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Title: Factors affecting the enhancement of Acacia hybrid particleboard
Author: Misran, Suffian
ISNI:       0000 0004 2712 3107
Awarding Body: Prifysgol Bangor University
Current Institution: Bangor University
Date of Award: 2011
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Abstract:
Acacia hybrid has been planted in Malaysia’s forest plantation for wood resources. Evaluation of the wood showed that the wood has density 446 kg m-3, good dimensional stability and low acid buffering capacity (0.10 mmol l-1). The amount of reactive polyphenols from 80 °C water extraction was 45.5% which is considered high for wood. The polyphenols tremendously decreased at extraction temperatures of 120 °C and over. Particleboards of Acacia hybrid bonded with urea formaldehyde (UF) resin consistently showed better physical and mechanical properties than recycled wood. Thickness swelling of the boards was 15%, water absorption 30%, modulus of elasticity 26.25 MPa and modulus of rupture 3811 MPa. The boards quality continued to be high when bonded with melamine urea formaldehyde (MUF) and phenol formaldehyde (PF) resins when compared to spruce particleboards. Internal bond strength of the boards ranged from 0.9 to 1.3 MPa. The work showed that the Acacia hybrid is potential for high quality particleboards. Decay of Acacia hybrid boards due to Pleurotus ostreatus, Trametes versicolor, Pycnoporus sanguineus and Coniophora puteana was investigated. Internal bond strength of boards bonded with UF and MUF resins strongly deteriorated (86 to 100% loss) due to decay fungi. T. versicolor and C. puteanaca used severe loss in weight (14.9%to 37.3%) of the boards. Improved decay resistance of the boards was achieved when bonded with PF resin. The board was dimensionally stable and has high degree of internal bond strength even after decay fungi exposures. Maximum weight loss was 8.3% due to P. ostreatus. Internal bond strength of the boards after decay test was between 0.5 and 1.1 MPa. Investigation on the effect of Acacia hybrid extractives (hot water extraction at 80, 100, 120 and 160 °C) to wood gluing was carried out using automatic bonding evaluation system (ABES). Significant increment in shear strength (5.2 MPa) of wood veneers was obtained when the UF resin was mixed with extractives from 80 °C extraction with 8% solids content. The effect of extractives on the UF resin was likely to be influenced by the amount of reactive polyphenols. Subtle changes occurred in the thermal behaviour of UF resinmixed with extractives at temperatures between 240 and 340°C probably caused by the decomposition of UF polymer. The FTIR analysis showed that the resin and extractive mixtures have similar structural peaks to those of a typical UF resin. The extractives were characterised using MALDI-TOF mass spectrometer. Extractives from 80, 100 and 120°C extraction contained compounds with molecular weight between 332 and 647 Da probably of simple polyphenols. Four major compounds were considered with molecular weights of 544, 560, 566, and 582 Da. Extractives from 80 and 100 °C extraction contained polymers with repetitive unit of 74 or 148 Da which could be of lignans. Extractives of high temperature extraction (160°C) had two different compounds, hexose polymers with 162 fragment unit and acetylxylose with 174 Da fragment. Better performance of Acacia hybrid particleboards could be related to reaction of simple polyphenols (galloyl glycosides, lignin glycosides and flavonoids) in the extractives with formaldehyde of the resins which involved methylolation and condensation processes. This is supported by the significant weight loss of UF and extractives mixtures from thermal analysis.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.543216  DOI: Not available
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