# Functionalization and Modification of Bitumen by Silica Nanoparticles
## 3 Results and Discussion
### Functionalization of SiO\({}_{2}\) Nanoparticles.
Instead, the **NH\({}_{2}\)@SNP-3** thermogravimetric curve is characterized by a much more pronounced initial weight loss owe to dehydration of ca. 8%. This is to be correlated to the more hygroscopic  
Figure 2: Reaction scheme of the functionalization of SNPs. character of the NH\({}_{2}\) superficial moieties with respect to the hydroxyl groups of the unfunctionalized **SNP-3** initial compound. With an increase in temperature, a second weight loss of ca. 6% starting at 300 \({}^{\circ}\)C is observed, which is associated with the thermal decomposition of the organic component, i.e., the aminopropyl chains. The thermogravimetric curve of **C14N@SNP-3** in contrast displays a more hydrophobic character shown by the small amount of water molecules evaporated during dehydration (ca. 2% of weight loss) and a much pronounced weight loss starting at 300 \({}^{\circ}\)C. The latter corresponds to ca. 15.4% of loss owing to the presence of a larger amount of organic component, in agreement with the increase of the organic part and therefore evidence of the success of the alkylation reaction. To study the effect of functionalized silica particles on the properties of bitumen, the rheological properties of bitumen and functionalized **SNPs (FSNPs)** modified bitumen were determined. Functionalized silica particles **NH2@SNP-3** and **C14N@SNP-3** (ca. 1% in weight) were used to modify the bitumen according to the procedure previously described in Section 2.3. Figure 4: Thermogravimetric analysis (TGA) traces of SNP-3, NH2@SNP-3 and C14N@SNP-3. Figure 3: Fourier transform infrared (FT-IR) spectra of **SNP-3**, **NH2@SNP-3** and **C14N@SNP-3**. Note that samples were dried in oven at 60 \({}^{\circ}\)C overnight prior to analysis. Figure 5 shows the temperature dependencies of the elastic modulus and loss tangent of the pristine bitumen and **FSNPs** modified bitumen in the temperature range of 20-90 \({}^{\circ}\)C. As can be seen from the results, for pristine bitumen, a decrease in the elastic modulus and an increase in the loss tangent are observed up to 60 \({}^{\circ}\)C, while for a bitumen sample modified with **NH2@SNP-3** particles, the dependency curves of viscoelastic properties decrease to 66-67 \({}^{\circ}\)C. At 60 \({}^{\circ}\)C, the elastic modulus is reduced to values of about 10\({}^{3}\) Pa that differ from the values 10 Pa obtained for pristine bitumen (two orders of magnitude). These data confirm the change in the viscoelastic properties of bitumen as a result of modification. Figure 5: Temperature dependencies of the loss tangent (tan \(\delta\)) (**a**) and elastic modulus (G’) (**b**) of the initial bitumen and after modification with 1% of **NH2@SNP-3** and **C14N@SNP-3**. Arrows indicate phase transition temperatures. The temperature dependencies of the elastic moduli and the loss tangent of bitumen modified by particles of **C14N@SNP-3** in the amount of 1 wt% differ significantly [18; 19]. It is worth noting that when 1% of **C14N@SNP-3** particles are added, the elastic modulus curves decrease to a temperature of 70 \({}^{\circ}\)C, and at this temperature the loss modulus reaches a vertical asymptote. These values are higher than those observed for the **NH2@SNP-3** modified bitumen. Thus, when modifying bitumen, a change in rheological characteristics is observed depending on the type of modifier. A comparison of the temperature dependencies of the dynamic parameters before and after modification showed that the addition of functionalized silica particles leads to a shift of the curves to higher temperatures, which confirms a qualitative change in the physico-mechanical characteristics of bitumen. At high temperatures, the elastic modulus G' has a non-linear behavior approaching the transition of a viscoelastic fluid into a fluid (60 and 70 \({}^{\circ}\)C for pure and modified bitumen, respectively).