Abstract
Worldwide use and disposal of plastics have reached a dramatic saturation point, polluting lands, oceans, and air across the globe. Responding to such a challenge requires, among other environmental remediation measures, the manufacture of alternative sustainable plastics. Recent studies in the area have enabled the development of degradable plastics; however, the rate and conditions required for the degradation of such materials remains under scrutiny. Here, we introduce a new class of fully plant-based, rapidly degradable lignin and zein composite blend that can be transformed into macroscopic structures using extrusion three-dimensional (3D) printing. Corn-derived zein forms the polymeric solution, while insoluble lignin granules act as a binder for enhanced printability and facile degradation. The blend showcases a shear-thinning behavior that is ideal for rapid extrusion printing into desired 3D structures, from cuvette caps to circuit boards. Biodegradation studies show that common bacteria readily found in soil and compost are able to decompose structures made with the lignin–zein composite in shorter time frames compared to a known biodegradable plastic, viz., polylactic acid. The rapid biodegradability and enhanced processability highlight the potential of lignin–zein composites to decrease our dependence on petroleum oil-based plastics.
Highlights
Plastics are the backbone of modern manufacturing with 8300 million metric tons produced worldwide from 1950 to 2015.1 only 9% of plastic in the world is recycled, and the vast majority is discarded into the environment after use.[1,2] Most plastics are synthesized using petroleum oil and, when discarded in nature, do not decompose readily and are expected to persist even at geological timescales.[3]
We find that the printed lignin−zein composite (LZC) is an insulator and is stable at elevated temperatures up to 120 °C (Figure S8 and Movie S2); we anticipate that LZCs can be an alternative to non-degradable thermoplastics for manufacturing biodegradable circuit boards.[58]
We presented a strategy to synthesize a new class of 3D printable, bio-based LZC, which degrades in the presence of model bacteria commonly found at waste sites
Summary
Plastics are the backbone of modern manufacturing with 8300 million metric tons produced worldwide from 1950 to 2015.1 only 9% of plastic in the world is recycled, and the vast majority is discarded into the environment after use.[1,2] Most plastics are synthesized using petroleum oil and, when discarded in nature, do not decompose readily and are expected to persist even at geological timescales.[3]. Recent trends in the development of sustainable manufacturing have pointed toward plant-based, biodegradable materials as precursors to move society toward a more circular economy.[10−13] Such materials should be designed to be sourced with biomass that is renewable and decentralized and to be destined for biodegradation into small molecules at the end of their lifecycle.[14,15] For example, polylactic acid (PLA) has garnered considerable attention as a biodegradable alternative in the packaging industry.[16] Despite its reputation, PLA shows no significant degradation in artificial sea and fresh water.[17,18] PLA-based materials require bio-augmented soils with specific microbial characteristics for complete degradation.[19] To address the challenge of material sustainability, alternatives should be derived from naturally occurring precursors that can be produced inexpensively at a large scale with low carbon impact.[20] Concurrently, these materials must rapidly decompose upon release into the environment. We introduce a new class of a lignin−zein composite (LZC) that can be processed into macroscopic materials using three-dimensional (3D) printing and shows rapid degradation by commonly found bacteria under ambient conditions
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