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Vol. 8. Issue 3.
Pages 3102-3113 (May - June 2019)
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Vol. 8. Issue 3.
Pages 3102-3113 (May - June 2019)
Original Article
DOI: 10.1016/j.jmrt.2017.05.021
Open Access
Fabrication of pandanus tectorius (screw-pine) natural fiber using vacuum resin infusion for polymer composite application
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Lukmon Owolabi Afolabia,b,
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afoolabs@gmail.com

Corresponding author.
, Puteri Sri Melor Megat-Yusoffb, Zulkifli Mohamad Ariffa, Muhammad Syahmi Hamizolb
a Mechanical Engineering Department, University Technology PETRONAS, Seri Iskandar, 32610, Malaysia
b School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia, 14300, Nibong Tebal, Pulau Pinang, Malaysia
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Table 1. Correlation of soaking time, percentage by weight concentration in extraction process of fiber cellulose content.
Table 2. Correlation of soaking time, percentage by weight concentration in extraction process of fiber content.
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Abstract

Natural cellulose fiber extract from Pandanus tectorius (Screw pine) leaves is comprehensively investigated as viable alternative for synthetic based fibers made from petro-chemical which is non-degradable and toxic. P. tectorius leaves fiber is extracted and investigated as reinforcement in polymer composite for engineering applications. The habitant are easily found and grown along mangroves and in local jungles located at shallow water. The plant can grow up to 14m tall. In order to use these continuous cellulose fibers as reinforcement in polymer composites, the microstructural analysis and yield content analysis were carried out using SEM micrographs to establish the certainty of using them as reinforcement fiber. The alkaline, bleaching and combined alkaline-bleach treatments are utilized in extraction of the cellulose fiber to evaluate the effect on the mechanical property. The cellulose percentage of the fiber was increased as the concentration and soaking time were increased. The extraction process resulted in 73% cellulose percentage for 10wt. % NaOH and 120min treatment. Hence, it caused 87% increment in cellulose percentage compared to the untreated leaf. The combined alkali-bleach cellulose fiber composite showed 40% higher tensile strength compared to untreated cellulose fiber composite at 35 2.8MPa.

Keywords:
Pandanus tectorius
Fibers
Chemical properties
Mechanical properties
Thermal properties
SEM
Full Text
1Introduction

Artificial mineral based fibers composites such as glass, aramid, ceramic and carbon fibers made from hydrocarbon resources are widely used in industries for different applications in textile, automobile, paint and plastic industries [1,2], due to their applicability and adaptability. However, limitation effect on their by-product, skin irritation, harmful chemical constituents, costly operation and non-biodegradable nature contributes to environmental degradation [3]. Natural fiber composites are potential alternatives to mitigate the problems associated with conventional composite. These composites are gaining importance due to their non-carcinogenic, bio-degradable nature and are very cost effective material especially in building and construction purpose, packaging, automobile and railway coach interiors and storage devices [4]. Possessing characteristics of low weight, higher strength, higher stiffness, environmental friendly, low cost of manufacturing and abundance in supply [2,5,6], natural fiber composites have gained interest and attention from researchers and practitioners in the composite industries [7] due to their potentials as possible substitute for high cost glass fiber used in low load bearing applications. In addition, with growing inclination towards the eco-friendly technology, natural fiber, in particularly polymer based composite have been gaining a lot of momentum nowadays because of their competitive properties, replicability and availability [8,9]. Natural cellulose-based fibers offer low cost, low density composite reinforcement with good strength and stiffness. Because of their annual renewability and biodegradability, natural fibers have materialized as environmentally-friendly alternatives to synthetic fibers in the last two decades [10].

Natural cellulose fibers have been frequently used as the reinforcement component in polymers to enhance specific properties in the final product [11–15]. The study of Kim et al. [16] investigated the influence of fiber extraction and surface modification on the mechanical properties using bamboo green composite. The results showed that the tensile properties of bamboo fiber bundle decreased in all conditions compared to raw bamboo fiber, but interfacial shear strength increased with chemical treatment due to the effective removal of hemicellulose and lignin from surface of bamboo fiber. Kommula et al. [17] extracted fiber strands from Napier grass and investigated the effect of acid treatment on the thermophysical and chemical properties of the fiber composites. The acid treatment used a glacial acetic acid solution with three varying concentrations (5, 10, and 15%) for 2h. In the reported chemical analysis, there were reductions in the amorphous hemicellulose content when the acid treatment is applied. Arundo donax L. leave fiber reinforced polymer composite was studied by Fiore et al. [12] for their microstructure, chemical composition and mechanical properties. Vinyl-ester binder was used in the vacuum moulding techniques comprising of alkali, steam and chemical extraction. The results described the effects of the binder on the physical properties, the cellulose membrane breakdown and microstructural transformation.

There has been relatively little research carried out on fibers of the screw pine leaves for possible utilization as fillers in polymer reinforcement composite. Their industrial usage is recent compared to other lignocellulosic fibers such as jute, flax and sisal. For this reason, the screw pine is not profitably planted for mass production and most of the plant materials are consume in local production of mat, beddings, chairs, basket etc. In the present study, extraction process of the Screw pine leaves were conducted in two phase; alkali treatment only and combination of alkali and bleaching. The influence of chemical concentration used and soaking time on cellulose percentage and tensile strength of the extracted fiber were studied. The relationship between cellulose percentage and tensile strength is also explored. Morphology of the extracted fiber was also investigated. Using the extracted fiber under optimized conditions, corresponding composites were fabricated and tested.

