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Industrial Crops and Products 45 (2013) 319– 326

Contents lists available at SciVerse ScienceDirect

Industrial Crops and Products

journa l h o me page: www.elsev ier .com/ locate / indcrop

haracterisation of sago pith waste and its composites

au Choy Laia,∗, Wan Aizan Wan Abdul Rahmana, Wen Yee Tohb

Department of Polymer Engineering, Faculty of Chemical Engineering, Universiti Teknologi Malaysia, 81310, Skudai, Johor, MalaysiaDepartment of Material Science, School of Applied Science, Republic Polytechnic, 9 Woodlands Avenue 9, 738964 Singapore

r t i c l e i n f o

rticle history:eceived 30 August 2012eceived in revised form9 December 2012ccepted 22 December 2012

a b s t r a c t

Sago pith waste (SPW), a fibrous residue resulted from the sago starch extraction process, was charac-terised in terms of moisture content (82%) and starch content (62%, dry weight basis). The dried andground SPW was irregular in shape and has a CE diameter of 29.41 �m, similar to that of pure sagostarch (28.43 �m). SEM micrograph showed that SPW is a mixture which consists of sago starch andfibre, verified by FTIR spectrum and XRD diffractogram observed from peaks which were attributed to

eywords:iodegradable compositehermoplastic starchago pith wastehermal degradation-ray diffraction

sago starch and SPW fibre. With glycerol and water as plasticisers, SPW was then plasticised successfullyto form a natural fibre filled thermoplastic starch composite using a twin screw extruder in the pres-ence of various quantities of glycerol. No synthetic polymer binder was added. Plasticisation led to thedisruption of the original C-type crystallinity of sago starch. However, VH and B type crystallinities weredeveloped after processing as a result of the reorganisation of amylose, amylose–lipid complex (very fast)and amylopectin chains (slow).

ourier transform infrared

. Introduction

Lignocellulosic and cellulose fibres originate from the naturalesources have drawn much attention to be utilised as a sustainablend cost saving filler or reinforcement to produce composites withnhance properties or lower raw material cost. Many papers haveeen published on the study of incorporation of materials such asice husk, coconut shell flour, oil palm frond, oil palm empty fruitunch, wood flour, hemp, cotton, sisal and jute fibres into ther-oplastics (Rozman et al., 1998; Premalal et al., 2002; Alves et al.,

010; Kaewtatip and Thongmee, 2012) and thermosets (Marcovicht al., 2001; Sapuan et al., 2003; Rozman et al., 2004; Ramirest al., 2010; Megiatto et al., 2010). Most of these studies focused onhe mechanical properties of the composites. They revealed thatenerally, the modulus of composites increased with filler contenthile showing a decrease in strength due to the incompatibility

etween the hydrophilic fillers and the hydrophobic matrix. Aoteworthy point here is that most of the aforementioned fibresre actually waste materials from agricultural sector. Utilisation

f these wastes not only serves as another option to improve theerformance of the unfilled plastic materials but also helps to solvehe problem of agricultural waste accumulation besides increasinghe income of the farmers.

∗ Corresponding author. Tel.: +60 7 5535536; fax: +60 7 5588166.E-mail addresses: jclai@cheme.utm.my, elijahlai@yahoo.com (J.C. Lai).

926-6690/$ – see front matter © 2013 Elsevier B.V. All rights reserved.ttp://dx.doi.org/10.1016/j.indcrop.2012.12.046

© 2013 Elsevier B.V. All rights reserved.

