Study On The Weatherability Of Architectural Membrane Materials

Architectural membrane materials are the new architectural materials which have been developed since 1970s, and it belongs to coated fabrics, that is called the fifth building material besides the steel, cement, wood and glass. The substrate is PET or glass fabrics, the coatings of two sides are been sticked or overlaid with polymer, and the surface is dealt with superior weatherability of polymer material. In the use of the process, the properties and functions of materials are affected by sunlight, temperature, wind, rain, snow, atmospheric pollutants and so on, the aging phenomenon presents as the decay of physical property and the darkens of color and so on, which needs us to study on the weatherability of membrane structure material to provide some reference for the further development of architectural membrane materials.According to the weatherability of architectural membrane material, in this subject, the properties of the membrane materials which are PVC and PVDF membrane materials after ultraviolet and thermal-oxidative aging were studied. Main contents of research are as follows:(1)The types and application status of architectural membrane materials were summarized, and the state of the weatherability of architectural membrane material were reviewed.(2)Surface Properties of membrane material were tested, for example, the infrared spectrum, hydrophilicity, transmittance and wear-resistance. Function bonds of PVDF membrane material were C-C, C-H₂, C-F and so on, PVDF was hydrophobic linear crystalline polymer. The material was hydrophilic because of presence of fluorine atoms to form very strong hydrogen bond, and hydrogen bond existed in wave-number range. Transmittance of visible light of PVDF membrane material was about 4%. Transmittance and reflectivity of ultraviolet were low, it was showed that material absorbed almost ultraviolet, which impacted the durability of membrane. In the beginning of friction, mass loss rate changed fast, and then change tended to slow, this was due to the binding force of PVC and PVDF were not strong.(3)The quadratic general rotary unitized design of two factors, the time and the intensity of UV irradiation, was used to study the influence of UV irradiation to architectural membrane material.The tensile property of the material was tested, and the mathematical models about breaking force and breaking elongation rate were built, the properties of material were anlysisedafter UV aging. With the increasing of UV irradiation time and intensity, Mechanical Properties took on downtrend and absorbtion peak became smaller and smaller in infrared spectrum picture, transmittance took on downtrend, In the beginning the change was obvious and then slowly, from the reflectivity picture, reflectivity of UV had no change, but reflectivity of visible light took on downtrend.(4)The quadratic general rotary unitized design of two factors, the time and the temperature of thermal, was used to study the influence of thermal condition to PVC and PVDF architectural membrane material. The whiteness of the materials was tested, and the mathematical models about whiteness were built, the properties of material were anlysised after thermal-oxidative aging. With the increasing of thermal treatment time and temperature, the whiteness took on downtrend, the downtrend of PVDF membrane material was slowly than PVC membrane material, In the beginning the change of the transmittance was obvious, when the time reached 8^th day, the change tended to slowly, from the reflectivity picture, reflectivity of UV had no change, but reflectivity of visible light took on downtrend. The Mass Loss Rate and Mechanical Properties of membrane material under 115℃were tested, In the beginning the change was obvious, when the time reached 10^th day, the change tended to slowly.