May 13, 2022

Mass production of recyclable bioplastics possible with cellulose

A new publication in the journal ACS Applied Polymer Materials describes a simple, large-scale preparation technique for producing high-performance cellulosic bioplastic films made from chemically compatible double-crosslinked (CMF) carboxymethylated cellulose fibers.

Study: Large-scale manufacturing of recyclable bioplastics from renewable cellulosic biomass derived from softwood kraft pulp. Image credit: Marco Lazzarini/Shutterstock.com

The accumulation of synthetic polyester on the planet has posed a danger to the ecology. Due to its advantageous recyclability, optical clarity and resource availability, cellulose film has recently become one of the most attractive alternatives to petroleum-based polymers.

Typical methodologies for manufacturing cellulose films, such as vacuum filtration and solution casting, however, are time consuming and expensive to industrialize. Moreover, these films still have poor water resistance and mechanical properties under high humidity conditions, which makes them unsuitable for real-world applications.

Cellulose: an important bioplastic

Plastics, made up of many petroleum compounds, play an essential role in human existence and in industry. However, due to their non-biodegradability and complicated sewage disposal, ever more pollutants have accumulated on our planet and have gradually seeped into the food supply, creating serious health and environmental consequences. environment.

Researchers have suggested the notion of “bioplastics” to completely replace polymers derived from petrochemicals to overcome such a dilemma.

Bioplastics derived from biomass-derived materials can reduce gasoline dependence, increase energy stability, and reduce carbon dioxide and plastic particulate pollutants.

Additionally, cellulose, the most common biomass generated from trees and plants on the planet, has been widely used to make traditional writing and paper products, as well as food and commodity packaging. .

Cellulose is a complex carbohydrate made up of hundreds or even thousands of glucose units that create a long chain when they connect.

Benefits and Applications of Cellulose Derivatives

Chemically synthesized cellulose compounds, such as cellulose nanofibers (CNF), cellulose nanocrystals (CNC), and others, can be made by reacting the hydroxyl groups of cellulose with different chemicals either partially or completely.

These cellulose compounds have been excellent choices to replace petrochemical-based plastic in packaging applications, building components, and electrical interfaces due to their recyclable, disposable, and environmentally friendly qualities.

In recent years, two main strategies to produce cellulose-based bioplastics have attracted a lot of interest: (1) the insertion of CNF or CNC as reinforcements in polymer matrices to improve the thermomechanical characteristics of composites.

(2) Manufacture of nanocellulose-based films directly using solution casting, vacuum filtering, vapor deposition and other methods.

Limits of nano-cellulose based films

However, nanocellulose’s strong attraction to water droplets can lead to limited dehydration and drying efficiency, as well as inadequate mechanical characteristics under high humidity.

Manufacturing a nanocellulose-based film takes several hours or more, which is time-consuming and expensive.

Despite the growing interest in disposable nano- and/or molecular cellulose, improving operational efficiency, mechanical properties and aqueous durability in the field of environmentally friendly biomaterials remains a challenge.

Accordingly, it is crucial to establish a simple, rapid, and large-scale technique for manufacturing biomaterials from abundant renewable natural sources, in which the finished version must be structurally sound and reliable in high humidity while being completely transparent. and environmentally friendly. , thus promoting the industrial growth of bioplastics.

A new process for manufacturing bioplastic films

The researchers presented an efficient and traditional paper production technique that can produce a robust, transparent and water-resistant bioplastic sheet to meet these criteria.

They focused on often overlooked micron cellulose fibers, which hold more promise for large-scale industrial manufacturing.

This method involves the rapid production of CMF and the adhesion of the electrostatic forces of Al3+ ions and PAE monomers to the CMF fibers, resulting in a homogeneous solution that can be easily formed into a film using traditional papermaking techniques. .

During the hot pressing and drying stages, bendable PAE plastics undergo both covalent crosslinking with cellulose fibers and a self-crosslinking process between PAE components.

Research results and conclusion

The resulting bioplastic sheet has good tensile strength (158.2 MPa), high water durability, increased wet strength, better optical efficiency, and exceptional thermal reliability, among other properties.

Significantly, this CMF-based bioplastic film can be mechanically disintegrated and recycled, allowing the substance to be recycled throughout the production cycle.

Moreover, the mechanical characteristics of the re-prepared CMF-based film using recovered sludge reached 145.9 MPa, which was hardly reduced compared to the initial films.

This simple, large-scale, and environmentally friendly manufacturing approach can lead to the development of bioplastic sheeting for the construction and manufacturing industries.

Reference

Chunfa Lei. et al. (2022). Large-scale manufacturing of recyclable bioplastics from renewable cellulosic biomass from softwood kraft pulp. ACS Applied Polymer Materials. Available at: https://pubs.acs.org/doi/10.1021/acsapm.1c01729

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