Upcycling leftover cardboard to make a new type of foam packaging
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THIS CARDBOARD-BASED FOAM REINFORCED WITH GELATIN COULD MAKE PACKAGING MATERIALS MORE SUSTAINABLE.
view moreCREDIT: JINSHENG GOU
With the holiday season in full swing, gifts of all shapes and sizes are being shipped around the world. But all that packaging generates lots of waste, including cardboard boxes and plastic-based foam cushioning, such as Styrofoam™. Rather than discard those boxes, researchers publishing in ACS Sustainable Chemistry & Engineering developed a cushioning foam from cardboard waste. Their upcycled material was stronger and more insulating than traditional, plastic foam-based cushioning.
Among the many kinds of trash that accumulate within a home, wastepaper is one of the most common. Everything from newspapers and junk mail to paperboard envelopes and cardboard boxes can pile up, especially as internet shopping has exploded in popularity. Researchers are interested in turning these containers and paper waste into something else that’s useful — sturdy but light mailing materials. Currently, to keep electronics and toys nestled tightly inside of 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 wastepaper require several chemical pretreatment steps. So, Jinsheng Gou and colleagues wanted to find a simpler way to make a wastepaper-based foam material that could withstand the roughest of deliveries.
To create their 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. Both paper-based foams served as good thermal insulators and strong energy absorbers — even better than some plastic foams. The team then created a heavy-duty version of their wastepaper foam by combining the pulp, gelatin, PVA glue, and a silica-based fluid that hardens as force is applied. This version of the cardboard-based foam withstood hits from a hammer without falling apart, and that result suggests the foam could be used in force-intensive deliveries, such as parachute-free airdrops. The researchers say their work offers a simple yet efficient method to upcycle cardboard to create more environmentally friendly packaging materials.
The authors acknowledge funding from the Beijing Key Laboratory of Wood Science and Engineering.
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JOURNAL
ACS Sustainable Chemistry & Engineering
ARTICLE TITLE
Biodegradable Wastepaper-Based Foam with Ultrahigh Energy-Absorbing, Excellent Thermal Insulation, and Outstanding Cushioning Properties
Researchers find way to weld metal foam without melting its bubbles
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COMPOSITE METAL FOAMS (CMFS) ARE FOAMS THAT CONSIST OF HOLLOW, METALLIC SPHERES – MADE OF MATERIALS SUCH AS STAINLESS STEEL OR TITANIUM – EMBEDDED IN A METALLIC MATRIX MADE OF STEEL, TITANIUM, ALUMINUM OR OTHER METALLIC ALLOYS. THE RESULTING MATERIAL IS BOTH LIGHTWEIGHT AND REMARKABLY STRONG, WITH POTENTIAL APPLICATIONS RANGING FROM AIRCRAFT WINGS TO VEHICLE ARMOR AND BODY ARMOR. IN ADDITION, CMF IS BETTER AT INSULATING AGAINST HIGH HEAT THAN CONVENTIONAL METALS AND ALLOYS, SUCH AS STEEL. THE COMBINATION OF WEIGHT, STRENGTH AND THERMAL INSULATION MEANS THAT CMF ALSO HOLDS PROMISE FOR USE IN STORING AND TRANSPORTING NUCLEAR MATERIAL, HAZARDOUS MATERIALS, EXPLOSIVES AND OTHER HEAT-SENSITIVE MATERIALS. BUT TO REALIZE MANY OF THESE APPLICATIONS, MANUFACTURERS WOULD NEED TO WELD MULTIPLE CMF COMPONENTS TOGETHER. AND TRADITIONAL WELDING TECHNIQUES MELT THE BUBBLES THAT MAKE CMF DESIRABLE. RESEARCHERS HAVE NOW SHOWN THAT A TECHNIQUE CALLED INDUCTION WELDING, THAT RELIES ON ELECTROMAGNETIC FIELDS, CAN WELD CMFS WITHOUT IMPAIRING THE BUBBLES IN THE FOAM. THIS ILLUSTRATION SHOWS HOW IT WORKS. NOTE THAT THE CMF IS COOL ENOUGH TO TOUCH WITH YOUR BARE HAND, ONLY INCHES AWAY FROM THE SITE OF THE WELD.
view moreCREDIT: AFSANEH RABIEI, NC STATE UNIVERSITY
Researchers at North Carolina State University have now identified a welding technique that can be used to join composite metal foam (CMF) components together without impairing the properties that make CMF desirable. CMFs hold promise for a wide array of applications because the pockets of air they contain make them light, strong and effective at insulating against high temperatures.
CMFs are foams that consist of hollow, metallic spheres – made of materials such as stainless steel or titanium – embedded in a metallic matrix made of steel, titanium, aluminum or other metallic alloys. The resulting material is both lightweight and remarkably strong, with potential applications ranging from aircraft wings to vehicle armor and body armor.
In addition, CMF is better at insulating against high heat than conventional metals and alloys, such as steel. The combination of weight, strength and thermal insulation means that CMF also holds promise for use in storing and transporting nuclear material, hazardous materials, explosives and other heat-sensitive materials.
However, in order to realize many of these applications, manufacturers would need to weld multiple CMF components together. And that has posed a problem.
“Traditional fusion welding uses a filler to connect two pieces of metal,” says Afsaneh Rabiei, corresponding author of a paper on the new research and professor of mechanical and aerospace engineering at NC State. “This is problematic, because the metal being melted to fuse two pieces of CMF is solid, so it lacks the desirable properties of the CMF on either side of it. In addition, any type of welding that uses direct heat to melt the metal results in some of the porosity in the CMF being filled in, which impairs its properties. In short, that means that most forms of traditional welding don’t work well with metal foams.”
However, the researchers have now identified a form of welding that works very well. It’s called induction welding, and it uses an induction coil to create an electromagnetic field that heats the metal for welding.
“Because CMF is only 30-35% metal, the electromagnetic field is able to penetrate deeply into the material – allowing for a good weld,” Rabiei says. “The air pockets that make up the remaining 65-70% of the CMF serve to insulate the material against the heat. This allows induction welding to heat up the targeted area for joining two pieces of CMF, but prevents the heat from spreading out from the site of the join. That helps to preserve the CMF’s properties.
“This is an important step forward, because CMF’s properties make it attractive for a wide range of applications, but it’s essential to have a means of welding the CMF components without impairing the properties that make it attractive in the first place.”
The paper, “A Study on Welding of Porous Metals and Metallic Foams,” is published in the journal Advanced Engineering Materials. The paper was co-authored by John Cance and Zubin Chacko, Ph.D. students at NC State. The work was done with support from the U.S. Department of Transportation’s Pipeline and Hazardous Materials Safety Administration, under grant number PH957-20-0075.
JOURNAL
Advanced Engineering Materials
METHOD OF RESEARCH
Experimental study
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
A Study on Welding of Porous Metals and Metallic Foams
ARTICLE PUBLICATION DATE
16-Nov-2023
COI STATEMENT
Afsaneh Rabiei is the inventor of composite metal foams. She has assigned her related IP to a small business in which she is a shareholder.
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