**3.3 Characterization of coated fibre sheets**

For the first phase of experiments, the ABS solution was prepared in three different percentages of 5, 10 and 15 per cents. The 20% ABS solution was excluded from the experiments since some gel-forming behaviour was observed. The specimens were soaked for one minute in 5%, 10% and 15% of ANS solution and the tensile test conducted for specimens according to ASTM D4595-86 (2001) specifications. The 15% solution was picked for the rest of the experiments because it gives the optimum results. For next stage, the specimens were soaked in 15% ABS solution and repeated the tensile tests to study the effect of soaking duration on tensile strength.

### **3.3.1 Fibre sheets**

OPEFB sheets are commercially available is Malaysia. These sheets are manufactured through a compaction process in which the fibres orient randomly (Figure 9). Sheets are

Application of Thermoplastics in Protection of Natural Fibres 339

The weight variations of sheets are determined before coating and after drying process. The results, which are shown in Figure 11, showed that by increasing the density of ABS

The ABS thermoplastic brings ductility and toughness for the sheets. When the amount of oriented ABS increases, the toughness and ductility of sheets increases too. The influences of

By comparing the results of untreated sheets and 5%, 10% and 15% ABS coated sheets, it could be realized that the coating resulted to a slight increase in average tensile strength and remarkable decrease of elongation percentages. The effect of those variations is more obvious in tensile modulus, since it was doubled for the coated OPEFB sheets. Enhancement of 15% ABS coating showed better improvements than the 5% and 10% ABS coating; the average tensile strength of sheets reached to approximately 12 kN/m. The obtained average tensile strength is relatively 6 times higher than the average tensile strength of untreated OPEFB sheets. The resulted average tensile modulus of these sheets was around 350.3 kN/m. As it was expected, the ABS improved the tensile properties of OPEFB sheets very significantly. The ductility and toughness of 15% ABS coated sheets were more sensible than the others (Table 6). The ABS covered approximately all of the fibres properly and filled the

such ductility and toughness could become clearer by conducting the tensile test.

**3.3.2 Effects of ABS percentage on OPEFB sheets** 

Fig. 11. Weight changes of ABS coated OPEFB sheets

**3.3.3 Effect of ABS percentage on tensile strength** 

void areas among the fibres.

solution, larger amounts of ABS were oriented on the fibres.

produced only in single direction that is the machine direction, so there is no warp or weft direction, the detailed sheet and cross section are presented in Figure 9 and Figure 10.

The size of merchandised sheets was 3000 mm in length, 1000 mm in width and 10 mm in thickness. The coated or uncoated sheets have a potential to be used as a kind of geotextile for soil reinforcement was named Geo-Mat.

Fig. 9. OPEFB sheet

Fig. 10. Longitudinal cross section of OPEFB sheet

produced only in single direction that is the machine direction, so there is no warp or weft direction, the detailed sheet and cross section are presented in Figure 9 and Figure 10.

The size of merchandised sheets was 3000 mm in length, 1000 mm in width and 10 mm in thickness. The coated or uncoated sheets have a potential to be used as a kind of geotextile

for soil reinforcement was named Geo-Mat.

Fig. 10. Longitudinal cross section of OPEFB sheet

Fig. 9. OPEFB sheet

### **3.3.2 Effects of ABS percentage on OPEFB sheets**

The weight variations of sheets are determined before coating and after drying process. The results, which are shown in Figure 11, showed that by increasing the density of ABS solution, larger amounts of ABS were oriented on the fibres.

Fig. 11. Weight changes of ABS coated OPEFB sheets

The ABS thermoplastic brings ductility and toughness for the sheets. When the amount of oriented ABS increases, the toughness and ductility of sheets increases too. The influences of such ductility and toughness could become clearer by conducting the tensile test.

#### **3.3.3 Effect of ABS percentage on tensile strength**

By comparing the results of untreated sheets and 5%, 10% and 15% ABS coated sheets, it could be realized that the coating resulted to a slight increase in average tensile strength and remarkable decrease of elongation percentages. The effect of those variations is more obvious in tensile modulus, since it was doubled for the coated OPEFB sheets. Enhancement of 15% ABS coating showed better improvements than the 5% and 10% ABS coating; the average tensile strength of sheets reached to approximately 12 kN/m. The obtained average tensile strength is relatively 6 times higher than the average tensile strength of untreated OPEFB sheets. The resulted average tensile modulus of these sheets was around 350.3 kN/m. As it was expected, the ABS improved the tensile properties of OPEFB sheets very significantly. The ductility and toughness of 15% ABS coated sheets were more sensible than the others (Table 6). The ABS covered approximately all of the fibres properly and filled the void areas among the fibres.

