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Using a vacuum pressure cylinder, Gigantochloa scortechinii was treated with boron and copper chrome boron (CCB) preservative at different concentrations of 2% and 3%. The treatability of untreated and treated bamboo, as well as its physical and mechanical properties, were investigated. Both preservatives showed a high level of penetration into the bamboo strips. Weight percent gain (WPG) and extent of retention of CCB-treated bamboo strips were higher than those of the boron-treated samples. Swelling and shrinkage were proportionately reduced with treatment, with a significant difference between radial and tangential dimensions. When compared to untreated bamboo, treated bamboo showed a greater reduction in radial swelling but a lower reduction in shrinkage. The mechanical properties of untreated and treated samples differed in modulus of elasticity (MOE) and compression. Untreated samples had the highest MOE of 26,100 N.mm-2, while boron and CCB had MOE values of 22,800 and 22,900 N.mm-2, respectively. Copper chrome boron samples had the highest compression value of 86.3 N.mm-2, while the boron and untreated samples had values of 84.0 and 78.3 N.mm-2, respectively.

The compatibility between isocyanate and polyol plays an important role in determining a polyurethane product’s performance. This study aims to evaluate the effect of varying the ratios between polymeric methylene diphenyl diisocyanate (pMDI) and Acacia mangium liquefied wood polyol on the polyurethane film properties. A. mangium wood sawdust was liquefied in polyethylene glycol/glycerol co-solvent with H2SO4 as a catalyst at 150 °C for 150 min. The A. mangium liquefied wood was mixed with pMDI with difference NCO/OH ratios to produce film through the casting method. The effects of the NCO/OH ratios on the molecular structure of the PU film were examined. The formation of urethane, which was located at 1730 cm−1, was confirmed via FTIR spectroscopy. The TGA and DMA results indicated that high NCO/OH ratios increased the degradation temperature and glass transition from 275 °C to 286 °C and 50 °C to 84 °C, respectively. The prolonged heat appeared to boost the crosslinking density of the A. mangium polyurethane films, which finally resulted in a low sol fraction. From the 2D-COS analysis, the hydrogen-bonded carbonyl (1710 cm−1) had the most significant intensity changes with the increasing NCO/OH ratios. The occurrence of the peak after 1730 cm−1 revealed that there was substantial formation of urethane hydrogen bonding between the hard (PMDI) and soft (polyol) segments as the NCO/OH ratios increased, which gave higher rigidity to the film.

Bamboo requires treatment to extend its service life. However, as bamboo strips could serve as a suitable candidate for lamination, the treatment may affect its bendability. The current study investigated the effects of boric acid treatment on the physical, mechanical, adhesion, and morphological properties of bamboo strips. Owing to their availability and popularity in local industries, four Malaysian bamboo species were used in this study, namely Gigantochloa scortechinii, Gigantochloa levis, Dendrocalamus asper, and Bambusa vulgaris. These four species’ bamboo strips were treated with 5% boric acid and their properties were evaluated. The findings revealed that the boric acid treatment had varying degrees of effect on the properties of the bamboo. Despite having lower treatability and stability, both G. scortechinii and G. levis have greatly superior mechanical properties that justify their use in the production of laminated products. The boric acid treatment was found to provide several benefits to bamboo strips intended for lamination, including increased wettability, dimensional stability, and mechanical strength.

Due to its inferior properties, oil palm wood (OPW) extracted from the inner layer of the oil palm (Elaeis guineensis) trunk, referred as inner OPW in this study, is frequently regarded as a waste. Phenolic resin treatment and lamination of inner OPW with other hardwoods may be an excellent way to improve the properties of the inner OPW. In this study, inner OPW were treated with two different concentrations (15% and 20%) of low molecular weight phenol formaldehyde resin (LmwPF) and compressed at different compression ratios (10%, 20%, and 30%). The physical and mechanical properties of the modified inner OPW’s were evaluated according to British Standards (BS) 373: 1957. The results revealed that inner OPW treated with the highest compression ratio (30%) and resin concentration (20%) exhibited the highest weight percent gain, polymer retention and density. In the following phase of the research, the treated inner OPW was used as the core layer in the fabrication of a three-layer laminated compreg hybrid composites, with untreated and treated sesenduk (Endospermum diadenum) wood serving as the face and back layers. The compression ratios of 10% and 20% and resin concentrations of 10% and 20% were used in this phase of study as laminated boards made with 30% compression ratio failed. The findings showed that resin concentration had a significant impact on both the inner OPW and the laminated compreg hybrid panels. Markedly, higher resin concentrations (20%) resulted in improved physical properties, i.e., thickness swelling and water absorption, as well as enhanced mechanical properties (modulus of rupture and modulus of elasticity). Although compression ratios had no significant effect on the properties of the laminated products, those compressed at higher compression ratios (20%) performed slightly better than the panels compressed at lower compression ratios (10%).

