Bonding properties and performance of multi-layered kenaf board

Kenaf (Hibiscus cannabinus) has recently been introduced to the Malaysian bio-composite industry. Based on their basic properties, both the bast fibres and core material of kenaf are distinctly different. While bast fibres are stiffer and low in wettability, the core material of kenaf is weaker and has excellent absorbing properties. This study evaluated the properties of kenaf board made from a combination of bast fibres and core material. The bast fibres were separated first from the core, followed by pre-treatment with NaOH, then combing until the fibres became loose. The properties of kenaf board were tested using MS standards 1787: 2005. An analysis of variance was carried out to study the effects of resin types and bast to core proportion on the boards. The buffering capacity study revealed that kenaf bast, kenaf core and rubberwood behaved similarly in alkali but differently in an acidic condition. Both the kenaf bast and core were relatively less stable in acid compared with rubberwood. Due to its morphological characteristics, the kenaf core inner surface exhibited higher wettability than the outer surface. There was significant interaction between resin type and the proportion of bast:core at p < 0.01. Generally, boards made from 100% kenaf core and bonded with urea formaldehyde (UF) resin had superior performance. The mechanical properties [modulus of elasticity (MOE), modulus of rupture (MOR), internal bond (IB)] of the boards were significantly influenced by the amount of bast fibre in the board––the higher the amount, the poorer the strengths. This effect, however, was reversed for thickness swelling (TS). Only UF-bonded kenaf-based boards had comparable water absorption (WA) property to that of the control (100% rubberwood). The incorporation of low molecular weight phenol formaldehyde (LPF) resin in the fibres had mixed effects on board properties. The effects varied based on the resin used; it improved the MOE and MOR of the board but not the IB, TS and WA when used with UF resin. It improved the IB only when used with melamine urea formaldehyde (MUF) resin. The best performance was given by boards made from 100% kenaf core irrespective of the type of resin used. All kenaf boards in this study had higher MOR than that of 100% rubberwood. Insufficient curing of LPF resin was identified as the main factor for the poor performance of LPF-bonded boards

Exfiltration from sewers: effects of different types of leakage / Mohd Ashaari Ab Wahab ... [et al.]

This research was conducted to study exfiltration of wastewater from gravity sewers. Exfiltration through different types of sewer leaks were studied. With the different size of leakage areas and a constant thickness of soil bedding, it was found that the exfiltration rate reduces and became constant over a duration of one (1) to three (3) days. Knowing the exfiltration rate, the time taken for the polluted water exfiltrate from sewer pipes to reach the groundwater can be determined so that preventive measures can be taken to prevent it. From studies conducted, it can be shown that the size of the leakage area was found to play an important role in determining the size of the clogging zone, the increased in the clogging zone resulted in the decreased of exfiltration rate due to the accumulation of organic matters at the edge of the leakage area and trapped in the pores of the bedding soil

Adhesion characteristics of phenol formaldehyde pre-preg oil palm stem veneers

The purpose of this study was to evaluate the adhesion properties of phenol formaldehyde-prepreg oil palm veneers that have potential for plywood manufacture. Phenol formaldehyde (PF) resin of three different molecular weights (i.e. 600 (low), 2,000 (medium), and 5,000 (commercial)) were used to pre-treat the veneers. The veneers were soaked in each type of PF resin for 20 seconds, pressed between two rollers, and pre-cured in an oven maintained at 103 ± 2 °C for 24 hours. The volume percent gain (VPG), weight percent gain (WPG), pH, buffering capacity, and contact angle of the phenolic pre-preg veneers were determined. The bonding shear was also evaluated according to British Standard European Norm BS EN 314. The results show that veneers from both inner and outer layers treated with low molecular weight PF (LMwPF) resin had significantly higher VPG and WPG compared to the other PF resins. The pH values of all of the veneers were slightly acidic (6.5 to 6.8) except for those that were treated with commercial molecular weight PF resin (7.8). A buffering capacity study revealed that untreated veneer had a greater resistance toward alkali, but was unstable under acidic conditions, while the phenolic pre-preg veneer behaved differently. This effect was more prominent as the molecular weight of the PF resin increased. An examination of the veneer surfaces demonstrated that phenolic treatment had increased the contact angle of the OPS veneer surfaces significantly. The bonding properties of plywood made from pre-preg palm veneers were found to be superior to those of commercial palm plywood

Influence of resin molecular weight on curing and thermal degradation of plywood made from phenolic prepreg palm veneers

The present work evaluates curing and the thermal behavior of different molecular weight phenol formaldehyde (PF) resins used to prepare PF prepreg oil palm stem veneers. The physical properties (solid contents, gelation time, pH, and viscosity) of PF resins were determined. The molecular weight of resins was characterized by gel permeation chromatography, whilst thermal properties were determined by differential scanning calorimetry and thermogravimetric analyses. The average molecular weight of PF resins were 526 g/mole (low), 1889 g/mole (medium), and 5178 g/mole (control - commercial). Among the resins, medium (MMwPF) gives better thermal stability with a retained weight of 48.9% at 300°C. High (Commercial PF) had a low decomposition temperature (109.3°C) which occurred within 11 min. Both low (LMwPF) and MMwPF started to melt at ≥120°C. Based on strength and shear values, phenolic prepreg palm veneers can be prepared using either low or medium molecular weight PF but with varying results. In all cases, the mechanical properties of palm plywood made from PF prepreg veneers were superior to those made from PF-bonded plywood using the commercial process