2Materials and methods2.1Materials

The main material used in the study was Pandanus tectorius (Screw pine) leaves as the main source of cellulose fiber. The fiber was extracted by chemical means using alkali treatment and then followed with bleaching to obtain high quality cellulose percentage. The leaves of the Screw pine were obtained from local shop at Kuala Kangsar, Perak. The leaves were in the form of a processed mat; cut, picked to remove torn, soaked in fresh stagnant water for several weeks and mild heating of the leaves surface. All the processes were assumed to have no appreciable effect on the structural and chemical composition of the fiber.

2.2Chemical reagents

The chemicals and reagents utilized are all of standard quality and were purchased from Avantis laboratory supplies in Ipoh, Perak, Malaysia. The alkali treatment involved sodium hydroxide (NaOH) diluted to the desired concentrations which were 2–10wt. % with increment of 2wt. % concentration. In bleaching process, sodium chlorite (NaClO2) was used and was dissolved from powder to solution of 1, 2 and 3wt. % concentration. In determining the cellulose content of the extracted fiber, several chemicals were used such as potassium dichromate (K2Cr2O7), ferrous (II) ammonium sulphate (Fe (NH4)2(SO4)2•6H2O), sulphuric acid (H2SO4), and sodium hydroxide (NaOH). Each chemical was prepared according to Technological Association of the Pulp and Paper Industry (TAPPI) Standard T203. The epoxy used in the fabrication of the cellulose based polymeric composite was EpoxAmite® 100 Laminating System with hardener, 102 Medium Hardener.

2.3Extraction of cellulose

Screw pine-mat was washed thoroughly with distilled water and dried under the sun. It was cut into 12cm long and 3cm wide strips and weighed accordingly. Each strip was approximately 0.3–0.35g. The leaves were treated with 2% up to 10% of NaOH at 200°C for 60 and 120min. The ratio of the leaves to liquor was 5:300 (g/ml). The leaves were washed with distilled water after each treatment, and then open dried for 3 days.

2.3.1Alkali Treatment

Fig. 1 displayed the visual inspection of the P. tectorius (Screw pine) before and after under-going alkali treatment and varying percentage concentration and soaking period. Following the pre-treatment process, the screw-pine strips were subjected to alkali treatment at 2wt. % concentration of NaOH for 60min soaking times and temperature of 170°C inside the oven. The ratio of leaves to liquor was 5:300 (g/ml). The treatment was repeated with 120min soaking time. The concentration of NaOH was then increased systematically to 4, 6, 8 and 10wt. % for both soaking times of 60 and 120min. There are several techniques of isolation and treatment of cellulose fiber, among the commonly used method is the chemical method that involves acid, alkali hydrolysis, steam explosion and extrusion [18,19]. The alkali and acid treatment method is adopted in the present study. All of the alkali treated screw-pine strips were washed thoroughly using distilled water to neutralize the remaining alkali and dried completely for 3 days under the sun. The selection of concentration and soaking time for NaOH were based on previous studies, findings and optimum performance.

Fig. 1.

Screw-pine strip before and after alkali treatment and varying percentage concentration of NaOH and soaking time: (a) Untreated screw-pine strip, (b) 2wt. % NaOH with 120min soaking time, (c) 8wt. % NaOH with 120min soaking time and (d) 10wt. % NaOH with 60min soaking time.

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2.3.2Bleaching treatment

Fig. 2 displayed the visual inspection of the Screw pine after under-going both alkali and bleaching treatment at varying percentage concentration and soaking period. Fibers extracted at 2, 4 and 6wt. % NaOH concentration during the alkali treatment were further subjected to bleaching process using NaClO2 solution. The bleaching process started with 1wt. % concentration of the NaClO2 solution. The mixture of the screw pine leaves in NaClO2 was placed inside the oven at 170°C for 60min soaking time. The ratio between screw pine strips and liquor was 5:300 (g/ml). The process was repeated at 2 and 3wt. % concentration of NaClO2 at both soaking times of 60 and 120min. All of the bleached screw pine strips were neutralized by washing thoroughly using distilled water. The leaves were open dried for 3 days. The selection of concentration and soaking time for NaClO2 were based on previous related work and findings.

Fig. 2.

Visual Inspection on screw-pine strips after bleaching treatment at varying percentage concentration of NaClO2 and soaking time: (a) 1wt. % NaClO2, 60min soaking time, (b) 2wt. % NaClO2, 60min soaking time, (c) 3wt. % NaClO2, 120min soaking time.

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2.4Fabrication methods

The Vacuum Resin Infusion (VRI) Process was employed in the fabrication of the continuous cellulose fiber (CCF) in this study. The corresponding CCF was placed on one-sided coated mould with wax in order to avoid fiber stacking on the mould during demoulding process. The CCF were vertically aligned and arranged into three layers with different arrangement to avoid gaps between fibers and to reduce porosity. A highly permeable medium of peeling ply and distribution mesh were laid over the surface of the fiber. The whole assembly was enclosed in a vacuum bagging film and sealed with sealant tape. The epoxy resin was injected into the assembly with ratio of epoxy to hardener of 10:3 (w/w) under vacuum pressure. The composite was cured at 70°C for 4h inside the oven and naturally cooled down to room temperature. The composite was then demoulded.

