New technology is adding to the functions of waterproof membranes and this was discussed at the AMI international conference, Waterproof Membranes 2009, held in Cologne, Germany. Although residential construction in Europe was down by around 6% in 2008, civil engineering and non-residential output held up reasonably well. In 2009, the market for building membranes consumed 650,000 tonnes of polymer in applications varying from flat roofing to tunnel linings, according to Jon Nash, Head of Strategic Research at AMI Consulting. There has been large scale destocking of the supply chain, with knock on effects on the manufacturers.
The major share of synthetic membrane markets is taken by polyethylene (48%), polypropylene (33%), PVC (16%) and EPDM (3%). This includes membranes in building substructures (23%), flat roofs (20%), landfill and tunnels (9%), and clean water (10%). Dow Europe supplies tailored blends of polyolefins into this market including EPDM, PE, CPE, PP and TPO, with customised additives for long term stability. The TPO formulations include colorants and flame retardants.
Building Envelope Technology and Research has tested thermoplastic olefin (TPO) membranes on full-scale roofs in 4 different climatic areas of North America. Early membranes had problems with fire retardants and UV stabilisers, as well as surface crazing. Four manufacturers joined a testing programme: Carlisle, Firestone, Genflex and Stevens Roofing Systems. Roofs were installed in Seattle, Las Vegas, Alaska and Texas. The project is now in its 7th year and changes are being monitored such as colour, reflectance and dimensional stability.
Lucobit is a leader in TPO waterproofing membranes. When ready made compound is used, only a single screw extruder is required for manufacture. The membrane can be combined with solar panel systems such as Polyfin 3020 PV. The membrane for swimming pools is available in a variety of colours including a range of blues.
Fire resistance is critical for membranes in the European market under the European Construction Products Directive. Albemarle Martinswerk supplies suitable mineral flame retardants. The fire performance is given in CPD ENV 1187. There are currently discussions in group CEN TC127 WG5 regarding other criteria such as flame penetration, construction type, damaged area, etc. The minerals used include aluminium hydroxide, magnesium hydroxide and synergists such as zinc borate.
The International Green Roof Association (IGRA) has outlined the quality criteria and state of technology for operating green roofs, including roof materials, installation and drainage material. There are standard tests for root penetration of roofing materials with a 4 year outdoor timescale or 2 years in a greenhouse. There is a European standard, EN13948 for root resistance for bitumen, plastic and elastomeric waterproofing, but IGRA has commented that it does not include couch grass rhizome (Agropyron repens). Intensive green roofs are actively cultivated and can include small trees - dry weight might be around 230 kg per square meter. Photovoltaic panels are sometimes installed too, and the vegetation underneath has a natural cooling effect, improving module efficiency. Thermal insulation can also be provided by the Floratherm system. Heat islands occur in heavily populated areas, raising local temperatures. According to Axter, green roofs which retain rain and evaporate it off can reduce temperature by around 2C. One example is Nanyang Technological University in Singapore.
Polyethylene geomembranes from Agru Kunststofftechnik offer root resistance, excellent weathering and chemical resistance. They are used as structured liners and caps in landfill, groundwater protection, hydraulic and civil engineering. New applications include linings for solar thermal hot water storage tanks. In Project Eggenstein a layered construction was used comprising an HDPE-Alu barrier liner with HALS and phenolic stabilisers, insulation and then another HDPE liner layer. One of the most spectacular projects was the lagoons and Jumeirah islands in Dubai. HDPE geomembranes are also produced by Sotrafa in Spain , and design consideration include mechanical performance, anchorage, underdrain seepage control and seam strength. The membranes are tested for oxidation induction time, thermal ageing and UV resistance to UNE EN 728. Liner failures occur due to shrinkage due to temperature changes, UV damage, creep, stress cracking, gas pockets, hydrostatic pressure, problems with installation, and damage due to people and animals.
Geomembranes can be manufactured with a range of surfaces from smooth to textured, and composite structures range from stitch bonded to laminate. GSE Lining Technology has studied slope sealing – forces on the membrane include friction such as shear stress and compression, water pressure, gas pressure and reduced strength due to ageing. There are test standards available, such as EN ISO 12957-1, ASTM D 5321 and GDA recommendation E3-8 to evaluate short-term shear strength.
Geosynthetica.net has outlined the trend to include photovoltaics in geomembrane covers, for example over 5.6 acres in the Tessman Road Landfill, San Antonio, Texas. The solar laminates are adhered to an exposed geomembrane cap (EGC) made of TPO. The EGC market is growing from municipal waste to water ponds. The challenges are wind uplift, UV and heat exposure, footfall, and landfill gas uplift. The geomembrane must be constructed to meet these requirements. The companies involved in this type of project include: Dow Geomembranes, DRS Japan, Firestone, I-CORP, Republic Services, Solar Integrated and United Solar Ovonic.
Coatema Coating Machinery is a major leader in membrane production equipment including direct and indirect coating. The company has developed technology and equipment to incorporate flexible solar modules from Uni-Solar into waterproof membranes. There were issues to be solved with adhesion and surface edge sealing. The modules are corona treated on the reverse side for improved adhesion. One example of a production line is found in Los Angeles at the Solar Integrated Technologies plant, which combines PVC membranes and solar cells. Bandera Luigi has focused on the production equipment for core production of membrane sheets. It has installed 3-layer blown film geomembrane lines across the world in the past 3 years including UAE, Egypt, Portugal and Brazil.
Tremco Illbruck provides cold fluid-applied aliphatic modified polyurethane liquid waterproofing technology. Traditional liquid systems had problems with gassing, blistering and pinholing and often required two coats, which were affected by weather conditions. The new polyurethane can be applied to green concrete 24 hours after the forms have been removed and have a high peel strength. Liquid Plastics is a member of the Sika group and supplies roofing membranes in liquid form, which can be more easily applied in adventurous architectural design, in a layered system to ensure durability. Membranes cover large areas, so joints are critical to waterproofing integrity. Leister Process Technologies provides welding equipment for plastics: the joint surfaces are plasticised and force is applied immediately. The thermal and mechanical forces must be kept as low as possible and coordinated with the speed of operation. Sensor S.r.o. of Slovakia has developed electrical leak detection systems: common causes of problems are burning at welds and by cigarette butts, punctures by stones, damage during installation, footfall and by machinery.
The next opportunity to network will be the AMI international conference on Waterproof Membranes 2010, which will be held from 30th November to 1st December at the Maritim Hotel, Cologne, Germany. The deadline for sending an offer of a paper is 28th May.