Overview of polyurethane elastomer

1. Performance Features

Polyurethane elastomer is a high-performance elastomer, also known as polyurethane rubber. It is a type of polyurethane rubber that contains more urethane groups in the molecular chain (NHCOO ) elastic polymer material.

From the molecular structure point of view, polyurethane is a block polymer. Generally, the soft segment is composed of long flexible chains of oligomer polyols, and the hard segment is composed of diisocyanate and chain extender. The hard segments and soft segments are alternated to form repeated Structural units. In addition to urethane groups, polyurethane elastomers also contain ether, ester or urea groups. Due to the presence of a large number of polar groups, hydrogen bonds can be formed within and between polyurethane molecules, and soft and hard segments can form microphase regions and produce microscopic phase separation. Even linear polyurethanes can form physical crosslinks through hydrogen bonding. These structural characteristics make polyurethane elastomers have excellent wear resistance and toughness, and are known as"wear-resistant rubber". And because there are many types of raw materials for polyurethane, the variety and ratio of raw materials can be adjusted to produce products with different performance ranges, and the processing methods are diverse, making polyurethane elastomers suitable for many application fields.

Although the production of polyurethane elastomers accounts for a small proportion of the total number of polyurethane products, it is an indispensable and important polyurethane material and a type of high-performance special synthetic rubber.

Polyurethane elastomer has excellent comprehensive properties, and its modulus is between that of general rubber and plastic. It has the following characteristics: higher strength and elasticity, and can be used in a wide hardness range (ShoreA10 ~ Shore D75) maintains high elasticity; at the same hardness, it has a higher load-bearing capacity than other elastomers; its wear resistance is excellent, 5 to 10 times that of natural rubber; it is resistant to grease and Excellent chemical resistance; aromatic polyurethane radiation resistance; excellent oxygen resistance and ozone resistance; good fatigue resistance and vibration resistance, suitable for high-frequency flexural applications; good impact resistance; good low temperature compliance; generally not required Plasticizer can be used to produce the required flexible material, so there is no problem caused by plasticizer migration; ordinary polyurethane cannot be used above 100°C, but a special formula can withstand high temperatures of 140°C; molding and processing costs Low.

In many cases, compared with metal materials, polyurethane elastomer products have the advantages of light weight, low noise, loss resistance, low processing cost and corrosion resistance; compared with plastics, polyurethane elastomers have the advantages of not being brittle and wear-resistant. Etc. Compared with conventional rubber, polyurethane elastomer has the following advantages: wear resistance, cut resistance, tear resistance, high load-bearing capacity, transparent or translucent, ozone resistance, can be potted and poured, and has a wide hardness range.

2. Development Overview

As early asin the early 1940s, Germany and the United Kingdom developed polyester polyurethane elastomers. In the 1950s, mixing type, casting type and thermoplastic polyurethane elastomers appeared one after another. Due to the development of various raw materials and the expansion of various application fields, polyurethane elastomers have developed rapidly since the 1960s and have become important polyurethane materials and special synthetic rubbers. Variety. In 2000, global polyurethane elastomer production was approximately 880,000 tons/year, accounting for about 10% of the total polyurethane products. In 2005, global polyurethane elastomer consumption was approximately 1.627 million tons/year, of which thermosetting polyurethane elastomer accounted for 76% and thermoplastic polyurethane elastomer accounted for 24%.

Our country has been conducting research since the late 1950s. In the 1960s, the pilot test of mixed polyurethane elastomer based on polyester polyol was successful, and the preliminary development of polyurethane elastomer based on polyether Casting polyurethane elastomers of polyols and polyester polyols. Mixed polyurethane elastomers were put into production in the 1970s. Casting polyurethane was on a pilot scale. Polyester and polyether thermoplastic polyurethane elastomers were successfully developed. Ester type polyurethane elastomer starts small batch production. According to statistics, the actual output of polyurethane elastomers in my country was less than 400t/year in 1976, about 1.1kt/year in 1984, about 15kt/year in 1989, about 23kt/year in 1994, and about 55kt/year in 1997. According to statistics from the China Polyurethane Industry Association, in 1998 elastomers (including traditional elastomer products, waterproof materials and paving materialsmaterials, etc.) output reached 67kt. The output of conventional casting type, thermoplastic polyurethane elastomer, waterproofing and paving materials, spandex, and sole solution in 2004 were 41kt/year, 82kt/year, 80kt/year, 11.8kt/year, and 18kt/year respectively, and in 2006 they were 64kt/year respectively. /year, 108kt/year, 112kt/year, 152kt/year, 242kt/year. With the improvement of the overall level of the polyurethane industry, the production technology of polyurethane elastomers has become increasingly mature. New technologies, new products, and new processes are constantly emerging, and their application scope has been further expanded.

3. Basic classification

There are many varieties of polyurethane elastomers. If divided according to oligomer polyol raw materials, polyurethane elastomers can be divided into polyester type, polyether type, polyolefin type, Polycarbonate type, etc., polyether type can be divided into polytetrahydrofuran type, polyoxypropylene type, etc. according to the specific varieties; according to the diisocyanate used, it can be divided into aliphatic and aromatic elastomers, which are further subdivided intoTDI type, MDI type, IPDI type, NDI type and other types. Conventional polyurethane elastomers are mainly polyester/polyether, TDI/MDI. Chain extenders mainly include diols and diamines. Strictly speaking, polyurethane obtained by chain extension of diamine is polyurethane-urea.

In terms of manufacturing process, polyurethane elastomers are traditionally divided into three categories: casting type, thermoplastic type, and mixing type. All of them can be synthesized by prepolymerization method and one-step method. However, the output of products prepared by some innovative processes has exceeded that of some traditional types. For example, the production of solid and microporous polyurethane elastomers by the reaction injection molding (RIM) process has become an important category. In addition, solution coating and solution casting molding are also important methods for manufacturing elastic polyurethane, which are mainly used in the production of synthetic leather. Centrifugal casting and spray molding are also new technologies that have developed rapidly at home and abroad in the past decade.