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How to choose seals for building doors and windows
May 11, 2018

        In recent years, the rapid development of China's chemical industry has enabled chemical new materials and new varieties to quickly follow international development levels, spurring the development of new materials in industries such as automotive, construction, wire and cable, and consumer industries, as thermoplastic elastomers for polymer alloy materials. The market demand for physical products is also growing. At present, the thermoplastic elastomer material has been listed as a national “High-Tech Research and Development Plan” (863 Program) support project, and the market prospect is more and more broad.

        Building doors and windows driven by the industry and market to improve product quality year by year, designing and manufacturing doors and windows that meet building energy efficiency standards, and building green building requirements, we have to start paying attention to the thermoplastic elastomer seals that affect the sealing performance of doors and windows are currently in construction. Field application.

         Classification of Thermoplastic Elastomers for Building Doors and Windows

         Thermoplastic elastomer TPE can be summarized as general TPE and engineering TPE. Polyurethane TPE was first discovered in Bayer, Germany in 1938; styrene-butadiene-styrene block polymer TPE was developed in 1963 and 1965 by Phillips and Shell in the United States; since the mass production of olefin TPEs in Europe and America in the 1970s The continuous innovation of technology and the constant emergence of new TPE varieties constitute a huge system for today's TPE, which makes the marriage of the rubber industry and the plastics industry a big step forward. So far, TPE has grown to more than 30 varieties in 10 categories and has entered mature industrial production stage. For the different needs of various industries provide the largest choice.

           The materials used in the manufacture of building door and window weather strips have gone through natural rubber, reclaimed rubber, neoprene, and vulcanized EPDM rubber, eventually being replaced by comprehensive factors. Since the 1970s, the company has rapidly transferred to thermoplastic elastomer materials. So far, there are three general types of rubber used in domestic tape companies:

   1. Vinyl chloride type TPE (PVC/CPE or PVC/NBR) ie modified PVC (TPVC);

   2. Olefin TPE (EPDM / PP) that is thermoplastic elastomer (TPS);

   3. Styrene-based TPE (SEBS) is a thermoplastic elastomer (TPS).

     

      At present, TPV (EPDM/PP) and TPS (SEBS) materials are widely used in building sealing strips around the world. Of course, due to its low cost, TPVC (modified PVC) still maintains a certain market share in China.

     Development Status and Characteristics of Thermoplastic Elastomers for Construction

1. Vinyl chloride tpE (tpVC)

This is the material of the most advanced entry-window sealing field, and it still occupies a large proportion in China, and is gradually being replaced by new elastomer materials in recent years. TPVC is divided into two forms: chemical polymerization and mechanical blending. It was first developed from Japan. It was first produced by Mitsubishi Monsanto Co. in San Prene in 1967, followed by more than 10 PVC manufacturers. The United States and Europe in the 1980s. Also R & D and production. Because TPVC has good weather resistance, aging resistance, chemical resistance, etc., it has rapidly developed into TPE.


     Foreign PVC resin is mostly high degree of polymerization PVC, the price is higher. The high degree of polymerization of PVC in domestic No. 2 Plant of China National Chemical Industry Co., Ltd., due to the high overall cost, has not been promoted in the window and door market. At present, most manufacturers of sealing tapes use medium-degree-of-polymerization PVC mechanical blending. In fact, it is only a derivative of soft PVC resin, but it has been improved due to compression and deformation, resulting in the formation of PVC. Its elasticity, compression set, and shape retention at high temperatures are relatively poor compared to other elastic materials, and research and improvement have continued over the years. With the increasingly stringent environmental protection requirements, TPVC will be difficult to solve in the use of acid gas, etc., and pollute the environment. In recent years, the world’s growth rate has declined, and the scope of use has been greatly affected.

