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International Journal of Biological Macromolecules 99 (2017) 265–273

Contents lists available at ScienceDirect

International Journal of Biological Macromolecules

j ourna l h o mepa ge: www.elsev ier .com/ locate / i jb iomac

ffect of seaweed on mechanical, thermal, and biodegradationroperties of thermoplastic sugar palm starch/agar composites

idhwan Jumaidina,d, Salit M. Sapuana,c,∗, Mohammad Jawaidc, Mohamad R. Ishakb,apar Saharie

Department of Mechanical and Manufacturing Engineering, Universiti Putra Malaysia, 43400, UPM, Serdang, Selangor, MalaysiaDepartment of Aerospace Engineering, Universiti Putra Malaysia, 43400, UPM, Serdang, Selangor, MalaysiaLaboratory of Biocomposite Technology, Institute of Tropical Forestry and Forest Products (INTROP), Universiti Putra Malaysia, 43400, UPM, Serdang,elangor, MalaysiaDepartment of Structure and Material, Faculty of Mechanical Engineering, Universiti Teknikal Malaysia, Melaka, Hang Tuah Jaya, 76100, Durian Tunggal,elaka, Malaysia

Faculty of Science and Natural Resources, Universiti Malaysia Sabah, 88400, Kota Kinabalu, Sabah, Malaysia

r t i c l e i n f o

rticle history:eceived 14 November 2016eceived in revised form 23 February 2017ccepted 25 February 2017vailable online 27 February 2017

a b s t r a c t

The aim of this paper is to investigate the characteristics of thermoplastic sugar palm starch/agar (TPSA)blend containing Eucheuma cottonii seaweed waste as biofiller. The composites were prepared by melt-mixing and hot pressing at 140 ◦C for 10 min. The TPSA/seaweed composites were characterized fortheir mechanical, thermal and biodegradation properties. Incorporation of seaweed from 0 to 40 wt.%has significantly improved the tensile, flexural, and impact properties of the TPSA/seaweed composites.

eywords:ompositeshermoplastic starcheaweed

Scanning electron micrograph of the tensile fracture showed homogeneous surface with formation ofcleavage plane. It is also evident from TGA results that thermal stability of the composites were enhancedwith addition of seaweed. After soil burial for 2 and 4 weeks, the biodegradation of the compositeswas enhanced with addition of seaweed. Overall, the incorporation of seaweed into TPSA enhances theproperties of TPSA for short-life product application such as tray, plate, etc.

© 2017 Elsevier B.V. All rights reserved.

. Introduction

Accumulation of petroleum based plastic wastes has cre-ted serious environmental problems since they are not readilyiodegradable nor renewable [1]. Increasing awareness amongociety to the impact of non-degradable plastics has brought toarious solutions. Bio-based polymer is among the most promis-ng solution since they are biodegradable and renewable as well.arious kind of bio-based polymer have been developed from nat-ral resources and starch is one of the most promising materialue to the renewability and wide availability at low cost [2,3].hermoplastic starch (TPS) is the resulting product of plasticizedtarch which possesses similarity with conventional thermoplas-

ic material, hence, allows the application of similar processinguch as extrusion, compression molding, and injection molding4]. However, the application of TPS in real life is limited due to

∗ Corresponding author at: Department of Mechanical and Manufacturing Engi-eering, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia.

E-mail address: sapuan@upm.edu.my (S.M. Sapuan).

ttp://dx.doi.org/10.1016/j.ijbiomac.2017.02.092141-8130/© 2017 Elsevier B.V. All rights reserved.

certain drawback such as poor mechanical properties. Thereforevarious studies were carried out to improve the properties of TPSby blending and reinforcing TPS with other material. Incorporationof TPS with synthetic polymer seems to be a promising approach,however, this could jeopardize the biodegradable aspect of TPS.Therefore, application of natural based material as blend compo-nent for TPS is more appropriate and desirable. A study on usingsodium alginate as blend material for TPS/low density polyethy-lene (LDPE) was reported earlier [5]. They reported remarkableimprovements with incorporation of sodium alginate i.e. smoothersurface, enchanced phase compatibility, lower number of voids,and faster degradability of the resulting blend. In addition, vari-ous kinds of material were also explored for its potential as blendcomponent for TPS i. e agar, carrageenan, chitosan, and chitin[6–9]. Agar is polysaccharide that consists of two main componentsnamely agarose and agaropectin. This polysaccharide is obtainedfrom marine algae of the class Rhodophyceae such as such as Gelid-

ium sp. and Gracilaria sp. [10,11]. This material is widely used infood and pharmaceutical industry as gelling and thickening agent.Miscibility of agar in TPS from waxy rice and potato has been inves-tigated in previous studies [6,12]. It is reported that agar is capable

dx.doi.org/10.1016/j.ijbiomac.2017.02.092http://www.sciencedirect.com/science/journal/01418130http://www.elsevier.com/locate/ijbiomachttp://crossmark.crossref.org/dialog/?doi=10.1016/j.ijbiomac.2017.02.092&domain=pdfmailto:sapuan@upm.edu.mydx.doi.org/10.1016/j.ijbiomac.2017.02.092

2 f Biological Macromolecules 99 (2017) 265–273

oi

cabbnwmb

mantH3aafbishpp

tTwafiosiis

2

2

JwsbsfitscRc

awcagcsm

Table 1Chemical composition of Eucheuma cottonii wastes.