Sago pith waste (SPW), known as sago hampas by locals, isa fibrous residue rich in sago starch which is formed from thesago starch extraction process after most of the starch have beenextracted from the rasped pith of the sago palm (Singhal et al.,2008). According to Chew and Shim (1993), SPW contains a largenumber (60–80 wt%) of sago starch granules which are trappedwithin the lignocellulosic fibre matrix. Manufacturers revealed thatapproximately one tonne of SPW is formed from every tonne ofsago starch produced (dry weight basis). However, SPW has notbeen utilised by manufacturers but is usually combined with thewaste water and discharged into the river. Statistics from MalaysiaStatistic Department shows that, Malaysia produces 52,000 tonnesof sago starch in 2011, a 64% rise relative to 2001. Meaning thatabout the same quantity of SPW was dumped into the river. Thecurrent practice resulted in two consequences; firstly, wastage ofthe valuable raw material since large amount of starch is throwninto the rivers. Mohd et al. (2001) estimated that the amount ofstarch disposed as SPW in the state of Sarawak alone accounted fornearly half of the total Malaysian annual imports of starch (40,000tonnes). Secondly, water quality drops severely and further endan-gers the aquatic lives because the microbiological degradation ofthe waste consumes oxygen dissolved in the water, leaving thewater with insufficient oxygen to support higher forms of life (Cecil,2002).

In view of the fact that SPW contains high percentage of starch,

it is believed that the waste can be plasticised into biodegradablecomposite material without adding any synthetic plastic as binder.In this context, the plasticised starch acts as the matrix whichholds the reinforcing fibres. This characteristic makes SPW a unique

3 s and Products 45 (2013) 319– 326

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high speed mixer at the speed of 2000 rpm. It was believed thatall the components are well mixed under such mixing speedand mixing time. The well mixed mixtures were then kept for

Table 1Formulations for plasticised SPW.

Formulation SPW Water Glycerol Calciumstearate

(wt%) (per hundred parts of SPW, phr)

20 J.C. Lai et al. / Industrial Crop

aterial as compared to other fibrous wastes. It is believed that theesulted plasticised SPW has the potential to be processed into var-ous useful consumer products via different processing techniquesuch as compression moulding, injection moulding and thermo-orming. Similar works have been done by some researchers whonitiated the attempt to utilise cassava bagasse, a starch-containingbrous wastes originates from the cassava starch extraction facto-ies. Cassava bagasse, predominantly consists of starch (40–60%)nd fibres (15–50%) was plasticised and processed into naturalomposite by Teixeira et al. (2005). Matsui et al. (2004) used theame raw material to produce a cardboard like composite. Kraftaper was added as long fibres to improve the mechanical andater resistance properties of the product.

Therefore, the objective of this article is to report the charac-eristics of the raw and plasticised SPW. Characterisation of theaw SPW in terms of their chemical and nutritional compositionas been carried out and reported comprehensively by severalesearchers (Wina et al., 1986; Chew and Shim, 1993; Sun andomkinson, 2003). However, the available characterisation resultsased on Fourier transform infrared spectroscopy (FTIR), Thermo-ravimetric analysis (TGA) and X-ray diffraction (XRD) are lessomprehensive and further improvement is needed (Zainuddin,003; Lim, 2006) as the authors analysed the results by treatingPW as a compound despite the fact that it is actually a mixture.oreover, to date, no report on the characteristics of the plasticised

PW is found since the research pertaining to the composites fromPW is still in blank. The results of the studies can also be applied tother similar, starch-containing agro wastes. Mechanical, thermalnd water absorption properties of the plasticised SPW are reportedn another separate paper.

. Experimental

.1. Raw materials and chemicals

Sago pith waste (SPW) was given free of charge by Ng Kia Hengago Industry, Johor, Malaysia. Raw SPW from the factory was firstried under sunlight and later ground into fine powder using arinder. Before being mixed with other components, SPW powderas dried completely in an oven at 105 ◦C for 6 h to ensure that theoisture was removed completely. Glycerol with 99.0% purity was

upplied by Fisher Chemicals. It acts as a non-volatile plasticiserhile calcium stearate, purchased from Sun Ace Kakoh (M) Sdn.hd, was added as an external lubricant to the blends.