The production of nanocrystalline cellulose (NCC) usually takes place through a series of chemical processes like pulping, bleaching and acid hydrolysis process. The hydrolysis processes using strong acid like H2SO4 can help the NCC to have a high degree of crystallinity and imparts a negative surface charge to NCC. However, the application of H2SO4 leads to increment in dehydration reaction and lowered the NCC thermal properties. Post alkaline treatment is the method that is commonly used to recover the effect of H2SO4 by neutralizing the acid using a strong base like sodium hydroxide (NaOH). On the other hand, the effect of lignin in fibres was able to help in improving the thermal properties and extraction of lignin was seen involving an excessive number of chemicals. The lignin part can remain in the pulp by controlling the bleaching process. Therefore in this study, NCC with different lignin content went through post alkaline treatment to remove the remaining sulphate groups. The thermal analysis revealed that the existence of lignin and removal of sulphate groups help to increase the thermal stability of the NCC by shifting the degradation and melting temperature to the higher value.

The study on the mechanical properties of cross laminated timber (CLT) panels made from tropical hardwood species is essential in order to promote the use of CLT as buildings material in Malaysia. The objective of this study were to evaluate the mechanical performance and failure characteristics of CLT fabricated from tropical timbers species, namely, batai (Paraserianthes falcataria), sesendok (Endospermum malacensis), rubberwood (Hevea brasiliensis) and kedondong (family Burceraceae). The modulus of rupture (MOR), modulus of elasticity (MOE), and compressive strength were determined. The failure characteristics of each samples were visually examined and recorded. The results indicated that CLT made from kedondong (KKK) had the highest value of MOR (82.63 N/mm2) and MOE (11,371.33 N/mm2) compared to other species. For compressive strength, CLT made from kedondong (KKK) and rubberwood (RRR) were not significantly different. The failure characteristics observed from bending test were tension, rolling shear and glue line failure while the crushing, shearing and splitting failure were found during compression test. Based on the results obtained, it showed that, the tropical hardwood is suitable to be used as raw material to produce CLT. However, more study should be conducted to observe the performance of CLT on durability and outdoor weathering.

The objective of this study is to determine the effects of alkaline copper quaternary (ACQ) treatment on the surface quality and bonding performance of four Malaysian hardwood species, namely batai, sesenduk, rubberwood and kedondong. The samples were impregnated with 2% ACQ preservatives and bonded with phenol-resorcinol–formaldehyde resin for cross laminated timber (CLT) fabrication. The changes in density and the retention of both ACQ and copper after the treatment were recorded. Surface roughness and wettability of both treated and untreated samples were measured. Block shear and delamination tests were performed to evaluate the bond-line strength of CLT. The study revealed that the average surface roughness (Ra) of each species increased significantly. Wettability of batai, sesenduk, rubberwood and kedondong was significantly higher than that of the untreated samples suggesting an improvement in surface wettability. For single-species CLT, treated rubberwood has the highest shear strength followed by kedondong, sesenduk and batai with values of 9.53 N/mm2, 6.00 N/mm2, 5.68 N/mm2 and 4.19 N/mm2, respectively. While for mixed-species CLT, the combination of ACQ-treated rubberwood-sesenduk-rubberwood has the highest block shear strength with a value of 8.05 N/mm2. No delamination was observed from all samples. ACQ treatment was found to not affect the block shear strength significantly. Therefore, ACQ preservatives can be used to produce CLT with good bonding performance.

Evaluation of the effects of 8% methanol (MeOH) pretreatment on the finishing performance of Acacia mangium wood was carried out using different coating systems, i.e., nitrocellulose (NC), acid cat...

