Cellulose and Chitin as Nanoscopic Biomaterials - The Nanoscience and Technology of Renewable Biomaterials - page 225

8.6 Nanocomposite Properties

Surface derivatized cellulose and chitin nanoparticles were melt processed with differ-
ent biobased plastic matrices to yield nanocomposites and the effects of the surface
modification on thermal and mechanical properties were measured. Maleated cellulose
nanoparticles were blended with a biodegradable co-polyester of adipic acid, terephalic
acid, and 1,4 butanediol.

The neat plastic is elastomeric at room temperature with a

32 ◦ C, and has a relatively low melt processing temperature of 140 ◦ C. The low
melt temperature of the matrix plastic reduces the risk of thermal decomposition of
the cellulose nanoparticles during processing. Nanocomposites prepared with varying
weight % filler showed improved mechanical properties. Table 8.3 provides the stor-
age modulus data for the nanocomposites. Modulus values were taken from dynamic
mechanical analysis profiles. The results indicate a large reinforcing effect imparted to
the materials by the nanoparticles. This reinforcing effect is more marked with sur-
face derivatization, presumably due to the greater surface compatibility. Tan δ plots
of the nanocomposites at different filler loadings indicate an improvement in damping
properties with reinforcement as shown in Figure 8.16.
Surface derivatized chitin nanoparticles were melt processed with a C-9 long chain
cellulose ester matrix plastic in a similar manner to the cellulose nanocomposites. The
neat C-9 cellulose ester was an experimental type provided by Eastman Chemical Com-
pany, and is also a low T g elastomeric thermoplastic with poor mechanical strength in
neat form. When reinforced with chitin nanoparticles surface derivatized with medium
to long chain aliphatic esters, a marked improvement in modulus of the composite
material is recognized. Mechanical data for the composite materials is provided in
Table 8.4. Tensile testing of the composites reveals that both the yield stress and
Young's modulus of the materials are increased nearly 2-fold with nanoparticle rein-
forcement. Figure 8.17 illustrates this effect, where the slope of the linear part of the
curve equates to the Young's modulus, and the point of deviation from linearity or elastic

T g =−

Table8.3 Comparativevaluesofstoragemodulusof the
thermoplasticfilledwithunmodifiedandsurfacemodified
cellulosenanoparticlesatdifferentfillerloadings.

Weight fraction (wf) Storage modulus (MPa)

25 ◦ C 25 ◦ C 75 ◦ C −

0.0 9100 5500 1400

Unmodified MFs
0.05 11200 6200 1800

0.10 14450 7400 1900

0.20 17300 8500 2400

0.30 20400 10500 2900

Maleated MFs
0.05 10700 6800 2600

0.10 16200 10500 3900

0.20 25100 16200 5700

0.30 39800 24500 8300