2.5Characterization and measurements

Different types of characterization methods are used in determining the quality of the extracted fibers. However, the present study utilizes the cellulose content determination, microstructural analysis and tensile strength test.

2.5.1Continuous cellulose determination

Each of the screw pine leaves under-went alkali and combined alkali-bleach treatment and then was analyzed for their cellulose content based on the standard of Technical Association of the Pulp and Paper Industry (TAPPI); T203. The extracted solutions were used in the amount of 25ml. The extracted solution was then added with 10.0ml of 0.5N potassium dichromate solutions. 50ml of concentrated H2SO4 was added cautiously followed by 50ml of water after 15min and cooled to room temperature. 2–4 drops of Ferron indicator were added and titrated with 0.1N ferrous ammonium sulphate solutions to a purple colour. The amount of ferrous ammonium sulphate solution used was recorded. The cellulose percentage was calculated using Eq. (3.1). All measurement was conducted in triplicate to minimize error.

where V1, titration of the pulp filtrate, ml 30; V2, blank titration, ml; N, exact normality of the ferrous ammonium sulphate solution; A, volume of the pulp filtrate, ml; W, weight of dried pulp specimen, g.

2.5.2Morphological analysis

Screw-pine strips were subjected to microstructural analysis using Field Emission Scanning Electron Microscope (FESEM) and Scanning Electron Microscope (SEM). The morphological structure of the un-treated screw-pine leaf was also analyzed as a control. The morphology was observed using SUPRA55VP with an accelerating voltage of 3kV. The images were digitally recorded and analyzed for changes in the morphology due to the varying extraction process parameters. The microstructure analysis provided relevant information on the fiber-matrix interface and the fracture characteristics of the composite.

2.5.3Mechanical properties analysis

Tensile strength test were conducted to investigate the effects of varying extraction parameters. The tensile strength of the cellulose fiber after being treated with alkali and combined alkali-bleach is presented with that of untreated fiber as the control sample. The tensile strength of the cellulose fiber composites was also measured. The results were compared with other cellulose-based composites. The entire tensile strength test was repeated five times and an average value reported.

Cellulose fiber composite: Tensile strength of fiber was based on ASTM 3822 using Titus Olsen Universal Tensile Machine with 100N load cells. The machine was equipped with pneumatic system in clamping, with adhesive layer for better gripers. The crosshead speed was 1.0mm/min with 50mm gauge length. Tests were conducted at 55% relative humidity and at 23°C. All data were recorded digitally.

Continuous cellulose fiber composite: Tensile strength of extracted cellulose fiber composite was determined using ASTM 3039. The specimen's dimensions were 230mm×16mm×1.6mm. Extensometer gauge length was 50mm with 2mm/min constant crosshead speed. Test was conducted using Zwick/Roell Z005 universal testing machine with 5k N cell load. The composite was clamped through a set of mechanical springs and mechanical zigzag gripers. All tests were conducted at 55% relative humidity and approximately 23°C temperature. Data obtained were recorded digitally.

3Results and discussion3.1Extraction of cellulose

The chemical composition of each of the fibers after under-going alkali and combine alkali-bleaching treatments methods are determined by examining their cellulose content. An untreated screw-pine fiber, alkali treated fiber and bleach treated samples were all analyzed and compared. The untreated screw-pine fiber is used as control sample. The fiber content is very important due to the effect it has on mechanical properties, particularly, tensile strength where engineering application is required.

3.1.1Alkali treatment

Naturally, the cellulose content of an untreated screw-pine is estimated at 37% [20,21]. However, the present study utilized screw-pine mat made from the leave which is expected to have slightly higher cellulose content due to pre-treatments undergone. Table 1 shows the effect of alkali concentration on the average extracted cellulose percentage upon varying concentration of NaOH and soaking time. The fiber cellulose content increases with the increase in volume concentration and soaking time for all the samples. A 75% percent cellulose content was extracted for 10wt. % NaOH treated for 120min soaking time, thus when compared with untreated screw-pine leaf a 45% cellulose percentage enhancement is achieved. The total average cellulose fiber extracted from all the sample is 42%, which implies a high yield content of lignin, pectin and hemicellulos was successfully removed therefore, producing an effective treatment for extraction of cellulose fiber. Similar claims of effective alkaline treatment in breaking down the bond in material have been reported elsewhere [17,22], there report showed that increase in alkali concentration increases the amount of cellulose fiber in extraction process but the correlation effect of soaking time was not reported. The summary of the enhancement of the cellulose extraction with increase in the alkali content and soaking time is shown in Table 1.

Table 1.

Correlation of soaking time, percentage by weight concentration in extraction process of fiber cellulose content.

Alkali treated screw-pine leaves  Wt. % conc. of NaOH
  10 
Soaking time (min)
30  33  39  42  46  52  57 
60  39  45  53  57  65  69 
90  41  50  58  65  69  75 
120  42  54  63  68  72  79 
Average cellulose content (%)  38  46  53  58  63  70 

Many other researchers have studied the effect of soaking time in the extraction process of cellulose content from various plant and found that the soaking time is at variance depending on other parameters such as type of treatment solution, concentration, extracting temperature, materials type etc [23–25].

