Why use nonwovens in construction?
With increasing oil prices, climate change, CO² regulations and building regulation codes on fire resistance, nonwovens are providing cost-effective and efficient solutions to building and construction challenges.
Non-perforated, nonwovens polymeric house wrap material decreases air infiltration, resulting in increased energy efficiency and maximum moisture control, while at the same time providing savings for the builder and homeowner during installation and after-sale.
House wrap developments such as translucency, which helps lower installation time and provides high strength, combined with no VOC (volatile organic compound) release in either production or application, satisfy ever stricter government sustainability programmes.
More and more demanding building standards, energy-saving schemes and to some extent changing weather patterns are driving the need for breathable and impervious underlays for pitched roofs and an improved basis for bituminous membranes, both of which can best be served with versatile nonwovens.
The application of non-woven fabrics in the construction field can be roughly divided into three categories: building waterproof non-woven fabrics, building covering non-woven fabrics and other building structural materials.
Non-woven fabric is the skeleton material of the modified bitumen waterproof membrane, which gives the waterproof membrane excellent tensile properties and prolongs its service life. A typical asphalt-based waterproofing membrane is actually a non-woven fabric reinforced composite material with a sandwich structure, the middle layer is a non-woven fabric, and the two layers are modified asphalt.
There are mainly three types of non-woven fabrics used as modified bitumen waterproofing membranes, namely polyester spunbond needle-punched non-woven fabrics, polyester staple fiber needle-punched non-woven fabrics and wet glass fiber mats. Although the cost of glass fiber mat is low, the synthetic fiber non-woven fabric can give the modified bitumen waterproof membrane better flexibility, adapt to thermal expansion and cold shrinkage, greatly reduce the possibility of water leakage, and extend the service life of the waterproof membrane.
Except for a small amount of non-quality modified asphalt waterproofing membrane, every square meter of modified asphalt waterproofing membrane needs at least the same area of non-woven fabric as the frame material. In order to meet market demand, modified bitumen waterproofing membranes are increasingly using polyester spunbonded non-woven fabrics.
The key to effective heat insulation is to strengthen the air and water tightness of the building. The European and American architectural circles began to widely use a layer of air film, laid on the insulation layer, and the entire building was covered, thereby effectively enhancing the air-tightness and water-tightness of the building. However, due to the impermeability of the membrane, moisture condensation in the exterior walls and roof of the building will seriously affect the performance of the insulation material and the durability of the building envelope.
Therefore, people invented a waterproof and breathable film with better performance. Its main functions include:
1) Air permeability. It can discharge water vapor in the maintenance system, solve the problems of condensation and dew, protect the insulation layer and prevent moisture.
2) Air tightness. It is used to maintain the structure, cover the building, enhance the air tightness of the building, and reduce the heat loss caused by air leakage and convection.
3) Water tightness. It has a certain auxiliary waterproof function.
The US National Institute of Standards and Technology has studied the impact of building airtightness on the energy consumption of commercial buildings. The results show that, compared with buildings without waterproof and breathable membranes, buildings with waterproof and breathable membranes to enhance airtightness can save up to 40% of heating and cooling costs.
The air separation membrane as the air separation layer is arranged on the inner side of the composite outer wall, and can be used in combination with the waterproof and moisture-permeable membrane or used independently. The diaphragm is suitable for heating buildings with air separation requirements and industrial equipment in the textile and food processing industries.
In the United States, general air barrier films and waterproof and breathable films are used at the same time. The air barrier film is used for the inner insulating layer, and the waterproof and breathable film is located outside the insulating layer. Diaphragms are also widely used in Germany. According to statistics, more than 80% of buildings will use diaphragms. In China, the use of partitions on walls is relatively small, mainly in the following two types of buildings:
(1) Roofing: a gas separation membrane is installed between the two-story steel structure of a steel structure workshop; or a steel wall, and the insulation layer is installed in the middle of the diaphragm.
(2) The temperature difference of the building is large, such as cold storage.
The simplest windproof membrane is made of polypropylene spunbonded hot-rolled non-woven fabric sandwiched between a layer of waterproof membrane composite material. The outer non-woven fabric needs to have UV resistance.
Non-woven fabrics used for breathable films mainly include spunbond hot-rolled non-woven fabrics, cast laminated spunbond fabrics and film composites, spunbond fabrics and microporous film composites, etc. The main functions of non-woven fabrics are tear resistance, abrasion resistance and puncture resistance. Resistance, generally requires anti-ultraviolet stability and a non-slip surface.
At present, China's polymer coils are showing a trend of diversification and high-end development, and they are widely used in building roofing, municipal engineering, underground space, environmental protection facilities, water conservancy facilities and the national defense industry.
Polymer waterproofing membranes occupy the mainstream of flat roofs in the US market, while the European market is still dominated by modified asphalt waterproofing membranes, and the Japanese market has three parts: asphalt membranes, polymer membranes and waterproof coatings. In the Chinese market, bituminous waterproofing membranes occupy the mainstream, but the polymer membrane market is gradually expanding.
Similar to the application in modified bitumen waterproofing membranes, non-woven fabrics are used as reinforcing materials in polymer waterproofing membranes. Non-woven fabrics can be used as an intermediate layer or backing substrate for polymer coils. The main non-woven fabric used for polymer waterproofing membranes is polyester staple fiber hot-rolled non-woven fabric. It can be made of recycled polyester material with recyclable, environmentally friendly and stable sound absorption and heat insulation properties.
As a non-woven fabric backing polymer rolled material, its main function is to facilitate construction, and under the action of a binder, the polymer rolled material can be closely combined with the concrete base layer.