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Characterisations of treated and untreated OPEFB fiber filled polymer nanocomposites at different fiber size.

INTRODUCTION

In order to make safer living environment, the growth of natural resources materials have gotten a lot of attention worldwide. Although in certain circumstances synthetic fibers materials are better, the natural one can still compete to one another. One of natural resources materials is oil palm empty fruit bunch (OPEFB) fiber. It is one of the products produced in oil palm mill which was extracted from empty fruit bunch (EFB). Like other natural fibers, OPEFB also has many advantages such as lower cost, lower density, reduced tool wear and non-corrosive. Presently, there are several researches on OPEFB as their filler in the composite structure. One of the researches is the investigation of the effect of OPEFB fiber size on tensile properties, where the outcome was tensile strength decrease with the increasing of untreated OPEFB fiber size. Whereas for the treated OPEFB, it slightly increased the tensile strength [1]. Another research is the effects of chemical treatment on OPEFB reinforced HDPE composite. In this study, it was found that variations of treatment have improved the mechanical properties of the composite but only to a certain concentration of treatment (Muhamad F. Arif 2010). In this paper, the investigation of the effects of OPEFB fiber size on mechanical properties was studied.

Materials Preparation:

The oil palm empty fruit bunch (OPEFB) fiber was obtained from Poly Region Sdn. Bhd. High density polyethylene (HDPE) and polyethylene nanoclay (PE nanoclay) were obtained from Titan Petchem (M) Sdn. Bhd and Nanocor Inc. respectively. As received OPEFB fiber was sieved by using sieve shaker in order to obtain required size which was 180 [micro]m, 250 [micro]m, 30 [micro]m and 355 [micro]m. Then, the particle size distribution of OPEFB fiber was obtained by using Malvern Mastersizer 2000 with water dispersant. A portion of OPEFB fibers were immersed in 5 % NaOH solution for 24 hours at room temperature. After that, the OPEFB fibers were washed with distilled water so that the excessive NaOH solution was removed. Then, the treated OPEFB fibers were dried in the oven at 80[degrees]C for 8 hours.

Sample Preparation:

The contents of the composite were 68 % HDPE/clay, 30 %OPEFB fiber and 2 % MAPE. The MAPE react as coupling agent and there was only one loading of PE nanoclay (5 per hundred). HDPE/clay and also MAPE were dry mixed before compounding in a dispersion mixer to produce HDPE/clay mixture. The compounding was done at 180[degrees]C according to HDPE's melting temperature with rotating speed of 50 rpm. After the mixture were melted and mixed well together, the OPEFB fiber was poured into the dispersion mixer. In order to produce well dispersed OPEFB fiber composite, the mixtures was compounded at the same speed before taken out and cool down for at least one day. Then, it was crushed into granules by crusher machine. The granules were injected into dogbone shape (160 mm x 11.5 mm x 6 mm) according to ASTM D 638.

Tensile Test:

The tensile test was performed according to ASTM D 638 using Instron 8032 Digital Control machine. An extensometer was attached to the sample during tensile test so that the modulus of elasticity was determined with accuracy and was removed after 1 % proof stress.

RESULTS AND DISCUSSION

Particle Size Distribution:

Fig. 1 shows the particle size distribution of the untreated and treated OPEFB fibers. The usage of water dispersant allowed the OPEFB fibers that tend to agglomerate during the sieving process to separate into individual particle (A Kalam 2010). Throughout the particle size distribution analysis, specific surface areas were also measured and are listed in Table 1.

Table 1, it can be concluded that smaller OPEFB fiber size has higher specific surface area which indicate the tendency of agglomeration. This is because higher surface energy was produced by higher specific surface area. Besides that, higher surface area was related to the inconsistency of OPEFB fiber shape and usually was exhibited by smaller OPEFB fiber size. This can be observed on the SEM micrographs of each OPEFB fiber sizes as shown in Fig. 2.

