Polyurethane elastomer (CPUE), referred to as casting polyurethane (CPU) or polyurethane pouring resin. "Pouring type" refers to a kind of chemical processing method in which the material system of the product is liquid before molding, which can be poured and solidified directly, and the material system does not contain volatile liquid in principle. Because the material system is liquid before molding, while TPU and MPU products are solid before molding, CPU can also be called liquid rubber or liquid elastomer. Compared with TPU and MPU, CPU has a wider range of raw materials and a wider range of product hardness, which is especially suitable for the production of large and medium-sized products, which makes up for the limitations and deficiencies of TPU and MPU products processing technology, and can maximize the performance advantages of polyurethane elastomer and broaden the application field of polyurethane elastomer.

CPU elastomer first appeared in Germany. In the early 1950s, the world's first CPU product was produced in German Bayer company with the brand name of Vulkollan. At the end of 1950s, DuPont company of the United States introduced the polyether type CPU with the commercial brand of adipenel with PTMG and TDI as the main raw materials, and then MDI CPU appeared, which made outstanding contributions to the development and application of polyurethane elastomer. Since the 1970s, new materials such as liquefied MDI, low unsaturation polyether, low free TDI prepolymer, amino terminated polyether and various environmental friendly amine chain extenders have successively entered the market. Reaction injection molding (RIM) and spray polyurea elastomer technology have been introduced one after another, which greatly promotes the traditional CPU product molding technology and broadens the application field of CPU products.

In addition to the traditional CPU, TPU and MPU, polyurethane elastomer should also include waterproof coating and paving materials, sole stock solution, synthetic leather slurry, spandex and adhesive, because they are in high elastic state (rubber state) at room temperature. Among them, waterproof and paving materials, sole stock solution are liquid before product forming, without solvent, which should be attributed to CPU. According to this classification, the consumption of polyurethane elastomer in China was about 870000 tons in 2005, which was close to 40% of the total consumption of polyurethane in China. Among the elastomers, the CPU consumption was 360000 tons, accounting for 41.3%. Among them, 200000 tons of rim products, 100000 tons of paving materials, 60000 tons of traditional CPU, accounting for 17%. The sole stock solution belongs to microporous elastomer.