Upcycling of Waste Polymer Using Surface Modified Hemp Derived Biochar Carbon for Sustainable Packaging Applications

Out of 300 million tons of plastics produced globally, only 10% are being recycled. Due to this, there is always a demand for alternative, effective methods to cope with this low recycling rate of plastics. This work demonstrates such an effective technique for recycling high-density polyethylene (HDPE) wastes, incorporating biochar synthesized from postharvest hemp crop residue as fillers. Generally, carbon-based materials are considered to have inert surface properties. However, hemp-derived carbon was successfully functionalized in this work using low-temperature plasma (LTP) treatment in the presence of sulfur hexafluoride (SF6) gas. Changes such as the presence of fluorine functional groups and alterations in the surface morphology, which resulted in surface area enhancement, were observed with the LTP treatment. An X-ray diffraction study of the carbon samples revealed the formation of a new peak at 18.98°, which corresponds to the [002] lattice planes because of the LTP treatment. The presence of fluorine in the LTP-treated carbon samples was confirmed with X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The composite films reinforced with LTP-treated carbon had a significant increase in crystallinity percentage and mechanical properties compared to those of films reinforced with untreated carbon. The HDPE/carbon films loaded with 1 wt % of LTP-treated carbon had superior mechanical and thermal properties compared to the rest of the samples. Compared to HDPE films without any carbon fillers, the HDPE/carbon films loaded with 1 wt % LTP-treated carbon significantly improved elastic modulus and maximum tensile strength by around 3.4 times and 3.7 times, respectively. However, when compared to the neat HDPE film, there was a significant drop in the ability to strain with the LTP-treated, carbon-loaded film samples. The overall crystallinity of HDPE increased by a maximum of 43.8% by the addition of LTP-treated carbon. The LTP treatment was found to be effective in enhancing the interfacial adhesion of carbon and its interaction with the HDPE matrix.