The collaboration between producers of recycled polymers and bottle blowers for better product quality

Today the production of HDPE bottles, using totally or only in part post-consumer granules, is a activity widely used by producers, due to the prices of raw materials, for an environmental and marketing issue.

But the use of post-consumer HDPE granules could cause some production problems if certain rules were not respected during production and the blowing of the granules.

The most common problems are:

- holes on the surface of the bottles

- Surface irregularities

- Low compression rate

- Low resistance to welding

- Smell of detergent of the final product

- Low resistance to vertical compression

- High waste during production, blow molding and visual test

To avoid these inconveniences we must intervene in the production of granules through some phases:

- choice of input material

- selection

- wash

- optical selection of granules

- correct analysis of odors through the test of ion mobility gas chromatography

- correct filtration during extrusion

- thermal management of the process

- creations of recipes according to the required mechanical resistance

- humidity control during the packaging phases

- correct storage of the product

There are also some precautions to follow during the blowing and packaging stages:

- check polymer blends based on the shape and size of the bottle

- control of the polymer extrusion phase in the machine

- temperature control

- Parison times

- verification of the gluing points and possibly modification of the recycled mixture

- surface quality testing and identification of problems and causes

- control of the correspondence of the requested colors and modification of the recipes

- test on the resistance of the full bottle and under load and possible problem solving

- control of the transparency or semi-transparency of the bottles, if required, with possible modification of the recipes

As we've mentioned, the production of bottles from recycled high-density polyethylene (HDPE), derived from post-consumer material, has become increasingly common among manufacturers.

The reasons behind this choice are manifold: from the economic savings resulting from the use of less expensive raw materials, to the undeniable environmental benefits, and the positive impact on corporate image.

Despite these benefits, transforming recycled HDPE into quality bottles is not without technical challenges.

One of the main problems encountered in the production of these containers includes the presence of holes and surface irregularities, which can compromise the integrity of the bottle. These defects are often caused by impurities not adequately separated during the recycling process or by suboptimal material mixing.

Other common issues include low resistance to compression and welding, issues that can be directly linked to material degradation during processing and recycling phases.

Another significant issue is odor management: the bottles can acquire a detergent smell, a residue of the chemicals previously used in the containers, if the washing process is not carried out with due care.

Moreover, the resistance to vertical compression may be insufficient, and production waste during blowing and visual tests can increase significantly if the process is not carefully monitored and optimized.

To address these problems, a rigorous and methodical control of the production process is essential. It starts with the careful selection of scrap material, which must be as undegraded and clean as possible.

The washing must be performed meticulously to remove all impurities and chemical residues, while the optical selection of granules allows for discarding those of inferior quality.

Odor analysis is equally important, for which ion mobility gas chromatography is used, a technique that allows for identifying and quantifying the molecules responsible for unwanted odors. During extrusion, effective filtration can remove the remaining impurities, and careful temperature management prevents further degradation of the polymer.

Creating customized recipes based on the mechanical resistances required by different types of bottles is another critical step. Proper management of humidity during the packaging phases and adequate storage are essential to maintain the quality of the material until its transformation.

Blowing and packaging require additional precautions: verifying polymer mixes based on the shape and size of the bottle is crucial, as is controlling the temperatures and extrusion times. Tests on surface quality and the resistance of the full and loaded bottle help identify problems and causes, allowing for timely interventions.

Finally, a close collaboration between suppliers of recycled HDPE granules and bottle manufacturers is vital. This relationship allows for continuously refining the quality of the recycled material and anticipating problems that could compromise the final product.

In conclusion, although the use of recycled HDPE presents significant challenges, with careful monitoring and optimization of processes, it is possible to produce not only economically advantageous but also high-quality bottles that meet market needs and significantly contribute to environmental sustainability.

Automatic translation. We apologize for any inaccuracies. Original article in Italian.