Increasing the concentration from 2wt. % to 10wt. % resulted in 34% increment in cellulose percentage during the 60min treatment. However, less than 12% enhancement in the extraction of the cellulose fiber is observed in soaking time of 60min to 120min in 4wt. % to 6wt. % samples. A linear regression analysis performed showed similar trend in the 60–120min soaking time. This increment was smaller at 36% for the same concentration range during the 120min treatment. 120min soaking time gave higher amount of extracted cellulose percentage compared to that at 60min soaking time. For instance, extraction at 2wt. % NaOH for 120min soaking time results in18% higher cellulose percentage than extraction at 2wt. % NaOH for 60min. However, the influence of soaking time is lesser at higher alkali concentration. For example, at 8% concentration of NaOH, extracting the fiber for 120min only resulted in 7% more cellulose percentage compared to that at 60min. The similar result of significant influence for alkali concentration in treatment had reported elsewhere [26,27].

3.1.2Combined alkali and bleaching treatment

Further treatment was carried out with bleaching of some selected samples. The extracted fibers from alkali treatment at 2, 4, 6 and 8wt. % concentration of NaOH at both 60 and 120min soaking times were selected. Table 2 shows the measured values and average values obtained after the combined alkali-bleach treatment extracted cellulose percentage upon varying concentration of NaOH and soaking time. The discussion here is based on four different parts (a, b, c and d).

Table 2.

Correlation of soaking time, percentage by weight concentration in extraction process of fiber content.

Combined alkali and bleaching treated screw-pine leaves  Soaking time (min)  Wt. % conc. of NaClO2
   
(a) Alkali treated fiber at 2 wt. % NaOH60  52  53  55  58 
120  57  61  63  65 
(b) Alkali treated fiber at 4wt. % NaOH60  58  66  74  78 
120  67  71  76  80 
(c) Alkali treated fiber at 6wt. % NaOH60  55  56  64  66 
120  58  64  65  69 
(d) Alkali treated fiber at 8wt. % NaOH60  65  68  69  71 
120  73  77  78  86 
Average cellulose content (%)    60  65  68  72 

First, the results on bleaching at varying NaClO2 concentration at 60 and 120min for alkali treated fibers at 2wt. % NaOH is presented and discussed. The second part discusses the bleaching results of alkali treated fibers at 4wt. % NaOH at both 60 and 120min soaking time. The third and fourth parts discuss the bleaching results of alkali treated fibers at 6wt. % and 8wt. % of NaOH for 60 and 120min soaking duration.

The highest cellulose percentage measured was 59% for the fiber bleached at 4wt. % NaClO2, soaked for 120min. This represents an increment of 41% in cellulose percentage compared to no bleaching of the fiber. However, increasing NaClO2 concentration and soaking time during bleaching have further increased the amount of cellulose percentage of the extracted fiber. An Interesting point is that the increment in cellulose content is proportional to the increment in NaOH concentration from the alkali treatment. It is also observed that soaking time have plenty of effect on the fiber cellulose content extracted. For example, at 2wt. % NaOH and 1wt. % NaClO2, 52wt. % cellulose content was measured at 60min soaking time whereas 57wt. % was measured for 120min.

Table 2, sample b, showed the highest cellulose percentage was 80% obtained with soaking duration of 120min in 4wt. % NaClO2 solutions. Whereas, an increment of 25.6% in cellulose percentage is obtained during soaking duration of 60min in concentration of NaClO2 solution from 1 to 4%. The measured average enhancement in the cellulose content is 16% due to further bleaching of the alkali treated fiber i.e. 2wt. %, 60min at 1wt. % NaClO2. When 2wt. % NaClO2 bleaching was involved, an average increment of 6% is measured when the soaking time is increased from 60min to 120min. Meanwhile for the samples (c), the highest cellulose percentage measured was 74% for fibers bleached at 4wt. % NaClO2, soaked for 120min. This represents an increase of 43% in cellulose percentage composed to no bleaching of the fiber, whereas the highest cellulose percentage of 86wt. % was achieved at 4wt. % with soaking time of 120min. A 58% increment is achieved with acid hydrolysis when compared with the alkali hydrolysis of 2wt. %, 60min fibers treatment. For alkali treated fibers at 2wt. %, 120minutes soaking time, the cellulose percentage has shown a more remarkable increase, which implies the effect of longer soaking time. Acid hydrolysis performed at 1wt. % for 60min resulted in 21% increment in cellulose percentage when compared to 18% for alkali hydrolysis at 2wt. %, 60min. As the soaking time increases to 120min the cellulose percentage further increased by 12%.

Based on the results on cellulose content determination for the alkali treated and combined alkali-bleach treated fibers, it has demonstrated that cellulose percentage of extracted fibers increases as concentration of the chemical reagent increases and also as the treatment or soaking time increases. However, the quality of extracted fiber does not only depend on the amount of cellulose but also on the microstructure of the fibers. Ultimately, the highest quality of extracted fiber should also results in highest tensile strength of the fiber.

3.2Morphological analysis

The morphological analyses were done to examine the microstructure of the screw-pine strips. The microstructures of the screw-pine strips were observed before and after treatment which included the untreated, after alkali treatment and after the combined alkali-bleach treatments.

