HDPE is one polymer family, but a grade made for crates will not blow a good bottle, and a film grade will not make pressure pipe. Two figures on the datasheet do most of the work: melt flow index and density.
The four main grade families
- Blow moulding (bottles, jerrycans, drums): low MFI for melt strength, with environmental stress-crack resistance for chemical containers.
- Injection moulding (crates, caps, buckets, housewares): higher MFI so the melt fills the mould quickly.
- Film (carrier bags, liners, thin packaging film): very low MFI, often bimodal, for strong thin film.
- Pipe (PE100, PE80): pressure-rated grades classified by long-term strength; see our PE100 vs PE80 guide.
Melt flow index (MFI)
MFI is measured in g/10 min under a stated load (2.16 kg or 5 kg, or 21.6 kg for high-load MFI). Always compare figures at the same load. Lower MFI means a stiffer melt and tougher parts; higher MFI means easier flow and faster cycles.
Density
HDPE density is typically about 0.941 to 0.965 g/cm³. Higher density gives stiffness and barrier; slightly lower density gives better impact and stress-crack resistance.
Other points
- Food-contact or pharmaceutical use, if required
- UV stabilisation for outdoor parts
- Natural, or a colour or black compound
What to send for a quote
- The product you make and your process
- MFI (with its load) and density range, or your current grade name
- Food-contact or other approvals your market needs
- Quantity, packing, destination port and Incoterm