Application of Thermoplastics in Protection of Natural Fibres 341

values of elongation which are practically useless. In soil structures large displacements are equal to failure of structures; basically, soil reinforcing materials must be able to reach to the peak tensile strength within the minimum displacement. Between all the materials mentioned in Figure 14, the 15% ABS coated OPEFB sheets are the most suitable choice based on the highest tensile strength along with the small elongation at the peak point.

Fig. 13. Rupture area for 5% ABS coated OPEFB sheet

Fig. 12. Comparison of tensile test results for 5%, 10% and 15% ABS coated OPEFB sheets

Since the 15% ABS solution covered the fibres and sheets more properly, it is expectable to experience higher tensile strength and also better durability for them. It is worth to mention that for all specimens, the complete rupture did not occur at the peak force. Although the failure area became clear, but the two parts of sheets were still joined together. The Figure 13 shows the rupture area of the failed specimens of ABS coated sheets.


Table 6. Tensile properties of ABS coated OPEFB sheets

### **3.3.4 Tensile strength comparison**

Among the previous works there is only one work which is comparable. Subaida et al. (2008) conducted experimental investigation on tensile strength of woven coir geotextiles. They reported that the tensile strength of the mesh mattings lies in range of 10 and 20 kN/m. The tensile test was carried out for three types of nonwoven geotextiles with commercial names of MTS 300, MTS 350 and MTS 400. MTS series geotextiles are a technical fabric mechanically bonded nonwoven needle punched made from 100% UV stabilized polyester. The average tensile test results of these fabrics are presented and compared by Figure 14. For all of these fabrics the peak tensile strengths are achieved at relatively large

Fig. 12. Comparison of tensile test results for 5%, 10% and 15% ABS coated OPEFB sheets

**Tensile Strength (kN/m)** 

Uncoated 0.359 1.79 37.08 4.80 5 % 0.392 1.93 20.60 9.37 10 % 0.542 2.71 12.27 22.00 15 % 2.41 12.05 3.44 350.30

Among the previous works there is only one work which is comparable. Subaida et al. (2008) conducted experimental investigation on tensile strength of woven coir geotextiles. They reported that the tensile strength of the mesh mattings lies in range of 10 and 20 kN/m. The tensile test was carried out for three types of nonwoven geotextiles with commercial names of MTS 300, MTS 350 and MTS 400. MTS series geotextiles are a technical fabric mechanically bonded nonwoven needle punched made from 100% UV stabilized polyester. The average tensile test results of these fabrics are presented and compared by Figure 14. For all of these fabrics the peak tensile strengths are achieved at relatively large

**Elongation** 

**Tensile Modulus ( kN/m)** 

**(%)** 

shows the rupture area of the failed specimens of ABS coated sheets.

**Specimen Breaking** 

**3.3.4 Tensile strength comparison** 

**Force (kN)** 

Table 6. Tensile properties of ABS coated OPEFB sheets

Since the 15% ABS solution covered the fibres and sheets more properly, it is expectable to experience higher tensile strength and also better durability for them. It is worth to mention that for all specimens, the complete rupture did not occur at the peak force. Although the failure area became clear, but the two parts of sheets were still joined together. The Figure 13 values of elongation which are practically useless. In soil structures large displacements are equal to failure of structures; basically, soil reinforcing materials must be able to reach to the peak tensile strength within the minimum displacement. Between all the materials mentioned in Figure 14, the 15% ABS coated OPEFB sheets are the most suitable choice based on the highest tensile strength along with the small elongation at the peak point.

Fig. 13. Rupture area for 5% ABS coated OPEFB sheet

Application of Thermoplastics in Protection of Natural Fibres 343

The fibres were also placed in to the silty sand and peat soil to estimate the weight loss of the fibres in soil. The discrete fibre and fibre sheet were weighed before test. The fibres also were coated with ABS solution for 24 hours and all the specimens were placed on soils for

Figure 16 shows the coated and uncoated OPEFB fibre after aging in the silty sand soil. The fibre sheets decayed after 3 months and it is shown that the uncoated fibre had the separate structure due to the biodegradation of the fibre.The coating was protected the fibres from

Fig. 16. a) before decay b) decayed ABS coated c) decayed uncoated fibre sheet in the silty

The same results are shown in Figure 17 for the fibres in organic clay soil. The uncoated sheet fibre in organic clay separated from each other and did not have the textile structure.

Fig. 17. a) before decay b) decayed ABS coated c) decayed uncoated fibre sheet in the

The results of these losses are graphically plotted in Figure 18. Loss of weight of the discrete fibres was higher than the fibre sheet due to their larger contact surface with the soils and

The result shows that in all condition coating decreases the biodegradation of the fibres both in discrete fibre and fibre sheet. The decay of the fibres in three conditions had

The uncoated fibre lost its weight due to biodegradation in the soil.

biodegradation; the shape of the coating fibres was kept.

about 3 months.

sand soil after 3 months

organic clay soil after 3 months

environment factors.

Fig. 14. Tensile test result of MTS fabrics and coated OPEFB sheets
