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Flame-Retardant Transparent Bamboo Outperforms Silica Glass

Central South University of Forestry and Technology (CSUFT) faculty members Yiqiang Wu and Caichao Wan and team developed a novel transparent material made from natural bamboo. With its three-layered flame-retardant barrier, this novel material effectively reduces heat release, slows the spread of flames, and limits the emission of toxic smoke, CO, and flammable volatiles. The results were published in the journal Research.

Flame-Retardant Transparent Bamboo Outperforms Silica Glass
Researchers have developed a novel flame-retardant, smoke-suppressing, and superhydrophobic transparent bamboo, poised as a promising substitute for silica glass. Image Credit: Research

Over the past 50 years, silica glass, a transparent material widely used in the construction industry, has seen increased adoption as a necessary building material. It is versatile, demonstrated by the fact that glass production will reach about 130 million tons worldwide in 2020.

Despite its numerous advantages, such as high transparency and the availability of raw materials, traditional silica glass still grapples with challenges, including brittleness, high density, and substantial CO2 emissions and greenhouse gases during the manufacturing process.

Caichao Wan, Full Professor and Corresponding Study Author, College of Materials Science and Engineering, Central South University of Forestry and Technology

Transparent wood products have gained a lot of attention lately because of their exceptional qualities, which include high transparency, superior mechanical strength, and superior thermal insulation. In addition to positively affecting the environment, transparent wood has enormous potential as a competitive substitute for conventional glass materials.

However, there are several restrictions related to using translucent wood:

  • The lack of wood worldwide, especially in China, presents a problem; even with initiatives to boost output through plantations, it is anticipated that the need for industrial roundwood will be in greater demand by 2050.
  • Incorporating polymers into transparent wood renders it highly susceptible to fire, potentially posing a significant hazard.
  • There exists a necessity to advance the functional properties of transparent wood beyond its fundamental optical and mechanical characteristics.

Wan said, “Bamboo, often referred to as ‘the second forest,’ boasts a fast growth and regeneration rate, allowing it to reach maturity and be utilized as a building material within 4 to 7 years of growth. With an output four times higher than wood per acre, bamboo is recognized for its exceptional efficiency.”

In terms of chemical composition, bamboo shares similarities with wood, mainly consisting of lignin, cellulose, and hemicellulose. Furthermore, the internal hierarchical structure of bamboo closely resembles that of wood, featuring high porosity and permeability because of neatly arranged vertical channels. This characteristic suggests the potential use of bamboo in the production of transparent composite materials.

Y. Yang, Ph.D. Student and Study Lead Author, Central South University of Forestry and Technology

The team's solution is to use a simple and effective vacuum-impregnation technique to impregnate an inorganic liquid sodium silicate (Na2O·nSiO2) into the delignified bamboo structure. The intermediate product is then subjected to a hydrophobic treatment.

Wan said, “Through this strategy, we can build a 3-layered flame-retardant barrier comprising a top silane layer, an intermediate layer of SiO2 formed through hydrolysis–condensation of Na2SiO3 on the surface, and an inner layer of Na2SiO3. This strategy achieves a long ignition time of 116 s, low total heat release of 0.7 MJ/m2, low total smoke production of 0.063 m2, and low peak CO concentration of 0.008 kg/kg.”

The exceptional mechanical properties of the transparent bamboo are evidenced by its extraordinarily high bending and tensile moduli, which reached 7.6 ± 1.3 and 6.7 ± 1.1 GPa, respectively.

As a result of its remarkable fog value of 96.7 % and high light transmittance of 71.6 %, transparent bamboo exhibits the potential to function as a light management layer when utilized as a substrate for perovskite solar cells. This could result in a notable increase in power conversion efficiency of 15.29 %.

They are happy that this finding allows for the use of green flame-retardant glass and optical devices.

In the future research, we will focus on the large-scale fabrication and multi-functionalization of this transparent bamboo,” adds Wan.

Journal Reference:

Su, J., et al. (2024) A Novel Flame-Retardant, Smoke-Suppressing, and Superhydrophobic Transparent Bamboo. Research.


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