Bonding with natural fibres

The earliest evidence of humans using fibres is the discovery of wool and dyed flax fibres found in a cave in the Republic of Georgia more than 30,000 years ago. It all started with the use of natural fibres in composite materials. Clay was reinforced by straw to build walls in ancient Egypt about 3,000 years ago. The famous Great Wall of China was made using a combination of clay and rice flour reinforced with straw. Now composites dominate our lives in many ways – automotives, buildings, sports, defence, aerospace, and the list continues. With its apparent endless uses, natural fibres are indeed phenomenal and eternal. Natural fibres are bio-based fibres, i.e.,fibres of vegetable or animal origin. Between the two, the former which is the focus of this book, has received tremendous attention for decades and the interest are still growing strongly. Natural fibres are sometimes referred to as plant fibres. These field crops are grown for their fibres, which are traditionally used to make paper, cloth , or rope, products that are responsible for its continued existence. While wood comes from forest trees that requires many years (>15 years) to mature, the non-woods mature between 3-10 years, and fibre crops are generally harvestable after a single growing season (5-6 months). In specific circumstances, fibre crops can be superior to single wood fibre in terms of technical performance, environmental impact and cost. Biomass is another source of fibres that can be derived from plants, either from forest trees or field crops, normally in the form of residues. It is usually associated with energy production and bio- refinery. In this book, the term “natural fibres” is used to describe fibres that are obtained from wood, non-wood, plant fibres and biomass. All natural fibres are chemically made up of cellulose, hemicellulose and lignin which are aligned in crystalline and amorphous regions in the form of microfibrils. Aggregates of microfibrils make up a fibre. These fibres are arranged in different manner depending on the type of plant. Some examples of wood are pines, spruce, oak, beech, hemlock (temperate woods), meranti, keruing, chengal, rubberwood, (tropical woods). Examples of non- woods are bamboo, rattan and all types of palms. Plant fibres are represented by many types depending on where the fibres are taken, e.g., bast fibres - the fibres that come from the phloem tissue of the plant, as exemplified by jute, kenaf, ramie, flax, and hemp. Other fibre crop fibres are from seed padding, such as coir, leaf fibre, such as those of pineapple, abaca, sisal, henequen, or from other parts of the plant. All plant fibre residues from the forests, plantations/ estates and processing mills are regarded as plant biomass. In recent years, materials scientists and engineers have begun exploring further uses of natural fibres through composite materials. This book reviews the basic properties of some natural fibres particularly those found in Malaysia, and highlights issues in bonding with polymer, surface wettability, buffering capacity and their influence on composite performance

A review on potentiality of nano filler/natural fiber filled polymer hybrid composites

The increasing demand for greener and biodegradable materials leading to the satisfaction of society requires a compelling towards the advancement of nano-materials science. The polymeric matrix materials with suitable and proper filler, better filler/matrix interaction together with advanced and new methods or approaches are able to develop polymeric composites which shows great prospective applications in constructions and buildings, automotive, aerospace and packaging industries. The biodegradability of the natural fibers is considered as the most important and interesting aspects of their utilization in polymeric materials. Nanocomposite shows considerable applications in different fields because of larger surface area, and greater aspect ratio, with fascinating properties. Being environmentally friendly, applications of nanocomposites offer new technology and business opportunities for several sectors, such as aerospace, automotive, electronics, and biotechnology industries. Hybrid bio-based composites that exploit the synergy between natural fibers in a nano-reinforced bio-based polymer can lead to improved properties along with maintaining environmental appeal. This review article intended to present information about diverse classes of natural fibers, nanofiller, cellulosic fiber based composite, nanocomposite, and natural fiber/nanofiller-based hybrid composite with specific concern to their applications. It will also provide summary of the emerging new aspects of nanotechnology for development of hybrid composites for the sustainable and greener environment

A study on the effects of environment on curing characteristics of thixotropic and room temperature cured epoxy-based adhesives using DMTA

This study investigated the thermal properties of three room temperature curing adhesives containing nano-particles which were thixotropic and shear thinning which allowed injection into overhead holes when exposed to different environmental conditions. Viscosity and shear stress of the adhesives were measured as a function of shear rate. The thermal behaviour of the adhesives were measured using dynamic mechanical thermal analysis following exposure to different temperatures and humidities which included temperatures of 20°C. 30°C and 50°C, relative humidities of 65% RH, 75% RH and 95% RH, soaked in water at 20°C and placed in the oven at 50°C. The dynamic thermal properties reported include storage and loss modulus, the loss tangent and the glass transition temperature (Tg). For nano- and micro-particles filled adhesives, the Tg increased with the temperature increase, even though the adhesives were subjected to high humidity and this was due to further cross-linking. The results showed that room temperature cured epoxies were only partially cured at room temperature

Effects of the improvement in thermal conductivity coefficient by nano-wollastonite on physical and mechanical properties in medium-density fiberboard (MDF)

The improving effect of an increase in the thermal conductivity caused by nano-wollastonite (NW) on the physical and mechanical properties of medium-density fiberboard (MDF) was studied. Nanowollastonite was applied at 2, 4, 6, and 8 g/kg, based on the dry weight of wood-chips, and compared with control specimens. The size range of wollastonite nanofibers was 30 to 110 nm. The results show that NW significantly (p < 0.05) increased thermal conductivity. The increased thermal conductivity resulted in a better curing of the resin; consequently, mechanical properties were improved significantly. Furthermore, the formation of bonds between wood fibers and wollastonite contributed to fortifying the MDF. It was concluded that a NW content of 2 g/kg did not significantly improve the overall properties and therefore cannot be recommended to industry. Because the properties of NW-6 and NW-8 were significantly similar, a NW-content of 6 g/kg can be recommended to industry to significantly (p < 0.05) improve the properties of MDF panels

