Research: Effect of antioxidant and compatibilizer on gel and heat sealing performance of recycled PE packaging film

The challenge of film quality brought about by the increase in recycled material content

In the field of packaging materials, increasing the recycled material content is an important path to achieve circular packaging. However, packaging films made from post industrial or post consumer recycled polyethylene (PCR PE) often have appearance and mechanical problems due to impurities and degradation, which affect their performance. A study published in Packaging Technology and Science investigated the existence of gel, heat sealing characteristics and quality fluctuations caused by batch differences around 100% single-layer PCR PE film and multi-layer commercial PE film with 30% and 50% PCR PE in the core layer and new materials in the surface layer and heat sealing layer.

Detection methods and main findings

The study used FTIR, microscope and a newly introduced image analysis method to analyze the existence and area proportion of recycled gel; Evaluate heat sealing performance through hot and cold bonding tests, and assess material properties through tensile testing. The FTIR results showed that among the impurities from PCR PE, the spherical impurities were polyamide based and the fibrous impurities were cellulose based. In non food contact commercial films containing PCR PE, the quality varies greatly with batch, and there are also significant fluctuations in the strength of heat sealing and cold sealing. In the 100% PCR PE film prepared in the laboratory, the addition of antioxidant during film formation has no significant effect on the existence of gel; A certain maleic anhydride based (MAH) compatibilizer used in the study reduced the number of gel from 432 pcs/9 cm ² to 375 pcs/9 cm ², and the proportion of gel area from 0.81% to 0.67%. Both additives delayed fracture failure in thermal bonding testing, providing a larger operating window. In the cold bonding test, the sample with added compatibilizer showed stronger sealing interface bonding at a sealing temperature of 100 ° C. The tensile test results showed that after adding antioxidants and compatibilizers, there was only a slight change in the Young’s modulus and elongation at break.

Significance for the polymer additive industry

This study provides a reference process and formulation ideas for the design of PE films containing recycled materials.

. For packaging materials, processing stability and food contact compliance are key considerations in the application of recycled materials: antioxidants play a role of processing stability in the film forming process, helping to inhibit degradation, but this study shows that their use alone has limited improvement in the number of gel; Maleic anhydride based compatibilizer shows more direct effect in reducing gel and improving heat sealing window. It is worth noting that the batches of non food contact commercial films involved in the study fluctuated greatly, indicating that the source of recycled materials and batch management have a significant impact on the final film quality. For film manufacturers who wish to increase the dosage of recycled materials, a reasonable combination of antioxidants and compatibilizers, and verification of hot and cold bonding process windows may be a feasible direction to balance processing stability, heat sealing performance, and mechanical properties. The study also pointed out that the relevant results can serve as a guiding basis for the recycling and design of PE films.

Information source:Effect of Antioxidants and Compatibilizers on Gel Formation and Film Quality of Polyethylene Films With Recycled Content， Organized by Herun Chemical.