Single-ply waterproofing membranes are factory made and delivered to the job-site in rolls or sheets. Once installed on the roof they are “welded” together either by applying heat (in case of the thermoplastic based membrane) or by a sealant/adhesive ( in case of synthetic rubber):
- Thermoplastics: (heat welding possible; reinforcement necessary)
- Synthetic Rubber: (adhesive welding; can accomodate expansion/contraction)
Sibelco’s mineral fillers help achieving the desired properties of the roofing material used in all 3 synthetic membrane systems:
- Flame-retardency (ATH)
- Good mechanical properties (especially tear-resistance) ,
- UV and abrasion resistance (Silica)
PVC Roofing membranes have the longest track record of thermoplastic membranes.
PVC is inherently self-extinguishing. Because PVC is not naturally flexible, plasticisers are added to the formulation. Now, all PVC membranes are reinforced, and new formulations minimise the loss of plasticisers from the membrane. The use of plastisiser and the use of polyester reinforcement creates the need of adding a flame retardant.
TPO membranes have become widely used as roof membranes in the past ten years. A TPO roofing membrane is typically made from polypropylene and ethylene-propylene (EP) rubber polymerised together. These TPO membranes are flexible at low temperatures without the use of polymeric or liquid plasticisers. TPO itself is not fire resistant and requires the addition of (high loadings of) fire retardants in order to obtain a fire rating.
Synthetic Rubber: EPDM
Virtually all synthetic rubber roof membranes are EPDM. Synthetic rubber is a thermoset, which means once it has cured, it cannot be re-melted and reshaped. The gap between two adjacent rubber sheets/rolls is sealed by an adhesive. EPDM is often used on buildings with very large roofs. EPDM can stretch and relax, so it can easily accommodate thermal expansion and contraction on large expanses of roof. EPDM is not self extinguishing and needs the addition of flame retardant filler. High filler loading levels are possible with EPDM even with the finer types of ATH.