DNS reagent which was used to determine the SPW starch con-ent was prepared using potassium sodium tartrate (Rochelle salt)nd 3,5-dinitrosalicylic acid (DNS) from Sigma–Aldrich, as wells sodium hydroxide supplied by Merck. Heat stable �-amylaseas purchased from Sigma–Aldrich. Ethanol 95% was supplied byerck. It was diluted into ethanol 80% before being used as a solvent

n the starch content determination procedure. Sodium acetate tri-ydrate was supplied by R&M Chemicals; it was used to prepare

buffer solution in the starch content quantification work. All thehemicals and enzyme were used directly without further purifi-ation.

.2. Characterisation of the sago pith wastes

Fresh SPW from sago starch extraction factory was collectedsing plastic bags at the collection ram. The fresh SPW was wet,inkish in colour and turned to light brown after drying, as depicted

n Fig. 1. SPW collected at the same factory on five differentays were characterised in terms of moisture content; its parti-le size distribution was obtained using Malvern Morphologi G3utomated particle characterisation system while the micrographs

Fig. 1. Dried sago pith wastes.

obtained from a JEOL JSM-6390LV scanning electron microscope(SEM) was used for complimentary and verification purpose.

Besides, a novel method developed by Jeong et al. (2010) wasused to determine its starch content. According to them, themethod is more accurate and also time saving.

The Morphologi G3 measures the size of particles by the tech-nique of static image analysis. For the case of dry powder samplee.g. SPW, the sample is dispersed using an integrated dry powderdisperser; at the same time, sample is scanned and the imagesof individual particles will be captured by the instrument. Thecollected images are in the form of 2-dimensional projectionof the particles’ profiles. Particle sizes can be calculated fromthese 2-dimensional projections using simple geometrical cal-culations. Particle size distributions can then be constructed bymeasuring tens to hundreds of thousands of particles per mea-surement. Hence, the particle size distribution data generated bythe instrument is based on number of particles measured (MalvernInstruments Limited, 2012).

SPW fibre was separated from sago starch by boiling the SPW ina water filled beaker for 30 min to gelatinise the starch. The mix-ture was then filtered; starch-containing water was discarded andthe remaining fibres went through the same procedure again toensure that the fibres are totally free from starch. The resultingSPW fibres were characterised via FTIR, TGA and XRD. As far asthe author aware of it, SPW fibres was not characterised separatelyand comprehensively via the three techniques in the past; instead,SPW was treated as a compound in those characterisation works(Zainuddin, 2003; Lim, 2006).

2.3. Extrusion of the SPW

A pre-determined amount of all the components in the com-posites, as indicated in Table 1, were mixed for 5 min using a

SPW-G70 100 0 70 2SPW-G60 100 10 60 2SPW-G45 100 25 45 2SPW-G35 100 35 35 2

s and Products 45 (2013) 319– 326 321

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presented in Fig. 4. Moisture release took place at the initial tem-perature and ended at around 150 ◦C. The mass losses within thisrange were taken as the moisture content of the compounds andthe composites, as shown in Table 2. The results also show that

J.C. Lai et al. / Industrial Crop

4 h before plasticisation and compounding process via a SinoSM30 B5B25 (Sino Alloy Machinery Inc.) twin screw extruderith screw diameter of 32 mm and 10 heating zones. The com-ounding process was carried out at a speed of 250 rpm when thewin screw extruder temperature profile (unit in ◦C) was set at5/95/100/90/90/90/90/90/100/105. The amount of glycerol in theormulations was varied from 35 to 70 parts per hundred parts ofPW, with total plasticiser content maintained at 70 parts in ordero study the effect of glycerol content on the properties of thelasticised SPW. The extrudates were pelletised using a pelletizer.

The pelletised extrudates were then moulded into60 (length) × 160 (width) × 1 (thickness) mm3 sheets via com-ression moulding. The compression moulding was done at theemperature and pressure of 120 ◦C and 13 MPa, respectivelyor 5 min. Prior to the application of pressure, the extrudatesere pre-heated at the same temperature for 8 min. Samples forifferent testing were cut from the compression-moulded sheetsccording to the standard requirements. All samples were thenonditioned at 54% relative humidity and room temperature for 33ays prior to the testing. The said 33 days of equilibration periodas chosen since the post-processing ageing of thermoplastic

tarch (TPS) needs more than 30 days to attain the equilibriumBelhassen et al., 2009).

