Wednesday 15-06-2022

NIKK Knowledge Base: P

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Polyether-ether-ketone is a high performance thermoplastic material with high mechanical properties and high thermal resistance (up to 310° C) as well as a high chemical resistance. The creep of PEEK is outmost low as well at high temperature. Furthermore has PEEK a high abrasion resistance, a low friction coefficient and a high resistance against high energy radiation like UV and x-ray.

Polymers have a low density and could therefore save energy. Due to the low density small molecules could pass through a polymeric material which is called permeation. The permeation coefficients of polymers depend on the polymer and the molecule that will permeate. For measuring of a permeation coefficient special instruments are necessary.

Phenolic resin
Phenolic resin (PF) also known as Bakelite is a synthetic polymer produced from phenol and formaldehyde. Phenolic resins are extremely brittle and were used in the industry mainly as coating or gluing agent. Phenolic resins have a high flame resistance and during burning only CO2 and water is emitted. Due to the very good electrical insulation of phenolic resin it is also often used in the field of transformers.

Polymethylmethacrylate (PMMA) is a transparent polymer produced from methylacrylate and also established under the name Plexiglas.

Poisson`s ration
The poissons`s ratio is a matter constant and describes the alteration of the cross section perpendicular to the applied load when the sample is stretched or compressed. Due to the volume constancy of a bulk material a sample will become smaller under tensile stress or bigger under compression: ν= εyy/εxx
ν: Poisson´s ratio
εxx: strain in direction to the applied load
εyy: strain perpendicular to the applied load and z-axis

De vaak gebruikte en meest bekende thermoplast Polyetheen (PE) wordt gemaakt door polymerisatie van etheen met bepaalde katalysatoren en vaak met een klein aandeel van een copolymeer (Hexeen, Penteen). Polyetheen kan in twee verschillende processen worden gemaakt:
- Hoge dichtheid polyetheen (HDPE) wordt gemaakt bij lage druk
- Lage dichtheid polyetheen (LDPE) wordt bij hoge druk gemaakt
HDPE wordt vaak in de industrie gebruikt als PE80 en PE100. Maar er bestaan ook nog andere benoemingen:
- PE300 voor PE80 of PE100. PE80 en PE100 worden vaak voor mechanisch belaste componenten (buizen, tanks ) gebruikt en de 80 en 100 staan voor de langtijd treksterke van de materialen. 8 MPa en respectievelijk 10 MPa.
- PE500 voor een hoog moleculaire HDPE (moleculair gewicht 500.000 g per Mol)
- PE1000 voor de ultra hoog moleculair HDPE (moleculair gewicht > 1.000.000g per Mol). Nieuwe ultra hoog moleculair HDPE bestaat uit een moleculair gewicht van meer dan 10.000.000g per Mol. 

Polyamide (PA) is a thermoplastic material with amorphous or crystalline structure. PA homopolymers consist of [-NH-(CH2)x-CO-]n or [-NH-(CH2)6-NH-CO-(CH2)y-CO-]n. In the industry well-known types are PA6, PA11 and PA12. Polyamides offer a high E-modulus, a high strength and hardness. 

The often used and well-known thermoplastic material polyethylene is produced by means of polymerisation of ethylene with the help of catalysts and some co-polymers like hexene or pentene. Polyethylene could be produced by means of two different process types:
- HD-PE: high density polyethylene produced in a low pressure process.
- LD-PE: low density polyethylene produced in a high pressure process.
HD-PE was for industrial purpose often used as PE80 or PE100. But there exists a variety other nomenclature:
- PE300: interchangeable also for PE80 or PE100, etc. PE80 or PE100 were often used for mechanically stressed components (e.g. tanks, pipe works). The number 80 and 100 come from the MRS of the materials 8 resp. 10 MPa.
- PE500: high molecular weight PE (PE-HMW) with a molecular weight of 500,000 g/mol
- PE1000: Ultrahigh molecular weight PE (PE-UHMW) with a molecular weight greater than 1,000,000 g/mol. Modern PE 1000 types have a molecular weight of more than 10,000,000 g/mol.

A polymer consists of sequences of different monomers chemically bonded together. Polymers are divided in different types:
- Condensation and addition polymerization
- Thermoplastic, thermosets, rubber

Polypropylene (PP) is a thermoplastic material with a broad range of applications in the industry. Polypropylene is produced with different catalysts out of propylene.
For industrial purpose only isotactic PP is used where the methylene substance is located exclusively on one side.
PP is produced as homopolymer and copolymer. The homopolymer consists exclusively out of propylene and the copolymers consists beside propylene also a co-monomer usually ethylene. The PP-copolymer additionally is subdivided in block-copolymer (PP-B) and random-copolymer (PP-R)

Pressure loss
The pressure loss of medium in a pipe is dependant from the medium, the velocity (Reynolds number), the diameter and the inner surface roughness.

Pressure resistance
The maximal allowable inner pressure of a pipe or fitting is strongly dependant of the plastic material, temperature and wall thickness.
Normally for pipes and fittings exist pressure classes (PN = nominal pressure) but due to further development of PE types a dimensional measurement was introduced: SDR = diameter per wall thickness d/s.

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