At present, most manufacturers of door seals in the domestic market adopt self-mixing manufacturing. In addition to some companies that have increased self-regulation in accordance with the GB and T12002-89 standards, many manufacturers use complex scrap for the production of low-cost competition, with or without the addition of rubber modifiers, or the use of low-cost aromatics. Substitution of plasticizers will make the strip smell pungent and injure the body. Not only will the heavy oil seep to make the window frame yellow and the seal will shrink and harden in the short term. Losing the sealing performance will affect the reputation of the doors and windows in the market and should cause us to choose glue. Pay attention to it. With the continuous improvement of the construction grade, we should phase out these products.


          2. Olefin tpE (tpV)

This type of elastomer is a blend of PP (polypropylene) as the hard segment and EPDM (ethylene propylene diene monomer) as the soft segment, abbreviated as TPO. Because it is lighter than other TPEs (only around 0.9, heat resistance is up to 100°C), and weather resistance and ozone resistance are also good, it has become another rapidly developing species in TPE. After the successful development of the fully dynamic vulcanized TPO named Santoprere by the American company Mansanto in 1981, the performance was greatly improved and the maximum temperature reached 120. C. This dynamically vulcanized TPO is abbreviated as TPV. It is mainly used in the melt blending of PP and EPDM in TPO. It can be used as a cross-linking agent to make it vulcanized. It is highly sheared by using machines such as precision machines and screw machines. The force to fully vulcanize the fine EPDM cross-linked rubber particles, fully dispersed in the PP matrix. The "particle effect" of this cross-linked rubber leads to a significant improvement in the TPO's resistance to compression deformation, heat aging, and scratch resistance. Therefore, TPV is also called thermoplastic EPDM vulcanizate. In recent years, TPV is the fastest growing family in the TPE world, with an annual growth rate of 10%-20%. At present, foreign seals, jackets, gaskets, etc. are transferred to TPV in large quantities.

            The use of TPV in China began in the second half of 1990. Due to the high price of imported materials at the time, it was the first to enter the auto industry. In recent years, with the rise of foreign-funded and joint-venture domestic-funded enterprises, the prices gradually converged with the domestic market, and they have only begun to enter the field of high-grade doors and windows sealed. In the past few years, the northern markets used vulcanized EPDM. TPV is commonly used in the southern region, and the northern region has recently begun to recognize this material.


        3. Styrene tpE (tps)

TPS is a block copolymer of butadiene or isodecadiene with styrene. About half of the TPE market. The representative variety is styrene-butadiene-styrene block copolymer SBS, widely used in the footwear industry, and is also an excellent modifier for abrasion resistance, crack prevention, anti-softness and anti-sliding of asphalt pavement. However, for building doors and windows sealant strips, the biggest problem of SBS is poor heat resistance, the use of temperature can not generally exceed the class 80 °C, while its tensile strength, weather resistance, etc. can not be compared with rubber. In recent years, the United States, Europe and other countries have carried out a series of performance improvements, developed SBS saturated hydrocarbon hydrogenation SEBS varieties, so that the impact strength is greatly improved, weather resistance and heat resistance are also applicable to the use of the building doors and windows This has given the building door and window seals a new choice of materials.


         For door and window TPS (SEBS) is a polymer alloy material with similar vulcanized rubber properties. It is a new material that has entered the field of building doors and windows in recent years. Its outstanding advantages are safety, non-toxic, halogen-free and lead-free heavy metals, and have obvious environmental protection features. It has good stability, soft texture, beautiful appearance, comfortable feel, good resilience, strong moisture-proof lubricity, and completely avoids the high ratio of soft PVC, stiff and creamy feel, plasticizer penetration, and material hardness with the environment. Defects such as obvious changes are more suitable for use on door and window seals.

Compared with the TPE physical property and economical efficiency of building doors and windows, the above indicators are recommended when selecting sealing material: due to price factor, TPVC material sealing strips that meet the standards can be selected for general buildings, and TPV or TPS is recommended for medium and high-grade buildings. Material sealing strips; TPS material sealing strips are recommended for medium to high-end green buildings; different materials can be selected according to the window type, for example: TPVC for sliding window fans and TPV or TPS for flat windows.