## 3 Results and Discussion  
### IFR Bioadditive Characterization  
3.1.1. Physicochemical and Electrical Characterization  
The physicochemical and electrical characterization of the IFR bioadditive formulations included the determination of pH, viscosity, density, solids content, and electrical conductivity (Table 3). In general, the average density of the bioadditive formulations was 1.33 g/cm\({}^{3}\). The electrical conductivity was approximately 4 to 5 (mS), without observing important differences between them. In addition, the pH values remained between 9.33 and 9.57, in an alkaline range typical of the base Mg(OH)\({}_{2}\) presence. Viscosity values ranged from 846.00 to 896.67 cP, and solids content was 57.40% to 62.17%. In terms of these properties, the strength of the adhesive bond tends to decrease when incorporating additives with lower viscosities than the base adhesive (Table 6); however, this property also evidences some degree of compatibility between the different elements that compose the IFR bioadditive formulation [54]. This is because viscosity also depends on the solid content and other components incorporated in the polymeric blend to modify its physicochemical, mechanical, thermal, and other properties [55]. This will be studied by modifying the commercial adhesive according to the quality of the bond line and the penetration of the adhesive. On the other hand, the formulations of the bioadditive presented a solid content, which rose according to the increase in the components of the formulation and reached magnitudes higher than those found in a PVAc adhesive (Table 6), where a higher solids content has a direct relation with the mechanical strength \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**ID IFR** & & & **Viscosity** & **Density** & **Solids** & **Electrical** \\
**Bioadditive** & & **(cP)** & **(g/cm\({}^{3}\))** & **Content (\%)** & **Conductivity** \\ \hline F1 & 9.33 & 846.00 & 1.32 & 57.40 & 4.32 \\ \hline F2 & 9.57 & 896.67 & 1.33 & 62.17 & 4.54 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Average values of bioadditive properties. of the bond [56]. In this regard, the evidence suggests that the reaction of the LS would favor the formation of bonds, for example, hydrogen bonds with the protein, or through other mechanisms, with the different elements of the IFR bioadditive, forming molecules of greater complexity. This is due to the hydrosoluble extremes (sulfonate and carboxylic groups) soluble and water dispersion of this biopolymer, as well as its less polar groups (aromatic and aliphatic), which facilitate the interaction with surfaces of other materials, favoring the formation of interfaces [57; 58]. 1.2 Characterization of IFR Bioadditive Formulations: Dynamic Mechanical Analysis (DMA), Shear Test, and Fire Resistance Test  
The average values obtained by the DMA, shear strength and fire resistance test are presented in Table 4.  
The dynamic mechanical analysis (DMA) was performed to observe the wood-bioadditive-wood interaction and the degree of stiffness of the composite material once the bond line had cured. The storage modulus E' (stiffness) values ranged between 2.041 \(\times\) 10\({}^{9}\) and 2.398 \(\times\) 10\({}^{9}\) Pa, where the highest magnitude was reached by formulation F2. This rheological behavior could be related to the presence of lignosulfonate and Mg(OH)\({}_{2}\) in the formulation, where F2 contains the highest fraction of Mg(OH)\({}_{2}\). Magnesium hydroxide has been used to improve thermal resistance and reduce costs in the manufacture of materials such as PVC [59], and as reinforcement in various polymeric matrices [60; 61]. Previous studies have highlighted a synergistic relationship between Mg(OH)\({}_{2}\) and casein [36], suggesting that yeast protein could form similar structures with Mg(OH)\({}_{2}\). Amino acids present in yeast protein, such as aspartic and glutamic acid, are also found in casein, which favors the synergistic reaction [36].