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SCIENCE & TECHNOLOGY l ANALYSIS ARTICLE

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Effect of Nano Clay on Rice

Husk Filled Polyethylene

Polymer Composite: Part A

Ibe Kevin Ejiogu1, 2

ABSTRACT

Rice husk is abundantly available and recent research interests are geared

towards its utilization as a bio-filler in the production of composites. In the

present study the reinforcing properties of nano-clay on rice husk polyethylene

composited was studied. In the composite preparation six level of loading (0-5 wt

%) for the nano-clay was used and Maleic anhydride grafted Polyethylene (MA-g-

PE) was used as the compatibilizer. The following physico-mechanical properties

were evaluated; tensile strength, tensile modulus, flexural strength, flexural

modulus, density, percent elongation, notched impact strength and percent water

absorption. The results showed that the tensile strength, tensile moduli, flexural

strength and flexural moduli improved with increased with increase in nano-clay

up to 3 wt %. However, above this weight (3 wt %) the mentioned properties

decreased. The results also showed a slight decrease in impact strength, density

and percent elongation with increase in nano-clay. Studies have shown that high

amount (≥ 3 wt %) of nano-particles have a negative effect on the mechanical

properties of the composite due to poor matrix fibre adhesion and limit their

application. The scanning electron microscope (SEM) morphology showed good

dispersion of the nano-clay at 1 and 2 wt % loading, however it showed poor

dispersion of the nano-clay at(≥ 3 wt %).The study showed the potential of

utilizing rice husk polyethylene composite for industrial applications.

Keywords: Polyethylene, Nano Clay, MA-g-PE, Physico-Mechanical Properties

1. INTRODUCTION

The utilization of bio-fibres as reinforcements in plastic composite is becoming

more popular, as a result of their flexibility during processing, high specific

stiffness, and lower cost which make them attractive substitutes and alternatives

for manufacturers [1]. In addition agro−wastes open up new market in agro-based

rural communities and make them more productive and viable [2]. Rice husk is

one of the agro wastes in Nigeria that has a lot of potentials to be utilized as bio-

fillers for industrial applications.

Nigeria produces about 4.3 million tons of rice paddies every year, and this is

estimated to produce 1.1 million tons of rice husks per year [2]. The major reason

why rice husk is not being utilised effectively is lack of awareness of its inherent

potentials. Rice husk is a by-product obtained after the rice milling process. The

husk to paddy ratio is usually estimated to be between 0.2 − 0.22[3], with global

production reaching 15 million tonnes per annum. Rice husk contains about

75−95% organo-cellulosic materials such as lignin and cellulose with other

SCIENCE &

TECHNOLOGY

7(23), 2021

To Cite:

Ejiogu IK. Effect of Nano Clay on Rice Husk Filled

Polyethylene Polymer Composite: Part A. Science &

Technology, 2021, 7(23), 23-29

Author Affiliation:

1Nigerian Institute of Leather and Science

Technology, Directorate of Research and

Development, Department of Research,

Development, Processes and Operations, Zaria,

Nigeria

2Ahmadu Bello University, Department of

Chemistry, Zaria, Nigeria

Corresponding author:

Email address: [email protected] (I.

K.Ejiogu)

Peer-Review History

Received: 20 January 2021

Reviewed & Revised: 22/January/2021 to

18/February/2021

Accepted: 20 February 2021

Published: March 2021

Peer-Review Model

External peer-review was done through double-

blind method.

© 2021 Discovery Scientific Society. This work is licensed

under a Creative Commons Attribution 4.0 International

License.

DISCOVERY SCIENTIFIC SOCIETY



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components such as silica and alkalis[4]. Table 1 shows the chemical components and physical properties of rice husk *5−12+ and

thermo-mechanical properties of composite [13].

Coupling agents are introduced to increase interfacial adhesion between the matrix and the fibre due to enhancement in the

formation of covalent and hydrogen bonds, Van der Waals forces, and mechanical cross linking [14].

