Table 2. Effect of polyurethane content on physical and mechanical properties of CBP

Physical and mechanical properties	Polyurethane content (%)				NWPCA standard
Physical and mechanical properties	2.5	3	3.5	4.5	NWPCA standard
Density (g/cm³)	0.57 (0.01)^a	0.57 (0.01)^a	0.58 (0.01)^a	0.61 (0.05)^a	-
Moisture content (%)	6.84 (0.05)^a	6.55 (0.05)^a	6.63 (0.06)^a	6.49 (0.07)^a	-
Dimensional stability (length; %)	2.17 (0.14)^a	1.41 (0.28)^a	1.72 (0.21)^a	1.78 (0.08)^a	≤ 2
Dimensional stability (width; %)	2.66 (0.49)^a	2.02 (0.56)^b	2.40 (0.36)^b	2.09 (0.44)^b	≤ 2
Dimensional stability (height; %)	11.36 (0.27)^a	9.71 (0.24)^b	10.49 (0.24)^b	10.84 (0.41)^b	≤ 6
Water absorption (%)	84.91 (4.09)^a	81.13 (3.19)^a	81.10 (5.39)^a	80.80 (5.98)^a	≤ 25
Compressive strength (MPa)	6.58 (1.74)^a	9.32 (0.69)^b	10.53 (2.76)^b	11.18 (0.63)^c	≥ 9.65
Screw holding strength (N)	104.68 (53.15)^a	145.31 (36.85)^ab	192.81 (24.67)^b	336.56 (71.07)^c	≥ 200

The results of the statistical tests denoted by the same letter indicate the absence of noticeable differences.
CBP: chip block pallets, NWPCA: National Wooden Pallet and Container Association.