Thermoplastic Elastomer Ether Esters: What are they, how do they work?
Exterior membranes for roofs and walls by pro clima incorporate a monolithic Thermoplastic Elastomer Ether Ester (TEEE) film. The TEEE forms a state-of-the-art Weather Resistive Barrier (WRB) and when combined with TESCON EXTORA® forms the SOLITEX system. The membrane, unlike conventional vapour permeable membranes, has no pores and is completely waterproof and wind/airtight. The membrane actively transports water vapour through molecular diffusion across the thickness of the TEEE film – an engineered property of this functional film.
Aren’t all vapour permeable membranes the same?
If vapour/water is present on the surface of the membrane, even the slightest differential in vapour pressure across the membrane (inside to outside) will promote vapour movement from one side to the other and dry out the moisture. Consequently, the membrane is very vapour open (0.4 MNs/g, 2.5 µg/Ns) in every condition. Conventional vapour permeable sarking membranes and underlays depend on creating a micro-porosity in a normally vapor closed material (PE or PP). In the production process these materials are made vapor open by either spun bonding them into a PE mesh, puncturing the PP or stretching the PP with calcium carbonate CaCO3 additives in production. These micro-pores then allow gaseous water vapor molecules to be moved through the water-resistant layer by convection (leaking through the micro-pores).
By being porous, perforated or stretched, these materials are not 100% airtight. They are therefore vapour open because air and water-vapour molecules, driven by convection, leak through the micropores. Since the pores are quite small – nanometre scale – a relatively high vapor pressure differential is required for vapor to actually dry outwards through the pores. This is true even if the actual vapour permeance (per ASTM E96B) is high, which could be the case because the pores are big or perforated. If you can easily blow through the membrane when placing it over your mouth, the pores are probably large – very vapor open, and not very airtight, and possibly not even watertight under driving rain conditions.
Through active vapour diffusion, pro clima SOLITEX MENTO® membrane remains dry (Figure 1). In the same roof, the microporous membrane causes condensation to form, because passive vapour openness is not sufficient for outward drying (Figure 2).
The example above shows that actively vapour open SOLITEX MENTO® membranes remain dry even when large amounts of humidity enter a roof enclosure with compromised interior airtightness. However, the conventional passively vapour open membrane in the same building is showing condensation – because water vapor wasn’t transported fast enough, causing a layer of condensate to build up. It looks like the membrane leaks, but the moisture is actually just interior humidity.
How is a vapour permeable membrane waterproof?
A micro-porous or perforated membrane is “waterproof” because the surface tension in liquid water holds the drops together and prevents water beads from passing through the membrane. But if that tension is broken by surfactants such as oils, wood preservatives, wood tannins, soap or contaminants, the waterproofing becomes compromised.
By contrast, the monolithic film in the pro clima SOLITEX product range is completely waterproof. In the lab tests depicted below, to the left you can see the effect of applying oil to membranes before testing the water column (DIN EN 20811) of each membrane (Figure 4 & 6). The conventional membrane leaks at low water pressures (Figure 5), while SOLITEX MENTO® membrane stays dry at a much higher column (notice the difference in bulge in Figure 7). This demonstrates that the waterproof qualities of the TEEE work even when exposed to surfactants such as oil.
SOLITEX range uses a monolithic membrane and is waterproof (DIN EN 20811) up to lab test limitation of 10 meters head of water. Half of each membrane sample is coated with oil without any effect on waterproofness as seen in Figure 7. Surfactant contamination on construction sites will have no effect on the water resistance of SOLITEX products.
Preventing wind washing
The pro clima SOLITEX range with a monolithic membrane is also absolutely wind & airtight. ASTM E2173 test result shows that the material is so airtight that it exceeds the capabilities of the lab calibration – and goes above and beyond the Air Barrier Association of America (ABAA) requirements and certainly well above the thresholds specified in AS/NZS 4200.1 or NZS 2295 measured using ISO 5636-5 (AUS) & BS 6538.3 (NZ).
The pro clima WRB roof & wall systems offer the ultimate protection against wind-washing of insulation when taped with TESCON tapes and following the other instructions found on SOLITEX MENTO® and SOLITEX EXTASANA® product webpages. When SOLITEX MENTO® is used as a roof underlay, the top layer offers slip resistance, while also protecting the TEEE layer below.
The TEEE functional layer is located in the middle of each product, providing active vapour permeability and waterproofing properties of the material. The SOLITEX product range allows exposure prior to cladding of: pro clima full scale weather testing in NATA and IANZ accredited laboratories has demonstrated world class weather tightness with the SOLITEX EXTASANA® flexible membrane system and rainscreen cladding.
Three layers – each with its own function
All pro clima WRB membrane systems are multi-layered products, with each layer having specific properties to assure the product offers first class performance during installation and the life of the building. The top layer serves as a protective cover made with a PP microfiber fleece. This offers the external exposure resistance needed for both roofs and walls.
When SOLITEX MENTO® is used as a roof underlay, the top layer offers slip resistance, while also protecting the TEEE layer below.
The TEEE functional layer is located in the middle of each product, providing active vapour permeability and waterproofing properties of the material. The SOLITEX product range allows exposure prior to cladding of:
- SOLITEX MENTO® 1000: 30 days
- SOLITEX MENTO® 3000: 90 days
- SOLITEX MENTO® 5000: 180 days
- SOLITEX MENTO® PLUS: 180 days
- SOLITEX MENTO® ULTRA: 180 days
- SOLITEX EXTASANA® (NZ): 180 days
- SOLITEX EXTASANA® (AUS): 180 days
- SOLITEX EXTASANA ADHERO® (NZ): 180 days
- SOLITEX EXTASANA ADHERO® (AUS): 180 days
The TEEE functional layer also has the added benefit that it holds the product together, acting as a bonding agent. Applied in a high temperature process, it eliminates any need for hot melt adhesives giving SOLITEX MENTO® and SOLITEX EXTASANA® ultimate temperature resistance behind hot cladding materials.
SOLITEX products without reinforcement scrim have shown no heat shrinkage up to 100°C in accordance with Australian and New Zealand Standard AS/NZS 4200.1. This elevated test temperature is 30°C above the requirement.
The heat shrinkage @ 70°C in accordance with AS 4200.1 and ADTM D 1204:
- SOLITEX MENTO® 1000, 3000, 5000, ULTRA: 0.0% shrinkage
- SOLITEX MENTO® PLUS: 0.4% shrinkage
- SOLITEX EXTASANA® : 0.0% shrinkage
- SOLITEX EXTASANA ADHERO®: 0.0% shrinkage
The top fleece protects the TEEE film from direct UV exposure during installation. Polymers are engineered for enhanced UV tolerance. Heavier duty fleeces provide more protection and allow for longer UV exposure prior to cladding.
TEEE: Thermoplastic Elastomer Ethyl Ester – is a material that combines the flexibility of rubber with the strength of a membrane, resisting tears, abrasion and corrosion. It also has good resistance to surfactants.
The bottom microfiber fleece protects the TEEE layer above from damage during construction.
Adapted from an article published on: https://foursevenfive.com/blog/the-pro-clima-solitex-mento-difference/
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