Biodegradable wood pulp derived glitter could “revolutionize cosmetics industry,” researchers find

24 Jan 2022 --- As glitter is made from toxic and unsustainable materials that contribute to plastic pollution, researchers from the University of Cambridge have examined a way to make non-toxic and biodegradable glitter from cellulose.

Speaking with PersonalCareInsights, Dr. Benjamin Droguet, postdoctoral researcher at the University of Cambridge, details how cellulose from wood pulp can make glitter that can be used in the cosmetic industry.

“The glitter and pigments we developed are only made from a single ingredient common in plants – cellulose.”

“More precisely, we used the crystalline part of the cellulose molecule because it forms a structure that can interact with light to make a color. Butterflies, birds and beetles use the same principle (light interaction with a tiny structure) to appear colorful,” explains Droguet.

Silvia Vignolini, professor at Cambridge's Yusuf Hamied department of chemistry, says the researchers “believe this product could revolutionize the cosmetics industry by providing a fully sustainable, biodegradable and vegan pigment and glitter.”

Echoing this, Drogue notes: “The sustainability credentials of the products we developed tick many of the boxes the beauty sector is looking into.”

Replacing plastic glitter particles
According to the researchers, in Europe, the cosmetics industry uses about 5,500 tons of microplastics every year.

Using self-assembly techniques that allow the cellulose to produce intensely-colored films, the researchers say their materials could replace the plastic glitter particles and tiny mineral effect pigments widely used in cosmetics.The glitter is made from cellulose nanocrystals, which can bend light in such a way as to create vivid colors through a process called structural color.

“Fabricated particles with a similar color vibrancy to animals and plants come in a variety of sizes, from a few millimeters down to a diameter in the order of tens of microns (about the width of a hair), meaning that these particles can be used both as glitters and as shiny effect pigment particles used in many cosmetic products,” adds Droguet.

Understanding cellulose nanocrystals
The films of cellulose nanocrystals prepared by the research team can be made at scale using roll-to-roll processes like those used to make paper from wood pulp.

“As of today, these nanocrystals are extracted at an industrial scale from wood pulp using acid hydrolysis. After dialysis to separate the acid, the cellulose nanocrystals can be retrieved as a colloidal suspension,” explains Drogue.

The cellulose nanocrystals are dispersed in ultrapure water. Therefore, the drying process occurs over several hours as no organic solvent was used, he continues.

“Under the right colloidal condition and upon removal of the solvent (drying), the nanocrystals will spontaneously assemble into helicoidal, chiral nematic structures. What happens during drying is that the cellulose nanocrystals pact closely follow the law of thermodynamics to form this ordered structure.”

By carefully optimizing the cellulose solution and the coating parameters, the research team could fully control the self-assembly process to make the material on a roll-to-roll machine.The cellulose from wood pulp can be transformed into shiny, colorful materials, which could replace toxic pigments used in cosmetics.

The researcher’s process is compatible with existing industrial-scale machines. Using commercially available cellulose materials transformed into suitable liquid suspension in just a few steps, the team showed continuous deposition and drying of the cellulose-containing suspension on a commercial roll-to-roll machine.

Formulating cellulose fibers
The nanocrystals of cellulose are slender rods with lengths of 150 to 200 nm (nanometer) and widths usually smaller than 10 nm, explains Drogue.

“Cellulose fibers are made of these crystals held together by more amorphous and disordered domains. You can retrieve these nanocrystals from cellulose-rich materials – wood, cotton, but also agricultural waste and cotton linter, for example.”

“The self-assembly of the cellulose nanocrystals into helicoidal, chiral nematic structure is triggered upon the evaporation of the solvent,” details Drogue. “Upon solvent removal, the cellulose nanocrystals pact closely following the law of thermodynamics and further assemble spontaneously into this chiral nematic architecture.”

After producing the large-scale cellulose films, the researchers ground them into particles of the size used for making glitters or effect pigments.

By Nicole Kerr