Polyurethane refers to a polymer containing a urethane chain end (-NH-COO-) in the molecular structure, but the urethane segment is not included in the polymer. Not the dominant chain segment. They are products of the stepwise polymerization of hydroxyl-terminated polymers such as polyether polyols or polyester polyols and isocyanates. Due to the diversity of raw material sources, it is often not possible to represent all polyurethanes in a general empirical way.
Most of the polyurethanes currently produced are foam plastics. There are soft, semi-rigid and rigid foam products. In addition, there are a variety of polyurethane products such as elastomers, coatings, adhesives, fibers, and films.
Polyurethane foam can be classified according to raw materials, production technology and product performance.
Based on the type of polyol used, it can be divided into polyether type, polyester type, etc. Due to factors such as raw material sources, price and performance, polyether foam currently accounts for more than 90% of the total soft foam and is the dominant type. Polyester foam is still retained in some special application fields due to its excellent solvent resistance and other properties. With a market share of 5%-10%.
From the perspective of product load-bearing performance, polyurethane soft foam can be mainly divided into ordinary type and high load-bearing type and high rebound type. In addition, there are special foams such as slow rebound, self-crusting, super soft, hydrophilic foam, and network foam.
If divided by the isocyanate used, there are three main types: TDI, MDI and TDI/MDI hybrid. At present, TDI is still mainly used as raw material in the production of block foam, but in recent years, full MDI high-resilience soft foam block materials have shown strong growth momentum; and in molded foam, TDI/MDI mixed isocyanate and full MDI has been widely adopted and is on the rise.
Looking at the synthesis process, most of them adopt the one-step method. Only in a few special occasions, the prepolymerization method (two-step method) or semi-prepolymerization method is used.
From the perspective of production methods, there are continuous and intermittent methods. The continuous method is the main production process of block foam. Currently, more than 80% of soft foams are produced by this method. The block foam is then cut and processed into the required foam parts. The intermittent molding process is mainly used when foaming directly in the mold to produce foam parts of the desired shape. The molding process is particularly necessary when producing foam bodies with complex geometric shapes. Box foam is a form of molding process. Due to the flexibility of the product, it is currently widely used in our country.
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Dongguan CityPolyurethane Materials Co., Ltd.
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