X-Ray Diffraction (XRD):

The XRD pattern for neat HDPE, HDPE/clay and OPEFB/HDPE/clay hybrid nanocomposites is shown in Fig. 3. All the above composite show two broad peaks at 29 value of 21.54[degrees] and 23.84[degrees] values. These peaks are because of cellulose crystalline phase of the OPEFB fiber [6]. While for HDPE/clay and the rest of OPEFB/HDPE/clay hybrid nanocomposites, there was another peak at 29 value of 6.32[degrees] which indicate the HDPE nanoclay. The existence of clay peak in OPEFB/HDPE/clay hybrid nanocomposites indicate that the clay has infused into the OPEFB fiber [6].

Thermogravimetric Analysis (TGA):

Thermogravimetric analysis is one of the methods to study the thermal stability in order to determine changes in weight loss of sample along with stable temperature increment. It is crucial due to the usage of the materials and its processing technique such as extrusion and injection molding. In order to produce or manufacture composites, it involves high temperature mixing between matrix and fibre. Therefore, the degradation of natural fiber can caused unsatisfactory properties in the composite [8]. TGA was conducted on neat HDPE, HDPE/clay and OPEFB/HDPE/clay hybrid nanocomposites with and without 5 % NaOH treated as shown in Fig. 4, in order to investigate the effects of fiber size and treatment on the weight loss and thermal decomposition. It can be seen that the decomposition of untreated and treated OPEFB/HDPE/clay hybrid nanocomposites were identical as well as neat HDPE and HDPE/clay. Generally, thermal decomposition of natural fiber happen in between 200[degrees]C to 400[degrees]C [8] and this can be proved by the TGA curves for OPEFB/HDPE/clay hybrid nanocomposites in Fig. 4. Besides that, the reinforcement of OPEFB fiber into HDPE/clay had produced two shoulders of a TG curve which specify the decomposition of two materials. The first shoulder is mainly because the decomposition of OPEFB fiber while the second shoulder is the decomposition of the remaining HDPE/clay [1].

The degradation temperature from TG analysis of the composite is given in Table 2. From the table, it can be seen that the transition temperature starts at 210.51[degrees]C to 410.67[degrees]C and the final transition temperature starts from 533.13[degrees]C to 552.42[degrees]C. Both neat HDPE and HDPE/clay did not degrade until 410.67[degrees]C and 409.21[degrees]C which show excellent thermal stability. However the incorporation of clay has made the composite degrade at lower temperature compared to neat HDPE. While for the OPEFB/HDPE/clay hybrid nanocomposites, the treatment also has significantly affect its initial degradation except for 180 [micro]m treated fibre size where the initial degradation occur at 210.51[degrees]C. The higher thermal stability of treated OPEFB fiber composite were happened simply because the outer surface of OPEFB fiber which consist of wax and oil had been removed during the alkali treatment. Actually, the existing of wax and oil on OPEFB fiber will make the composite degrade earlier than the main component of OPEFB fiber which are cellulose and lignin where these two substances will lead to higher degradation temperature [8,4].

Tensile Strength:

Fig.5 shows tensile strength of different sizes of the untreated and treated OPEFB/HDPE/clay hybrid nanocomposites. From Fig.4, it can be seen that the incorporation of 5 phr nanoclay dropped the tensile strength of neat HDPE about 1.1 %. But when the fibers were reinforced, the tensile strength readings were increased significantly, especially for the treated fiber composite. This is because, the most important factor that can affect the mechanical properties of fiber reinforced composite is the fiber-matrix interfacial bonding [3,5]. The good characteristics of fiber-matrix interfacial bonding are affected by a number of factors for example the type of fiber and polymer, the aspect ratio of the fiber and the treatment of the fiber [5]. Natural fiber surface are covered by waxy substances that contain hydroxyl group which inhibit it to react and form good bonding with hydrophobic matrices [2]. Therefore, the alkali treatment on natural fiber removes the impurities, hemicelluloses and lignin which increased the surface roughness. This rougher surface of natural fiber will increase the bonding between fiber and matrix by interlocking mechanism [7,5]. Obviously,

The highest tensile strength for both untreated and treated OPEFB fiber composite is at 300 pm which are 20.4 MPa and 22.6 MPa respectively. While the lowest tensile strength for the untreated fiber is 18.6 MPa at 180 pm and 20.7 MPa at 355 pm for the treated fiber. It might be because the irregular shape of OPEFB fiber that cannot sustain the stress transferred from the matrix which can weaken the composite interfacial bonding (Chinomso M. Ewulonu 2011)(M. Khalid 2008). Another explanation is the uneven distribution of fibers in the composite can caused decrement in mechanical properties [10].