The aim of this study is to assess the curing behaviour and thermal properties of phenol–formaldehyde (PF) adhesives with different degree of tannin substitution using several thermal analysis techniques. Tannin from Acacia mearnsii bark was copolymerized with PF to form a bonding agent for plywood. The resin mixture was heated at 50 °C prior to adding 40% w/w tannin solution, followed by a continuous stirring for 2 h. The amounts of tannin substitution were 20%, 30% and 40% (w/w of PF solids) and 100% PF were used as control. The study shows that the addition of tannin quickened the gel time of the resin notably, parallel with the increase in viscosity of the resin. The dry shear bond strength of the tannin phenol–formaldehyde (TPF) co-polymer ranged between 1.71 and 2.58 MPa as compared to 3.41 MPa for PF. At higher addition of tannin, the shear bond strength reduced significantly predominantly the 40% tannin substitution. Formulation containing 20% tannin was found comparable to that of neat PF. Thermal test revealed that TPF starts to degrade at a lower temperature than PF resin. All TPF resins started to cure at about 125 °C and peaked at 160 °C compared to PF that began to cure at 145 °. The DMA of the resin showed an increase in the resin stiffness with an addition of tannin. These results imply that even though TPF starts to degrade at lower temperature, the cured TPF is relatively stronger than pure PF.

An effective statistical tool for increasing and boosting the production of xylanase and pectinase by Bacillus amyloliquefaciens ADI2 during submerged fermentation (SmF) appears to be the response of surface methodology (RSM) using the central composite design (CCD). Optimum production was achieved under fermentation conditions of a temperature of 28 °C, pH of 8.38, inoculum size of 4% (w/v) and agitation speed of 94 rpm for 48 h. The experimental responses demonstrated a near agreement with the expected responses under optimum conditions of independent variables, suggesting the model’s validity. The optimised CCD model had a 1.34-fold, 159 ± 6 U/mL greater xylanase and 5.96-fold, 205 ± 9 U/mL greater pectinase production than the one factor at a time (OFAT) approach. The production of concurrent enzymes of xylanase–pectinase resulted in a ratio of 1:1.3.

Forest covers 4.06 billion hectares (ha) or 31% of the total land area worldwide, where 93% (3.75 billion ha) are natural regenerating forests and the remaining 7% (294 million ha) are planted forests. Eucalyptus spp., being one of the most important plantation species, has been planted in 95 countries around the world, and the area of plantation has exceeded 22.57 million ha. In the southern hemisphere, it is a significant industrial fast-growing tree species. These plantations serve as a valuable resource for the timber and fibre-based industries. Eucalyptus is the main fibre resource for the pulp and paper industries in developed countries. Timber extracted from the planted eucalyptus trees has long been used for solid wood and its fibres were used for manufacturing medium-density fibreboard. In comparison to most softwood species, Eucalyptus timber is reported to have a higher rigidity, making it ideal for manufacturing structural products. Therefore, this paper presents a review and analysis of the recent state of research on the utilisation of planted eucalyptus for engineered wood products (EWPs) manufacturing. This study investigated Eucalyptus-based EWPs such as particleboard, fibreboard, oriented strand board, laminated veneer lumber, plywood, glue laminated lumber, and cross-laminated lumber. The feasibility of using planted Eucalyptus in the production of EWPs, as well as the challenges encountered, was also discussed.

Lignin is a natural biopolymer with a complex three-dimensional network and it is rich in phenol, making it a good candidate for the production of bio-based polyphenol material. This study attempts to characterize the properties of green phenol-formaldehyde (PF) resins produced through phenol substitution by the phenolated lignin (PL) and bio-oil (BO), extracted from oil palm empty fruit bunch black liquor. Mixtures of PF with varied substitution rates of PL and BO were prepared by heating a mixture of phenol–phenol substitute with 30 wt.% NaOH and 80% formaldehyde solution at 94 °C for 15 min. After that, the temperature was reduced to 80 °C before the remaining 20% formaldehyde solution was added. The reaction was carried out by heating the mixture to 94 °C once more, holding it for 25 min, and then rapidly lowering the temperature to 60 °C, to produce the PL−PF or BO−PF resins. The modified resins were then tested for pH, viscosity, solid content, FTIR, and TGA. Results revealed that the substitution of 5% PL into PF resins is enough to improve its physical properties. The PL−PF resin production process was also deemed environmentally beneficial, as it met 7 of the 8 Green Chemistry Principle evaluation criteria.

