Sunday, 13 November 2016

PROPERTIES OF SMALL DIAMETER ACACIA HYBRID LOGS FOR BIOCOMPOSITES PRODUCTION

Author
Rafeadah Rusli*, Hashim W. Samsi,
Roszaini Kadir, Salmiah Ujang, Zaihan Jalaludin, & Suffian Misran

Biocomposite and Wood Protection Programme,
Forest Research Institute Malaysia (FRIM), Kepong 52109 Selangor, Malaysia E-mail: rafeadah@frim.gov.my


ABSTRACT. This study was conducted to determine the feasibility of using juvenile Acacia hybrid in manufacturing biocomposite boards. The mechanical, physical and fungal resistance properties of the boards produced were determined. The four year-old Acacia hybrid was obtained from several clones. The particleboards and medium density fibreboards (MDF) were manufactured at a target density of 750 kg/m3 and resin levels of 6, 8 and 10%. The results indicated that all particleboards and MDF complied with the Particleboard- specifications (BS EN 312:2010) and the Fibreboard specifications: Requirement for dry process boards (MDF) (BS EN 622-5: 2009, respectively. The fungal resistance properties of particleboard and MDF showed better in resistance compared to particleboard. The mechanical and physical properties of the particleboard were compared with the A. mangium particleboards.

KEYWORDS. Acacia hybrid, particleboard, medium density fibreboard, mechanical and physical properties, fungal resistance

INTRODUCTION
The increasing difficulty in obtaining solid wood materials, the utilization of wood-based panel (WBP) products as substitutes are enhanced, as these products represent a more efficient way of utilizing wood and other resources. To date, the Malaysian wood-based industries comprise of approximately 1019 sawmills, 183 plywood/veneer mills, and 373 moulding factories, 32 particleboard mills, 15 MDF mills and several hundred other factories. In an effort to increase awareness of the importance of the biocomposite products, the raw materials have been researched widely.
Acacia mangium Willd. and Acacia auriculiformis are both fast growing timber species, which have the potential for timber and pulp production. The hybrid between these two species may occur either naturally (Skelton, 1987), or can also be produced through biclonal orchards (Wickneswari, 1989) and controlled crosses (Sedgley et al., 1992). Acacia hybrid inherits the better stem straightness of A. mangium and the self-pruning ability and better stem roundness of A. auriculiformis. It possesses intermediate physical and mechanical properties between both parents’ species. The hybrid’s height and diameter increments are significantly better and it also appears to be more resistant to heart rot (Lemmens et al, 1995). Henceforth, these hybrids, upon appropriate exploitation, could become a potential alternative raw material for wood based industry. The present study was to determine the feasibility of using small diameter Acacia hybrid logs for particleboard and MDF manufacture. 


Acquiring of raw materials

MATERIALS AND METHODS

Four-year-old Acacia hybrid was obtained from Negeri Sembilan, Malaysia. Four clones of Acacia hybrid namely M2, M4, M5 and C14 were selected for the study. For each clone, three trees to be removed for first thinning process were designated and felled. A total of three trees of 4-year-old A. mangium were also taken for comparison purposes. Approximately 25 mm thick disc samples were taken at the bottom and top most of the tree (before first branch). The logs were cut into billets of 2 m length and converted into wood particles and fibres for particleboard and MDF manufacture.
Specific gravity and strength property tests (green condition)

The specific gravity and strength property tests of the Acacia hybrid wood were conducted according to the British Standard procedure (BS 373:1957).

Particleboard manufacture

The billets were debarked and split-cut into planks before disintegrated by a Pallmann drum- chipper and by a knife ring flaker; turning the wood material into wood chips and flakes respectively. The particles were dried and screened by using a vibrating screen to remove the fines from coarse particles. The selected wood particles were dried in an oven at 70 C to moisture content 5% and below prior to particleboard manufacture. The single-layered particleboard were produced at a target density of 750 kg/m3 and three levels of resin urea formaldehyde (UF) were used at 6, 8 and 10% level of admixtures. A measured quantity of particles was put in a batch mixer and sprayed with a resin mix of urea formaldehyde, hardener and wax emulsion. The resinated flakes were laid in a wooden square mould and prepressed at 350 kg/cm2. The consolidated particle mat was finally pressed to 12 mm metal stops between two stainless steel caul plates in an electrically heated hydraulic press maintained at 160 C for six minutes until the resin completely cured.

MDF manufacture

Acacia hybrid billets were sawn separately into planks and converted into wood chips by using Taihei chipper. For the preparation of MDF fibres, acceptable chips of size of 2.0 x 2.5 x 0.2 cm were used. The wood chips were steamed at pressure of 70 kg/cm2 for 5 min and subsequently refined at disc clearance of 0.381 mm in the Sprout-Bauer Pressurised Refiner. The dried fibres were screened and only fibres retained on the screen with slot size between 0.5 and 1.0 mm were collected for MDF manufacture. These fibres were dried in the oven to achieve low moisture content of 5% and below. The UF resin was used for this study. One series of single-layered MDF comprised of four panels were set at a target density of 750 kg/m3 and resin levels of 6, 8 and 10% were used. The dried fibres were sprayed and blended with resin and wax before being consolidated into a wooden mould of dimensions 34 x 34 x 1.2 cm. The fibre mat was pre-pressed at 350 kg/cm2 for about 1 minute before the wooden mould was taken out. The consolidated mat was pressed to the desired thickness in a hot press maintained at 190 C for about 4.5 min. 

For further details log on website :
http://borneoscience.ums.edu.my/wp-content/uploads/2013/09/PROPERTIES-OF-SMALL-DIAMETER-ACACIA-HYBRID-LOGS-FOR-BIOCOMPOSITES-PRODUCTION1.pdf

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