PRODUCTION OF WOOD POLYMER COMPOSITE FROM AFRICAN COPAIBA BALSAM (DANIELLA OLIVERI) WOOD DUST : EFFECTS OF WOOD DUST PARTICLE SIZE

ABSTRACT

This thesis explore the effects of wood dust particle size distribution and contents on the functional properties of wood plastic composites WPCs prepared from virgin high density poly-ethylene (vHDPE) and dilute sodium hydroxide (NaOH) treated   African Copaiba Balsam (Daniella oliveri) wood dusts via compression moulding technique. Changes in the structure and the properties of WPCs resulting from variation in daniella oliveri wood dusts particle size distribution and contents were studied by scanning electron microscopy (SEM) as well as physical and mechanical tests. Findings from this study suggested that appropriate choice of the wood particle size distribution and contents improved interactions between the dust and the vHDPE matrix. It could be inferred from this study that the mechanical, physical and  micro-structural  properties  of the WPCs  were optimised  when  dilute NaOH treated daniella oliveri wood dusts of particle size distribution and contents of +300-425µm and 35wt% respectively were blended with vHDPE matrix at 1600C when the pressure was 3.05 MPa within 5 seconds.. Mechanical properties of WPCs obtained from this study indicated that  engineering  items  such  as  television  frames  for  household  applications  could  be produced with the optimised daniella oliveri wood dusts characteristics.

CHAPTER ONE

1.0 INTRODUCTION

1.1 Background to the Study

Generally, woods are mainly grown for the production of furniture, roof frames and related constructions. Therefore, most of the woods from tree plantations end up in wood factories or saw-mills. As a result, large quantities of saw-dust or wood dust particles are generated as waste which needs to be disposed of because of their degrading effect on the environment and health hazards. The high availability of low value wood dust as a result of milling and their negative environmental impact is a concern to researchers and industrialists. This has brought about the long search to convert low value wood dust into other high value products. The focus then was to combine wood dust with thermoplastic resin which resulted in wood polymer composites (WPCs). This development attracted huge interest of the manufacturers and the consumers due to their added value aesthetics. As a result, average yearly increase in demand for WPCs products between 2003 and 2007 improved. This has grown more than ten times the polymer market (Wood-plastic, 2008). Wood dusts have high specific strength and modulus, they can be bought at reduced prices with assistance of workers in the industry and above all, it is natural (Shinoj, P., Raju, S.S, and Joshi, P.K, 2011). Furthermore, at the expiration of their useful period, they can be disposed off either to be used to produce more composites or by recovery of their calorific values in a furnace which is not possible with conventional inorganic fillers like talc, calcium carbonate, clay, carbon, non-ferrous metals and glass fibre composites (Kuo, P.Y., Wang, S.Y., Chen, J.H., Hsueh, H.C. & Ysai, M.J, 2009).

However, wood dusts show some un-required peculiarities like having affinity for water absorption and easily degraded by heat (Tajvidi, M., Najafi, S.K. and Moteei, N, 20006). Thermoplastic resins such as polypropylene (PP), polyethylene (PE), polystyrene (PS) and polyvinylchloride (PVC) soften (lowering viscosity) when heated and harden (increasing viscosity) when cooled. These properties allow materials such as wood dust particles to be mixed with the plastic to form composites of many products and shapes which could also be recycled. However, the polar wood dusts (hydrophilic) naturally do not adhere with non-polar polymers (hydrophobic) as a result of incompatibility between wood dusts and the polymer matrix. As a result of this poor interfacial adhesion between wood dust and thermoplastic composites, problems such as debonding of dusts within the interface of matrix may occur (Kuo et al, 2009). For economic reason, wood dusts are often subjected to various surface treatments and modification. The degree of molecular interaction within polar dust and non- polar polymer is the essential characteristic of WPCs. To optimise WPCs engineering performance, research work is currently exploring the effects of various surface treatments and methods, as well as materials with a view to improving matrix-reinforcement interfacial bonding, hence, the functional properties.

