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**Sources and Main Applications of Polyurethane**
Polyurethane, often referred to as PU, is a broad category of macromolecular materials that contain repeating carbamate groups (–NH–CO–O–) in their molecular structure. It is produced through the reaction between an organic diisocyanate or polyisocyanate and a diol or polyol. This chemical process leads to the formation of long-chain polymers with unique properties. In addition to the carbamate group, polyurethane molecules may also contain other functional groups such as ether, ester, urea, biuret, or allophanate, depending on the specific formulation. The name "polyurethane" comes from its chemical composition, where the urethane group plays a central role in its structure.
**Preparation and Origin**
Polyurethane is created when a diisocyanate or polyisocyanate reacts with a diol or polyol, resulting in the formation of a highly branched or cross-linked polymer. This reaction typically occurs through a step-growth polymerization mechanism. The basic chemical reaction can be represented as: –N=C=O + –OH → –NH–CO–O–. This simple yet powerful reaction allows for the creation of a wide range of materials with varying mechanical, thermal, and chemical properties.
The discovery of polyurethane dates back to the 1930s when German chemist Otto Bayer first synthesized thermoplastic polyurethane (TPU). By the 1950s, TPU began to be used as a textile finishing agent in Europe, primarily in solvent-based coatings. However, due to environmental concerns, water-based TPU coatings emerged in the 1960s, driven by growing awareness of pollution and stricter regulations. From the 1970s onward, water-based polyurethane coatings gained popularity, leading to widespread use in textiles and other industries. Since the 1980s, significant advancements have been made in the development and application of TPU, especially in fields like automotive, medical, and consumer goods. In comparison, research into polyurethane-based textile finishes in China started later.
**Main Applications**
Polyurethanes are versatile materials that can be tailored to meet various performance requirements based on the raw materials used. They are generally classified into two main types: polyester-based and polyether-based. These materials find extensive use in manufacturing plastics, rubbers, fibers, rigid and flexible foams, adhesives, and coatings. Their ability to be modified for different applications makes them one of the most widely used polymers in modern industry. Whether it's in soft furniture, insulation materials, or high-performance sports equipment, polyurethane continues to play a vital role in everyday life.
With ongoing innovations and environmental improvements, the future of polyurethane looks promising, offering sustainable and high-performance solutions across multiple sectors.