Semantan (Gigantochloa scortechinii) and beting (Gigantochloa levis) bamboo are the two Malaysian bamboo that are suitable to be converted into laminated bamboo boards. One of the main criteria for laminated board is its good bondability, which is determined by shear performance. The shear performance of laminated board is influenced by several factors such as the species used, adhesive types and lamination configurations. Therefore, in this study, laminated bamboo boards were produced using Semantan and Beting bamboo bonded with phenol–resorcinol–formaldehyde (PRF) and polyurethane (PUR) adhesives. Different configurations (lay-up patterns and strip arrangements) were used during the consolidation of the laminated boards. The bamboo strips were arranged in three different arrangements, namely vertical, horizontal and mixed, and then assembled into a three-layered structure with two lay-up patterns, which are perpendicular and parallel. Shear performances, such as shear strength, bamboo failure and delamination of the boards, were evaluated. The results revealed that the adhesive type and lay-up pattern were the most influential factors on the shear performance. PRF-bonded laminated bamboo boards outperformed PUR-bonded laminated bamboo boards in terms of shear strength and bamboo failure but PUR bonding had better bond durability as indicated by its low delamination. Boards laminated parallelly significantly outperformed those bonded perpendicularly. As for strip arrangement, PRF-bonded laminated boards were less influenced by it compared to PUR-bonded laminated boards. The results suggested that PRF is a better adhesive for bamboo lamination due to its higher shear performance and more consistent performance across structural configurations (lay-up patterns and strip arrangements).

In this study, the effects of stem canker disease caused by Chrysoporthe deuterocubensis on the chemical properties and durability of a Eucalyptus hybrid (E. urophylla x E. grandis) were investigated. Eleven-year-old healthy and infected trees were collected. The samples were grouped into four different classes based on the infection severity: healthy (class 1), moderately infected (class 2), severely infected (class 3), and very severely infected (class 4). The changes in chemical properties were evaluated via chemical analysis and Fourier transform infrared spectroscopy (FTIR) analysis. A resistance test against fungal decay (Pcynoporus sanguineus and Caniophora puteana) and termite (Coptotermes curvignathus) was also performed. The results showed that reductions in cellulose and hemicellulose content from 53.2% to 45.4% and 14.1% to 13.9%, respectively, were observed in the infected samples. Meanwhile, the percentages of lignin and extractives increased from 18.1% to 20.5% and 14.6% to 20.2%, respectively. The resistance against fungi and termites varied between severity classes. Generally, infected wood behaved better than healthy wood in terms of durability against fungi and termites. The durability classes for both tests were significantly improved, from resistant to highly resistant and poor to moderately resistant, respectively. These results suggest that E. urograndis that is infected by C. deuterocubensis might have a better potential use in lumber production with regard to its durability and processing cost compared to pulp and paper products.

This study investigated the effects of different citric acid content on the physico-mechanical and biological durability of rubberwood particleboard. Particleboards with density of 700 kg/m3 were produced with three different citric acid contents, namely 10, 15 and 20 wt%. Particleboards made from 10 wt% urea formaldehyde (UF) resin were served as control for comparison purposes. FTIR analysis was carried out and the formation of ester linkages between -OH on cellulose and carbonyl groups of citric acid was confirmed. The peak intensity increased along with increasing citric content, which indicated that a higher amount of ester linkages were formed at higher citric acid content. Citric acid-bonded particleboard had inferior physical properties (water absorption and thickness swelling) and mechanical properties (internal bonding strength, modulus of rupture and modulus of elasticity) compared to that of the UF-bonded particleboard. However, the performance of particleboard was enhanced with increasing citric acid content. Meanwhile, citric acid-bonded particleboard displayed significantly better fungal and termite resistance than UF-bonded particleboard owing to the acidic nature of citric acid. It can be concluded that citric acid is a suitable green binder for particleboard but some improvement is needed during the particleboard production process.

Oil palm empty fruit bunch (EFB) is the most significant waste generated from the agricultural industry in Malaysia. Composting is one of the potential approaches to utilize EFB. However, composting of EFB is a time-consuming process, thus impractical for industrial application. The composting process can be shortened by introducing competent fungi into an optimal EFB composting system. This study was conducted to isolate and identify competent fungi that can naturally compost EFB. Samplings were carried out at eight different time points over a 20-weeks experimental period. The physical properties of EFB samples such as pH, residual oil content, and moisture content were measured and the EFB composting process that was indicated by the contents of cellulose, hemicellulose, and lignin were assessed. The fungal growth, distribution, and lignocellulolytic enzyme activities were evaluated. The results indicated that the changes in physical properties of EFB were correlated to the fungal growth. The gradual reduction in moisture content and residual oil, and the increment in pH values in EFB samples throughout the experimental period resulted in reduced fungal growth and diversity. Such phenomenon delayed EFB composting process as revealed by the changes in EFB lignin, hemicellulose, and cellulose contents. The most dominant and resilient fungi (Lichtheimia ramosa and Neurospora crassa) survived up to 16 weeks and were capable of producing various lignocellulolytic enzymes. Further understanding of these factors that would contribute to effective EFB composting could be useful for future industrial applications.

