PVC-coated polyester fabrics are widely used for tensile structures. Its high mechanical strength and flex cracking resistance make it a favorite for both permanent and retractable membrane designs. Due to the low cost of its raw materials and production, polyester-PVC is one of the inexpensive membrane materials available on the market. Polyester-PVC membranes are enhanced for construction in order to improve their longevity. Polyester can also be coated by PVDF lacquers or PVF laminates. These top coats made from fluoride lacquer also create a smooth, anti-adhesive finish that help prevent dust and dirt clinging to the surface. However, as these materials have a much higher melting point than PVC coatings, it is sometimes necessary to roughen their surface prior to the welding. Occasionally the PVC fabric surface is coated with a layer of TiO2 to promote a self-cleaning feature. Absolute recyclabilityand printability are some of the unique characteristics of PVC fabrics.
Perhaps the most recent development in the fabric structures arena is the introduction of ETFE (ethylene tetrafluoroethethylene), a transparent membrane with fabric like qualities and the advantages of PTFE, such as a self-cleaning capability. Resistant to atmospheric pollution and UV light, ETFE has a very long expected lifespan of more than 20 years. Effective thermal performance and high light transmission (95% visible light, 85% UV light) enable a range of applications where traditional materials, such as glass, would not be practical. It is more than 20 times lighter than glass and is ecologically friendly and energy efficient. It is 100% recyclable. Films of ETFE are used in wind roofs or covers to form an air pillow. The internal pressure of the air pillow and primary applied stress make it resistant against any force. Printability is another feature of ETFE fabrics.
Glass-fiber fabric coated with PTFE (polytetrafluoroethylene, also known as Teflon) is regarded as one of the most durable membrane materials because the coating is self-cleaning and very resistant to chemical substances and mold growth. Newly coated material is initially beige in color but fades after erection through the decomposition of the wetting agent in contact with UV rays. This process takes approximately 2-3 months in Northern Europe, a correspondingly shorter time in regions with higher levels of solar radiation.The PTFE coating is chemically inert, withstands temperatures from minus 73°C to 232°C, is immune to UV radiation and can be cleaned with water. PTFE-coated fiberglass is available with as much as 25% translucency, providing diffused interior light. Its ability to allow natural daylight and provide night time interior lighting can reduce energy consumption. Coated and Uncoated PTFE fabric:This material is constructed of PTFE fibers woven into a fabric. Woven PTFE combines the environmentally-resistant advantages of the material with its ability to withstand repeated flexing and folding, an advantage it has over coated-fiberglass, therefore PTFE fabric is frequently used for high quality watertight retractable membrane roofs. It is characterized by its high flex cracking resistance, light weight, high light transmittance and anti-adhesive surface.
Knitted fabrics such as high-density polyethylene (HDPE) can provide shade as well as shelter from the wind, but since they’re porous, they are not considered as good a shelter against rain and snow. However these fabrics are an excellent protection against UV rays therefore they are a suitable alternative against sun and heat in dry climates. Additionally they are inexpensive and have been used for some low-cost membrane structures. Nowadays there are water resistant coated meshes available, although they cannot withstand heavy loads. These fabrics can also be used to reinforce other fabrics.
These lightweight knitted fabrics are available in various colors. Lycra has very good elastic properties which allow it to accept different forms and shapes and make it an ideal choice for interior designs and temporary structures but it is not used in outdoor structures due to its low tensile strength and porous texture. Another advantage of these fabrics is their printability.
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