## 3 Results
### Impregnation of Wood Boards  
#### 3.3.1 Morphology  
Micrographs of red oak impregnated with MCPMs are shown in Figure 7. Microcapsules are clearly visible, filling some initial wood big vessels, as shown in A. The microcapsules seems to merge in aggregates in some of the vessels. Sometimes there is also a small quantity of MPCM at the periphery of a big vessel, as shown in B.  
Most of the small vessels of red oak were not containing any microcapsules, as visible in Figure 8a, in C. However, a few vessels were containing a small quantity of microcapsules, as visible in Figure 8b, in E. Some microcapsules were also observed over red oak fibers, as shown in D. Cutting the samples for observation could have displaced some microcapsules. The small vessels were mostly empty, as if the microcapsules size (8.4 microns) is, in average, widely inferior than the final wood small vessels average size (66.6 microns).  
Figure 5: Weight enhancement for several microcapsules ratios.  
Figure 6: Weight enhancement of small samples for several pressures.  
Figure 8: _Cont._  
Figure 7: Red oak impregnated with MPCM.  
Only some of the big vessels are filled with the MPCM. As no other study of wood impregnation with microcapsules was found in literature, there is not any other results to compare with and help understand this phenomenon. Yet, red oak big vessels are sometimes clogged by tyloses. The tyloses could block the progression of microcapsules, and as a consequence, some of the vessels would stay empty. In this case, dissolving the tyloses before impregnation could lead to a larger quantity of filled vessels. In 2018, [PERSON] et al., improved poplar sapwood permeability by autohydrolyze coupled with a sodium hydroxide treatment [32]. They found a partial dissolution of tyloses while the skeletal structure of the fiber and vessel cell walls remained intact. This could be an efficient way to remove red oak tyloses. However, such treatment could lead to wood degradation. As making wood flooring required a wood of good appearance, this could be a limit. Yet, further experiments would be required to have a better understanding of microcapsules distribution within red oak.  
Micrographs of the sugar maple impregnated with MCPMs are shown in Figure 9. Only a few vessels were containing microcapsules, as visible in F.  
For both woods, only a few small vessels were containing microcapsules. Still, these vessels are, in average, much larger than the capsules and should be able to be filled. An explanation could from the poor dispersion of the microcapsules in the impregnation liquid. As observed by microscopy, the capsules tend to form aggregates. These aggregates could be too big to fill the small vessels, explaining the small amount of capsules in it.  
The impregnated wood boards were cut and observed at several locations within the treated volume. Microcapsules were found in each zone. It indicates that the microcapsules are able to fill the central part of the wood boards. Indeed, the boards are cut so the vessels are oriented according to the length direction. Thus it may have been difficult for the microcapsules to reach the middle of the boards. Still, it is difficult to quantify how much microcapsules are filling the different parts of the samples.  
Figure 8: Impregnated red oak microscopy. (**a**) Small late wood vessels are mostly empty; (**b**) Some small vessels are filled with a few microcapsules.