Bending properties of Laminated Veneer Lumber produced from Keruing (Dipterocarpus sp.) reinforced with low density wood species

Low density wood such as Pulai (Alstonia sp.), Sesendok (Endospermum sp.) and Kekabu Hutan (Bombax sp.) have never been regarded as structural material due to their inferior strengths. Converting these timbers into Laminated Veneer Lumber (LVL) and reinforcing them with stronger timber could turn them into much sought after materials. This study discusses the effects of incorporating Keruing veneers into LVL panels made from low density wood. Laminated Veneer Lumber comprised 11-ply and 15-ply veneers fabricated by arranging Keruing veneers located at the surface and the low density woods were arranged as core. Phenol Formaldehyde (PF) resin was used as the binder. The LVLs were subjected to cyclic boil-dry test according to voluntary product Standard PS1-95: Construction and Industrial Plywood. The bending properties and percent delamination were determined according to the Japanese Agricultural Standard (JAS) for Structural LVL: 1993 before and after the cyclic boil dry treatment. Result showed through incorporating low density wood with Keruing veneers, both 11-ply and 15-ply LVL panels achieved the minimum requirements for various grades stipulated in the JAS for Structural LVL Standard: 1993. At the same panel thickness, 15-ply LVL shows a better performance compares to those of 11-ply LVL. Presence of Keruing veneers as surface layers significantly increased the strength of the LVL panels. All panels passed the delamination test stipulated on the JAS for Structural LVL: 1993. Conclusively, combining Keruing and the low density wood veneers in LVL fabrication gave greater strength and more stable material

Density distribution of oil palm stem veneer and its influence on plywood mechanical properties

Oil Palm Stem (OPS) has been introduced as potential raw material for plywood manufacture in Malaysia. Two 25 years old OPS were selected for the study which aim to establish the veneer density distribution of the stem. The main purpose of this study is to improve the strength and to determine the optimum resin spread rate for oil palm stem plywood manufacture. The study comprised (1) the establishment of veneer density profile and (2) the effects of resin consumption and lay-up pattern on the strength and bond integrity of the plywood. The method used to determine the veneer density was a standard oven-dry method. The OPS veneer were fabricated into 5-ply plywood panels using UF (urea formaldehyde) resin adhesive. Three types of OPT veneer were classified which were 100% from outer veneer, 100% from inner veneer and mix (2-ply of outer veneer as face and Three-ply of inner veneer as core material) with four different glue spread rate (250, 300, 350 and 400 g m-2). The results show the veneer density of the OPS can be categorized into three classes: 400-500, 300-400 and 200- 300 kg m-3. The outer-layer veneers have density between 358 to 442 kg m-3, whilst the densities of the inner-layer veneer were 272 to 446 kg m-3. Segregating the oil palm veneers by density classes prior to plywood manufacture improved the strength and bond integrity of the OPS plywood greatly

Resistance of Laminated Veneer Lumber (LVL) produced from rubberwood, radiata pine and larch against subterranean termites and white rot fungi

Laminated veneer lumbers (LVLs) were fabricated using rubber wood, radiate pine and larch wood. Solid rubber wood was used to serve as control for comparison purpose. All of the wood samples were exposed to subterranean termites and white rot fungi for durability evaluation. The results showed that rubber wood LVL had the highest resistance against both deterioration agents in comparison to control, confirming that the resistance of non-durable wood species could be improved by converting them into LVL

Properties of some thermally modified wood species

The objective of the study was to investigate the influence of heat treatment and exposure time on surface roughness, wettability, shear strength and hardness of rubberwood, Eastern redcedar and red oak samples. The anatomical structure of each species was also observed using scanning electron microscope (SEM). All specimens were exposed to two different temperature levels, namely 120°C and 190°C for 2 and 8 h. Red oak samples had the most enhanced surface quality along with less wettability characteristics followed by rubberwood and Eastern redcedar specimens as function of increased heat exposure. On the other hand, it appears that heat exposure adversely affected shear strength and hardness properties of all three types of samples. These two properties of heat treated samples had reduction values ranging from 52.7% to 69.4% and 10.8% to 33.3%, respectively as compared to those of control samples

Development a new method for pilot scale production of high grade oil palm plywood: effect of hot-pressing time

The main objective in this study were to investigate the physical properties, mechanical properties and bonding qualities of oil palm stem (OPS) plywood pre-preg using low molecular weight phenol–formaldehyde (LmwPF). The properties evaluated were physical properties (resin uptake, weight percent gain), mechanical properties (bending strength) and bonding qualities (dry test, WPB test). The results showed that, the physical properties of OPS plywood were significant at resin concentration and veneer moisture content. Moreover, the mechanical properties and bonding performance of the pre-preg OPS plywood were influenced by the pressing time. The high grade OPS plywood with improved at least 227% MOR and 348% MOE compared to commercial OPS plywood, with greater in MOR (31%) and MOE (12%) higher compared than the commercial tropical mix light hardwood (MLHW) plywood. All the shear strength of pre-preg OPS plywood panel were achieved with their minimum requirements and satisfied all the specific testing based on the standard European Norms EN 314-1 and EN 314-2 for the interior and exterior application purposes. The output of this pilot scale study proved that high performance OPS plywood could produced through pre-preg enhancement method in the current plywood mills in which provides broader area of applications compared with conventional OPS plywood. For instant, the pre-preg OPS plywood which is suitable for structural application, concrete formwork, heavy duty interior structuring board, load bearing plywood, marine grade plywood, was obtained, thus consequently increases the price of OPS plywood panels