About hdpe & industrial plastic scrap
The most valuable plastic scrap is factory waste, because it is a known polymer in a known colour with no contamination: sprues, runners, purgings, moulding rejects and trimmings. Sold consistently, this material is close to a raw material rather than a waste product.
Post-use HDPE — drums, crates, jerry cans and pipe — is graded on what was inside and how much colour and dirt it carries. Natural (uncoloured) HDPE grades above coloured; anything that held chemicals, pesticide or oil is either refused or routed for special handling, never sold into general recycling.
PP crates and PVC pipe often arrive in the same load. They are different polymers and are weighed separately, since mixing polymers is what most reduces the value of a plastic consignment.