## 3 Results and Discussion
### Mechanical Properties  
The results showed that the mean MOR values of the cup-plant PBs (3 LCP, 1 LCP) were below the mean measured for spruce PBs. Further, mean MOR of the three-layer cup-plant PB (3 LCP) was above the one-layer cup-plant PB (1 LCP), although not statistically significant. Additionally, MOR of three-layer cup-plant PB (3 LCP) was not different to the one-layer spruce PB (1 LSP, \(p>0.05\); Figure 8). The spruce PB types and the three-layer cup-plant PB did meet the EN312 class P1 standard [39], which is for general use in dry conditions. In contrast, average MOR of the one-layer cup-plant PB did not reach the P1 standard.  
Figure 6: 3D-visualisation of the spruce particle–particle bondlines, using TOF SIMS data, reconstructed by the ORS software (Object Research Systems, Montreal, QC, Canada); (**A,B**) spruce PB with visible particle–particle bondline, (**C**) pMDI bondline imaging (Q/m 26).  
Figure 7: 3D-visualisation of cup-plant particle–particle bondlines, TOF SIMS data reconstructed by the ORS software (Object Research Systems, QC, Canada); (**A,B**) cup-plant PB with visible particle–particle bondline, and (**C**) the pMDI bondline imaging (Q/m 26).  
Average MOE measured for both cup-plant PBs types (3 LCP, 1 LCP) did not differ, (\(p>0.05\)), and were also not statistically different from the one-layer spruce PB (1 LSP, Figure 9). In addition, MOE of both cup-plant PBs were significantly (\(p<0.05\)) lower than the three-layer spruce PB. Even with all seen MOE variability (Figure 9), the cup-plant PBs could be classified as P1 of EN 312, which refers to PBs used in dry conditions for interior FITents, including furniture.  
The measured MOR and MOE of the one-layer spruce PB, and the three-layer spruce PB were consistent with data reported by [PERSON] et al. [40]. It was also documented that MOE and MOR of three-layer PBs were above the one-layer PBs [41]. MOE and MOR were both affected by particle alignments, surface layer density, as well as by the nature of the  
Figure 8: Modulus of rupture (MOR) of measured particleboards (PBs). 3 LCP—three-layer cup-plant PB, 3 LSP—three-layer spruce PB, 1 LCP—single-layer cup-plant PB, and 1 LSP—single-layer spruce PB (\(n=10\)).  
Figure 9: Modulus of elasticity (MOE) of measured particleboards (PBs). 3 LCP—three-layer cup-plant PB, 3 LSP—three-layer spruce PB, 1 LCP—single-layer cup-plant PB, and 1 LSP—single-layer spruce PB (\(n=10\)).  
used raw material [42]. As cup-plant particles differ in their anatomical structure [8] and sizes when compared to spruce particles, this has evidently an effect on the properties of the produced PBs. [PERSON] et al. [43] reported a rise in MOE and MOR of three-layer PB made from Kenaf stalk cores, when the surface layers were made of rubberwood. MOR and MOE of the produced one-layer cup-plant PB showed similar values than PBs made from waste tea leaves [44], bleached straw [13], eggplant stalks [45], or rice straw [9].  
Internal bonding values (IB) of the cup-plant PBs (3 LCP, 1 LCP) were also below the spruce PB types (Figure 10). One-layer cup-plant PB showed an average IB of 0.30 MPa, which was not significantly different from the IB of the three-layer cup-plant PB (0.34 MPa). Overall, the PBs made from cup-plant were again found suitable as general usage panels in dry conditions, as defined in EN 312 P1 [39]. In PBs, the core layers strongly determine the internal bonding, which explains why there are no significant differences for IB between single-layer and three-layer PBs. [PERSON] et al. [40] reported that surface layer characteristics of PBs have no significant effect on the IB. Additionally, [PERSON] et al. [22] showed that the surface layer of three-layer Miscanthus PBs had no significant influence on the measured IB. A reduced IB was found for rice husks PBs [46], hazelnut husks [47], or waste tea leaves [36]. An IB lower than 0.2 MPa was measured for rice straw [9], and for waste grass clipping PBs [48].