Material Composition (wt.%)

Carbohydrate 58.70Crude protein 4.20Cellulose 6.95

66 R. Jumaidin et al. / International Journal o

f increasing the mechanical properties of TPS without compromis-ng its biodegradable aspect.

In addition to improving the properties of TPS, its mechani-al properties can be enhanced by addition of natural filler suchs talc, clay, and eggshell [13–15] in order to obtain fully bio-ased composite material. Such green composites are completelyiodegradable and environmental friendly since their disposal willot cause any harm to the environment [16]. The usage of organicastes fillers i. e eggshell and coconut shell as reinforcementaterial is also a promising alternative since they are renewable,

iodegrable, and extremely low cost.Eucheuma cottonii (also known as Kappaphycus alvarezii) is a

arine alga that belongs to the “red seaweed” family. This macrolgae is largely cultivated for the production of its hydrocolloidsamely kappa-carrageenan (k-carrageenan) which were used forhickening and gelling agent for food and non-food application.owever, the content of k-carrageenan varies from only 25 to5% from the whole seaweed weight, hence, leaving enormousmount of solid wastes which is yet to be utilized [17]. Therere various kind of research has been done on natural filler rein-orced polymer composite, however, research on seaweed fillerased polymer composites is very rare. Most of the present stud-

es utilized the incorporation of seaweed from various species inynthetic polymer matrix such as polypropylene, poly(lactic) acid,igh density polyethylene (HDPE), Poly-(�-caprolactone) (PCL) andoly(hydroxyl-butyrate) (PHB) which results to non-compatiblehase of the composite [18–21].

To the best of our knowledge, there is no study conducted onhe incorporation of Eucheuma cottonii seaweed wastes into TPS orPS/agar blends. The present research work has been undertakenith an objective to explore the potential of using seaweed wastes

s reinforcement in TPS/agar blends. In our previous work, modi-cation of TPS with agar has led to improvement in the propertiesf the biopolymer blends [22]. Significant increase in the tensiletrength and modulus was evidence with incorporation of agarnto TPS which was accompanied by increased in thermal stabil-ty. Therefore, TPS/agar (TPSA) blend was used as the matrix in thistudy in order to investigate the effect of seaweed addition.

. Materials and methodology

.1. Materials

Sugar palm starch (SPS) was extracted from sugar palm tree atempol, Negeri Sembilan, Malaysia. The interior part of the trunk

as crushed in order to obtain the woody fibers which contain thetarch. These woody fibers were soaked in fresh water followedy squeezing in order to dissolve the starch into the water. Waterolution that contained starch was filtered in order to separate thebers from the solution. This solution was then left for sedimen-ation of the starch. The supernatant was discarded and the wettarch was kept in an open air for 48 h followed by drying in an airirculating oven at 105 ◦C for 24 h. Agar powder was procured from&M Chemicals, Malaysia and glycerol was purchased from Sciencehem, Malaysia.

Seaweed waste from Eucheuma cottonii species was obtaineds waste material from seaweed extraction. The solid wastesere obtained after hot alkaline extraction process to obtain k-

arrageenan. This by-product were cleaned with water and driedt 80 ◦C for 24 h in a drying oven. The dried seaweed wastes were

round and sieved then kept in zip-locked bags until further pro-ess. The moisture content and average particle size of the groundeaweed are 0.75 ± 0.2% and 120 �m, respectively. Fig. 1 shows theicrograph of Eucheuma cottonii seaweed in various form i.e. raw,

Hemicellulose 3.33Lignin 4.83Ash 34.49

waste, and ground form. Table 1 shows the chemical compositionof Eucheuma cottonii wastes.

