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Dr Sally Humphreys
Applied Market Information Ltd
Market and technology trends for waterproof
membranes
Pages | 1 | 2 | 3 |
Production equipment for membranes is a big
investment. A typical reinforced geomembrane comprises one or more synthetic
sheets coated or laminated to a fabric reinforcement. The interadhesive layer
can be extruded on the top and underside of the fabric. Typically the amount
of plastic used in coating is 200 to 500 gsm according to Davis-Standard, the
machinery suppliers. A combination of two co-located extruders can extrude
adhesive and bulk polymer simultaneously and the edge trim can be added back
in to reduce waste and cut material use. Krauss-Maffei Berstorff has looked
at the different requirements for extruders, depending on the form in which
the material is supplied to the membrane manufacturer. For example, a single
screw extruder is sufficient for processing precompounded TPO and PVC pellets
at a rate of up to 500 kg/h, while a co-rotating twin screw extruder is
needed for high output (over 1500 kg/h)and direct compounding.
TPO-based membranes are now widely used, for example in the Tempodrome in
Berlin (Sika). LyondellBasell have compared it to other materials: less is
needed, which can reduce transport and other logistical costs. It has good
root resistance for green roofs and can be produced in light colours to
reflect sunlight and cut building cooling costs. To reduce dust and dirt on
the roof, a thin polypropylene film can be added by heat lamination –
this was tested on a roof in Ferrara, Italy in 2009.
In 1987, a 2-component spray on membrane based on polyurea was introduced in
the USA and this market is growing globally at 10%/year, mainly in the US and
Asia as Europe is only now developing an interest in this technology. BASF
supplies this polymeric material in the form of an isocyanate and an amine.
The reaction of the 2 components is very fast, reaching green strength in
seconds. It is used in landscaping with geotextiles, in containment, in truck
beds and roofing and as a simple way to repair flat roofs.
Another innovation in the US that is now being offered in Europe is the
polyurethane foam adhesive system from ADCO Roofing Products. It can be used
to attach fleece-backed EPDM, TPO, PVC, and SBS-modified bitumen membranes. A
similar 2-part polyurethane system has been in use for attaching insulation
since the 1970s. According to the SPRI, 52% of membranes are now attached
using adhesives, 43% by mechanical methods and 5% use ballast.
Fluoropolymers are at the top of the range of roofing membranes and are used
in transparent domes and other structures: this is an area where Hightex has
expertise. In a project at Green Point Stadium in Cape Town in 2009, 27,000
square metres of PTFE-coated silver glass fabric was used, while in
Johannesburg 50,000 square metres of the same structure (sand-coloured) was
used in the Soccer City Stadium. Hightex currently has projects in the
Olympic Stadium in the Ukraine, BC Place in Vancouver and the National
Stadium in Warsaw. At the company office a pneumatic ETFE membrane
incorporates flexible photovoltaic panels. If the Gottlieb –Daimler
Stadium in Stuttgart incorporated photovoltaics over 80% of the area, it
could generate 730,000kWh/a.
Dow Elastomers has studied formulation for membranes: an aluminium trihydrate
flame retardant is halogen-free and allows high production rates. The
polyolefins can have high stabilizer additions to reduce the effects of
weathering, without causing plate out or affecting welding.
Pages: | 1 | 2 | 3 |
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