.4. Characterisation of the plasticised SPW

Morphology of the plasticised SPW was studied through theide-angle X-ray diffraction (XRD) using a Siemens D5000 Diffrac-

ometer (Germany) with copper anode X-ray tube, using Cu K�adiation (wavelength: 1.5406 A) at room temperature. Samplesere scanned at the range 2� = 5◦–40◦, and at the speed of 0.03◦ per

s. Attenuated total reflectance-Fourier transform infrared (ATR-TIR) spectrums of the plasticised SPW were recorded with a Perkinlmer System 2000 FTIR spectrometer in the wavelength range000–700 cm−1. For each spectrum, 128 scans were co-added.hanges occurred in the major peaks of the samples were beingecorded and related to the changes which took place at molecularevel after the plasticisation of SPW.

. Results and discussion

.1. Characterisation of the sago pith wastes

Moisture content analysis showed that the fresh SPW contains2%, by weight of moisture. Before the results of particle size dis-ributions are presented, it is instructive to explain a term i.e. CEiameter. SPW particles are 3-dimensional objects with irregularhapes, thus they cannot be fully described by a single dimensionuch as a radius or diameter. In order to simplify the measurementrocess, it is often convenient to define the particle size using theoncept of equivalent circles. In this case, the particle size is definedy the CE diameter that is the diameter of an equivalent circleaving the same surface area as the actual SPW particle (Malvern

nstruments Limited, 2012).In terms of particle size distribution, as depicted in Fig. 2(a),

ean CE diameter of the SPW particles is 29.41 �m. Analysis alsondicates that the CE diameter of 50% of the total particles are4.82 �m or smaller while the CE diameter of 90% particles are4.82 �m or smaller. As for the pure sago starch, the result asxhibited in Fig. 2(b) shows that 50% and 90% of the sago starch

ranules are 27.85 and 40.91 �m or smaller in CE diameter, respec-ively while the mean CE diameter is 28.43 �m. The two samplesre similar in terms of mean CE diameter and also particle sizeistribution.

Fig. 2. Particle size distribution of (a) sago pith wastes and (b) sago starch.

The results of the particle size analysis were verified and fur-ther investigated using SEM. SEM micrograph (Fig. 3) clearly showsthat the SPW consists of two major components i.e. the deformedprolate ellipsoidal sago starch particles (as pointed by the smallarrows) and sago pith fibre scraps in various shapes and sizes (aspointed by the bigger arrows). The micrograph also indicates thatthe sago starch granules are more similar in size, while for the sagopith fibre particles, the particle size range is wider.

Starch contents of the SPW range between 58 and 67% (dryweight basis) and the obtained results agree with previous resultsreported by other researchers i.e. Chew and Shim (1993), Shahrimet al. (2008) and Kumoro et al. (2008) who obtained 66%, 66% and70%, respectively.

3.2. Characterisation of the plasticised SPW

3.2.1. Thermal degradationTGA derivative mass loss curves of each component in the

plasticised SPWs, namely SPW fibre, sago starch and glycerol are

Fig. 3. SEM micrograph of ground SPW (200X).

322 J.C. Lai et al. / Industrial Crops and Products 45 (2013) 319– 326

Table 2Plasticised SPW and their individual component analysis.