3.2.1Untreated screw-pine Fiber

The image depicting the microfibril of the screw-pine fiber before treatment is described in Figs. 3 and 4. The microfibril is wrapped by hemicellulose and lignin on the outer surface. As a consequence, it created an impurities layer on the microfibril. Those impurities will cause poor adhesion between epoxy matrix and the fiber. Thus, the strength of the composite could suffer. Hemicellulose and lignin bond is in form of amorphous, hereby depicting a weak structure. Therefore, the removal of the hemicellulose and lignin in an extraction in an extraction process is required for improved bonding between composite matrix and fiber.

Fig. 3.

Fibril microstructure of untreated screw-pine fiber.

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Fig. 4.

Microstructure of untreated screw-pine leaf strip: (a) Lines of microfibrils from screw-pine strip (50× magnification), (b) Hemicellulose and Lignin structure of the screw-pine Mat (100× magnification), (c) Microfibril structure of screw-pine strip (100× magnification).

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3.2.2Alkali treatment fiber

Longitudinal cross-section of the screw-pine strips after alkali treatment at various NaOH concentrations and soaking time is shown in Figs. 5–7 by scanning electron micrographs (SEM) imaging. The SEM imaging clearly shows presence of hemicellulose and lignin on the microfibrils after being treated with 2wt. % NaOH at 60min in Fig. 5a. The structures were held closed-up together while the void sizes is small, the reason can be traced to inability of the alkali treated samples to completely remove the cementing substances.

Fig. 5.

Micrographs of alkali treated screw-pine leaf strips. (a) Microstructure of alkali treated fiber at 2wt. % NaOH for 60min (50× magnification). (b) Microfibril structure of alkali treated fiber at 2wt. % NaOH for 60min (500× magnification).

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Fig. 6.

Micrographs of alkali treated screw-pine leaf strips. (a) Microstructure of alkali treated fiber at 4wt. % NaOH for 120min (50× magnification). (b) Microfibril structure of alkali treated fiber at 4wt. % NaOH for 120min (100× magnification).

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Fig. 7.

Scanning electron micrographs of the screw-pine fibril after alkali treatment at (a) 2wt. % NaOH for 60min (b) 2wt. % NaOH for 120min. All micrographs are at 500× magnification.

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Furthermore, Fig. 5b clearly shows the fibers is intact and well bonded. Although different behaviour is observed when the soaking time was doubled as displayed in Fig. 6a. The SEM image in Fig. 6a showed that bigger void sizes implies complete breakdown of the bond structure. In addition, smaller particles and dribs are noted in Fig. 5b, this implies that there are fiber content remaining in the strip or incomplete extraction process. However, increasing the chemical concentration and soaking can improve the extraction process.

For example, the measured value from 6 and 8wt. % clearly showed weaker cementite bonding in the fibril and the void space were very small. The breakdown of fiber or microfibrils was due to high alkali concentration used, the fiber structure became distorted due to the removal of cementing material such as hemicellulose. Surely distortion will have effect on the characteristics of the fibril and to a large extend the microfibril.

Fig. 7a, b captured the SEM micrograph of the continuous cellulose fibril, after alkali treatment at varying extraction parameters. There are several microfibrils contained in a cellulose fibril, thus the effect of the alkali hydrolysis on the size fibril is discontinuous which makes the isolate the microfibril in the spore or void spaces as observed in Fig. 7a and b. Similar observation was reported on alkali treated in agave and borassus fruit fiber [28,29]. Diameter of fibril was reduced as alkali concentration and soaking time increased. This was due to removal of impurities from the surface of the fibril.

3.2.3Combined alkali and bleaching treatment fiber

The alkali treated screw-pine strips at 2, 4, 6 and 8wt. % concentration at both 60 and 120minutes soaking times were further treated with bleaching. The influence of bleaching on the alkali treated strips was examined by visual inspection and microstructural analysis. The longitudinal cross-section of the alkali-bleach screw-pine leaves is shown in Figs. 8–10 by SEM micrograph. All the bleached screw-pine leaves were alkali treated with mentioned extraction process parameters. Fig. 8 shows microstructure of the bleached leaf at 1wt. % NaClO2 for 60min after undergone alkali treated at 2wt. % NaOH at 60min soaking time.

Fig. 8.

Scanning electron micrographs of screw-pine leaves after bleaching at 1wt. % NaClO2 for 60min following alkali treatment at 2wt. % NaOH for 60min. (a) Leaf microstructure (50× magnification). (b) Microfibril microstructure (100× magnification).

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Fig. 9.

Scanning electron micrographs of screw-pine leaves after bleaching at 2wt. % NaClO2 for 60min following alkali treatment at 4wt. % NaOH for 120min. (a) Leaf microstructure (50× magnification). (b) Microfibril microstructure (100× magnification).

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Fig. 10.

Scanning electron micrographs of Mengkuang leaves after bleaching at 3wt. % NaClO2 for 120min following alkali treatment at 6wt. % NaOH for 120min. (a) Leaf microstructure (200× magnification). (b) Microfibril microstructure (500× magnification).

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The structural arrangement depicted in Fig. 8a is notably still packed and covered with hemicellulose and lignin, although the bonding is weak and distorted.

