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JapaneseHDPE SPIRAL PIPE Information PP-B. part 2
Key material properties
Different types of polypropylene
Polypropylene is a semi crystalline material. The regularity of the molecule chain is supporting the development of crystallineareas. Due to entanglement of the ends of the molecule chains, amorphous areas are built that are laid between the crystalline ones. The crystalline structure is supporting the strenght and stiffness of the material, whereas the unorganised amorphous part is responsible for flexibility and toughness above the glass transition temperature.
By the use of copolymerisation of propylene with ethylene the PP property profile is increased, basically isotactic polypropylene can be divided in three classes.
- PP-H (Homopolymer)
- PP-B (Impact copolymer also called block copolymer)
- PP-R (Random copolymer)
Homopolymers are polymerised only by the use of proplyen-molecules, providing high strength, stiffness and hardness with some limitations in impact performance.
Impact copolymers are produced in a multistage polymerisation process. During this process, beside of the PP-Homopolymer a copolymer, in most of the case ethylene, is also polymerised and embedded in the PP-Homopolymer matrix. This is increasing the toughness and improving the impact performance of the material..
In random copolymers, preferably ethylene is randomly distributed and isolated in the polypropylene chain. These comonomer units are disturbing the regularity of the polymer chain and reducing the crystallinity and consequently the stiffness of the material.
article source:
Handbook on large plastic pipe
KRAH COMMUNITY
https://www.krah.net