Component Major degradationrange (MDR)

Weight loss in theMDR

Peak degradationrate in the MDR

Moisturecontent

(◦C) (%) (%/min) (%)

Glycerol 150–303 100.0 19.8 0.68SPW fibre 220–420 70.9 15.7 7.97Sago starch 275–450 69.2 11.5 15.14SPW-G35 245–390 51.1 13.9 10.05SPW-G45 255–395 43.9 12.6 16.17SPW-G60 255–400 40.3 10.8 18.90

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SPW-G70 250–396 37.8

lycerol started to evaporate at 150 ◦C and volatilised completelyhen the temperature reached around 310 ◦C, corroborates with

he fact that the boiling point of this compound is 290 ◦C. The onsetegradation temperature for SPW fibres (without sago starch) andure sago starch is 220 ◦C and 275 ◦C, respectively. By referring tohe onset degradation temperatures, sago starch is considered ashe most heat resistant compound among the three components.

The derivative mass loss curve of sago starch and SPW fibresere analysed based on the similar works published by other

esearchers (Lluch et al., 2005; Yang et al., 2007; Souza et al., 2009;c ıkalın, 2011). As a lignocellulosic material, SPW fibres consistf three major components, namely hemicellulose, cellulose andignin. The three components are of different thermal behaviour.he weight loss which occurred at 220–315 ◦C was ascribed to theemicelluloses. Hemicellulose consists of various saccharides e.g.ylose, mannose, glucose and galactose. Besides having a randomnd amorphous structure, their molecules are rich of branches. As

result, the molecules are vulnerable to heating, releasing smallolecules like carbon dioxide and some hydrocarbons at relatively

ow temperatures. Different to hemicellulose, cellulose consists of aong polymer of glucose without branches; its structure is in a goodrder and very strong. This explains the high thermal stability ofhis compound. The main thermal decomposition of cellulose tooklace at 315–390 ◦C. The presence of a small shoulder at around15 ◦C in the derivative mass loss curve may possibly indicate theransition from hemicelluloses to cellulose fragmentation (Morianat al., 2011). Lignin is the most thermally stable compound amonghe three components. According to Yang et al. (2007), its decompo-

ition happened at a very low mass loss rate and covers the wholeemperature range from ambient to 900 ◦C. Therefore, the tail dis-layed at the higher temperature was mainly contributed by theegradation of lignin. In terms of structure, lignin is full of aromatic

ig. 4. TGA derivative mass loss curves of individual components in plasticised SPW.

9.9 21.22

rings with various branches; the activity of the chemical bonds inlignin covered an extremely wide range, which led to the degrada-tion of lignin occurring in a wide temperature range (100–900 ◦C)(Yang et al., 2007; Souza et al., 2009; Ac ıkalın, 2011).

As for sago starch which comprises two major components,namely linear amylose and branched amylopectin, the degrada-tion of the two components overlapped and thus not differentiablefrom the derivative mass loss curve. It was reported by otherresearchers who studied the starches from corn, rice, potato andcassava (Guinesi et al., 2006; Liu et al., 2010), and verified in thecurrent work that, in the inert condition, the starch moleculesremained stable until 275 ◦C, only moisture loss was observed.The derivative mass loss curve showed that starch degradationoccurred between 275 and 450 ◦C, the apparently higher upperlimit of the degradation range with respect to the previous works(Guinesi et al., 2006; Liu et al., 2010) was believed to be attributedto the higher heating rate (20 ◦C/min) applied in the current work.At this stage, hydrolysis of �-1,4 as well as �-1,6 glucosidic link-ages in the amylose and amylopectin molecules took place; carbondioxide, carbon monoxide, water and other small molecules wereliberated. After this range, further heating the starch resulted in acarbonaceous residue.

In the light of the individual component analysis results as tab-ulated in Table 2, each peak in the derivative mass loss curvesof the plasticised SPW as depicted in Fig. 5(b) can be roughlyassigned to the decomposition or evaporation of each compo-nent. Taking SPW-G70 as the example, the weight loss observedbetween 30 and 120 ◦C is due to the evaporation of free water in thecomposite while the chemically bound water and mostly glycerolcontributed to the weight loss between 120 and 220 ◦C (Dobircauet al., 2009). The third mass loss which occurred between 220 and310 ◦C corresponds to the evaporation of the remaining glycerol.It is noteworthy that at this range, degradation of the SPW fibres(approximately at 220 ◦C) as well as sago starch (approximatelyat 275 ◦C) also took place. As the degradation of SPW fibres andsago starch continued, maximum degradation rate was achieved at312 ◦C.

