Polyethylene (PE) is a semi-crystalline thermoplastic made from ethylene monomers and sold in five grades from PE-LD to PE-X depending on its chain structure. Electrically, PE is one of the best insulators among commodity plastics: volume resistivity above 10¹⁶ Ω·cm, relative permittivity around 2.3 and one of the lowest loss factors among engineering plastics. For food contact PE is considered safe, it is chemically inert and free of plasticisers. This article explains the PE grades, their property values and the four applications in which GOBA slits polyethylene as web material from its range of insulation materials: battery separators, protective films, foam tapes and filter fleece.
High pressure or low pressure: the process sets the chain structure
Polyethylene belongs to the polyolefin group and is produced by polymerising ethylene (C₂H₄). It consists exclusively of carbon and hydrogen and, with more than 100 million tonnes produced worldwide each year, is the most widely produced plastic overall.
Two manufacturing processes determine the resulting molecular structure. The high-pressure process (around 2,000 bar, radical polymerisation) creates branched chains and therefore PE-LD. The low-pressure process using Ziegler-Natta or metallocene catalysts creates linear chains and therefore PE-HD. Almost every property difference between the PE types traces back to this difference in chain structure, not to a different chemistry.
What types of polyethylene exist?
Density is the fastest indicator of PE type, because it depends directly on the degree of chain branching. The more linear the chain, the more densely the material packs, and the harder and stiffer it becomes.
| Type | Density | Characteristic | Typical use |
|---|---|---|---|
| PE-LD (Low Density) | 0.915 to 0.935 g/cm³ | Highly branched, flexible, transparent | Films, shrink film |
| PE-LLD (Linear Low Density) | similar to PE-LD | Linear with short side chains, higher tear strength than PE-LD | Thin, tough films |
| PE-HD (High Density) | 0.94 to 0.97 g/cm³ | Barely branched, stiff, chemically resistant | Moulded parts, pipes, containers |
| PE-UHMW (Ultra High Molecular Weight) | 0.93 to 0.94 g/cm³ | Molar mass 3 to 6 million g/mol, extremely abrasion resistant | Sliding elements, wear parts |
| PE-X (cross-linked) | depends on base type | Chemically cross-linked, more heat resistant and dimensionally stable | Piping, cable insulation |
For cutting and converting, PE-LD and PE-LLD matter most: both can be slit precisely into thin webs and rolled without tearing during handling.
What electrical properties does polyethylene have?
PE ranks among the best electrical insulators of the standard plastics, a result of its non-polar chains built purely from carbon and hydrogen. Without polar groups in the chain, there is little for charge displacement to grip onto, which is exactly why its dielectric loss factor is so low.
| Characteristic | Typical value for PE |
|---|---|
| Dielectric strength | 20 to 45 kV/mm (standard test specimen), thin films significantly higher |
| Volume resistivity | above 10¹⁶ Ω·cm |
| Relative permittivity (εr) | around 2.3, largely frequency-independent |
| Dielectric loss factor (tan δ) | about 2 × 10⁻⁴, one of the lowest values among engineering plastics |
For comparison: polyimide reaches over 200 kV/mm and withstands far higher temperatures, at a higher cost and more demanding processing. PE wins where the temperature requirement stays moderate and the low loss factor matters, for example in high-frequency applications. A broader overview of insulating plastics and how to choose between them is available under electrically insulating plastics.
Where does GOBA process polyethylene?
GOBA does not process PE as a standalone insulating material for motors or transformers, but wherever its combination of mechanical toughness, chemical resistance and low weight is needed. Four applications run regularly through the converting line:
- Battery separators: PE separators, single-layer and multi-layer, for standard and high-performance cells. The microporous structure separates anode and cathode while still letting ions pass through.
- Protective films: PE protective films are the classic surface protection film, temporarily adhesive and available in various tack levels.
- Foam tapes: PE foam is lightweight, closed-cell and chemically resistant, used for insulation and cushioning.
- Filter fleece: PE filter fleece, together with PP and PET fleece, forms the basis of many standard filtration systems.
In all four cases, GOBA supplies precise roll or sheet cutting from customer material or semi-finished stock, not the raw PE resin itself. Details on material widths and tolerances are available on the respective cutting page and on Insulating materials.
Polyethylene compared to other thermoplastics
Polypropylene (PP) is the closest relative: chemically similarly resistant, but stiffer and with a higher continuous-use temperature, at the cost of being more brittle in cold conditions. PVC gains higher strength from its polar carbon-chlorine bond, but has a significantly worse loss factor than PE and is therefore unsuitable for high-frequency applications. The full picture of PE within the thermoplastics family is available under Thermoplastics.
Is polyethylene harmful to health?
No. PE is chemically inert, contains no plasticisers or bisphenol A, and is considered food-safe, which is why it is widely approved for packaging and drinking bottles. It only becomes health-relevant under improper incineration, which produces carbon monoxide and other combustion gases that can be toxic, as with most plastics. For its intended use, including food and medical contact, there is no risk.
GOBA Takeaway
Polyethylene is no substitute for high-performance insulators such as polyimide or mica where high temperatures or maximum dielectric strength are required. Its strength lies in combining a low dielectric loss factor, chemical resistance and low weight with a material cost that makes PE economical for large-area applications such as battery separators, protective films and filter fleece. For cutting and converting from customer material, GOBA is the right partner.