Tensile Modulus:

Fig.6 depicts tensile modulus of both untreated and treated OPEFB/HDPE/clay hybrid nanocomposites. The incorporation of 5 phr nanoclay into neat HDPE has increased tensile modulus about 7.4 %. After the reinforcement of untreated and treated OPEFB fiber, the tensile modulus has increased and decreased significantly. The most effective OPEFB fiber size for both untreated and treated fiber is at 355 pm which is 2.1881 GPa for the untreated and 2.1176 GPa for the treated. The lowest tensile modulus for the untreated and treated is 1.9633 GPa at 180 pm and 2.0262 GPa at 250 pm respectively. The alkali treatment on the OPEFB fiber has removed the waxy cuticle layer and amorphous hemicelluloses from its surface which caused the fiber become more stiff where the reinforcement of treated fiber into matrix subsequently made the composite become stiffer which resulting higher tensile modulus [7,10].

Fracture Surface Analysis:

The fracture surface of OPEFB/HDPE/clay hybrid nanocomposites can be observed from Fig. 7 below. From the observation of all fracture tensile tested samples, it showed the matrix area consist of brittle appearance. Besides that, there were many voids on the fracture surface of the untreated OPEFB/HDPE/clay hybrid nanocomposites due the fibers pull out. But, there was less void on the fracture surface of the treated OPEFB fiber composite which can prove the higher tensile strength reading.

Conclusion:

The presence of filler which is OPEFB fiber in the HDPE/clay has enhanced the mechanical properties of the composite especially the treated OPEFB fiber. The treated OPEFB fiber has enhanced the initial degradation temperature for thermogravimetric analysis and also for tensile strength but not for tensile modulus. In term of variation of sizes, the mechanical properties were good at higher fiber size which is 300pm. The treatment on OPEFB fiber size of 300pm gave the improvement of 10% of tensile strength.

ARTICLE INFO

Article history:

Received 28 February 2014

Received in revisedform 25 May 2014

Accepted 6 June 2014

Available online 20 June 2014

ACKNOWLEDGEMENT

This research was supported by a grant (600-RMI/DANA 5/3/RIF(657/2012)) from Research Management Institute (RMI) of Universiti Teknologi MARA (UiTM). The author would like to acknowledge the Centre of Advanced Material and Research (CAMAR) for providing the facilities.

REFERENCES

[1] Kalam, A., M.B.A. H.I., 2010. "Physical and mechanical characterizations of oil palm fruit bunch fiber filled polypropylene composites." Journal of Reinforced Plastics and Composites.

[2] Chiachun Tan, I.A., Muichin Heng, 2011. "Characterization of polyester composites from recycled polyethylene terephthalate reinforced with empty fruit bunch fibers." Materials and design.

[3] Chinomso, M., A.I.O.I. Ewulonu, 2011. "Properties of Oil Palm Empty Fruit Bunch Fibre Filled High Density Polyethylene." International Journal of Engineering and Technology.

[4] Kabir, M.M., H. Wang, 2012. "Chemical treatments on plant-based natural fibre reinforced polymer composites: An overview." Composites Part B: Engineering, 43(7): 2883-2892.

[5] Khalid, M., C.T.R., T.G. Chuah, Salmiaton Ali , S.Y. Thomas Choong, 2008. "Comparative study of polypropylene composites reinforced with oil palm empty fruit bunch fiber and oil palm derived cellulose." Materials & Design.

[6] Mohan, T.P. and K. Kanny, 2012. "Chemical treatment of sisal fiber using alkali and clay method." Composites Part A: Applied Science and Manufacturing, 43(11): 1989-1998.

[7] Muhamad, F., P.S.M. Arif, M.Y. Faiz Ahmad, 2010. "Effects of Chemical Treatment on Oil Palm Empty Fruit Bunch Reinforced High Density Polyethylene Composites." Journal of Reinforced Plastics and Composites.

[8] Norul Izani, M.A., M.T. Paridah, 2013. "Effects of fiber treatment on morphology, tensile and thermogravimetric analysis of oil palm empty fruit bunches fibers." Composites Part B: Engineering 45(1): 1251-1257.