Cross laminated timber (CLT) was fabricated from Acacia mangium wood by using phenol resorcinol formaldehyde (PRF) and one component polyurethane (PUR) as binders. The purpose of the study was to evaluate the bond integrity of A. mangium CLT produced using different working parameters. The assemblies were pressed at 30 °C for 30 min using three pressing pressures (0.9 N/mm2, 1.2 N/mm2, and 1.5 N/mm2). Delamination and block shear tests were conducted on the CLT according to European Standards, EN 391 and EN 392, respectively. The results revealed that PRF-bonded CLT experienced lower percent delamination compared to that bonded with one component PUR. It appears that a higher clamping pressure i.e. 1.5 N/mm2, is needed to sufficiently bond A. mangium lumbers as indicated by a marked increase in bond shear strength with an increase of pressing pressure. PRF was found to be a more superior adhesive than PUR irrespective of cramping pressure and loading direction. A. mangium wood is relatively dense thus requires quite high pressure, 1.5 N/mm2, irrespective of adhesive used. PRF appears to bond A. mangium wood better compared to PUR with shear bond strength of 21% and wood failure percentage of 220% higher.

Thermosetting epoxies are low-density polymers with excellent adhesion, mechanical properties, and resistance to environmental degradation. They are widely used as molds and castings for manufacturing, protective coatings, and reinforcement material for aircraft. However, polymer brittleness is a major disadvantage preventing its widespread application. The addition of filler materials such as nanoparticles has attracted considerable attention. Using reinforcement materials for biocomposite derived from a natural, renewable and sustainable material will lower the manufacturing cost for epoxy composites. This study investigated the physical and mechanical properties of epoxy composites reinforced with amorphous and crystalline silica. The amorphous and crystalline silica were obtained by the precipitation method from the carbonization of rice husk at 700 °C and 1000 °C for 6 h, separately. The epoxy resin was mixed with 5 wt%, 10 wt%, and 15 wt% concentrations (by weight) of amorphous and crystalline silica, separately. Silica 10 nm to 30 nm in size was obtained, as observed by scanning electron microscopy (SEM). The epoxy nano-crystalline silica composite had a significantly lower thickness swelling value compared to the epoxy nano-amorphous silica composite. However, the epoxy nano-crystalline silica composite had significantly better mechanical properties.

The manufacturing of fiberboard from wood fiber with the help of adhesive is highly developed and widely commercialized technique. However, with an increasing concern over health issues and biomass conservation, the fiber boards from agriculture residues with or without using adhesives are under intensive investigation. In last three decades, several researches have been done various methods and technique dealing the development of binderless fiberboards such as wet process and dry process. This review article also covered pretreatments of fiber which helps to find out optimum criteria for fabrication of fibreboards. Fibre sizes in fibreboard were studied and found that the dimensions of fibres effect the physical, mechanical and thermal properties. The pressing time and temperature influence the internal bonding of binderless fibreboards. The mechanical and thermal properties of binderless fibresboard were discussed on various pressing time and temperature and compared with different type fibreboards. Effect of hygrothermal properties on the physical, mechanical and thermal behavior of binderless were also discussed. This review summarized various aspects of self-bonding mechanism in binderless fibresboard with a focus on agriculture residues based raw materials. Various aspects of binderless fiberboard manufacturing such as raw material suitability, effects of pretreatments and manufacturing process on physical, mechanical and thermal properties are discussed. The chemical changes in fiber during pretreatments and hot pressing is also discussed in detail. These binderless fiberboard showed the suitability in use for indoor applications due to its non-toxic characteristics.