2.2. Sample preparation

Preparation of thermoplastic SPS/agar was conducted accordingto the previous work [22]. Thermoplastic SPS/agar (TPSA) was pre-pared by addition of glycerol followed by pre-mixing using highspeed mixer at 3000 rpm for 5 min. The ratio of starch, agar, andglycerol was maintained at 70:30:30. After this preliminary step,the resulting blend was melt-mixed using Brabender Plastographat 140 ◦C and rotor speed of 20 rpm for 10 min. This mixture wasgranulated by means of a blade mill equipped with a nominal 2 mmmesh and thermo-pressed in order to obtain laminate plate with3 mm thickness. For this purpose a Carver hydraulic thermo-presswas operated for 10 min at 140 ◦C under the load of 10 ton. Thesame processes were used for the modification of TPSA with 10, 20,30, and 40 wt.% of seaweed. All samples were pre-conditioned at53% RH for at least 2 days prior to testing.

2.3. FT-IR analysis

Fourier transform infrared (FT-IR) spectroscopy was used todetect the presence of functional groups existing in thermoplas-tic SPS blends. Spectra of the material were obtained using anIR spectrometer (Nicolet 6700 AEM). FT-IR spectra of the sample(10 × 10 × 3 mm) was collected in the range of 4000–400 cm−1.

2.4. Scanning electron microscope (SEM)

The morphology of tensile fractured surfaces was observedunder scanning electron microscope (SEM), model Hitachi S-3400Nwith acceleration voltage of 10 kV.

2.5. Tensile testing

Tensile tests were conducted according to ASTM D-638 at thetemperature of 23 ± 1 ◦C and relative humidity of 50 ± 5%. Thetests were carried out on 5 replications using a Universal TestingMachine (INSTRON 5556) with a 5 kN load cell; the crosshead speedwas maintained at 5 mm/min.

2.6. Flexural testing

Flexural tests were conducted according to ASTM D-790 at thetemperature of 23 ± 1 ◦C and relative humidity of 50 ± 5%. Thesample was prepared with dimensions of 130 mm (L) × 13 mm(W) × 3 mm (T). The test was carried out on 5 replications usinga Universal Testing Machine (INSTRON 5556) with a 5 kN load cell;the crosshead speed was maintained at 2 mm/min.

2.7. Impact testing

Izod impact tests were conducted according to ASTM D256at the temperature of 23 ± 1 ◦C and relative humidity of 50 ± 5%.The sample was prepared with dimensions of 60 mm (L) × 13 mm

R. Jumaidin et al. / International Journal of Biological Macromolecules 99 (2017) 265–273 267

aw sea

(dst

I

2

btfri

2

fiKaebdmp9dT2vAtu

W

Fig. 1. Micrograph of Eucheuma cottonii seaweed (a) r

W) × 3 mm (T). The tests were performed on 5 replications using aigital INSTRON CEAST 9050 pendulum impact tester. The impacttrength was calculated based on the impact energy and cross sec-ion area of the specimen as follows:

mpactstrength = Impactenergy(J)/area(mm2)

.8. Thermogravimetric analysis (TGA)

The thermal degradation behavior of composites were analysedy TGA with respect to weight loss due to increase in tempera-ure. TGA was performed with a Q series thermal analysis machinerom TA Instrument(New Castle, DE, USA). The analysis was car-ied out in aluminum pans under a dynamic nitrogen atmospheren temperature range 25–900 ◦C at a heating rate of 10 ◦C/min.

.9. Soil burial

Soil burial degradation test was carried out according to modi-ed method by González & Alvarez Igarzabal [23] and Bootklad &aewtatip [15]. Samples of dimension 15 × 15 × 3 mm were buriedt 10 cm depth in characterized soil which was regularly moist-ned with distilled water. Iron mesh was used to wrap the samplesefore buried into the soil in order to facilitate removal of theegraded samples while maintaining the access of moisture andicroorganism. The physico-chemical properties of the soil were

H: 6.52; organic carbon: 1.14%; total nitrogen: 0.07%; phosphorus6.6 �g/g; and potassium: 45.93 �g/g. Prior to testing, samples wasried at 105 ◦C for 24 h and weighed to obtain the initial weight, Wi.wo sets of experiments were made for predetermined intervals of

and 4 weeks. Samples were taken from soil at the specified inter-als and gently cleaned with distilled water to remove impurities.fterwards, they were dried at 105 ◦C for 24 h and weighed to obtain

he final weight, Wf. The weight loss of samples was determinedsing the following equation:

eight loss (%) = Wi − WfWi

× 100

weed (b) seaweed wastes (c) ground seaweed wastes.

2.10. Statistical analysis

Statistical analysis of tensile properties has been carried out byone-way analysis of variance (ANOVA) and the significance of eachmean property value was determined (p < 0.05) with the Duncan’smultiple range tests.

