Types and Nomenclature of Polyethylenes

Industrial polyethylenes are commonly classified and named using acronyms that incorporate resin density or molecular weight. lUPAC names are not typically used. In a few cases, copolymers are named using abbreviations for the comonomer employed. Nomenclature typically used for industrial polyethylenes will be discussed in this section. (Molecular weight will be discussed in section 1.4.) 

Density is measured using density gradient columns and hydrostatic (displacement) methods. Density is directly related to crystalline content and in fact can be used to estimate % crystallinity in polyethylene. 

The Society of the Plastics Industry (SPI), an industry trade association founded in 1937, identifies three main categories of polyethylene based on density  

The American Society for Testing and Materials (ASTM) has also defined various types of polyethylene. An ASTM publication entitled Standard Terminology Relating to Plastics (ASTM D 883-00) provides the following classifications based upon density  

While useful as starting points, SPI and ASTM classifications are not sufficient to describe the wide range of polyethylenes available in the industry. Classifications have been further subdivided to convey additional information, such as molecular weight or comonomer employed. Eurther, manufacturers use their own nomenclature and trade names. Clearly, the names used for various polyethylenes are somewhat arbitrary and subjective. The reader should not rigidly construe classifications and may encounter other nomenclatures. An overview of various classifications of polyethylene in common use in industry is provided below  

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