**4. Conclusions**

**Percentage of cellulose (v%) Percentage of STO nanoparticles (wt%) pH value** 15 0 4.78 15 10 4.78 15 20 5.00 25 0 5.08 25 10 5.08 25 20 5.20

**Figure 9.** Tensile analysis for composites made of 1.5 v% chitosan/0.5 v% cellulose considering 20, 10 and 0 wt% of STO

**Table 1.** Measurements of pH value for the solutions containing different percentages of cellulose and STO nanoparticles.

shortcoming, when designing a device with these composites, one must consider this finding. Further testing of these composites under high humidity environment could shed light on the

A different behavior was observed in the composites with STO nanoparticles where the Tdeg and UTS increased. The polymer-polymer interaction and the polymer-particle interaction can be responsible of these results. The addition of STO nanoparticles could have furthered the entanglement of the polymer's chains and, consequently, the free volume. However, the water present in these free spaces can be removed during the drying process because the mol-

In addition, the presence of more nanoparticles heightens the polymer-nanoparticles interfacial energy, which could cause cracks through the nanoparticles in the polymeric matrix. Besides, any agglomeration of nanoparticles can be detrimental for the polymer-nanoparticle interfacial bonding. Such agglomerates can favor the presence of pores and nucleate microspaces through the nanoparticles, raising the brittleness of the composites. All these are factors that

require further experimentation, which falls beyond the scope of the present research.

potential water absorption leading to swelling.

nanoparticles.

84 Ferroelectrics and Their Applications

ecules of water are not confined between the polymer's chains.

The present work aimed at studying the electrical, thermal, and mechanical properties of composites made of chitosan, cellulose and strontium titanate nanoparticles. The compositional variables considered encompassed: cellulose content (15 and 25 v%) and amount of strontium titanate nanoparticles (10 and 20 wt%).

The chitosan-cellulose and polymer-nanoparticles composites were successfully fabricated via sol gel casting method. Strontium titanate nanoparticles were dispersed in the polymeric matrix using a double-layered technique. To achieve a better dispersion of the nanoparticles, the particles size was reduced from 43 to 18 nm using the high ball mill technique. As a result, a high dispersion of the nanoparticles in the polymeric matrix was achieved.

With respect to the measured electrical properties, the addition of the strontium titanate nanoparticles raised the dielectric constant, capacitance, and electrical resistivity of the composites, as expected from a dispersed dielectric material. Similarly, the addition of the nanoparticles decreased the current density passing through the biocomposite. In addition, the dielectric rupture of the composites was not observed up to a maximum applied voltage of 60 V.

Furthermore, mechanical and thermal analysis tests of the composites revealed that the addition of cellulose adversely affected the ultimate tensile strength and the degradation temperature of the composites without strontium titanate due to the high content of water. However, an opposing behavior was observed on the composites with strontium titanate nanoparticles, in which higher content of cellulose raised both the ultimate tensile strength and the degradation temperature while the addition of titanate nanoparticles lowered it.
