*3.2.2.1. Strain sweep tests*

carbon content after silanization is due to the additional carbons brought to the surface by the long chains (C16) of hexadecyltrimethoxysilane. For oxygen instead, the surface atomic concentration becomes lowered since a not-significant amount of oxygen is added by silanes.

In general, thermal, morphological, and chemical characterization of fibers is necessary when lignocellulosic materials are prepared as reinforcing fillers. The knowledge of important factors like the degree of lignin removal, distribution of silane, and hydrophobic character of fibers are very important to ensure that the material will behave successfully during compounding with polymeric matrices and then to obtain suitable mechanical properties of biocomposites.

The influence of bagasse fiber addition on the PP flexural and impact properties was evaluated. **Table 1** presents the values of the flexural modulus, flexural strength, and impact strength of the materials. Biocomposites showed different mechanical properties, indicat-

The results show that bagasse fiber incorporation induces a significant improvement of flexural properties of PP. For PP-bagasse and PP-Bag+NaOH biocomposite flexural modulus (FM) increased 60 and 42%, respectively. On the same way, flexural strength (FS) reached improvements of 20 and 8% compared to neat PP. For PP-Bag+NaOH+Silane, FM was enhanced 16%, respectively, in comparison with PP. However, the FS value was not significantly different (p ≥ 0.05). Similar results were reported by Cerqueira et al. [34] when they studied the morphology and mechanical properties of PP-bagasse biocomposites. The authors reported that biocomposites present higher FM and FS values in comparison with neat PP and suggested a good interaction under the compressive stresses developed in part of the transverse section of

On the other hand, the impact tests did not show significant differences between the PP matrix and the biocomposites PP bagasse and PP-Bag+NaOH. However, for PP-Bag+NaOH+Silane an

> **Flexural properties Impact properties Modulus (MPa) Strength (MPa) Impact strength (kJ/m2**

**)**

Silicon, as expected, almost doubles his surface concentration.

ing that the treatments affect the fiber-matrix interaction.

the biocomposite specimens during bending.

\*Mean of five replications ± standard deviation.

**Sample Impact and flexural properties\***

PP 1296 ± 70<sup>a</sup> 40.0 ± 0.7<sup>a</sup> 4.4 ± 0.5<sup>a</sup> PP-Bag 2069 ± 30<sup>b</sup> 48.0 ± 1.1<sup>b</sup> 4.2 ± 0.2<sup>a</sup> PP-Bag+NaOH 1847 ± 114c 43.3 ± 0.5<sup>c</sup> 5.1 ± 0.5<sup>a</sup> PP-Bag+NaOH+Silane 1505 ± 94<sup>d</sup> 38.6 ± 1.9a 6.2 ± 0.1<sup>b</sup>

Different letters (a–d) in the same column indicate significant differences (p < 0.05).

**Table 1.** Flexural and impact properties of PP and PP-bagasse biocomposites.

**3.2. Biocomposite characterization**

140 Characterizations of Some Composite Materials

*3.2.1. Mechanical properties*

**Figure 8** shows the results of the strain sweep tests of the PP matrix. Images of the PP specimen are included at a strain of 0.01% (linear region) and 0.6% which corresponds to the nonlinear zone. In this zone it is observed that the specimen has been highly deformed. From these results a strain of 0.01% was used for subsequent temperature ramp tests.
