**3. Thermoplastic coat**

330 Thermoplastic Elastomers

Many different kinds of natural cellulosic fibre such as cotton, hemp, sisal, coconut fibres and oil palm fibres are used in different composite products. Properties of the natural fibres depend mostly on the nature of the plant, locality in which it is grown, age of the plant, and the extraction method that is used (Sreekala et al., 1997). Coir is a hard and tough multi cellular fibre with a central portion called ''lacuna.'', On the other hand, banana fibre is weak and cylindrical in shape. Sisal is an important leaf fibre and is strong. Pineapple leaf fibre is soft and has high cellulose content. Many studies have been done on the natural fibre based composite products (Maldas & Kokta, 1990; Pavithran et al., 1987; Shah & Lakkad, 1981; Sreekala et al., 1997). Table 1 summarised the chemical and mechanical properties of

Oil palm is one of the most economical and very high-potential perennial oil crops. It belongs to the species of Elaeis guineensis under the family Palmacea, and originated in the tropical forests of West Africa. Major industrial cultivation is in Southeast Asian countries such as Malaysia and Indonesia. Large-scale cultivation has come up in Latin America. In India, oil palm cultivation is coming up on a large-scale basis with a view to attaining self

Oil palm fibre is non-hazardous biodegradable material, extracted from oil palm's empty fruit bunch (EFB). Oil palm fibre is an important lignocellulosic raw material. OPEFB fibre and oil palm mesocarp fibre are two types of fibrous materials left in the palm-oil mill. The mesocarp fibres are left as a waste material after the oil extraction. These fibres must be cleaned of oily and dirty materials. The only current uses of this highly cellulosic material are as boiler fuel and in the preparation of potassium fertilizers. When left on the plantation oor, these waste materials create great environmental problems. Therefore, economic

utilization of these fibres will be beneficial (Sreekala et al., 1997).

Physical properties of oil palm fibre

Cellulose 65 Hemi cellulose - Lignin 19 Ash content 2 Table 2. Chemical constituents of oil palm empty fruit bunch fibre

> Diameter (mm) 0.15-0.50 Density (g/mm³) 0.7-1.55 Linear density (denier)\* 2150 Tensile strength (MPa) 100-400 Young's modulus (MPa) 1000-9000

Table 3. Physical and mechanical properties of oil palm empty fruit bunch fibre

Elongation at break (%) 14 Microfibrillar angle (°) 46

Chemical constituents (%)

\* 1 denier= 1/9000 g/m

**2. Natural fibres** 

some natural fibres.

**2.1 Properties of oil palm fibres** 

sufficiency in oil production.

Thermoplastics as a coating can lead to improving the natural fibre performance in two ways: 1. the thermoplastics cover the fibres and keep the fibres from any fungi or bacteria attacks by decreasing the water absorption and contact of the fibres to the soil and any organism inside it, 2. The physical performance of the fibre such as tensile strength and elongation can be affected by modification and coating with any kind of thermoplastics. Therefore, a method was developed to coat the fibres with the thermoplastics. The solvent was used to prepare soluble thermoplastic since the natural fibres cannot reside in high temperature. Different density of the thermoplastic solution was used to evaluate the coated fibres to reach the best strength and resistance. Two types of the fibre were used as a reinforcement of composites such as soil, first the discrete fibres where it needs to be coated one by one, and second is the sheet fibres that were made by compaction of bulk fibres. The fibre was coated by acrylonitrile butadiene styrene (ABS) solution and the characterisation test results for both single and sheet fibres are described in the following sections.

#### **3.1 Acrylonitrile butadiene styrene**

ABS is an important engineering copolymer widely used in industry due to superior mechanical properties, chemical resistance, ease of processing and recyclability (Yang et al., 2004). ABS is a common thermoplastic used to make polymeric wood composites, has good physical properties in comparison with other commodity plastics and is cheap in comparison with other engineering plastics (Huang & Mo, 2002).

ABS is derived from acrylonitrile, butadiene, and styrene. The chemical structure of the ABS is shown in Figure 1. Acrylonitrile is a synthetic monomer produced from propylene and ammonia. Butadiene is a petroleum hydrocarbon obtained from butane. Styrene monomers, derived from coal, are commercially obtained from benzene and ethylene from coal. The advantage of ABS is that this material combines the strength and rigidity of the acrylonitrile and styrene polymers with the toughness of the polybutadiene rubber. The most amazing mechanical properties of ABS are resistance and toughness.

Fig. 1. Chemical structure of ABS

Application of Thermoplastics in Protection of Natural Fibres 333

the chemical reactions of ABS and fibres have increases. This increase led to a more physical

2237

2362 2347

2347

2239

4000 3500 3000 2500 2000 1500 1000 500

Wave number (cm-1)

The porous surface morphology was useful for better mechanical interlock of fibre with the ABS coating. The SEM micrograph of fibres and the coated fibres clearly shows the surface structure of an uncoated OPEFB fibre and the quality of thermoplastic coat (Figure 3). The micrographs show porous and grooves on the surface of the fibre. The uniform cover and fully coating of the fibre surface is an important factor in protecting the fibres while surface

1445

1636 1039

1634

1495

<sup>1455</sup> <sup>1032</sup>

970 914

762

702

960

910

<sup>757</sup> <sup>700</sup>

stability of ABS coating over fibres and thus fibres were more resistant.

3307

(a)

(b)

(c)

(d)

3400

% Transmittance

3420 3306

c) ABS Coated Fibre - 6 hour d) ABS Coated Fibre - 24 hour

Fig. 2. FTIR of ABS coated and uncoated fibres

b) OPEFB Fibre

**3.2.2 Fibre surface topology** 

3025

2922

2931

3032 2929

a) Acrylonitrile butadiene styrene (ABS)

The chemical resistance for ABS is relatively good and it is not affected by water, non organic salts, acids and basic. The material will dissolve in aldehyde, ketone, ester and some chlorinated hydrocarbons. The properties of moulded ABS are shown in Table 4 based on MatWeb (2009) material specification data sheet.


Table 4. Physical properties of moulded ABS

### **3.2 Characterization of coated fibres**

An ABS solution was prepared by adding ABS pieces to methyl ethyl ketone (MEK) solvent. Fibres were chopped into 30 mm length for water absorption tests and 100 mm length for tensile strength tests. The average aspect ratio for 100 mm length fibre was found to be equal to 250. The chopped OPEFB fibres were incubated in the 15% ABS solution to be coated. Coated fibres were dried over a mesh at room temperature.