The maximum degradation rate of the composite, as shown inFig. 5, decreased but occurred at higher temperature with increas-ing glycerol content. On the other hand, the percentage of theresidues at 700 ◦C decreased when higher content of glycerol waspresent in the composite. Fig. 5 also seems to illustrate a trend thatSPW composites became less thermal resistant as more glycerolwas added to plasticise the SPW. For example, at T = 150 ◦C, weightloss of SPW-G35, SPW-G45, SPW-G60 and SPW-G70 is 10.1%, 16.2%,18.9% and 21.2%, respectively.

This phenomenon was actually attributed to the apparently dif-ferent moisture content of the composites (data not shown). The

actual thermal resistance trend exhibited by the composite is dis-cussed in another separate paper.

A mixture comprising SPW, glycerol and water (composition ofSPW-G35) was prepared and its mass loss curve was compared

J.C. Lai et al. / Industrial Crops and Products 45 (2013) 319– 326 323

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ig. 5. (a) Mass loss curves and (b) derivatives mass loss curves of plasticised SPWith different glycerol contents.

ith that of SPW-G35. Fig. 6 apparently shows that the mass lossurve of the latter is ‘smoother’, meaning that different portions inhe mass loss curve which indicate the decomposition of differentomponents in the composite are unable to be identified, vice versaor the unplasticised mixture. Such characteristic serves to echo the

laim that interactions were developed between water, glycerol,tarch and fibre after the plasticisation process via the twin screwxtruder.

ig. 6. Comparison between the mass loss curve of the plasticised and the physicallyixed SPW-G35.

Fig. 7. XRD diffractograms of sago starch, SPW and SPW fibres.

3.2.2. X-ray diffractionThe XRD diffractograms for sago starch, SPW and SPW fibre are

presented in Fig. 7. It is obvious that the peaks which represent thecrystalline region of the compound are generally broad, confirmingan already well known fact that small and imperfect crystals givebroadened diffractions since sago starch and SPW fibres are partialcrystalline compound with relatively low crystallinities.

On the diffractogram of sago starch, peaks appear at 2� = 5.6◦,15.0◦, 17.1◦, 17.9◦, 23.0◦, and 26.3◦; a typical diffraction pat-tern exhibited by type-C starches. This is in agreement with theresults obtained by other researchers (Ahmad and Williams, 1999;Pukkahuta and Varavinit, 2007). It indicates that sago starch hasthe crystalline type which is intermediate to that of cereal (type-A) and tuber (type-B) starches. According to Ahmad and Williams(1999), the latter are characterised by a small peak at 5.68◦, onlyone peak at 17.8◦ instead of a doublet at 17.8◦ and 18.8◦ for theA-type and a doublet at 22.8◦ and 24.8◦ instead of a single peak at23.8◦ for the A-type. As a lignocellulosic material, SPW fibres gave apeak at 2� = 22.5◦, the fingerprint peak of the type I cellulose (Fordet al., 2010). All the natural fibres fall into this category. Simaraniet al. (2009) and Alhasan et al. (2010) obtained the similar diffrac-tograms for oil palm empty fruit bunch fibres and rubber woodfibres, respectively. As for SPW, its diffractogram consisted of thepeaks which were ascribed to the existence of sago starch and SPWfibres. The intensities of the peaks were smaller comparing to thepure sago starch and SPW fibres, proving that the compound is amixture of these two components.

