:
- BRoof (t1) – BRoof (t4) (SikaRoof® MTC 15, non-combustible substrates)
- BRoof (t1) – BRoof (t4) (SikaRoof® MTC 18, build up roofs)
- BRoof (t1) (SikaRoof® MTC 22, Build up roofs)
Composition
One-component, moisture-triggered aliphatic polyurethane
Shelf life
9 months from date of production
Storage conditions
The product must be stored properly in original, unopened and undamaged sealed packaging in dry conditions at temperatures between 0 °C and +25 °C.
Higher storage temperatures may reduce shelf life of product.
Reference shall also be made to the storage recommendations within the safety data sheet.
Density
~1.44 kg/l (23 °C) | (EN ISO 2811-1) |
Solid content
~81.3 % by weight
~87.4 % by volume
System Structure
Please refer to System Data Sheets of SikaRoof® MTC Systems
Chemical Resistance
Salt spray | 1000 h |
| Prohesion testing | 1000 h cyclic exposure |
Strong resistance to a wide range of reagents including paraffin, petrol, fuel oil, white spirit, acid rain, detergents and moderate solutions of acids and alkalis. Some low molecular weight alcohols can soften the material. Contact Technical Department for specific information.
Solar Reflectance Index
≥ 109* | (ASTM 1980) |
*All values refer to the initial (properly cured, non-weathered) status of Sikalastic®-621 TC white (RAL 9016).
Service Temperature
-30 °C min. / +80 °C max.
Application
Ambient Air Temperature
+5 °C min. / +35 °C max.
Relative Air Humidity
5 % r.h. min. / 85 % r.h. max.
Substrate Temperature
+5 °C min. / +60 °C max.
≥ 3 °C above dew point
Substrate Moisture Content
≤ 4 % pbw moisture content.
Test method: Sika®-Tramex meter
No rising moisture according to ASTM (Polyethylene-sheet).
Substrate Pre-Treatment
Please refer to System Data Sheets of SikaRoof® MTC Systems
Pot Life
Sikalastic®-621 TC is designed for fast curing. High temperatures combined with high air humidity will increase the curing process. Thus, material in opened containers should be applied immediately. In opened containers, the material will form a film after 1 – 2 hours approximately (+20 °C / 50 % r.h.).
Waiting Time / Overcoating
| Ambient conditions | Minimum waiting time |
| +5 °C / 50 % r.h. | 18 h |
| +10 °C / 50 % r.h. | 8 h |
| +20 °C / 50 % r.h. | 6 h |
*After four days the surface must be cleaned and primed with Sika® Reactivation Primer before continuing.
Note: Times are approximate and will be affected by changing ambient conditions particularly temperature and relative humidity.
Applied Product Ready for Use
Ambient conditions | Rain resistance | Touch dry | Full cure |
+5 °C / 50 % r.h. | 10 min | 8 – 12 h | 16 – 24 h |
+10 °C / 50 % r.h. | 10 min | 4 h | 8 – 12 h |
+20 °C / 50 % r.h. | 10 min | 3 h | 6 – 8 h |
*Be aware that impact of heavy rain or rain showers can physically damage the still liquid membrane.
Note: Times are approximate and will be affected by changing ambient conditions particularly temperature and relative humidity.
SUBSTRATE PREPARATION
The surface must be sound, of sufficient strength, clean, dry and free of dirt, oil, grease and other contamination. Depending on the material the substrate must be primed or mechanically cleaned. Grinding may be necessary to level the surface. Suitable substrates are such as: concrete, bituminous felts and coatings, metal, brickwork, asbestos cement, ceramic tiles, wooden substrates.
For detailed information regarding substrate preparation and primer chart please refer to Method Statement.
MIXING
Mixing is not required, however if the product is settled or separated on opening, stir Sikalastic®-621 TC gently but thoroughly in order to achieve a uniform colour. Stirring gently will minimise air entrainment.
APPLICATION
Prior the application of Sikalastic®-621 TC the priming coat if used must have cured tack-free. For the Waiting Time / Overcoating please refer to the Product Data Sheet of the appropriate primer. Damageable areas (handrails etc) have to be protected with tape or plastic wrapping.
Please note, always begin with details prior to the installation of the horizontal surface.
- Apply first coat of Sikalastic®-601 BC. Work only so far in advance that the material stays liquid.
- Roll in the Sikalastic® Reemat. Overlap the Reemat a minimum 5 cm and ensure overlaps are sufficiently wet to bond both layers.
- The roller may require only a little extra material to keep wetted but no further significant material needs to be added at this stage.
- After the coat is dry enough to walk on, seal the roof area with second coat of Sikalastic®-621 TC.
- For SikaRoof MTC 22 apply a third coat of Sikalastic®-621 TC.
CLEANING OF EQUIPMENT
Clean all tools and application equipment with Thinner S immediately after use. Hardened and/or cured material can only be removed mechanically.