Polybutylene

Polybutylene

Homopolymer

Polyolefin with good creep strength and chemical resistance

Fixed

930-945 kg · m-3

124-126 ° C

Partially crystalline

290-295 MPa

> 50%

Polybutene -1, also called polybutylene ( PB abbreviation ), is a thermoplastic polyolefin. In contrast to branched polyisobutylene constructed monomers are linear and arranged substantially in the isotactic PB, a total of high molecular weight from 700,000 to 3,000,000 g / mol are obtained.

Synthesis and processing

The polymerization is carried out using PB -specific Ziegler- Natta catalysts. Upon cooling, the polymer crystallizes tetragonal about half, resulting in a soft and gummy material. The density is then · m -3 at about 890 kg. Vacuum or on further cooling leads to a post-shrinkage, since the tetragonal transforms into a hexagonal phase. Here, take density ( at about 950 kg · m -3), strength and hardness.

Polybutene -1 can be melt processed at temperatures above 190 ° C by means of injection molding or extrusion. To ensure the prompt removal from the mold during injection molding the mold temperatures are only about 40 to 80 ° C.

Properties

With respect to the mechanical properties of PB is approximately between PE and PP. Due to its high molar mass, it is good temperature stability, as reflected for example in its high creep strength (or low creep ). Also PB has good chemical resistance to many solvents, oils, greases, acids, alkalis, hot water, alcohols and ketones. In addition, it is safe in contact with food. Compared to some engineering plastics, it is less resistant to aromatic and chlorinated hydrocarbons and oxidizing acids.

Like all polyolefins is also well PB -flammable and without additional stabilization is not weather resistant.

Applications

Typical application fields for PB pipes and along with PE and PP films for food packaging. Furthermore, PB is a component in many melt adhesives or is mixed in blends other polyolefins as processing aids.