The industrial application of rice husk is still very limited with little or no economic value, thus the research scrutiny is to

identify the potential of using rice husk as a bio-filler in polyethylene for industrial applications. The introduction of nano-clay as a

reinforcing agent enhances the overall physic-mechanical properties.

Table 1. (a) Physical properties and (b) Components of rice husk [12].

(a). Physical properties

Density(ρ) g/cm3 1.00

Particle size (µm) 26.63

Surface area (m2/g) 0.93

Moisture content (%) 5−10

(b). Components

Solubles (%) 2−5

Hemicellulose (%) 18−21%

Lignin (%) 26−31

Silica (%) 15−17

Figure 1. Structures of (a). Cellulosic content of rice husk, (b). Maleic anhydride (c). Maleic anhydride grafted with polyethylene

(MA-g-PE) [16, 22, 24].

Figure 2. Chemical interaction between natural fibre (rice husk) and MA-g-PE [16, 20, 21].

2. MATERIALS AND METHOD

Materials

Unprocessed raw rice husk from local farms in Zaria Kaduna State, Nigeria was used as natural fiber reinforcement. The fibres were

chopped with cutlass and ground with a Thomas –Wiley mill no 4 and was subsequently sieved using a 60 mesh size sieve. The rice



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husk powder (RHP) was then dried in an oven at 100°C for 12 hrs to an average moisture content of 2.8 wt %. Linear Low density

polyethylene (Film grade) was obtained from Eleme Petrochemical Company Limited Eleme in Rivers State. The Polyethylene was

in pellet form and with a melt flow index of 190°C /2.16 Kg of 1 gm/10 mins and a density of 0.919 g/cm3 (ASTM D 1238) [26]. The

compatibilizer was MA-g-PE obtained from USA and has an acid number of 7.99and a molecular weight of 80,000. Natural nano-

clay (montmorillonite) that is modified with a dimethyl, dehydrogenated tallow, 2-ethylhexyl quaternary ammonium with a CEC of

95 meq/100 g clay and doo1 = 18.6 A˚ was utilized for the work and was obtained from Southern Clay Products Co. USA. The nano-

silica powder utilized for the work was whitish in colour and in powdery form, with a density, diameter and specific surface of 0.37

g/m3, 11 nm and 200 m2/g respectively. The nano- silica was obtained from Degussa Co., Germany.

Table 2. Formulation Table.

Composition (wt %)

Sample Code PE MA-g-PE RHP Nano-clay

CT 67 3 30 0

A 66 3 30 1

B 65 3 30 2

C 64 3 30 3

D 63 3 30 4

E 62 3 30 5

Key: CT = Control Sample

Method

Formulation and Preparation of Composites

The formulations for the preparation of the composites are shown in Table 1.Prior to mixing the RHP was placed in an oven for 2hrs

until average moisture content of 2.8 wt % was obtained [28]. Similarly the PE was also kept at 100°C in the electric oven for 3

hrs[28].The PE and MA-g-PE were hand mixed in a bag before being introduced into the two roll mill (No: 5183).

The RHP and nano-clay were also properly hand mixed in a bag before being introduced in the two roll mill. These materials

were all compounded in the two roll mill at a temperature of 170⁰C for 6mins before the composite was sheeted out. The rolls

revolved at a speed of 50 revs/min.

The composites were taken to a compression moulding equipment and compressed in a mould at a temperature of 150°C for

4mins at 22.5 MPa to obtain the composites. The composites were allowed to cool to and released from the mould.

