LDPE film recycling — from waste to granule

Low-density polyethylene — LDPE — is the polymer of thin films, flexible packaging, and stretch wrap. It is everywhere in agriculture, logistics, and consumer goods. It is also one of the more challenging plastic waste streams to recycle — its very properties that make it useful (thinness, flexibility, light weight) also make collection, sorting, and washing difficult.

Where does LDPE scrap come from?

Agricultural film

Mulch film, tunnel film, and greenhouse film are major sources of LDPE scrap in India. Agricultural film is typically 20–100 micron LDPE, and it comes off the field heavily contaminated with soil, plant residue, and moisture. It is among the hardest LDPE waste to process — but because it is generated in large, concentrated volumes, it is a significant feedstock.

Stretch wrap and pallet wrap

Industrial stretch wrap from logistics and warehousing is typically cleaner than agricultural film. Pallet wrap recycling has grown significantly with the rise of e-commerce logistics in India.

Packaging bags and pouches

Carry bags, courier pouches, garment bags, and industrial packaging bags are all LDPE or LLDPE. Monolayer clear LDPE packaging is the easiest to process; printed multi-layer structures require more intensive sorting and washing.

Post-industrial film scrap

Film extrusion trim, bubble wrap production waste, and manufacturing rejects are post-industrial LDPE with known composition and minimal contamination — the preferred feedstock for quality regrind production.

The film recycling process

Pre-sorting and size reduction

Film waste is pre-sorted to remove non-LDPE materials, then shredded. Specialised film shredders with cutter and separator configurations are used — thin film tends to wrap around standard shredder blades.

Washing — the critical step

Film washing is more intensive than rigid plastic washing. Agricultural film requires a hot wash with surfactant to dislodge embedded soil particles, followed by friction washing and float-sink separation. LDPE floats (density 0.910–0.940 g/cm³), helping separate it from sand and dirt. Water consumption in film washing is high — well-run operations treat and re-use wash water rather than discharging it.

Drying

Film carries significantly more surface moisture per unit weight than rigid plastic due to its high surface area-to-volume ratio. Mechanical drying (squeeze rolls, centrifuge) removes bulk moisture first; thermal drying removes residual moisture to below the 0.1% threshold needed for clean extrusion.

Extrusion with degassing

Clean, dry film regrind is fed into the extruder. Film recycling extruders typically use a two-stage screw with a degassing vent — this removes volatile organics, moisture vapour, and trapped air. The output is cooled and pelletised.

LDPE regrind quality parameters

MFI: Film-grade LDPE regrind typically targets 0.5–4.0 g/10min @ 190°C / 2.16 kg. Agricultural film scrap can have a wider MFI distribution than post-industrial scrap.

Contamination: Yellow or brown gel specks indicate carbonised contamination from soil or polymer degradation — a sign of inadequate washing or excessive extruder temperatures. Clean regrind should be essentially speck-free.

Odour: Agricultural film regrind can carry residual odour from crop residue. This limits use in odour-sensitive applications, but is acceptable for general packaging film and industrial applications.

Applications for recycled LDPE regrind

Quality LDPE regrind is used in: blown film extrusion for refuse bags, agricultural sheeting, and protective packaging; co-extrusion as a secondary layer in multi-layer packaging; shrink wrap and stretch film production; cable jacketing; and injection-moulded flexible parts. The key for buyers: ask your supplier where their LDPE feedstock comes from — post-industrial waste produces a cleaner, more consistent regrind than agricultural film.