Post-consumer Recycled Polyethylene Research Articles

The effect of post-consumer recycled polyethylene (PCRPE) on the properties of polyethylene blends of different densities

Polyethylene (PE), a versatile polymer present nearly everywhere, poses many challenges as more of it becomes terrestrial and marine waste and used for everything from packaging such as plastic bag production (LDPE) to construction pipes (HDPE). As more companies are required to follow government regulations and consumers’ requests to produce more sustainable products, the general interest in PE recycling continues to gain momentum. Several processes have been developed to recycle PE, but current data gaps exist on the impact of adding post-consumer recycled polyethylene (PCRPE) to different virgin feedstocks on final product performance. To better understand this impact, a single source of PCRPE was melt blended with four different virgin PE grades at different concentrations (0, 20, 40, 60, 80, and 100 wt% of PCRPE), and changes in the physical, thermal, and mechanical properties were evaluated. Different trends and behaviors were observed depending on the PE density, however, most properties still followed the Law of Mixtures. For example, low-density PE's mechanical strength improved up to 70% increase in tensile modules and 56% in yield strength. The density was increased by ~5%, and no toxic heavy metals (Cd, Cr, Hg, Pb) were found, with less than 4 ppm of Al, Fe, and Ti detected. The insights obtained when mixing polyethylene of different densities with a single recycled grade PE allows plastic manufacturers and recyclers to gain a more comprehensive view of possibilities associated with PCRPE. The results presented herein and previously from our group suggest most physical properties of PCRPE blends follow the Law of Mixtures, enabling the possibility for performance property predictive modeling of different compositions by understanding properties from the virgin and PCR materials alone. The introduction of PCRPE blends also reduces costs by tailoring products to optimal performance and maximum recycled content.

Post-consumer Recycled PET Packaging for Fresh Berries: A Comparative Study between Incorporating an Antifungal Agent Superficially and into the Main Body of the Packaging

This study proposes to incorporate an antifungal agent (potassium sorbate, KS) to post-consumer recycled polyethylene terephthalate (PCRPET), by adding KS to the dip solution through which PCRPET normally passes after extrusion, in order to acquire a non-stick silicone coating, which prevents individual packages from adhering to each other while stacked. This method of imparting antifungal activity to the packaging is far more advantageous than adding KS to the extruder feed because it results in virtually no alterations to the colour and mechanical properties of PCRPET, which is a major issue when KS is added to the extruder feed. The antifungal efficacy of the active packaging was demonstrated against Botrytis cinerea growth by a novel method which mimics the action of the antifungal agent under fruit contact conditions. A reduction by 2 log cycles was observed when the initial concentration of the mould was 105 conidia/mL. The active packaging was effective over a test period lasting 6 months. The packaging microstructure was visualized by scanning electron microscopy (SEM); its thermal properties were characterized using a differential scanning calorimeter (DSC); its optical properties were characterized using CIE Lab colorimetry; and its mechanical properties were characterized by measuring resistance to dynamic compression. The mechanical properties showed no significant difference (P > 0.05) with those of the control (PCRPET without KS), and despite a statistically significant difference (P < 0.05) in the colour parameters (L*, a* and b*), the total colour difference (ΔE*) was found to be too small to be visually noticed. This study achieved the aim of adding antifungal activity to PCRPET packaging with little or no perceptible changes to its mechanical, thermal and optical properties and virtually no changes being made to the standard high-speed packaging production line.

Migration of Residual Nonvolatile and Inorganic Compounds from Recycled Post-Consumer PET and HDPE

Migration of nonvolatile and inorganic residual compounds from post-consumer recycled polyethylene terephthalate (PET) submitted to cleaning processes for subsequent production of materials intended to food contact, as well as from multilayer packaging material containing post-consumer recycled high-density polyethylene (HDPE) was determined. Tests were carried out using food simulants. Nonvolatile organic contaminants from PET, determined by liquid chromatography-mass spectrometry (UPLC-QqQ/MS), showed significant migration reduction as consequence of the more complex cleaning technologies applied. However, contaminants not allowed by Brazilian and European Union regulations were identified even in deep cleaning samples. Results from multilayer HDPE showed a greater number of contaminants when compared to recycled pellets. Inorganic contaminants, determined by inductively coupled plasma mass spectrometry were below the acceptable levels. Additional studies for identification and quantitation of unknown molecules which were not possible to identify in this study by UPLC-QqQ/MS are required to ascertain the safety of using post-consumer recycled packaging material.