The cell structure is irregular in formation, yet the microfibrils are still closely packed but with weak bonding. When the fibers are subjected to extended soaking period, the void space will be bigger and the cementite will be washed away. Recall, from Tables 1 and 2, increasing the soaking time from 60 to 120min during the alkali treatment and subsequent increasing the chlorite concentration from 1 to 2wt. % resulted in considerable changes in the microstructure of the fibril as shown in Fig. 9. More hemicellulose and lignin were bleached away and in fact defibrillation starts to set-In. Acid hydrolysis thus remove the lignin as well as the Hollocellulose of the natural fiber [30]. This is depicted in Fig. 10a and b. Further defibrillation is also observed as the percentage concentration of the NaClO2 and soaking time is increased from 4 to 8wt. %.

The bleaching treatment causes rapidly oxidized lignin due to the chlorine content. This act causes degradation lignin content. Fig. 11 shows the SEM micrograph screw-pine after 4wt. % NaClO2 for 120min after alkali treatment. Complete structural disorder was observed in the microstructure of the acid hydrolysis fiber at 4wt. % NaClO2 for 60 and 120min for alkali treated at 8 and 6wt. % NaOH for 120min respectively. The rectangular structure became wider; hemicellulose and lignin were completely removed. The fiber bundles were no more intact, separated from its bundle. Though, the cellulose fibers started to show sign of degradation.

Fig. 11.

Scanning electron micrographs of screw-pine leaves after bleaching at 4wt. % NaClO2 for 120min following alkali treatment at 8wt. % NaOH for 60min. (a) Leaf microstructure (50× magnification). (b) Microfibril microstructure (100× magnification).

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Fig. 12 demonstrated the effects of combined alkali-bleaching treatment on fibrils microstructure of the screw-pine leaves. Bleaching the alkali treated leaf (2wt. % NaOH, 60min) at 1wt. % NaClO2 for 60min was not very effective in removing the hemicellulose and lignin content. Increasing the bleaching time to 120min alone, resulted in smoother surface of the fibril.

Fig. 12.

Microstructure of Fribil after combined alkali-bleach treatment. (a) Alkali treatment at 2wt. % NaOH for 60min followed by bleach 1wt. % NaClO2 for 60min. (b) Alkali treatment at 2wt. % NaOH for 60min followed by bleaching 1wt. % NaClO2 for 120min (500× magnification).

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The extended bleaching time allowed more effective extraction of the lignin. The combined treatments have caused the elementary fibers to be exposed due to complete removal of hemicellulose and lignin. Although some degradation in the cellulose was observed, meaning the combined alkali-bleaching did not only remove completely the cementite bond but gave some negative effect on the fiber content.

3.3Cellulose yield content

The cellulose yield percentage is plotted against soaking time and chemical concentration in Figs. 13–16. Among all the various process-parameter evaluated, only the yield content of the fiber cellulose for combined alkali-bleached treatment is considered and presented. The 2wt. % NaOH at 60 and 120min is plotted in Figs. 13 and 14 respectively.

Fig. 13.

Plot of cellulose yield content against process-parameter of screw-pine leaves after bleaching at 1, 2, 3wt. % NaClO2 for 60min following alkali treatment at 2wt. % NaOH for 60min.

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Fig. 14.

Plot of cellulose yield content against process-parameter of screw-pine leaves after bleaching at 1, 2, 3wt. % NaClO2 for 120min following alkali treatment at 2wt. % NaOH for 120min.

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Fig. 15.

Plot of cellulose yield content against process-parameter of screw-pine leaves after bleaching at 1, 2, 3wt. % NaClO2 for 60min following alkali treatment at 4wt. % NaOH for 60min.

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Fig. 16.

Plot of cellulose yield content against process-parameter of screw-pine leaves after bleaching at 1, 2, 3wt. % NaClO2 for 120min following alkali treatment at 4wt. % NaOH for 120min (a).

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The yield content of the cellulose increases with increase in the chemical concentration and soaking time. However, optimal measured value for yield increment is at 3wt. % NaClO2 whereas the 1 and 2wt. % of NaClO2 should no enhancement in the cellulose. The percentage increment in cellulose content is estimated at 8% when the NaClO2 is varied in ascending order for both soaking time, but it is noted that the soaking time have limited effect when 2wt. % of NaClO2 was used in the combined treated.

The increment in chemical concentration from 2 to 4wt. % of NaOH alkali treated and subsequently increasing the bleaching chemical concentration should slim difference in terms of yield content. A mere 2.5% increment was measured. The small difference can be traced to the reduction in the void space and further breaking down of the bond structure. Overall the different treatment has increased tremendously the yield content compared to the un-treated yield measured. In addition, the bleaching further enhanced the cellulose content by 25%. The effect of the processing parameters varied are obvious on the cellulose yield content however, an optimal process-parameter is need to get the best cellulose fiber devoid of degradation.

3.4Tensile strength

Tensile strength test was conducted on the alkali and combined alkali-bleached treated fiber. The influence of the optimum treatment of the fibers on the composite's strength is discussed. The effectiveness of the fiber-matrix interaction will be apparent from the tensile test results. Fig. 17 describes the correlation between the process parameter effect on the tensile strength of the untreated screw-pine and treated fiber with respect to soaking time and percentage concentration of the alkali solution.

Fig. 17.

The correlation between process parameter and tensile strength the untreated Screw pine.