This research work makes use of soft wood particles of African Copaiba Balsam Tree (Daniella-oliveri) waste materials from a local saw-mill in Maitumbi area of Minna in Niger State causing environmental and health hazards to the community. Daniella-oliveri is abundantly available in Nigeria. It is called Kadaura (Maje) in Hausa language, Danchi in Nupe language, Iyaa in Yoruba language, Oziya-ato in Bini language and Ozabua in Igbo language. The waste wood particles were modified with dilute sodium hydroxide (NaOH) solution  in order to  improve  their interfacial  adhesion  before blending  with  virgin  high density polyethylene (vHDPE). The mechanical, physical and micro-structural characteristics of the composites were investigated by varying wood particle size distribution and their contents with a view to determining the optimal particle size and content for optimising the functional properties of WPCs.

1.2 Statement of Problem

Solid wood has been traditionally utilised for different applications in many parts of the world. It has been argued that the effects of pollution and inhalation of chemicals used in treating solid wood were unhealthy and the resulting degradation of the wood materials on usage in  those  applications  have brought  about  shift  to replace solid  wood with  WPCs (Smith, P.M. and Wolcot, M.P, 2005). The shift is largely due to the improved properties and environmentally friendly attributes of WPCs one of which is colour. Indeed, colour is an attribute that adds value to wood-polymer based products. The demand for value-added wood based composite products were higher than the conventional wood products in the market. These could be attributed to quality and aesthetic appeal shown by wood based composites (Bennington, 1996). Also in the past, problems associated with compatibilisation of polymer with inorganic materials (fillers) like carbonates, talc, carbon and glass fibre have made composites of these reinforcements for both domestic and industrial applications undesirable. The undesirability of these reinforcements are due to the following reasons:

(i) The cost of compatibilising the fillers with the host polymer is quite high.

(ii) The weight of their composites after compounding was undesirable.

(iii) Related production and transportation cost was also quite irrational.

(iv) The environmental effect (pollution) was unhealthy.

(v) Dermatological effect on employees were devastating.

Therefore in this study, it is believed that material composition contribute significantly to mechanical and physical properties of WPCs. Hence, it is imperative to first understand the chemical constituents and nature of woods and plastics in order to produce quality WPC products.

1.3 Justification for the Study

Nigeria, being an oil producing country and having the plant; Daniella-oliveri dotting her landscape can annex the two resources for production of non-structural components. The economic advantages of the two materials could be utilised to solve the problem of job creation; employment for the teeming population in the country and reduction of inclusive capital flight. Furthermore, the multiplying economic effects will be a plus in re-generating employment, conserving our resources and generating foreign exchange for the country, diversification of the economy, reservation of petroleum based products, exportation and reduction of capital flight from the country.

1.4 Aim and Objectives of the Study

The primary focus of this research is to find the optimal influence of particle size distribution and  contents  of  wood  dust  of  Daniella-oliveri  modified  with  dilute  sodium  hydroxide (NaOH) solution on the properties of WPCs when blended with virgin high density polyethylene matrix. The objectives of this study are as follows:

1.   To investigate the effects of particle size distribution of modified Daniella-oliveri wood dust blended with virgin high density polyethylene (vHDPE) matrix on the functional characteristics of the resultant composition.

2.   To investigate the effects of wood dust contents of modified Daniella-oliveri blended with virgin HDPE matrix on the physical and other functional characteristics of the produced composites.

3.   To  investigate  the  effects  of  particle  size  distribution  and  contents  of  modified Daniella-oliveri wood dust on the adhesion bond between the dust and the polymer matrix as well as its inter-relationship with the mechanical properties.

4.   To identify the optimal wood dust particle size distribution and content for optimising the functional properties of WPCs.

1.5 Scope and Limitation of the Study

The scope of this  research  is  using derived  optimal  4% dilute concentration  of sodium hydroxide (Na0H) solution and time of 150 minutes to modify wood dust of daniella-oliveri in order to determine the optimal wood dust particle size distribution and contents on composites made from virgin high density polyethylene (vHDPE) in relation to their mechanical and physical properties for non-structural applications. The study is limited by the available particle size distribution supplied by the saw-mill.

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