Natural Nanofibres for Composite Applications
Cellulose and chitin are the two most abundant natural polysaccharides. Both have a semicrystalline microfibrillar structure from which nanofibres can be extracted. These nanofibres are rod-like microcrystals that can be used as nanoscale reinforcements i
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stract Cellulose and chitin are the two most abundant natural polysaccharides. Both have a semicrystalline microfibrillar structure from which nanofibres can be extracted. These nanofibres are rod-like microcrystals that can be used as nanoscale reinforcements in composites due to their outstanding mechanical properties. This chapter starts by reviewing the sources, extraction methods and properties of cellulose and chitin nanofibres. Then, their use in the fabrication of structural and functional nanocomposites and the applications that have been investigated are reviewed. Nanocomposites are materials with internal nano-sized structures. They benefit from the properties of the nanofillers: low density, nonabrasive, nontoxic, low cost, susceptibility to chemical modifications and biodegradability. Diverse manufacturing technologies have been used to produce films, fibres, foams, sponges, aerogels, etc. Given their natural origin and high stiffness, these polymers have attracted a lot of attention not only in the biomedical and tissue engineering fields but also in areas such as pharmaceutics, cosmetics, agriculture, biosensors and water treatment.
1 Introduction Nanocomposites are polyphasic1 materials where the reinforcement has at least one dimension in the nanometre range (1–100 nm). Nanoscale reinforcements present high aspect ratio and high surface-to-volume ratio, which ensure optimum strength 1
Usually biphasic: comprising a soft phase (the matrix) and a strong and stiff phase (the reinforcement).
C.F.C. João A.C. Baptista I.M.M. Ferreira J.P. Borges (&) CENIMAT/I3N, Departamento de Ciência dos Materiais, Faculdade de Ciências e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal e-mail: [email protected] J.C. Silva CENIMAT/I3N, Departamento de Física, Faculdade de Ciências e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal © Springer Science+Business Media Singapore 2016 S. Rana and R. Fangueiro (eds.), Fibrous and Textile Materials for Composite Applications, Textile Science and Clothing Technology, DOI 10.1007/978-981-10-0234-2_8
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Table 1 Properties of cellulose and chitin and several reinforcement materials. Adapted from [4] Material
ρ (g cm−3)
σf (GPa)
EA (GPa)
ET (GPa)
Reference
Kevlar-49 fibre 1.4 3.5 124–130 2.5 [4] Carbon fibre 1.8 1.5–5.5 150–500 – Steel wire 7.8 4.1 210 – Clay nanoplatelets – – 170 – Carbon nanotubes – 11–63 270–950 0.8–30 Boron nanowhiskers – 2-8 250–360 – Cellulose nanofibres 1.6 7.5–7.7 110–220 10–50 Chitin nanofibres 1.425 – 150 15 [6, 7] ρ density; σf ultimate tensile strength (UTS); EA elastic modulus along the crystal axial direction; ET elastic modulus along the crystal transverse direction
and maximum tolerance to flaws (robustness) of nanocomposites [1]. Nanoscale reinforcements can be particles (e.g., minerals), sheets (e.g., nanoclays) or fibres (e.g., carbon nanotubes, electrospun fibres or polysaccharide nanofibres) [2]. Polysaccharide nanofibres have received increased attention because of their
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