Researchers have developed a cushioning foam from cardboard waste. Their upcycled material is reportedly stronger and more insulating than traditional, plastic foam-based cushioning.

A new biodegradable foam with low density (0.065–0.081 g/cm3), high porosity (>92%), low thermal conductivity (0.044 W/mK), excellent mechanical properties, and outstanding cushioning properties was prepared by a simple green method using wastepaper without any chemical pretreatment as the raw material. The porous structure and the reinforced cell skeleton formed by the wastepaper fibers coupled with PVA and gelatin, respectively (“bridge-linking” and “membrane-linking” structure), give the foam excellent coordination between thermal insulation and energy absorption properties, which are typically considered incompatible with each other in conventional cushioning foam materials.

Furthermore, by impregnating a shear thickening fluid (STF) into wastepaper-based foam, a biodegradable cushioning packaging material with ultrahigh energy absorption for product delivery in extreme environments, such as parachute-free airdrops, was successfully prepared. The findings demonstrate that when the external impact velocity surpasses the critical shear rate of STF, the increased mass fraction and content of STF can enhance the energy absorption properties of the wastepaper-based foam, significantly enhancing its dynamic cushioning performance (STF can decrease the maximum impact acceleration by up to 85%).

Waste paper is one of the most common kinds of waste accumulated domestically. Newspapers and junk mail, but also paperboard envelopes and cardboard boxes can often be found in abundance, as e-commerce shopping continues to be popular.

The researchers wanted to turn these containers and paper waste into sturdy but light mailing materials. Currently, to keep electronics and toys nestled tightly inside a box, molded cushioning materials, such as styrofoam, are typically used.

A sustainable alternative could be lightweight cellulose aerogels, but current methods to produce them from waste paper require several chemical pretreatment steps.

Therefore, Jinsheng Gou, associate professor at the Beijing Forestry University and visiting associate professor at the University of British Columbia, and colleagues wanted to find a simpler way to make a wastepaper-based foam material that could withstand rough packaging deliveries.

Stronger than plastic foams

To create the foam, the team broke down cardboard scraps in a blender to create a pulp, then mixed it with either gelatin or polyvinyl acetate (PVA) glue. The mixtures were poured into molds, refrigerated, then freeze-dried to form cushioning foams.

The paper-based foams served as good thermal insulators and strong energy absorbers — even better than some plastic foams, the scientists found. The team then created a heavy-duty version of their waste paper foam by combining the pulp, gelatin, PVA glue and a silica-based fluid that hardens as force is applied.

The cardboard-based foam withstood hits from a hammer without falling apart. The foam could be used in force-intensive deliveries, such as parachute-free airdrops, according to the researchers. The scientists say their work offers a simple yet efficient method to upcycle cardboard to create more environmentally sustainable packaging materials.

The study was published in ACS Sustainable Chemistry & Engineering.