This polymer has been referred to as polybutylene, PB, PB-1 and polybutene, as well as its correct chemical name, Polybutene-1.
Polybutylene is a polyolefin
Polybutylene is a member of the polyolefin family of thermoplastic materials which also includes polyethylene and polypropylene. Polybutylene exists in two isomeric forms depending on where the carbon double bond is positioned in the monomer molecule. If it is between the first and second carbon atoms in a linear molecule (Butene-1), then the chemically accurate name of the resulting polymer is 'Polybutylene' (PB-1).
If it is a branched monomer molecule then the resulting polymer is called Polyisobutylene (PIB). The polymer PBPSA members use is Polybutylene. In the past this polymer has been referred to as polybutene, PB, PB-1 and polybutylene, as well as its correct chemical name, Polybutene-1.
As a matter of interest, polyisobutylene, produced from the alternative isomeric monomer form, is a non-crystalline, low-viscosity polymer used as a viscosity modifier in the oil products business, and also in the manufacture of hot melt adhesives and chewing gum.
The Polybutylene raw material grades are manufactured in the world's largest Polybutylene manufacturing plant in The Netherlands.
The balance of properties of Polybutylene make it the technically preferred material for the production of pressurised hot and cold water piping systems.
Polybutylene – A highly isotactic thermoplastic
In chemical structure Polybutylene differs from polyethylene and polypropylene only by the number of carbon atoms in the monomer molecule.
Polybutylene is manufactured utilising Zeigler-Natta type catalysts which produce a highly isotactic thermoplastic. A unique crystalline structure, combined with carefully controlled molecular parameters give Polybutylene a combination of properties ideally suited to applications requiring both high strength and flexibility at temperatures up to 100°C.
As an essentially 'pure' highly isotactic homopolymer, Polybutylene is more easily specified to consistently achieve quality performance. The properties of Polybutylene can be tailored by copolymerisation with PE or PP to create random copolymers suitable for special applications in underfloor heating. Polybutylene has a density similar to water of 0.92 gm/cc.
The technically preferred property balance
Polybutylene can be processed via standard injection moulding or extrusion into a broad range of pipes and fittings for hot and cold pressurised water systems. In its most simple homopolymer form, the balance of properties of Polybutylene make it the technically preferred material for the production of pressurised hot and cold water piping systems.
In contrast to other thermoplastics used in these applications, performance modification via compounding, cross-linking or copolymerisation is not necessary for Polybutylene piping systems to fulfill the stringent performance standards applied to their use.
In comparison with other polyolefin materials, Polybutylene has a higher level of resistance to strain under continually applied stress over long periods of time. This is known as creep behaviour and the graph illustrates the increasingly superior performance of Polybutylene at times in excess of 100 hours.
In addition to its superior mechanical and thermal properties, Polybutylene provides a high level of resistance to chemical attack and also meets a level of flammability resistance meeting the demands of most applications.
Polybutylene Physical | Mechanical | Thermal properties more
Polybutylene is not sold by PBPSA members for use in pipe applications intended for use in North America, and those parties require their customers or distributors not to sell products made from PB-1 into pipe applications for North America.