Cellulose Nanocrystals Used to Develop Wood-Based Foam for Cooler Buildings, Robust Materials for Different Environments

Researchers have recently designed a lightweight foam made from wood-based cellulose nanocrystals, reflecting sunlight, emitting absorbed heat, and thermally insulating.

As indicated in a Phys.org report, it's almost summer, the season when many people are trying to beat the heat, but running air condition units constantly can be costly, not to mention wasteful.

In this new research, the study authors have suggested that material could decrease the cooling energy of buildings by more than one-third.

Even though scientists have developed cooling materials, such inventions have disadvantages. Some materials passively releasing absorbed heat are letting a lot of heat through buildings and structures under the direct, midday sun of the summer months.

Cooling Material Produced

Other materials which are reflecting sunlight do not work well in humid, cloudy, or hot weather. Therefore, Yu Fu and Kai Zhang, together with colleagues, wanted to develop a strong material that could reflect sunlight, passively emit heat, and keep errant heat from passing through.

To produce a cooling material, the study authors connected cellulose nanocrystals together with a silence bridge, prior to the freezing and freeze-drying of the material under a vacuum.

This process aligned the nanocrystals vertically, creating a white, lightweight foam that reflected 96 percent of visible light and emitted 92 percent of absorbed infrared radiation.

When the material was placed over a box lined with an aluminum foil sitting outdoors at noon, it kept the temperature inside the box at 16 degrees Fahrenheit, cooler than the temperature outside it.

Cellulose-Based Foam

The materials also kept the temperature inside the box 13 degrees Fahrenheit cooler when the air was humid. As the cellulose-based foam was compressed, there was a drop in its cooling ability, demonstrating tunable cooling properties.

In their study published in the Nano Letters journal, the team estimated that placing the foam on the exterior walls and roofs of a building could decrease its cooling energy needs by an average of 35.4 percent.

Since the performance of the wood-based cellulose can be tuned according to weather conditions, the researchers said the technology could be employed in a wide range of environments.

Cellulose Nanocrystals

A report published in ScienceDirect describes cellulose nanocrystals as representing the "crystalline regions extracted from cellulose nanocrystals, primarily by strong acid hydrolysis at increased temperature.

CNCs are characterized by extraordinary properties of "high aspect ratio, high surface area, high mechanical strength, and liquid crystalline nature," the same report specifies.

Essentially, CNCs' crystalline nature is mainly obtained from naturally-occurring cellulose fibers by the elimination of amorphous segments from renewable resources through strong acid hydrolysis.

Consequently, the obtained CNCs offer low-cost sustainable, and eco-friendly materials for diverse applications.

Hydrophilic in Nature

Basically, CNCs are hydrophilic in nature, although they can be functionalized with a diversity of materials to satisfy challenging requirements, including high-performance composites and hydrophobic polymer matrices.

As they are nearly detect-free, the cellulosic nanocrystals' modulus is close to the theoretical restriction for cellulose. It is potentially more robust than steel and akin to Kevlar.

Related information about cooling materials is shown on Maryland Nanocenter's YouTube video below:

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