106
nanoreinforcements (Paralikar et al. 2008; Sanchez-Garcia et al. 2008b; Svagan
et al. 2009). The improvement in the barrier performance is related to the increase
in the tortuosity that leads to slower diffusion and lower WVP values (SanchezGarcia et al. 2008b). Nanosized cellulose fibrils have also a potential to improve the
thermal properties of biobased polymers (Helbert et al. 1996; Oksman et al. 2006;
Petersson and Oksman 2006).
Starch nanocrystals are one of the distinguished polysaccharide-based nanofillers, which have been shown to improve the mechanical properties of biobased
polymers when incorporated up to a 10 wt.% content (Aldao et al. 2018; Villa et al.
2019). The native starch granules are hydrolyzed below the gelatinization temperature to separate the crystalline lamellae, which are more resistant to hydrolysis
(Azeredo 2009). The crystalline starch particles generally have a thickness of
6–8 nm and show a platelet morphology (Kristo and Biliaderis 2007).
Chitin whiskers or Cs NPs have been used successfully to improve mechanical
strength and barrier performance. Cs NPs have also improved thermo stability and
reduced affinity with water when used in the nanocomposite formulations (Antoniou
et al. 2015). Cs NPs can be produced by ionic gelation. In this technique, the positively charged amino groups of Cs, interact electrostatically with crosslinking
polyanions such as tripolyphosphate (López-León et al. 2005).
6.4 Processing Techniques for Biobased Nanocomposites
The biobased nanocomposites are obtained by incorporating nano-fillers into the
biobased polymer matrices providing a considerable improvement of the mechanical, barrier, thermal and biodegradation properties of the films due to the favorable
interactions between the polymer and the nano-filler (Xie et al. 2013). Three thermodynamically viable structures can be formed for these systems: phase separated
(tactoid), intercalated or exfoliated (Ojijo and Sinha Ray 2013) as mentioned previously (see sect. 6.3 – Nanoreinforcement). The desired performance of the nanocomposite is influenced by many factors such as the fillers’ spatial arrangement, the
morphology of the final product (polymer with nano-filler), the distribution of nanofiller through the polymer matrix and the interfacial interactions between filler and
polymer (Unalan et al. 2014). Although several strategies have been applied to
develop biobased nanocomposites, the three most commonly used techniques are
the following: (1) in-situ polymerization, (2) melt processing or (3) solution casting
is mostly adopted (Alexandre and Dubois 2000). In addition, other preparation techniques, such as roll milling, high shear mixing, micro pattern approaches, using
supercritical conditions and sonication have gained interest lately. In the following
sections, we will focus on three main synthesis approaches and recent techniques to
form biobased nanocomposites.
H. Cakmak and E. Sogut
nanoreinforcements (Paralikar et al. 2008; Sanchez-Garcia et al. 2008b; Svagan
et al. 2009). The improvement in the barrier performance is related to the increase
in the tortuosity that leads to slower diffusion and lower WVP values (SanchezGarcia et al. 2008b). Nanosized cellulose fibrils have also a potential to improve the
thermal properties of biobased polymers (Helbert et al. 1996; Oksman et al. 2006;
Petersson and Oksman 2006).
Starch nanocrystals are one of the distinguished polysaccharide-based nanofillers, which have been shown to improve the mechanical properties of biobased
polymers when incorporated up to a 10 wt.% content (Aldao et al. 2018; Villa et al.
2019). The native starch granules are hydrolyzed below the gelatinization temperature to separate the crystalline lamellae, which are more resistant to hydrolysis
(Azeredo 2009). The crystalline starch particles generally have a thickness of
6–8 nm and show a platelet morphology (Kristo and Biliaderis 2007).
Chitin whiskers or Cs NPs have been used successfully to improve mechanical
strength and barrier performance. Cs NPs have also improved thermo stability and
reduced affinity with water when used in the nanocomposite formulations (Antoniou
et al. 2015). Cs NPs can be produced by ionic gelation. In this technique, the positively charged amino groups of Cs, interact electrostatically with crosslinking
polyanions such as tripolyphosphate (López-León et al. 2005).
6.4 Processing Techniques for Biobased Nanocomposites
The biobased nanocomposites are obtained by incorporating nano-fillers into the
biobased polymer matrices providing a considerable improvement of the mechanical, barrier, thermal and biodegradation properties of the films due to the favorable
interactions between the polymer and the nano-filler (Xie et al. 2013). Three thermodynamically viable structures can be formed for these systems: phase separated
(tactoid), intercalated or exfoliated (Ojijo and Sinha Ray 2013) as mentioned previously (see sect. 6.3 – Nanoreinforcement). The desired performance of the nanocomposite is influenced by many factors such as the fillers’ spatial arrangement, the
morphology of the final product (polymer with nano-filler), the distribution of nanofiller through the polymer matrix and the interfacial interactions between filler and
polymer (Unalan et al. 2014). Although several strategies have been applied to
develop biobased nanocomposites, the three most commonly used techniques are
the following: (1) in-situ polymerization, (2) melt processing or (3) solution casting
is mostly adopted (Alexandre and Dubois 2000). In addition, other preparation techniques, such as roll milling, high shear mixing, micro pattern approaches, using
supercritical conditions and sonication have gained interest lately. In the following
sections, we will focus on three main synthesis approaches and recent techniques to
form biobased nanocomposites.
H. Cakmak and E. Sogut