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Figs. 18 and 19 present the correlation between the tensile strength and the percentage concentration with respect to soaking time. The Tensile strength is observed to decrease after alkali hydrolysis. Longer soaking demonstrated consistent effect on the tensile strength of the Fiber whereas, reduced soaking period (60min) initially enhanced the tensile capability by 57%.

Fig. 18.

The correlation between tensile strength and process parameter for alkali treated Fiber at 2% concentration for 60min.

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Fig. 19.

The correlation between tensile strength and process parameter for alkali treated Fiber at 2% concentration for 120min.

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Similar trend is noted when the concentration of NaOH solution is doubled, the obvious effect was observed when the concentration soaking time was reduced to 60min. Increased in tensile strength of the Fiber can be traced to the higher concentration of the chemical solution and reduced soaking time. This prevents damages to the Fiber micro Fibrils and simultaneously breaking-up the bond and removing the cementite from the structure.

Fig. 20 describes the comparison between the various treatments in their composites. The combine alkali and acid treated Fiber composite gave the highest tensile strength capability compared to others. The combined alkali-bleach cellulose fiber composite showed 40% higher tensile strength compared to untreated cellulose fiber composite at 35 2.8MPa. The alkali treated cellulose fiber composite is 15% higher in tensile strength compared to the untreated CF composite. However, tensile strength of untreated cellulose fiber was lower than that of unfilled composite by 5% due to poor adhesion between fiber-matrix bonding.

Fig. 20.

Correlation showing the tensile strength with the process parameters for the fiber composite.

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4Conclusion

Conclusively, the morphological analyses carried out on each of the treated fiber have considerable effect on the extraction, chemical concentration and soaking time. Higher cellulose percentage can be obtained by increasing the chemical concentration and soaking time, however, fiber roughening and separation of the elementary fiber are the observed set-back. However, if the impurities can be separated very well, this set-back may as well be overcome. Increasing the NaClO2 concentration and soaking caused defibrillation to occur. Nonetheless, it is an indicator of complete removal of the hemicellulose and lignin. Void space and weaken of the bond is reduced or eliminated but porosity also increased.

In brief, higher cellulose fiber content can be obtained by increasing the process parameters, although caused some damage to the cellulose fiber structure. In view of the set-back, optimum extraction process parameters should be considered to obtain smooth fiber surface and intact microfibrils structure. The present study observed optimal parameter in range of 6 and 8wt. % of NaOH alkali treated and 2 and 3wt. % of NaClO2 after passing through 4 and 6wt. % NaOH respectively. Longer soaking time have obvious effect on the tensile strength as it helps remove almost the cementite and breakdown the Fiber structure. In addition, longer soaking time increases the yield content but the optimal mixing combination of the process parameter varies with respect to percentage concentration of the acid hydrolysis. The alkali and combined alkali-bleached treated cellulose composite resulted in the highest tensile strength compared with the untreated composites. Further investigation on the continuous cellulose fibers extraction using the combined alkali-bleach treatment can be investigated for possible usage in polymer composite for engineering applications.

Conflicts of interest

The authors declare no conflicts of interest.

Acknowledgements

This research funding was provided by University Technology Petronas (UTP), through Fundamental Research Grant. This support was gratefully acknowledged. And also to School of Material and Mineral Engineering, Universiti Sains Malaysia for providing the test facilities.