Agarwood is a valuable aromatic resinous wood that is biosynthesised when a fungal attack injures the healthy wood tissue of the Aquilaria tree. The magnitude of infection related to sap flow (SF) is one of the most critical functional traits to evaluate the tree’s response to various adverse conditions. Therefore, the objective of this study was to investigate the reliability of sonic tomography (SoT) and sap flow meter (SFM) in studying the influence of inoculation fungi Pichia kudriavzevii Boidin, Pignal and Besson, and Paecilomyces niveus Stolk and Samson, on deteriorated wood (Dt) and SF rate in Aquilaria malaccensis Lam. A. malaccensis trees with small, medium, and large diameters were inoculated with each fungus separately at the bottom, middle, and top positions of the tree and the area of sapwood was measured after 6, 12, and 24 months to stimulate the agarwood formation. Furthermore, the SF rate was assessed using SFM in the position of the selected trees. There was a significant difference (p ≤ 0.05) in Dt% and SF rate between inoculated and uninoculated trees. The Dt percentage in trees inoculated with P. kudriavzevii, P. niveus, and control trees was 25.6%, 25.7%, and 15.0%, respectively. The SF rate was lower in P. kudriavzevii, with 207.7 cm3/h, than in the control trees, with 312.9 cm3/h in the small-diameter class. In summary, the results of this study emphasise the importance of inoculation duration (24 months) and the effects of water conductivity, especially tree diameter class (small), on the biosynthetic response of resinous substance.

The present work reports the biobleaching effect on OPEFB pulp upon utilisation of extracellular xylano-pectinolytic enzymes simultaneously yielded from Bacillus amyloliquefaciens ADI2. The impacts of different doses, retention times, pH, and temperatures required for the pulp biobleaching process were delineated accordingly. Here, the OPEFB pulp was subjected to pre-treatment with xylano-pectinolytic enzymes generated from the same alkalo-thermotolerant isolate that yielded those of higher quality. Remarkable enhanced outcomes were observed across varying pulp attributes: for example, enzyme-treated pulp treated to chemical bleaching sequence generated improved brightness of 11.25%. This resulted in 11.25% of less chlorine or chemical consumption required for obtaining pulp with optical attributes identical to those generated via typical chemical bleaching processes. Ultimately, the reduced consumption of chlorine would minimise the organochlorine compounds found in an effluent, resulting in a lowered environmental effect of paper-making processes overall as a consequence. This will undoubtedly facilitate such environmentally-friendly technology incorporation in the paper pulp industry of today.

Eucalyptus pellita F. Muell. is currently the predominant tree species deployed for tree plantation establishment in some parts of Borneo, particularly Sabah state, Malaysia. Its low disease susceptibility, good growth and form, and desirable wood properties make E. pellita particularly suitable for plantation development in the wet tropical regions of south-east Asia. In spite the many positive traits, practical field observations indicate that the species is susceptible to end-splitting. There is some anecdotal evidence to suggest a genetic relationship with the incidence of end-split, although these observations were not statistically tested. This study evaluates the occurrence of end-splitting in five-year old plantation E. pellita in Sabah as affected by family and growth attributes. An existing progeny tree breeding trial, involving seeds that originated from Papua New Guinea, China, Vietnam, Australia, Sabah, and Sarawak with 106 families, was used to carry out the split assessment. Logs from the second thinning were cut into 2.2-m-long sections. The end splits were measured three days later, the incidence and severity of splitting were assessed at both the large and small ends of each log by using a designated split scoring system. The study shows that 99% of all log cross sections (per cut surface) experienced signs of splitting, with an average of 2.7 splits per cut surface. Overall, 54% of all splits were classed as ‘Three-Quarter Radial Splits’ while the occurrence of internal splits was negligible. Split severity showed a heritable and significant difference (h2 = 0.24 at p ≤ 0.05) among the family levels. Splitting was also significantly related to growth factors such as tree height and diameter at breast height (DBH). The findings suggest that end-splitting is caused by family–environment interactions. This offers the opportunity to improve the wood resource of E. pellita via breeding strategies.

