Recycled High-density Polyethylene (R-HDPE)

Recycled HDPE applications

What products can be made of recycled HDPE?

Nowadays, high-density polyethylene (HDPE or PEHD) is one of the most commonly used plastics. HDPE is used for a wide range of rigid plastics applications. HDPE regrind is suitable for HDPE injection and blow-molded applications. While HDPE was first introduced during World War II as high-frequency radar cables, the use of HDPE today ranges from pipe systems to 3D printer filaments.

Commonly, non-food-grade HDPE packaging or in some cases food-grade HDPE packaging are among the recycled HDPE (R-HDPE) applications. Packaging commonly made from HDPE regrind includes shampoo bottles, chemical and cosmetic containers, recycling bins and grocery bags, beverage bottles, bottle caps, milk jugs, and many more.

Non-food applications such as cable and wire covering can also be made from HDPE recyclates. A very common recycled HDPE application is pipe systems. The attributes that recycled high-density and low-density polyethylene (HDPE and LDPE) compounds need to fulfill for the manufacture of pressure pipes and fittings for buried or above-ground applications are specified in the international standard ISO 4427. Furthermore, since recycled HDPE can be rather stiff, it is optimal for producing hard shells such as computer cases. Moreover, recycled HDPE can be used to produce technical fibers for various non-food applications such as plastic lumber as well as indoor or outdoor furniture, flower pots, floor tiles, and toys. To sum up, HDPE regrind can be used in non-food and food-grade applications such as packaging, textile fibers, and furniture.

R-HDPE material properties

What are the benefits and drawbacks of recycled HDPE?

HDPE is one of the polyethylene (PE) types, which belongs to the family of polyolefins and represents the largest constituent of plastic waste. HDPE (PEHD) recyclates have a low density and significantly higher stiffness compared to LDPE. The density of HDPE ranges between 0,94 and 0,97 g/cm3.

HDPE recyclates are known for their high resistance to most of the chemical solvents and corrosion, high hydrophobicity (moisture resistance), high impact resistance, and electrical insulation properties as well as low price and very good recyclability. The chemical resistance and the water-repellent effect allow a wide range of applications. By using suitable stabilizers, the low UV stability of R-HDPE can be significantly improved for outdoor applications. The maximum continuous service temperature of 80° C is sufficient for most applications.

Moreover, recycled HDPE granules are available in food-grade quality and can be easily processed using all thermoplastic methods. Yet, a limited amount of food-grade HDPE is commercially available. HDPE regrind can also be used as a carrier material in masterbatches. By using R-HDPE of different molecular weights, recyclates can be produced for HDPE injection molding, (pipe) extrusion, and rotational molding. In general, the material properties of HDPE recyclates are similar to those of the virgin HDPE. At the same time, the exact properties of a given HDPE regrind depend mainly on the input stream and the used process parameters during recycling like sorting, washing, and filter-based extrusion.

HDPE waste feedstock

Which sources can be used for HDPE recycling?

HDPE waste feedstock is often also referred to as HDPE scrap. Currently, HDPE is mainly recycled using a mechanical recycling approach. The type of HDPE feedstocks or HDPE scrap can be broadly classified into food-grade and non-food-grade HDPE, as well as post-consumer and post-industrial HDPE. Non-food-grade post-consumer recycled HDPE (PCR HDPE or HDPE PCR) can be manufactured from any of the above-mentioned applications, such as cables, computer cases, and chemical containers. Commonly used HDPE feedstock are materials like HDPE cans, foils, packaging, boxes, shampoo bottles, and pipes, among others.

Food-grade PCR HDPE is often retrieved from food containers like milk and juice bottles or other HDPE cans. Recycling food-grade HDPE feedstock increases the value for further sales, as the amount of recycled food-grade HDPE on the market is currently limited. Similar to non-food-grade post-consumer HDPE, post-industrial HDPE scrap is also commonly found on the market in a variety of forms of production waste or leftovers.

The content of this page has been created in collaboration with independent experts: 
Dr. Madina Shamsuyeva (Head of Department Plastics recycling and Technology, Plastics analytics at the IKK - Institute for Plastics and Circular Economy of the Leibniz University Hanover)

Dr. Uwe Zander (Co-owner of Voelpker Wax Academy GmbH with more than 30 years experience in the plastic processing industry, with a focus on compounding engineering plastics)