Plastic bags that are consumed worldwide are made from low-density polyethylene (LDPE); a polymer used in food packaging and agriculture applications. One of the main characteristics of LDPE is its inertness, which despite being important for maintaining the stability of the packaged material, critically hinders the natural biodegradation of LDPE leading to long-term persistence within the environment. Herein, we present an energy-efficient high throughput pre-treatment of LDPE using a fast, reactive extrusion (REX) assisted oxidation technique followed by bacterial attachment as an indicator for bio-amenability. Silicon dioxide (SiO2) was selected as an oxidizing reagent. Optimized 5-minute duration pre-treatment conditions were determined using Box-Behnken design (BBD) with respect to screws speed, operating temperature, and concentration of SiO2. The crystallinity index, carbonyl index and weight loss (%) of LDPE were used as the studied responses for BDD. FTIR and DSC spectra of the residual LDPE obtained after pre-treatment with the REX assisted oxidation technique showed a significant increase in residual LDPE carbonyl index and a decrease of LDPE crystallinity index. Up to 5-fold molecular weight reductions were also demonstrated using gel permeation chromatography. Biofilms were successfully formed on pre-treated LDPE samples after 14 days of incubation. Furthermore, in the present study bioinert LDPE has been efficiently converted to bio-amenable LDPE using energy favorable, and industrially scalable, fast high throughput REX-assisted oxidation process. Such achievements give rise to a high potential route towards an industrially scalable post-consumer LDPE biodegradation.

Enhanced bio-amenability of low-density polyethylene via high throughput reactive extrusion assisted oxidation

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ACS Fall 2022

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