The changes took place in the crystallinity of SPW as a resultof the plasticisation process via twin screw extrusion in the pres-ence of glycerol as well as the effects of glycerol content can beseen in Fig. 8. The most striking feature is that SPW lost its originalC-type crystalline structure after going through the plasticisationprocess. The original peaks at 2� = 5.6◦, 15.0◦, 17.1◦, 17.9◦, 23.0◦,and 26.3◦ were gone and the new peaks which illustrate the newstructure were formed. The most pronounced change in the crys-talline peaks occurred at 2� = 13.1◦ and 19.9◦, which was attributedto VH-type crystallinity. Besides, B-type crystallinity which is signi-fied by the peaks at 2� = 16.9◦ and 22.4◦ was also developed. All theplasticised SPW, regardless of their glycerol content gave the sameresult (location of the peaks), the difference only lies in the peak

intensity whereby the highest belongs to the formulation with thelowest glycerol content, in this case SPW-G35 and vice versa. Thisobservation corroborates with Van Soest and Knooren (1997) and

324 J.C. Lai et al. / Industrial Crops and Products 45 (2013) 319– 326

Table 3Major peaks in the FTIR spectrum of SPW.

Peak (cm−1) Assignment Sources References

3421 OH stretching Sago starch, SPW fibre Kondo and Sawatari (1996), Yaacob et al. (2011)2928 CH symmetrical stretching Sago starch, SPW fibre Kondo and Sawatari (1996), Yaacob et al. (2011)1736 C O stretching vibration SPW fibre (pectin, waxes, hemicellulose) Merk et al. (1998)1638 OH bending of the absorbed water Water Dai and Fan (2011)1503, 1456, 1427 Lignin triplet SPW fibre (lignin) Ibarra et al. (2005), Río et al. (2007)1372 In-the plane CH bending SPW fibre (cellulose, hemicellulose) Kondo and Sawatari (1996)1338, 1244 Syringyl ring stretching SPW fibre (lignin) Kubo and Kadla (2005)1160 C O C Asymmetrical stretching SPW fibre (cellulose, hemicellulose) Dai and Fan (2011)925, 861, 767, 707 Out-of-plane bonded OH

deformation and CH deformationSago starch

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ig. 8. Comparison of XRD diffractograms of raw SPW and plasticised SPW (after 34ays of equilibration in a desiccator).

hi et al. (2007) who reported that high glycerol content can restrictecrystallisation.

The disappearance of the original C-type crystalline structure

as linked to the disruption of the sago starch granular structure

s a result of the application of heat and shear stress in the pres-nce of glycerol when it was extruded. The products of the extrusionrocess are, initially amorphous and hence, will not give any peak

Fig. 9. FTIR spectra of SPW fib

Yaacob et al. (2011)

in the XRD diffractograms. However, during extrusion process, theamylose will react with the lipids present in the starch to formcomplexes. These amylose-lipid complexes are accountable for theVH-type crystallinity in the composites. On the other hand, amy-lopectin and the free amylose will recrystallise into the B-typestructure which was recognised by the peaks at 2� = 16.9◦ and 22.4◦.In terms of the recrystallisation speed, the linear amylose is veryfast in comparison to the highly branched and bulky amylopectin(Pushpadass and Hanna, 2009). Thus, as can be seen in Fig. 8, thepeaks which represent the VH-type crystallinity are very obviousover those of the B-type crystallinity.

The recrystallisation of the starch components is the mainculprit which causing the ageing problem in the starch basedbiodegradable polymers (Van Soest and Knooren, 1997; Avérous,2004), this topic has been studied and will be discussed in greaterdetail in another separate paper.

3.2.3. Fourier transform infrared spectroscopyThe Fourier transform infrared spectrum of SPW is presented

in Fig. 9. For comparison and verification purpose, the spectra ofsago starch and SPW fibres are also included. It is pronounced thattheir spectra are very close to one another due to the similarity offunctional groups present in these compounds. However, the originof the major peaks in SPW is still identifiable and their assignmentis as tabulated in Table 3.

All the compounds exhibited a broad peak at around3600–3000 cm−1 which is ascribed to the stretching of the OHgroups while the peaks at around 2930 cm−1 and 1640 cm−1 aredue to the CH stretching and the presence of the absorbed water,

re, sago starch and SPW.