[9] Rajini, N., J.W. Jappes, 2013. "Effect of montmorillonite nanoclay on temperature dependence mechanical properties of naturally woven coconut sheath/polyester composite." Journal of Reinforced Plastics and Composites, 32(11): 811-822.

[10] Razak, N.W.A. and A. Kalam, 2012. "Effect Of Fibre Size On The Tensile Properties Of Oil Palm Empty Fruit Bunch Fibre Composites." Advanced Materials Research: pp: 1-4.

(1) Nur Amanina Mohd Fadzil, (2) Anizah Kalam, (1) Rahilah Kamarudzaman, (2) Koay Mei Hyie

(1) Faculty of Mechanical Engineering, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor Darul Ehsan, Malaysia

(2) Centre of Materials Research, Faculty of Mechanical Engineering, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor Darul Ehsan, Malaysia

Corresponding Author: Nur Amanina Mohd Fadzil, Faculty of Mechanical Engineering, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor Darul Ehsan, Malaysia

Tel: +60129711987 E-mail: ninafadzil@gmail.com

Table 1: Specific surface area of OPEFB fiber.

OPEFB fiber                         Treated
size ([micro]m)
                      180      250      300      355

Specific surface      0.0248   0.0162   0.0142   0.0113
area ([m.sup.2]/gm)

OPEFB fiber                       Untreated
size ([micro]m)
                      180      250      300      355

Specific surface      0.0300   0.0194   0.0143   0.0122
area ([m.sup.2]/gm)

Table 2: The degradation temperature of neat HDPE, HDPE/clay and
OPEFB/HDPE/clay hybrid nanocomposites with untreated and NaOH treated,

                           Transition temperature
Type                           ([degrees]C)

[T.sub.i]               [T.sub.m]      [T.sub.f]
([degrees]C)            ([degrees]C)   ([degrees]C)

HDPE                    410.67         492.77
HDPE/clay               409.21         487.00
180 [micro]m            251.50         489.31
180 [micro]m treated    210.51         473.03
250 [micro]m            245.92         463.34
250 [micro]m treated    296.70         470.49
300 [micro]m            236.18         478.41
300 [micro]m treated    298.39         479.10
355 [micro]m            237.30         489.83
355 [micro]m treated    305.67         491.44

                            Residual
Type                       weight (%)

[T.sub.i]
([degrees]C)

HDPE                    552.42   15.72
HDPE/clay               536.62   18.17
180 [micro]m            554.21   23.80
180 [micro]m treated    538.87   15.13
250 [micro]m            540.39   10.17
250 [micro]m treated    536.47   11.18
300 [micro]m            533.13   10.90
300 [micro]m treated    537.47   3.50
355 [micro]m            543.04   27.25
355 [micro]m treated    544.36   19.80

[T.sub.i]: Initial temperature

[T.sub.m]: Maximum temperature

[T.sub.f]: Final temperature

Fig. 5 : Tensile strength of neat HDPE, HDPE/clay and OPEFB/HDPE/clay
hybrid nanocomposites with untreated and NaOH treated.

OPEFB fiber size

               untreated   5% NaOH treated

HDPE
 HDPE/clay          18          17.8
180 [micro]m      18.6          22.5
250 [micro]m      18.8          22.1
300 [micro]m      20.4          22.6
355 [micro]m      19.9          20.7

Note: Table made from bar graph.

Fig. 6: Tensile modulus of neat HDPE, HDPE/clay and OPEFB/HDPE/clay
hybrid nanocomposites with untreated and NaOH treated.

               untreated    5% NaOH treated

HDPE
 HDPE/clay       1.0624         1.1478
180 [micro]m     1.9633         2.1157
250 [micro]m     2.0956         2.0262
300 [micro]m     2.1162         2.0691
355 [micro]m     2.1881         2.1176

Note: Table made from bar graph.
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Author:Fadzil, Nur Amanina Mohd; Kalam, Anizah; Kamarudzaman, Rahilah; Hyie, Koay Mei
Publication:Advances in Environmental Biology
Article Type:Report
Date:Jun 5, 2014
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