Characterization Techniques

The Tensile and Flexural strengths tests were carried out using ASTM D638 and ASTM D790- 10 standards. The Instron Model 4301

universal testing machine was utilized at room temperature. Tensile test was done at crosshead speed of 50 mm−1.Tensile elongation

at break was calculated by the ratio between change in length and the initial length after fracture of the tested specimen at a

controlled temperature. It is a measure of the ability of the plastic to resist changes in shape without failure. Flexural test was done

at cross head speeds of 3 mm−1. The impact (notched) test was done using ASTM D256-10 standard using Toyoseiki (Tokyo Japan)

impact tester with a capacity of 11J and a weight of pendulum of 31.90 N. The samples are notched to provide a stress concentration

that provides a brittle failure. The notch of the test samples faced the hammer. The densities of the composites of dimensions 3 ×10×

5 mm were obtained by dividing the mass by the volume. The mass was obtained with an electronic weighing balance. The water

absorption test was carried out in water at a temperature of 23°C with sample dimensions of 2 × 10 × 5 mm using ASTM D570-18

standard for 48hrs. The SEM morphology of the fractured surfaces was characterized using scanning electron microscope machine

(SEM) machine (Phillips XL 40, Phillips). Five specimens of each formulation were tested and the average values are reported.

3. RESULTS AND DISCUSSION

Tensile Strength and Modulus of Composite

Figure 3 (a) showed the tensile strength and modulus of the composite. There was a gradual increase in the tensile strength and

modulus of the composite as the amount of nano-clay introduced in the polyethylene matrix increased [27]. This could be

attributed to exfoliation of the nano clay [15]. However, as more of the nano-clay was added, the increment peaked at 3 wt% of

nano-clay and further addition of nano-clay showed a slight reduction in tensile strength and modulus. This could be attributed to

agglomeration of nano- clay particles which led to poor transmission of stress in the matrix. In a study it was stated that maximum



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tensile strength ranges from 2.67 to 2.74Gpa for composite filled with nano-clay [16]. In the work of Karumuri et al.,[17] it was

shown that introduction of nano-clay gradually reduced the tensile strength with a reduction of 11% at 6 wt% nano-clay due to

poor dispersion and exfoliation of the nano-clay in the Polyethylene matrix. In the work of Hosseini et al.,[18] they found out that

the fibre reinforced composites (FRCs) showed moderate increase in tensile strength with introduction of bagasse fibres and nano-

SiO2which showed that the fibres added had a reinforcing effect on the FRCs. In the work of Salemane and Luyt [19] they showed

that there was improvement in mechanical properties of wood/PP composite with introduction of wood flour. In a similar study

Mirjalili et al.,*29+ showed that addition of α- Al2O3 nono- particlesinto PP matrix improved the strength of the nano-composite

produced until at 3 wt% where they found a high level of agglomeration of theα- Al2O3 which cause a reduction in the strength of

the nanocomposite.

Flexural Strength and Modulus of Composite

Figure 3 (b) showed an increase in flexural strength and modulus as the quantity of nano- clay introduced in the matrix increased

showing significant reinforcement by the nano-clay. The flexural strength and modulus increases up to a clay content of 3 wt%, and

further increase resulted in a decrease in flexural strength and modulus. This was also experienced in Figure 3 (a) where the

composite at 3 wt% nano-clay had the highest tensile strength and modulus. In a related research of Hosseini et al.,[18] their work

followed similar trend as the results showed that the composites made with natural fibre (bagasse) and nano-SiO2 showed the

highest flexural strength and modulus of rupture(MOR) and neat HDPE exhibited the lowest flexural strength and MOR.

Impact Strength and Percent Water Absorption of Composite

Figure 3 (c) showed that the water absorption increased as the percent weight of nano-clay introduced in the composite increased.

However the water absorption remained relatively constant with the introduction of more quantities of nano-clay, this may indicate

that introduction of hydrophilic RHP could also be a major factor affecting the water absorption capacity of the composite. Figure 3

(c) also showed that the impact strength of the composite decreased as the percent weight of nano-clay introduced in the composite

increased, this could be as a result of agglomeration of the nano-clay in the matrix of the composite. The lower impact strength and

poor dispersion of nano-clay could also be attributed to poor homogeneity, voids and un-exfoliated nano-clay respectively. In the

work of Hosseini et al., [18] he reported that the water absorption (WA) of nano-biocomposite increased with increasing water

content, he went further to state that the water absorption of HDPE increased with increase in the addition of natural fibre and

nano-SiO2 content. In a similar study Rosa et al., [23], it was shown that increased filler loading increased the water absorption of the

composite. Similarly in the work of Prachayawarakorn et al., [24] he stated that the rice husk filled polypropylene composite

produced increased their ingress of water through lumen cell wall of the rice husk and void spaces within the composite due to

poor interfacial adhesion between matrix and fibre.