J.C. Lai et al. / Industrial Crops and Products 45 (2013) 319– 326 325

700 cm

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Fig. 10. FTIR spectra (1650–

espectively. The fingerprint feature of the sago starch is the broadbsorption bands in the range 1100–990 cm−1, features the C Otretching in the C O C and C OH in the glycosidic rings. As forPW fibres, the significant peaks which differentiated it from otherompounds are those related to lignin since this compound is onlyresent in the SPW fibres. Those exclusive peaks include the ligninriplet at 1508 cm−1, 1453 cm−1 and 1424 cm−1 (Ibarra et al., 2005;ío et al., 2007) as well as 1335 cm−1 and 1246 cm−1. The former isorresponded to the syringyl ring stretching while the latter can beinked to the combined effect of the C C, C O, and C O stretchingn the lignin–carbohydrate complex (Kubo and Kadla, 2005). Theresence of the peak at 1335 cm−1 corroborates with Kuroda et al.2001) who found that sago pith lignin is of syringyl type by usingnalytical pyrolysis method. As seen in Fig. 9 and as tabulated inable 3, the FTIR spectrum of SPW contains the characteristic peaksf SPW fibres and sago starch; this is not surprising since SPW is aixture of the two components.The variation of the peaks at 1028 cm−1 and 853 cm−1 as

he function of glycerol content is presented in Fig. 10. From028 cm−1 and 853 cm−1 at 35 phr glycerol, the peaks exhibited

displacement to 1033 cm−1, 856 cm−1; 1032 cm−1, 854 cm−1 and040 cm−1, 857 cm−1 for glycerol concentrations of 45, 60 and 70hr, respectively. According to van Soest et al. (1995) and Bergot al. (2009), these two peaks are sensitive to the changes in crys-allinity whereby the peak frequency increases with decreasingrystallinity. As mentioned in Section 3.2.2, the crystallinity in theomposites developed as a result of the thermoplastic starch age-ng. FTIR spectra indicated that when more glycerol is present in theomposite, the crystallinity of the composite developed at a lower

ate. This observation is in good agreement with the XRD result ashown in Fig. 8. It can be clearly seen that the peaks which repre-ent the VH and B type crystallinities were more obvious for theomposites which contained less glycerol.

−1) of the plasticised SPW.

4. Conclusion

This study provided an insight into the application and char-acteristics of SPW in thermoplastic starch–fibre composites. SPWcollected from a sago starch extraction plant was characterised.Its moisture and starch content were high i.e. 82% and 62% (dryweight basis), respectively. The dried and ground SPW was irregularin shape and has a CE diameter of 29.41 �m, similar to that ofpure sago starch (28.43 �m). It was found that the FTIR spectrumand XRD diffractogram of SPW contained the peaks which wereattributed to sago starch and SPW fibre; proving that SPW is amixture of sago starch and SPW fibres. With glycerol and water asplasticisers, SPW was then plasticised successfully to form a natu-ral fibre filled thermoplastic starch composite without the additionof any synthetic polymer using a twin screw extruder. Plastici-sation led to the disruption of the original C-type crystallinity ofsago starch; However, VH and B type crystallinities were devel-oped after processing as the result of the reorganisation of amylose,amylose–lipid complex (very fast) and amylopectin chains (slow).As a conclusion, SPW is an interesting candidate for producingbiodegradable composites. It is freely available from the factories.Moreover, this application offers another sustainable alternativein dealing with this water-polluting waste and even providing anincentive to sago starch extraction plant. Nevertheless, comple-mentary studies must be carried out in order to have an in-depthunderstanding of certain characteristics such as ageing of thismaterial so that appropriate strategy could be taken to ensure itsapplicability to produce useful consumer products.

Acknowledgements

Sincere thanks are due to Malaysian Ministry of Higher Edu-cation and Universiti Teknologi Malaysia for the SLAI scholarship

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nd study leave, respectively. Special thanks to Mr. Samuel Howehuen, Loh for helping in checking and refining the language of thisrticle.

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