Recyclable and Biodegradable Materials in Extrusion Blow Moulding: Progress or Greenwashing?
As consumer pressure mounts and legislation tightens, the plastics industry finds itself at a crossroads. Nowhere is this more apparent than in extrusion blow moulding — the workhorse of bottle and container manufacturing. Traditionally reliant on HDPE and other non-biodegradable resins, the industry is rapidly adapting to new expectations around sustainability.
But with terms like recyclable, biodegradable, compostable and bio-based often used interchangeably (and sometimes misleadingly), it’s important to cut through the noise. What materials are actually being used in blow moulding today that offer a credible path forward? And what are the engineering implications?
Recyclable Materials: Still the Most Practical Option
Let’s start with recyclables — because for extrusion blow moulding, they remain the most scalable and widely adopted approach.
HDPE (High-Density Polyethylene) is the dominant material for blow moulded products, and it’s already widely recycled. What’s changing is the increasing use of PCR (Post-Consumer Recycled) HDPE. These recycled resins can now match much of the performance of virgin plastic — especially for non-food-contact applications.
The challenge is consistency. PCR materials often vary in colour, density and melt flow, meaning tooling and process settings must adapt. Mould surface finish, wall thickness control, and cooling rates can all be affected. At Beaubury, we’re seeing more demand for tool refurbishments that allow greater processing flexibility — especially where clients are moving between virgin and recycled material batches.
PET is also gaining ground in blow moulding, especially in two-stage processes, due to its clarity and established recycling infrastructure. However, it’s less common in traditional extrusion blow moulding because of its processing requirements.
Biodegradable and Compostable Materials: Still Early Days
Biodegradable materials are often presented as the future of plastic, but in the context of extrusion blow moulding, viable options are still limited.
Materials such as PLA (Polylactic Acid) and PHA (Polyhydroxyalkanoates) are theoretically biodegradable and sourced from renewable feedstocks like corn starch or sugarcane. However, these materials tend to struggle under the thermal and mechanical demands of extrusion blow moulding. Their melt strength, barrier properties and long cooling times often fall short of commercial viability — especially when compared to HDPE.
That said, ongoing developments in blended bio-resins are promising. Some suppliers are introducing bio-HDPE — chemically identical to fossil-derived HDPE but made from plant-based ethanol. While not biodegradable, it is recyclable and has a significantly lower carbon footprint.
From a tooling perspective, biodegradable and bio-based materials tend to behave differently under pressure and heat. They can degrade more quickly if overheated, and some are more abrasive — leading to premature wear on mould surfaces. Tool coatings, cooling channels, and venting all need to be reconsidered when trialling alternative materials.
Green Expectations, Engineering Realities
There’s a growing gap between what consumers expect from “eco-friendly plastics” and what’s currently practical in industrial blow moulding. While recyclability is already well-integrated into many workflows, true biodegradability — especially in uncontrolled environments — remains a work in progress.
Still, the pressure to act is real. Brands are demanding greener packaging, retailers are imposing material restrictions, and regulations are increasingly targeting single-use plastics. For blow moulders, that means being ready to adapt.
