Phenol Formaldehyde (PF) resin has been extensively used in the manufacturing industry as a binding agent, especially in the production of wood-based panels because of its ability to provide good moisture resistance, exterior strength and durability as well as excellent temperature stability. However, due to the use of limited petroleum-based phenol in its formulation, there is a strong interest in exploring renewable biomass material to partially substitute the petroleum-based phenol. In this study, the slow pyrolysis of biomass decomposition process was used to convert two types of biomass, namely, oil palm frond and Rhizophora hardwood, into bio-oil. The phenol-rich fraction of the bio-oil was separated and added into the formulation of PF resin to produce an environmentally-friendly type of PF resin, known as bio-oilphenol-formaldehyde (BPF) resin. This BPF resin was observed to have comparable viscosity, better alkalinity, improved non-volatile content and faster curing temperature than conventional PF resin. Moreover, the particleboard bonded with this BPF resin was observed to have just as excellent bonding strength as the one bonded using conventional PF resin. However, the BPF resin exhibited an increased level of free formaldehyde and less thermal stability than the conventional PF resin, probably due to the addition of the less reactive bio-oil.
The particleboards were fabricated using Rhizophora spp. wood particles with particles size less than 74 μm. The corn starch was used as a bio-adhesive in the fabrication of Rhizophora spp. particleboards. The corn starch bonded particleboards were fabricated at 5% and 10% corn starch based on dry mass of Rhizophora spp. wood particles. The measurement of mass attenuation coefficients of the particleboards were made at low and intermediate photon energies. The mass attenuation coefficient at low photon energy was measured using X-ray fluorescent (XRF) configuration based on attenuation of Kα1 X-ray energies between 16.59 and 25.26 keV given by niobium, molybdenum, palladium and tin metal plates. The calculated mass attenuation coefficients of samples were compared to the theoretical values mass attenuation coefficients of water calculated using the photon cross-section database (XCOM). The results showed that mass attenuation coefficients of 10% corn starch added Rhizophora spp. particleboards were in good agreement of water within 7.96 and 4.94% for 5% and 10% corn starch Rhizophora spp. Particleboards, respectively compared to 14.57 and 16.16% in binderless Rhizophora spp. particleboards and raw Rhizophora spp. wood, respectively.
The mass attenuation coefficients of solid water phantoms, Perspex® phantoms and Rhizophora spp. particleboards were determined by using Compton scattering technique measured using Ludlum configuration. The gamma energy of 137Cs sealed source were measured at 30°, 45°, 60° and 75° angles providing scattered gamma energies between 337.72 and 564.09 keV. The mass attenuation coefficients of solid water and fabricated Rhizophora spp. particleboards were the nearest to XCOM values of water with average percentage of discrepancies of 6.8% and 5.9%, respectively. The results indicated similar attenuation properties of solid water and fabricated Rhizophora spp. particleboards and the suitability of the Ludlum configuration to determine the mass attenuation coefficient of materials using Compton scatter technique.