The development of the particleboards based on cacao tree

The development of particleboards of umbrella tree wood and cacao tree prunings was carried out in two phases.The first phase focused on the feasibility of producing PB based on the raw materials and the second phase was focused on investigating the effect of the coarser core layer chips of the various raw materials on the properties of the boards. For this purpose, the wood chips of the surface and the core layers of the various raw materials were blended separately with UF-resin of reduced molar ratio of the group K 340 in a laboratory-scale rotating drum mixer with the help of an air-pressure atomizer. The wood chips of the Norway spruce (Picea abies) were also blended to serve as a reference. The resin load was based on the oven-dry weight of the furnish. As much as possible, the rotating drum mixer equipped with an air pressure atomizer uniformly blended the wood chips for about 10 minutes. A hardener, ammonium sulfate (40% solid content v/v) in the amount of 1.5% based on the solid content of the resin was added to the glue. The hydrophobic agent, hy-drowax 138 (50% solid content v/v) from the company Sasol GmbH in the amount of 1.5% based on the oven-dry weight of the wood chips was also

83 blended with the wood chips. Table 6 shows the production parameters for the development of the particleboards.

After the blending was completed, the resinnated furnish was formed into a mat by hand with the help of a transparent-plastic laboratory-scale mat former of dimensions 605 mm x 455 mm. The surface layers and the core layer were of the ratio 40:60 percent the total mass of each of the board.

The mat was formed on metal press plates of dimensions 800 mm x 600 mm overlaid with PTFE (Polytetrafluoroethylene) film to serve as a re-lease agent to allow for easy removal of the boards after the press opens.

Table 6: The production parameters for the development of the partic-leboards based on cacao tree prunings and umbrella tree wood in a labo-ratory scale.

The resulting mat was evenly pre-pressed with a wooden board to reduce its thickness and then hot-pressed to a target thickness of 20 mm to achieve panels of the targeted densities (see table 6). The boards were

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pressed at a temperature of 200 ^oC and a pressure of 200 bar for 4 minutes.

Three boards were produced for each board variant, giving a total of 27 boards. The resulting particleboards were conditioned overnight to cool down to room temperature, then sanded and sawn to the dimension as required by the testing standard for the physical-mechanical properties as well as formaldehyde emissions.

Figure 25: Laboratory-scale drum mixer equipped with an air-pressure atomizer for blending wood chips for particleboards.

The dependence of the physical-technological properties on the coarseness of the wood chips of the core layer of the raw materials; cacao tree prun-ing and umbrella tree wood was the focus of the next phase of the PB manufacturing process. It investigates the effect of increasing the coarse-ness of the core layer chips on the physical and technological properties of the particleboards of umbrella tree wood and cacao tree prunings.

Air-pressure atomizer Laboratory-scale drum mixer

85 Figure 26: Hot press from the company Siempelkamp, D-47803 Krefeld (Left), and pre-pressed mat ready for hot-pressing (Right).

It has been scientifically established that the dimensions of the wood chips used in particleboard production significantly affect the physical-mechanical properties, surface quality and processing properties of the resulting Particleboards (Istek et al., 2018; Youngquis J.A., 1999; Frybort et al., 2008).

For this purpose, detailed sieve analysis of the wood chips of the core layer was conducted as described in chapter 4.2.1. The fractional composi-tions of the chips of cacao tree prunings and umbrella tree wood were compared to the fractional composition of the industrially produced core layer wood chips from the company Pfleiderer GmbH. From the analysis,

PTFE Film Pre-pressed mat

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it was found that the laboratory-produced wood chips of the core layer for both cacao tree prunings and umbrella tree wood were not as coarser as the industrially-produced wood chips. For this reason, the fractional com-positions of the chips of the study materials (umbrella tree wood and ca-cao tree prunings) were adjusted to contain about 10 percent of chips with sizes greater than 6 mm (see Figures 27 and 28). Finally, the core layer chips with the adjusted fractional composition were used to produce an-other series of three-layered particleboards with the same production pa-rameters as shown in Table 7. Three boards were produced per board vari-ant thus giving 18 boards in total. The resulting boards were also condi-tioned overnight to cool to room temperature, then were sanded and sawn to the dimensions for evaluating their physical-technological properties as well as formaldehyde emissions.

Table 7: The production parameters for the development of the partic-leboards based on coarser core layer chips of cacao tree prunings and umbrella tree wood in a laboratory scale.

Raw

87 Figure 27: A comparison of the fractional composition of the core layer wood chips of cacao tree prunings and umbrella tree wood with the in-dustrially produce core layer wood chips.

Figure 28: The fractional composition of the adjusted particle sizes of the chips of cacao tree prunings and umbrella tree wood compared with the industrially produced wood chips of the core layer.

0 10 20 30 40 50

>6.3 6.3-4.0 4.0-3.15 3.15-2.0 2.0-1.0 1.0-0.8 <0.8

Amount [%]

Particle sizes [mm]

Cacao tree prunings chips Umbrella tree wood chips Industrially produced chips

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4.7.2 The development of non-formaldehyde bonded particleboards