Polybutylene PIB Piping systems;Hot melt adhesives;Compounding and masturbatches lubricants Polybutylene IdentifiersPropertiesRelated compounds

Other names[hide]polybutene-1, poly(1-butene), PB-1
CAS number	9003-28-5
Molecular formula	(C4H8)n
Density	0.95 g/cm3[1]
Melting point	135 °C[1]
Related compounds	1-butene (monomer)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Polybutylene (polybutene-1, poly(1-butene), PB-1) is a polyolefin or saturated polymer with the chemical formula (C4H8)n. It should not be confused with polybutene, a low molecular weight oligomer with a different repeat unit.

Polybutylene is produced by polymerisation of 1-butene using supported Ziegler-Natta catalysts. PB-1 is a high molecular weight, linear, isotactic, and semi-crystalline polymer. PB-1 combines typical characteristics of conventional polyolefins with certain properties of technical polymers.

PB-1, when applied as a pure or reinforced resin, can replace materials like metal, rubber and engineering polymers. It is also used synergistically as a blend element to modify the characteristics of other polyolefins like polypropylene and polyethylene. Because of its specific properties it is mainly used in pressure piping, flexible packaging, water heaters, compounding and hot melt adhesives.

Application areas

Piping systems

The main use of PB-1 is in flexible pressure piping systems for hot and cold drinking water distribution, pre-insulated district heating networks and surface heating and cooling systems. ISO 15876 defines the performance requirements of PB-1 piping systems.[8] The most striking features are weldability, temperature resistance, flexibility and high hydrostatic pressure resistance. The material can be classified PB 125 with a minimum required strength (MRS) of 12.5 MPa. Other features include low noise transmission, low linear thermal expansion, no corrosion and calcification.

PB-1 piping systems are no longer being sold in North America. The overall market share in Europe and Asia is rather small but PB-1 piping systems have shown a steady growth in recent years. In certain domestic markets, e.g. UK, Korea and Spain, PB-1 piping systems have a strong position.[7]

[edit] Plastic packaging

Several PB-1 grades are commercially available for various applications and conversion technologies (blown film, cast film, extrusion coating). There are two main fields of application:

Peelable easy-to-open packaging where PB-1 is used as blend component predominantly in polyethyelene to tailor peel strength and peel quality, mainly in alimentary consumer packaging and medical packaging. Lowering seal initiation temperature (SIT) of high speed packaging polypropylene based films. Blending PB-1 into polypropylene, heat sealing temperatures as low as 65 °C can be achieved, maintaining a broad sealing window and good optical film properties. [edit] Hot melt adhesives

PB-1 is compatible with a wide range of tackifier resins. It offers high cohesive and adhesive strength and helps tailoring the "open time" of the adhesive (up to 30 minutes) because of its slow crystallisation kinetics. It improves the thermal stability and the viscosity of the adhesive.[9]

[edit] Compounding and masturbatches

PB-1 accepts very high filler loadings in excess of 70%. In combination with its low melting point it can be employed in halogen-free flame retardant composites or as masturbatch carrier for thermo-sensitive pigments. PB-1 disperses easily in other polyolefins, and at low concentration, acts as processing aid reducing torque and/or increasing throughput.

[edit] Other applications

Other applications include domestic water heaters, compression packaging, wire and cable, shoe soles and polyolefin modification (thermal bonding, enhancing softness and flexibility of rigid compounds, increasing temperature resistance and compression set of soft compounds).

[edit] Environmental sustainability

Plumbing and heating systems made from PB-1 have been used in Europe and Asia for more than 30 years. First reference projects in district heating and floor heating systems in Germany and Austria from the early 1970s are still in operation today.[7]

One example is the installation of PB-1 pipes in the Vienna Geothermal Project (1974) where aggressive geothermal water is distributed at a service temperature of 54 °C and 10 bar pressure. Other pipe materials in the same installation failed or corroded and had been replaced in the meantime.[7]

International standards set minimum performance requirements for pipes made from PB-1 used in hot water applications. Standardised extrapolation methods predict lifetimes in excess of 50 years at 70 °C and 10 bar.[7]

Polybutylene plumbing was used in several million homes built in the United States from 1970 to the mid-1990s. Problems with leaks led to a class action lawsuit, Cox vs. Shell Oil, that was settled for $1 billion.[10][11] The leaks were associated with degradation of polybutylene in chlorinated water.[12]

Polybutylene 950