The major hurdle in melt-processing of ultra-high molecular weight polyethylene (UHMWPE) nanocomposite lies on the high melt viscosity of the UHMWPE, which may contribute to poor dispersion and distribution of the nanofiller. In this study, UHMWPE/cellulose nanofiber (UHMWPE/CNF) bionanocomposites were prepared by two different blending methods: (i) melt blending at 150 &deg, C in a triple screw kneading extruder, and (ii) non-melt blending by ethanol mixing at room temperature. Results showed that melt-processing of UHMWPE without CNF (MB-UHMWPE/0) exhibited an increment in yield strength and Young&rsquo, s modulus by 15% and 25%, respectively, compared to the Neat-UHMWPE. Tensile strength was however reduced by almost half. Ethanol mixed sample without CNF (EM-UHMWPE/0) on the other hand showed slight decrement in all mechanical properties tested. At 0.5% CNF inclusion, the mechanical properties of melt-blended bionanocomposites (MB-UHMWPE/0.5) were improved as compared to Neat-UHMWPE. It was also found that the yield strength, elongation at break, Young&rsquo, s modulus, toughness and crystallinity of MB-UHMWPE/0.5 were higher by 28%, 61%, 47%, 45% and 11%, respectively, as compared to the ethanol mixing sample (EM-UHMWPE/0.5). Despite the reduction in tensile strength of MB-UHMWPE/0.5, the value i.e., 28.4 &plusmn, 1.0 MPa surpassed the minimum requirement of standard specification for fabricated UHMWPE in surgical implant application. Overall, melt-blending processing is more suitable for the preparation of UHMWPE/CNF bionanocomposites as exhibited by their characteristics presented herein. A better mechanical interlocking between UHMWPE and CNF at high temperature mixing with kneading was evident through FE-SEM observation, explains the higher mechanical properties of MB-UHMWPE/0.5 as compared to EM-UHMWPE/0.5.

Conventional UHMWPE molding involves long pressure holding duration, nevertheless in the presence of filler such as cellulose nanofiber (CNF), this may contribute to filler degradation. This study optimized the compression molding parameters of UHMWPE/ CNF bio-nanocomposite by using response surface methodology (RSM) in consideration of temperature, pressure and duration as variables. An optimal processing condition of 180°C, 15 MPa, and 20 minutes contributed to more than 80% desirability with tensile strength, yield strength, elongation at break, and Young’s modulus values of 22.83 MPa, 23.14 MPa, 487.31%, and 0.391 GPa, accordingly. Mechanical properties of UHMWPE/CNF bio-nanocomposites molded at optimized processing conditions were comparably similar to those prepared at conventional processing condition, and with the advantage of having shorter processing time. The results presented herewith provides insight towards a more practical approach for UHMWPE/CNF bio-nanocomposites consolidation process.

The properties of CLT can be affected by the type of adhesives used. The thermal properties of the adhesive that join the timber together is essential to determine the thermal endurance of the CLT product. In this study, two types of adhesives were used to join the cross laminated timber (CLT) manufactured from Acacia mangium namely phenol resorcinol formaldehyde (PRF) and one component polyurethane (PUR). The thermal properties of the adhesives, A. mangium wood and the glue lines were determined via Thermogravimetric Analysis (TGA) and Dynamic Mechanical Analysis (DMA) tests. The TGA test showed that PRF adhesive had higher degradation temperature at 530 ºC compared to PUR adhesive at 430 ºC. Meanwhile, the PRF adhesive as a glue line in CLT also showed better thermal resistance where a higher amount of residue of 20,94 % was recorded at temperature up to 900 ºC compared to PUR glue line with 18,26 % residue. The integrity of the CLT over temperature was determined via DMA test and the results showed that PRF adhesive as glue line had superior properties, indicating better interfacial bonding with the woods.

Mechanical strength, thermal conductivity and electrical breakdown of polypropylene/lignin/kenaf core fiber (PP/L/KCF) composite were studied. PP/L, PP/KCF and PP/L/KCF composites with different fiber and lignin loading was prepared using a compounding process. Pure PP was served as control. The results revealed that tensile and flexural properties of the PP/L/KCF was retained after addition of lignin and kenaf core fibers. Thermal stability of the PP composites improved compared to pure PP polymer. As for thermal conductivity, no significant difference was observed between PP composites and pure PP. However, PP/L/KCF composite has higher thermal diffusivity. All the PP composites produced are good insulating materials that are suitable for building. All PP composites passed withstand voltage test in air and oil state as stipulated in IEC 60641-3 except PP/L in oil state. SEM micrograph showed that better interaction and adhesion between polymer matrix, lignin and kenaf core fibers was observed and reflected on the better tensile strength recorded in PP/L/KCF composite. This study has successfully filled the gap of knowledge on using lignin and kenaf fibers as PP insulator composite materials. Therefore, it can be concluded that PP/Lignin/KCF has high potential as an insulating material.

