ABSTRACT
This work was carried out to produce wood polymer composites (WPCs) based on virgin high density poly-ethylene (vHDPE) and Daniella oliveri wood dusts using compression molding technique. Wood dusts were treated with different concentrations of sodium hydroxide (NaOH) at varying time. The surface modification of both untreated and treated wood polymer samples were monitored by Fourier transform infrared (FTIR) spectroscopy while the changes in the structure and the properties of WPCs resulting from these treatments were explored by the scanning electron microscopy (SEM)as well as physical and mechanical tests. The experimental results indicated that the alkali treatment of the wood dust improved the interactions between the wood dust and the vHDPE matrix, and enhanced mechanical properties of the composites. It was concluded that the physical, mechanical and microstructural properties of the WPCs were optimised when wood dusts were treated with 4wt% concentration of NaOH solution for 150 minutes.
CHAPTER ONE
1.0 INTRODUCTION
1.1 Background to the Study
The quest to turn low-quality wood materials into high-quality products and the concern for environmental sanity have attracted researchers and manufacturers’ interest in blending wood fibre with thermoplastic resin, which result in wood polymer composites (WPCs). This had resulted in an average yearly growth of 23% in the WPC market between 2003 and 2007 and ten times as fast as the polymer market (Alireza, 2008). Wood fibres are eco- friendly, have high specific strength and modulus, and can be gotten at a cheaper price using manual labour available in the locality. (Shinoj et al. 2011). In addition, they can be easily incinerated of at the end of their life cycle by upturning or by the composting of their calorific value in a furnace, which is not possible for glass fibre (Kuo et al. 2009). However, wood fibres also show some unwanted characteristics such as high water absorption and low heat resistance (Mylsamy and Rajendran, 2011). Thermoplastic resins, such as polypropylene (PP), polyethylene (PE), polystyrene, and polyvinyl chloride (PVC), soften when heated and harden when cooled. This property allows materials such as wood fibres, to be mixed with the plastic to form a composite product. The resulting WPCs can be easily processed into various shapes and then recycled. However, the hydrophilic wood fibres do not adhere to the hydrophobic polymers as a consequence of the poor interfacial bond between the fibres and the matrix. Therefore, in order to increase the compatibility and adhesion between the fibres and the matrix, the wood fibres are always subjected to various surface modification and treatments.
The properties of WPCs depend on the degree of interfacial bonding between the polymer matrixes e.g. virgin High Density Polyethylene (vHDPE) and the wood fibre. When wood fibres are used as reinforcement in WPCs, problems such as debinding of the wood fibres within the polymer matrix may occur at the interface due to incompatibility (Kuo et al. 2009). To optimise WPCs’ engineering performance, researchers are currently exploring the effects of various surface modification techniques and their treatment parameters as well as additives and compatibilizers with a view to improving matrix-reinforcement interfacial bonding. Surface modification of the wood fibres by means of cost effective alkaline treatment is one of the major areas of current research to develop compatibility and interfacial bond strength in the WPCs (Kuo et al. 2009; Mylsamy & Rajendran, 2011).
This study makes use of wood dust from a locally available soft wood, African Copaiba Balsam wood (Daniella-oliveri) waste materials (from saw-mill) causing environmental and health hazards to the Nigerian society; compounded with virgin high density polyethylene (vHDPE) to produce WPCs for structural applications. Daniella-oliveri is widely available in Kotangora, Niger state, Nigeria.
1.2 Statement of the Problem
Wood polymer composites have gained a wide range of utilisation most especially in the construction and automobiles industries (McKeever, 1999). However, in Nigeria most of the WPC products are still imported while there are large deposits of raw materials that can be utilised in WPC production. Wood wastes generated as waste product in our saw mills create a large chunk of environmental problems because they are not usually disposed properly. Judicious use of these waste wood dusts through the production of WPCs for household structural applications will ensure that they no longer constitute environmental hazards while they are also turned to wealth.
Furthermore, by virtue of Nigeria’s oil deposit, polymeric materials which are by-product of the refineries exist in large deposit as well. Therefore there is availability of major materials for the production of WPC however, before the actualization of qualitative WPC there is a need for proper treatment of the wood dust.
1.3 Significance of the Study
This work is significant as it is expected to provide most appropriate surface modification treatment parameters using NaOH for optimising the properties of WPCs. This in essence will ensure a straight forward formulation of the wood and polymer for the production of household structural engineering component (photo frame, name plate, phone casing) made of WPC by existing and emerging industries. This is a source of economic boost for Nigeria as most imported WPC materials will now be produced locally, hence, a huge saving on Nigeria’s foreign exchange earnings. Employment creation, proper waste management which transform to better health status for Nigerians, conversion of waste to wealth, and a more stable economy for Nigeria are among the benefits of carrying out this research.
1.4 Aim and Objectives of Study
This research work aims at investigating the effect of varying concentration and time of NaOH treatment on the physical, mechanical, and microstructural properties of WPCs obtained by reinforcing vHDPE with African Copaiba Balsam (Daniella-oliveri) wood saw dust. The specific objectives are to determine:
(a) The effect of the concentration of NaOH on the physical, mechanical and microstructural properties of WPC produced by blending vHDPE and wood dust from Daniella-oliveri.
(b) The effect of the time of treatment of NaOH on the physical, mechanical and microstructural properties of WPC produced by blending vHDPE and wood dust from Daniella-oliveri.
(c) The most appropriate surface modification NaOH treatment parameters for optimising the properties of the WPC.
1.5 Scope and Limitation of the Study
The research work is based on alkalisation treatment of wood dust and then compounding with virgin high density polyethylene (vHDPE) to produce composite samples using compression technique. The samples produced were subjected to tensile, density, moisture absorption, Fourier Transform Infra Red (FTIR) and Scanning Electron Microscopy (SEM) tests in other to obtain the optimum NaOH concentration and time of treatment.
This material content is developed to serve as a GUIDE for students to conduct academic research
PRODUCTION OF WOOD POLYMER COMPOSITE FROM AFRICAN COPAIBA BALSAM (Daniella oliveri) WOOD DUST: EFFECTS OF ALKALINE CONCENTRATION AND TIME OF TREATMENT
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