2. Materials and methods
2.1. Sample preparation and particleboard manufacturing
Oil palm trunks with an average age of 25 years old were used
in this study. Trunks were cut into 7 cm thick disks before they
were first reduced into chip and ground into small particles using
a hammermill. Later particles were dried to a moisture content of
5% in an oven having a temperature of 50 C. Dried particles were
screened on a sieve having particle size ranging from 0.5 mm to
5 mm. Particles were boiled in hot water and soaked in sodium
hydroxide with 2% concentration for 30 min before they were
redried to a moisture content of 5% in an oven.
Urea formaldehyde (UF) was used as adhesive, supplied by
Malayan Adhesive Company Sdn. Bhd., Shah Alam for panel manufacturing.
The adhesive had a solid content of 64.5%, viscosity of
2.00P at 30 C, pH of 8.15 and specific gravity of 1.27 g/cm3. A single
layered particleboard 21 21.1 0.5 cm was manufactured
with a target density of 0.65 g/cm3. Pre-weighed oil palm particles,
untreated and treated were blended separately with 10% (w/w of
particles) of UF resin and 1% (w/w of solid resin) hardener. The furnish
were formed in a former, pre-pressed at a pressure of 500 kg/
cm2 for two minutes before being hot pressed for 10 min at 150 C
under pressure of 500 kg/cm2. All boards were conditioned in a
conditioning room maintained at 20 C and 65% relative humidity
for one week.
2.2. Determination of particles pH
The pH values of raw materials were determined according to
TAPPI T 509 om-83 [11]. Approximately 1 g of samples was mixed
with distilled water and soaked at room temperature for 1 h. The
pH meter (Mettler Toledo) was used to measure the pH values of
untreated and treated particles.
2.3. Mechanical and dimensional stability testing
The boards were cut into required size for testing the mechanical
properties and dimensional stability. The bending strength
included Modulus of Rupture (MOR) and Modulus of Elasticity
(MOE) was determined using samples with size of
150 50 5 mm. The internal bonding strength (IB) and bending
strength test were carried out using Instron Machine according
to EN 319 (1993) and EN 310 (1993) [12,13]. Three samples with
dimensions of 50 mm 50 mm 5 mm were cut from each panel
for internal bond strength test. Three samples with dimension
50 mm 50 mm 5 mm from each panels were used for thickness
swelling (TS) and water absorption (WA) test. The dimensions
and weight of each sample were measured before they were submerged
in distilled water for 24 h. After a total of 24 h submersion,
the dimensions and weight of each sample were measured and
recorded.