Citric acid (CA) can be found naturally in fruits and vegetables, particularly citrus fruit. CA is widely used in many fields but its usage as a green modifying agent and binder for wood is barely addressed. Esterification is one of the most common chemical reactions applied in wood modification. CA contains three carboxyl groups, making it possible to attain at least two esterification reactions that are required for crosslinking when reacting with the hydroxyl groups of the cell wall polymers. In addition, the reaction could form ester linkages to bring adhesivity and good bonding characteristics, and therefore CA could be used as wood binder too. This paper presents a review concerning the usage of CA as a wood modifying agent and binder. For wood modification, the reaction mechanism between wood and CA and the pros and cons of using CA are discussed. CA and its combination with various reactants and their respective optimum parameters are also compiled in this paper. As for the major wood bonding component, the bonding mechanism and types of wood composites bonded with CA are presented. The best working conditions for the CA in the fabrication of wood-based panels are discussed. In addition, the environmental impacts and future outlook of CA-treated wood and bonded composite are also considered.

Carboxymethyl starch (CMS) was produced from sago starch via carboxymethylation. The CMS with different degree of substitution (DS) ranges from 0.4 to 0.8 were mixed with polyethylene glycol (PEG) of different molecular weight and distilled water and the hydrogel was cured by electron beam irradiation with doses ranging from 25 to 35 kGy. The results revealed that CMS-PEG hydrogels with DS 0.4 give the optimum gel content when radiated at 30 kGy and with PEG 600. Thermogravimetric analysis (TGA) revealed that there are two phases exist in CMS with DS 0.4 in contrast to the three steps decomposition occurs in DS 0.6 and 0.8. It shows that the CMS with DS 0.4 is more thermally stable. Surface morphology revealed crosslinking among the blends when subjected into the radiation dose. The study shows both radiation and PEG addition improved most of the properties of CMS irrespective of the DS value.

Oil palm trunk (OPT) veneers have the potential to be used in the production of plywood for marine applications. However, OPT is not resistant to fungal decay and termites, limiting its use in the production of marine plywood. As a result, in this study, phenolic resin treatment was used to improve the biological durability of OPT and produce marine grade equivalent (MGE) plywood. The OPT veneer was treated with medium molecular weight phenol formaldehyde (MmwPF) resin. The results showed that MmwPF resin with a solid content of 30% resulted in higher weight percent gain and polymer retention. Veneers treated with 30% MmwPF resin were then pressed for more than 10 min at temperatures above 140 °C. Dimensional stability, shear strength, bending strength, fungal decay resistance, and termite resistance were all tested on the plywood produced. The results of this study revealed that MGE plywood has satisfactory bonding quality and excellent biological durability. Good bending strength was recorded for the MGE plywood with modulus of rupture and modulus of elasticity ranged between 31.03 and 38.85 MPa and 4110 and 5120 MPa, respectively. Rubberwood, as a reference sample in this study, is not durable (Class 5) against white rot fungi and is moderately durable (Class III) against subterranean termite attacks. Interestingly, MGE plywood produced in this study was found very durable (Class 1) against white rot fungi. It is also durable (Class II) and very durable (Class I) against termite attacks, depending on the pressing parameters employed. Based on their outstanding bonding quality, bending strength, and biological durability, the study confirmed the feasibility of OPT plywood for marine applications.

Kenaf core contains a fairly high amount of cellulose and lignin; hence, any attempt to use both components would be beneficial. In this study, kenaf core was used as reinforcement in PP/kenaf core nanocomposites. The core was prepared in two forms: (i) as micron-size reinforcement and (ii) as nanocrystalline cellulose. The bleaching process for nanocrystalline cellulose was conducted at different intensities in order to retain different amounts of lignin in the pulp. Then, the nanocrystalline cellulose was prepared via hydrolysis reaction. Both the micron-size kenaf core pulp and the nanocrystalline cellulose of different bleaching intensity were loaded in the polypropylene matrix with the aid of maleic anhydride grafted polypropylene coupling agent. The mixtures were then hot pressed at 180°C for 8 min to form into standard testing size sample according to standard ASTM D638 (dumbbell shape for tensile test) and D790 (for flexural and impact test). The chemical, mechanical and morphological properties of the composites were evaluated. The results revealed that composites added with unbleached nanocrystalline cellulose (11.48% lignin content) had lowered the tensile and flexural strength. On the contrary, the impact strength was increased when unbleached nanocrystalline cellulose was added.