Density and Percent Elongation

Figure 3 (d) showed a reduction in the percent elongation of the composite as the quantity of Nano-clay introduced in the

composite increased. This could be attributed to the increase in brittle nature of the composite. The reduction in the percent

elongation can be attributed to poor adhesion between particles of the nano-clay and the PE matrix. The density showed a slight

reduction as the quantity of nano-clay introduced in the composite increased as a result of poor dispersion, voids and

agglomeration of the nano-clay in the composite. This could be attributable to the poor compatibility between hydrophobic polymer

matrix and the nano-clay.it could also be attributed to agglomeration of the nano- clay, presence of voids and unexfoliation of the

nano clay aggregates.

SEM Micrographs

Figure 4 (a) and (b) showed that at the 1 wt % and 2 wt % nano-clay loading there was good dispersion of the nano-clay in the

composite. This showed that there was some degree of exfoliation of the clay particles which was marked by the increase in

mechanical properties [32-32]. However, in Figure 4 (c) the SEM morphology showed some agglomeration of the nanoparticles

indicating some defects in the composite structure such as void spaces and pores.



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Figure 3. Effect of nano-clay and weight percent composition on the mechanical properties of composite

Figure 4. SEM micrographs of (a) uniform dispersion (1 wt% nano-clay), (b) uniform dispersion (2 wt% nano-clay), (c)

agglomeration(3 wt% nano-clay) [30, 31]increase of nano-clay up to 3 wt % and then decreased slightly.

In addition the SEM morphology results showed that exfoliation is dependent on the interaction between the polymer and

nano- clay and can be improved by the strength of the hydrogen bonding and the strength of matrix fibre interaction. Thus this

emphasizes the need to utilize functionalized polymer with polar groups such as MA-g-PE to improve fibre/matrix interaction,

intercalation and exfoliation. In a related study Ibrahim et al., [25] during the SEM analysis the study revealed that the presence

of PP-g-MA showed better compactibilization in the compabilized PP/ABS composite compared to the uncompatibilzed PP/ABS

nano composite, his study furher showed dispersion, intercalation and also agglomeration of the structure of montmorillonite

(MMT) layers of the samples analysed.

4. CONCLUSION

The following conclusions can be drawn from the results of study:

Some of the discrepancies seen in the test could be attributed to poor dispersion and agglomeration of nano-clay in the composite

The tensile strength, flexural strength, tensile modulus and flexural modulus increased.

The impact strength decreased slightly with increase in the wt % of nano-clay introduced in the composite.



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The water absorption increased with increase in nano-clay; however introduction of hydrophilic RHP also played an important

role in the ingress of water in the composite. Impact strength reduced with increase of weight percent of nano- clay in the

composite due to agglomeration which introduced void spaces in the composite.

The percent elongation decreased with increase in nano-clay. The physico-machanical properties of the composite can be

improved by utilizing coupling agents.

Biography of Author

Engr. Dr. Ibe Kevin Ejiogu is currently a principal research officer in Nigerian Institute of Leather and Science Technology in the

department of Research, Development, Processes and Operations. He Has a Ph.D in Polymer Science and Technology from the

prestigious Ahmadu Bello University Zaria. Nigeria. He had his M.Sc and B.Eng from Federal University of Technology Owerri

Imo State. Nigeria in Polymer Science and Engineering Technology and Polymer & Textile Engineering Technology respectively. His

research interests are in the areas of environmental technology and composite technology

Funding

The study received no funding from any external body or agencies.

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical approval

This article does not contain any studies with human participants performed by any of the authors.

Data and materials availability:

All data associated with this study are present in the paper.

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