References
[1]
H. Shaikh, M. Andaç, N. Memon, M.I. Bhanger, S.M. Nizamani, A. Denizli.
Synthesis and characterization of molecularly imprinted polymer embedded composite cryogel discs: application for the selective extraction of cypermethrins from aqueous samples prior to GC-MS analysis.
RSC Adv, 5 (2015), pp. 26604-26615
[2]
V. Chaudhary, P. Gohil, A. Shaikh.
Development of potential composites through natural fiber reinforcement.
J Sci Ind Res, 74 (2015), pp. 93-97
[3]
M. Tsunoda, K. Takamasa, M. Sachiyo, Y. Sugiura, E. Miyajima, K. Yuichiro, et al.
Skin irritation to glass wool or continuous glass filaments as observed by a patch test among human japanese volunteers.
[4]
D. Verma, P. Gope, A. Shandilya, A. Gupta, M. Maheshwari.
Coir fiber reinforcement and application in polymer composites: A.
J Mater Environ Sci, 4 (2013), pp. 263-276
[5]
A.R.S. Neto, M.A. Araujo, F.V. Souza, L.H. Mattoso, J.M. Marconcini.
Characterization and comparative evaluation of thermal, structural, chemical, mechanical and morphological properties of six pineapple leaf fiber varieties for use in composites.
Ind Crops Prod, 43 (2013), pp. 529-537
[6]
V. Nagarajan, M. Misra, A.K. Mohanty.
New engineered biocomposites from poly (3-hydroxybutyrate-co-3-hydroxyvalerate)(PHBV)/poly (butylene adipate-co-terephthalate)(PBAT) blends and switchgrass: fabrication and performance evaluation.
Ind Crops Prod, 42 (2013), pp. 461-468
[7]
K. Srinivas, A.L. Naidu, M.R. Bahubalendruni.
A review on chemical and mechanical properties of natural fiber reinforced polymer composites.
Int J Perf Eng, 13 (2017), pp. 189
[8]
A. Kumar, T. Abishek, S. Jegatheesh Raja, A. Gokul Krishnan.
A review on mechanical properties of natural fiber reinforced hybrid polymer composites.
(2016),
[9]
F.S. Tong, S.C. Chin, S.I. Doh, J. Gimbun.
Natural fiber composites as potential external strengthening material – a review.
Indian J Sci Technol, 10 (2017),
[10]
O. Güven, S.N. Monteiro, E.A. Moura, J.W. Drelich.
Re-emerging field of lignocellulosic fiber–polymer composites and ionizing radiation technology in their formulation.
Polym Rev, 56 (2016), pp. 702-736
[11]
V.K. Thakur, M.K. Thakur.
Processing and characterization of natural cellulose fibers/thermoset polymer composites.
Carbohydr Polym, 109 (2014), pp. 102-117
[12]
V. Fiore, T. Scalici, A. Valenza.
Characterization of a new natural fiber from Arundo donax L. as potential reinforcement of polymer composites.
Carbohydr Polym, 106 (2014), pp. 77-83
[13]
F.M. Al-Oqla, S. Sapuan.
Natural fiber reinforced polymer composites in industrial applications: feasibility of date palm fibers for sustainable automotive industry.
J Clean Prod, 66 (2014), pp. 347-354
[14]
K.O. Reddy, B. Ashok, K.R.N. Reddy, Y. Feng, J. Zhang, A.V. Rajulu.
Extraction and characterization of novel lignocellulosic fibers from Thespesia lampas plant.
Int J Polym Anal Charact, 19 (2014), pp. 48-61
[15]
S. Saravanakumar, A. Kumaravel, T. Nagarajan, P. Sudhakar, R. Baskaran.
Characterization of a novel natural cellulosic fiber from Prosopis juliflora bark.
Carbohydr Polym, 92 (2013), pp. 1928-1933
[16]
H. Kim, K. Okubo, T. Fujii, K. Takemura.
Influence of fiber extraction and surface modification on mechanical properties of green composites with bamboo fiber.
J Adhes Sci Technol, 27 (2013), pp. 1348-1358
[17]
V. Kommula, K.O. Reddy, M. Shukla, T. Marwala, E.S. Reddy, A.V. Rajulu.
Extraction, modification, and characterization of natural ligno-cellulosic fiber strands from napier grass.
Int J Polym Anal Charact, 21 (2016), pp. 18-28
[18]
D. Trache, M.H. Hussin, C.T.H. Chuin, S. Sabar, M.N. Fazita, O.F. Taiwo, et al.
Microcrystalline cellulose: isolation, characterization and bio-composites application—a review.
Int J Biol Macromol, 93 (2016), pp. 789-804
[19]
N. Yongvanich.
Isolation of nanocellulose from pomelo fruit fibers by chemical treatments.
J Nat Fibers, 12 (2015), pp. 323-331
[20]
S. Gunnarsson.
(2003),
[21]
S. Beck, M. Méthot, J. Bouchard.
General procedure for determining cellulose nanocrystal sulfate half-ester content by conductometric titration.
Cellulose, 22 (2015), pp. 101-116
[22]
O.S. Neto, F. Cláudio, C. Paulo de Tarso, M.A. Araujo-Silva, R.F. do Nascimento.
ModIfIcations of lignocellulose fibers and its application in adsorption of heavy metals fromaqueous solution.
Surf Modif Biopolym, 113 (2015),
[23]
B. Ramavandi, S. Akbarzadeh.
Removal of metronidazole antibiotic from contaminated water using a coagulant extracted from Plantago ovata.
Desalin Water Treat, 55 (2015), pp. 2221-2228
[24]
A.J. Jadhav, C.R. Holkar, A.D. Goswami, A.B. Pandit, D.V. Pinjari.
Acoustic cavitation as a novel approach for extraction of oil from waste date seeds.
ACS Sustain Chem Eng, 4 (2016), pp. 4256-4263
[25]
O. Ezeh, M.H. Gordon, K. Niranjan.
Enhancing the recovery of tiger nut (Cyperus esculentus) oil by mechanical pressing: moisture content, particle size, high pressure and enzymatic pre-treatment effects.
Food Chem, 194 (2016), pp. 354-361
[26]
M.Z. Rong, M.Q. Zhang, Y. Liu, G.C. Yang, H.M. Zeng.
The effect of fiber treatment on the mechanical properties of unidirectional sisal-reinforced epoxy composites.
Compos Sci Technol, 61 (2001), pp. 1437-1447
[27]
J. Gassan.
Natural fiber-reinforced plastics – correlation between structure and properties of the fibers and the resultant composites [Unpublished doctoral dissertation].
University of Kassel, (1997),
[28]
K. Mylsamy, I. Rajendran.
Influence of alkali treatment and fiber length on mechanical properties of short Agave fiber reinforced epoxy composites.
Mater Des, 32 (2011), pp. 4629-4640
[29]
L. Boopathi, P. Sampath, K. Mylsamy.
Investigation of physical, chemical and mechanical properties of raw and alkali treated Borassus fruit fiber.
Compos Part B: Eng, 43 (2012), pp. 3044-3052
[30]
Y.C. Ching, T.S. Ng.
Effect of preparation conditions on cellulose from oil palm empty fruit bunch fiber.
BioResources, 9 (2014), pp. 6373-6385
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Journal of Materials Research and Technology

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