Tunicin whiskers

Surprisingly, the association between TPS and cellulose fibres (polysaccharide-based composites) has been little analysed. In the literature, cellulose fillers used in association with a plasticized starch matrix are commercial paper fibres,10 potato pulp microfibrils,11 12 tunicin whiskers and paper bleached pulp.13-14 The literature reports that these cellulose fillers improve the tensile strength. Besides, the composite water sorption seems to be decreased. This behaviour is related to the well known lower water uptake of cellulose compared to starch.10-14... 

ANG 01 ] Angles M.N., Dufresne A., Tlasticized starch/tunicin whiskers nanocomposite materials. 2. Mechanical behavior , Macrawo/ecufes, vol. 34, no. 9, pp. 2921-2931,2001. 

MAT 02] Mathew A.P., Dufresne A., Morphological investigation of nanocomposites from sorbitol plasticized starch and tunicin whiskers . Biomacromolecules, vol. 3, no. 3, pp. 609-617,2002. 

Figure 2.2 shows a TEM micrograph of cellulose whiskers prepared from cotton. Geometrical characteristics of cellulose whiskers depend on the origin of cellulose microfibrils and on the conditions of the acid hydrolysis process such as time, temperature, and purity of materials. Samir et al. [75] have reported the dimensions of cotton and tunicin whiskers. The length (L) and lateral dimension (D) of cotton whiskers were around 200 and 5 nm, respectively (ratio L/D = 40). The length and lateral dimension of tunicin whiskers were reported to be around 1,000 and 15 nm, respectively (ratio L/D = 67). De Souza [76] studied cotton and tunicate whiskers in aqueous suspensions as well. The average size whisker dimensions reported were L = 255 nm and D = 15 nm for cotton whiskers (ratio L/D — 17) while the values were L — 1,160 nm and D = 6 nm (ratio L/D = 72.5) for tunicate whiskers. 

Angles, M.N., Dufresne, A. Plasticized starch/tunicin whiskers nanocompositcs 2. mechanical behavior. Macromolecules 34, 2921-2931 (2001)... 

Figure 19.13 Logarithm of the normalized storage shear modulus (log G G oo, where G200 corresponds to the experimental value measured at 200 K) versus temperature at 1 Hz for tunicin whiskers reinforced poly(St-co-BuA) nanocomposite films, obtained by water evaporation and filled with 0 ( ), 1 (O), 3 (A), 6 (A) and 14 wt% ( ) of cellulose whiskers. Reproduced with permission from Reference [31].

Cellulose whiskers without surface modification display strong interactions and have been reported as difficult to disperse in water. Sulfate-functionalized tunicate whiskers were prepared by sulfuric acid hydrolysis of cellulose pulp derived from tunicates (StyelacldVa). These high aspect ratio nanoparticles formed colloidal suspensions in water (Figure 14.4). A stable suspension of tunicin whiskers was obtained in an organic solvent (Af,Af-dimethylformamide) without surfactant addition or chemical surface modification. Both the high value of the dielectric constant of DMF and the medium wettability of tunicin whiskers were supposed to control the stability of the suspension (Figure 14.5). 

Fig. 7.6 Scanning electron micrographs from the fractured surfaces of (a) unfilled plasticized starch matrix and related composites filled with (b) 25 wt% tunicin whiskers (Angles and Dufresne 2000) (copyright (2000) American Chemical Society)...

Angl s MN, Dufresne A (2000) Plasticized starch/tunicin whiskers nanocomposites. 1. Structural analysis. Macromolecules 33 8344—8353... 

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