Material reference: thermoplastic types and welding
Quick reference guide: select a thermoplastic type and read about the material's properties, welding, application, and identification. The information is extracted from Holm & Holm's material guide.
PE – Polyethylene (PE – Polyethylene – PEL – PEM – PEHD ( Polyethylene ) ( Polyten ) ( Polyethylene ))
PE (Polyethylene) is a semi-crystalline thermoplastic and one of the most widely used plastic materials, available in types such as PELD, LLDPE and PEHD. The material has good chemical resistance, low friction, high notched impact strength and very low moisture absorption. It is considered one of the most environmentally friendly types of plastic and is widely used for packaging, pipes and technical wear components.
Properties
- Good abrasion resistance to bulk materials
- High notched impact strength even at low temperatures
- High coefficient of thermal expansion
- Tendency to cold flow
- Low friction
- Good chemical resistance
- Low weight (density 0,91 – 0,96)
- Highly vibration-damping and withstands severe impact loads
- Very low moisture absorption (less than 0,01%)
- One of the best insulating plastic materials against electrical effects with low dielectric loss
- Does not withstand UV light particularly well (unless black pigment or UV stabilisers are added)
- Difficult to paint, print on, polish and glue
Welding
Can be welded using heated tool, hot air welding (300-340°C) and friction welding (100-300 m/min). Butt welding temperatures: PE80 (200°C to 220°C), PE100 (220°C with short changeover time) and PE100 Uponor ProFuse pipes (240°C +5 -2°C with short changeover time). Extrusion welding of PE-HD is performed with a melt temperature of 200-230°C and an air temperature of 250-300°C. Ultrasonic welding is applicable, whereas high-frequency welding is not possible. PEHD 500 and especially PEHD 1000 are difficult to weld. The addition of release agents, anti-slip agents and antistatic agents can make welding more difficult. Work is carried out at temperatures far below the decomposition temperature.
Application
Water pipes, sewer pipes, drainage pipes, gas pipes, cable ducts, cable insulation, plastic bags, packaging film, refuse sacks, freezer elements, fittings, valves/fixtures, PE-HD sheets for welding tanks, containers and electroplating drums, gears, chain guides, wear strips, silo lining, cutting boards in the food industry, moulds, chemical tanks, lining in slurry tanks and HHRT Phantom for calibration and quality control of PET scanners.
Identification
Flame test: Burns with a clear, non-sooting flame that is blue at the bottom and yellow at the top. The material drips and smells like paraffin wax (not self-extinguishing). Ignition temperature: 340°C. May occur with added flame retardants.
Source: PE – Polyethylene (opens in a new tab) at holm-holm.dk
Put numbers on the material?
If you are welding PE or PP, you will find the relevant parameters in the welding tables. The knowledge base also features articles on material identification and quality assurance of joints.
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