## 3 Results and Discussion
### Water Contact Angle (WCA)  
The contact angle analysis is crucial in determining the surface properties of modified materials, providing insight into the influence of modifiers on hydrophilic-hydrophobic  
Figure 14: DSC curves of (**A**) PLA/alcohols first heating cycle; (**B**) PLA/alcohols second heating cycle; (**C**) PLA/alcohol/silanes or siloxanes first heating cycle; (**D**) PLA/alcohol/silanes or siloxanes second heating cycle.  
properties. For hydrophilic and hygroscopic materials like polylactide and PET-G, it is recommended to dry them before processing to eliminate the excess moisture, which could cause complications during extrusion or printing. The contact angle value of PLA is 73.7\({}^{\circ}\), while that of PET-G is 74.7\({}^{\circ}\). Figure 15A shows the contact angle values for PLA/alcohols/silanes/siloxane samples, while Figure 15B shows the contact angle values for PET-G/alcohols/silanes/siloxanes. Short alkyl-chain alcohols like methanol (MeOH) and ethanol (EtOH) have little effect on the hydrophilic-hydrophobic properties of polylactide. On the other hand, composite materials modified with alcohols with branched, cyclic, or aromatic structures have higher contact angle values compared to pure PLA. Factors that influence the contact angle include changes in surface energy or chemical interactions between R-OH and the polymer, affecting wettability. Microscopic results reveal that contact angle values are dependent on defects that occur in the structure after the printing process, with samples having air gaps and poor fusion of layers having higher wetting angles due to increased surface roughness.  
Composites modified with organosilicon compounds, like siloxane with amino groups, generate weak interactions with the polymer matrix, resulting in the highest contact angle values. AMS233 (2-4% aminoethylaminopropylmethoxysiloxane)--a dimethylsiloxane copolymer--creates a hydrophobic layer on the material surface, acting as a barrier that prevents water and other polar substances from penetrating. Using modifiers based on organosilicon compounds increases the contact angle value, reducing the surface tension of hydrophilic polylactide [25]. DMS-S14 has silanol units (Si-OH) in its structure, which can interact with the PLA matrix [26]. The L-FDM method modifies not only the polymer surface but also the entire composite structure. In contrast, PET-G modification does not alter contact angle values due to the matrix's physicochemical properties, which are insoluble in most alcohols like methanol, ethanol, or isopropanol. PET-G + BRB276/MeOH and PET-G + DMS-S14/MeOH have angle values characteristic of hydrophobic materials (>90\({}^{\circ}\)). The vinyltrimethoxysilane acts as a crosslinking agent, with hydrolysis leading to the formation of Si-OH groups that condense under appropriate conditions, affecting the composite's hydrophobic properties [27]. DMS-S14 and AMS233 also have a similar effect on polylactide modifications, increasing the contact angle values. Research by [PERSON] et al.  
Figure 15: Water contact angle (WCA): (**A**) PLA/alcohols/silanes/siloxanes; (**B**) PET-G/alcohol/silanes/siloxanes.  
indicates that different solvents and their ability to wet the polymer have the effect of reducing surface energy [28].