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Molecular Origin of Strength and Stiffness in Bamboo Fibrils.

Youssefian S, Rahbar N - Sci Rep (2015)

Bottom Line: Good agreement was observed between the simulation results and experimental data.We also found out that the amorphous regions of cellulose microfibrils are the weakest interfaces in bamboo fibrils.Hence, they determine the fibril strength.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, Worcester Polytechnic Institute, Worcester, MA.

ABSTRACT
Bamboo, a fast-growing grass, has a higher strength-to-weight ratio than steel and concrete. The unique properties of bamboo come from the natural composite structure of fibers that consists mainly of cellulose microfibrils in a matrix of intertwined hemicellulose and lignin called lignin-carbohydrate complex (LCC). Here, we have used atomistic simulations to study the mechanical properties of and adhesive interactions between the materials in bamboo fibers. With this aim, we have developed molecular models of lignin, hemicellulose and LCC structures to study the elastic moduli and the adhesion energies between these materials and cellulose microfibril faces. Good agreement was observed between the simulation results and experimental data. It was also shown that the hemicellulose model has stronger mechanical properties than lignin while lignin exhibits greater tendency to adhere to cellulose microfibrils. The study suggests that the abundance of hydrogen bonds in hemicellulose chains is responsible for improving the mechanical behavior of LCC. The strong van der Waals forces between lignin molecules and cellulose microfibril is responsible for higher adhesion energy between LCC and cellulose microfibrils. We also found out that the amorphous regions of cellulose microfibrils are the weakest interfaces in bamboo fibrils. Hence, they determine the fibril strength.

No MeSH data available.


Related in: MedlinePlus

Hierarchical structure of bamboo.The vascular bundles in the parenchyma matrix are surrounded by supporting fibers which are known to be the source of remarkable mechanical properties of bamboo. Bamboo fibers have a hierarchical structure in which cellulose microfibrils reinforce the intertwined hemicellulose-lignin matrix. Linear chains of glucose with orderly hydrogen bonds form the crystalline regions of microfibrils while irregular hydrogen bonds create the amorphous regions. The cross section of these microfibrils is either rectangular or hexagonal.
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f1: Hierarchical structure of bamboo.The vascular bundles in the parenchyma matrix are surrounded by supporting fibers which are known to be the source of remarkable mechanical properties of bamboo. Bamboo fibers have a hierarchical structure in which cellulose microfibrils reinforce the intertwined hemicellulose-lignin matrix. Linear chains of glucose with orderly hydrogen bonds form the crystalline regions of microfibrils while irregular hydrogen bonds create the amorphous regions. The cross section of these microfibrils is either rectangular or hexagonal.

Mentions: Figure 1 presents the structure of bamboo fibers at different scales down to its building unit cell. The most abundant carbohydrate in bamboo fibrils is cellulose with the volumetric percentage around 73.83%. Cellulose microfibrils are formed by assembling linear chains of aldehyde sugars often referred to as glucose molecules, to make either rectangular or hexagonal cross sections with diameters of 3 to 5 nm1024. If the hydrogen bonds between the hydroxyl groups form in an order, highly ordered (crystalline) regions are formed. However, if random hydrogen bonds form, disordered (amorphous) regions develop1025. The positions of the hydroxyl groups determine the crystal system. These can be either triclinic or monoclinic unit cells (α or β type, respectively) with latter being the building block of plants such as bamboo. In a bamboo fiber, cellulose microfibrils are surrounded by lignin-carbohydrate complex (LCC) matrices that mainly contain lignin and hemicellulose with volumetric percentages of 10.50% and 12.49%, respectively.


Molecular Origin of Strength and Stiffness in Bamboo Fibrils.

Youssefian S, Rahbar N - Sci Rep (2015)

Hierarchical structure of bamboo.The vascular bundles in the parenchyma matrix are surrounded by supporting fibers which are known to be the source of remarkable mechanical properties of bamboo. Bamboo fibers have a hierarchical structure in which cellulose microfibrils reinforce the intertwined hemicellulose-lignin matrix. Linear chains of glucose with orderly hydrogen bonds form the crystalline regions of microfibrils while irregular hydrogen bonds create the amorphous regions. The cross section of these microfibrils is either rectangular or hexagonal.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4459167&req=5

f1: Hierarchical structure of bamboo.The vascular bundles in the parenchyma matrix are surrounded by supporting fibers which are known to be the source of remarkable mechanical properties of bamboo. Bamboo fibers have a hierarchical structure in which cellulose microfibrils reinforce the intertwined hemicellulose-lignin matrix. Linear chains of glucose with orderly hydrogen bonds form the crystalline regions of microfibrils while irregular hydrogen bonds create the amorphous regions. The cross section of these microfibrils is either rectangular or hexagonal.
Mentions: Figure 1 presents the structure of bamboo fibers at different scales down to its building unit cell. The most abundant carbohydrate in bamboo fibrils is cellulose with the volumetric percentage around 73.83%. Cellulose microfibrils are formed by assembling linear chains of aldehyde sugars often referred to as glucose molecules, to make either rectangular or hexagonal cross sections with diameters of 3 to 5 nm1024. If the hydrogen bonds between the hydroxyl groups form in an order, highly ordered (crystalline) regions are formed. However, if random hydrogen bonds form, disordered (amorphous) regions develop1025. The positions of the hydroxyl groups determine the crystal system. These can be either triclinic or monoclinic unit cells (α or β type, respectively) with latter being the building block of plants such as bamboo. In a bamboo fiber, cellulose microfibrils are surrounded by lignin-carbohydrate complex (LCC) matrices that mainly contain lignin and hemicellulose with volumetric percentages of 10.50% and 12.49%, respectively.

Bottom Line: Good agreement was observed between the simulation results and experimental data.We also found out that the amorphous regions of cellulose microfibrils are the weakest interfaces in bamboo fibrils.Hence, they determine the fibril strength.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, Worcester Polytechnic Institute, Worcester, MA.

ABSTRACT
Bamboo, a fast-growing grass, has a higher strength-to-weight ratio than steel and concrete. The unique properties of bamboo come from the natural composite structure of fibers that consists mainly of cellulose microfibrils in a matrix of intertwined hemicellulose and lignin called lignin-carbohydrate complex (LCC). Here, we have used atomistic simulations to study the mechanical properties of and adhesive interactions between the materials in bamboo fibers. With this aim, we have developed molecular models of lignin, hemicellulose and LCC structures to study the elastic moduli and the adhesion energies between these materials and cellulose microfibril faces. Good agreement was observed between the simulation results and experimental data. It was also shown that the hemicellulose model has stronger mechanical properties than lignin while lignin exhibits greater tendency to adhere to cellulose microfibrils. The study suggests that the abundance of hydrogen bonds in hemicellulose chains is responsible for improving the mechanical behavior of LCC. The strong van der Waals forces between lignin molecules and cellulose microfibril is responsible for higher adhesion energy between LCC and cellulose microfibrils. We also found out that the amorphous regions of cellulose microfibrils are the weakest interfaces in bamboo fibrils. Hence, they determine the fibril strength.

No MeSH data available.


Related in: MedlinePlus