HDPE (High-Density Polyethylene)

HDPE (High-Density Polyethylene) is a semi-crystalline thermoplastic produced by low-pressure polymerisation of ethylene, with a density of 0.93–0.97 g/cm³ and a melting point of 120–180°C. It is identified by Resin Identification Code (RIC) 2. HDPE's high density relative to LDPE or LLDPE comes from its linear molecular chain with very little branching, which allows tight molecular packing. Key applications in India include: FMCG containers (shampoo, detergent, motor oil bottles), milk cans and jerry cans, industrial drums (200-litre), water supply pipes (as per IS 4984), cable insulation, and plastic crates for logistics. Annual HDPE consumption in India is approximately 2.5–3 million tonnes, placing it among the top three plastic types by volume.

HDPE is considered one of the most recyclable plastics commercially available in India. Post-consumer HDPE sorted by colour commands prices of Rs 22–35 per kg for clean, baled natural (white/translucent) bottles, and Rs 16–24 per kg for coloured/mixed HDPE. Mixed HDPE without sorting trades at Rs 10–16 per kg through kabadiwala channels. Processing of HDPE for recycling involves shredding, washing (caustic and hot water at 70–90°C), drying (moisture ≤0.1%), and extrusion at 200–240°C. Recycled HDPE pellets (rHDPE) sell at Rs 55–90 per kg depending on colour, application, and MFI (Melt Flow Index), with food-grade rHDPE commanding a further 20–30% premium.

Quality grading of HDPE recyclate centres on contamination control: labels and adhesives reduce pellet quality; cross-contamination with PVC (melting point 80°C) causes charring and structural failure at HDPE processing temperatures. Even 1% PVC in an HDPE stream causes visible degradation in the final product. Colour sorting is important — natural (unpigmented) HDPE is the highest value; mixed colour is the lowest. The Melt Flow Index of rHDPE (typically 0.1–1.0 g/10 min at 190°C/2.16 kg per ASTM D1238) must match the application spec — pipe-grade rHDPE needs lower MFI than injection-moulded parts.

For Indian recyclers, the practical margin in HDPE recycling depends entirely on stream purity at intake. A well-run HDPE line processing clean, sorted post-consumer bottles at 500–1,000 kg/hr can achieve gate-to-gate margins of Rs 6–15 per kg of output pellet, after accounting for 10–15% material loss in washing and extrusion. Industrial HDPE (drums, pipes) is cleaner and commands less washline cost but requires more aggressive size reduction. Set up a colour-sorting conveyor before the shredder: it is a Rs 2–5 lakh capital spend that pays back within 6–12 months through pellet price uplift.