3. Results and discussion

3.1. FT-IR

Fig. 2 shows the FT-IR data for TPSA/seaweed composites andthe native seaweed respectively. In general, all the spectra of TPSAcomposites showed similar pattern of bands. This finding sug-gests that the TPSA is neither chemically affected nor modifiedby the amount of seaweed in the composites. Similar finding wasreported for incorporation of coconut fiber into thermoplastic cas-sava starch [24]. The bands at approximately 3100–3700 cm−1

were assigned to hydrogen bonded hydroxyl group (O H) fromthe complex vibrational stretching, associated with free, inter andintra molecular bound hydroxyl groups [12]. Meanwhile, the bandat approximately 2900 cm−1 were characteristics of C H stretch-ing from CH2 and/or CH3 [6]. The spectra of the TPSA matrixand its composites show a new band at 1720 cm−1, which canbe associated to stretching vibrations of carbonyl groups (C O).According to Lomeli-Ramirez et al. [24], this is possibly due to theprobable presence of carboxylic acid, ketones or aldehydes com-pounds produced by thermal decomposition of the native starchfollowing the preparation of TPSA matrix and its composites atthe Brabender plastograph. This carbohydrate decomposition cat-alyzed by temperature (>100 ◦C) is a well-known mechanism calledcaramelization, and it can also occur due to the conditions of themolding process [24].

The peaks in the range of 1400–1450 cm−1 were assignedfor O H bonding [25]. Meanwhile, the peaks at approximately1020–1089 cm−1 were characteristic of the anhydro-glucose ring

C O stretch [12,26]. The peak at approximately 1380 cm−1 wascorresponding to methyl (CH3) bending [27]. In the IR spectrumof native seaweed, the band located at 1648 cm−1 corresponds toadsorbed water in the sample. The bands at 925–935 cm−1 and

268 R. Jumaidin et al. / International Journal of Biological Macromolecules 99 (2017) 265–273

comp

83[gtbCrapp

isebtbswTgp

Fig. 2. FT-IR spectra of TPSA/seaweed

40–850 cm−1 were assigned to seaweed polysaccharide namely,6-anhydro-d-galactose and d-galactose-4-sulphate respectively28]. It should be noted that carrageenan is made up from thislucose repeating unit. Therefore, these functional groups indicatehe presence of residual carrageenan in the seaweed wastes. Theand at approximately 1260 cm−1 and 1240 cm−1 corresponds to

O C stretching and ester sulphate stretching of k-carrageenanespectively [27,29]. Moreover, the spectra of methyl group atpproximately 1380 cm−1 also indicates the presence of seaweedolysaccharide [28]. Fig. 3 shows the chemical structure of seaweedolysaccharide namely k-carrageenan.

FT-IR spectra of composites material enabled the filler-matrixnteraction to be identified where lower wavenumber indicatestronger interaction between the components [12]. Acording to Wut al. [12], the shifting of hydroxyl group band to lower wavenum-er indicates new hydrogen bonding formation existed betweenhe composites’ component. It was observed that the hydrogenonded hydroxyl peak at 3303 cm−1 for TPSA and 3443 cm−1 foreaweed has shifted to 3275 and 3267 cm−1 for 10% and 40% sea-eed composites, following the incorporation of seaweed into the

PSA matrix. This finding shows that the formation of new hydro-en bonds between TPSA and seaweed has taken place duringreparation of the composites. This result is in agreement with pre-

Fig. 3. Chemical structure of k-carrageenan.

osites with various seaweed contents.

vious studies on natural fiber composites that uses thermoplasticstarch as the composite’s matrix [24,25]. The shifting in peak posi-tion at this range also indicates good filler-matrix compatibilityof the composites. On the other hand, formation of new hydro-gen bonding between filler and matrix in a composite might beassociated with improvement in the mechanical properties of thematerial due to stronger resistance to deformation provided by thehydrogen bonding.

3.2. Tensile properties

Fig. 4 shows the tensile properties of TPSA/seaweed compos-ites i. e tensile strength, tensile modulus, and elongation at break,respectively. Table 2 shows the analysis of variance (ANOVA) of thetensile properties. Since the P-value is less than 0.05, there is a sta-tistically significant difference between the mean tensile strength,modulus, and elongation from one level of composites to another.Both tensile strength and tensile modulus of composites increasedwith increasing seaweed content to reach their maximum values at30 and 40 wt.% filler content, respectively. Increasing filler contentfrom 0 to 30 wt.% increased the composite tensile strength by 56.5%while significant increase in tensile modulus by 78.6% was evidenceat 40 wt.% filler content. The elongation of composites also showsa maximum values at 30 wt.% and continue to decrease at 40 wt.%filler content.

Decrement in the tensile strength of composites can be seenat 40 wt.% filler loading. This phenomenon can be ascribed to theeffect of matrix discontinuity upon high filler content in the matrixwhich led to lack of stress transfer from matrix to filler [30].Similar findings were also reported for seaweed/polypropylenecomposites [30], thermoplastic starch/silk fiber composites [31],sugar palm fiber/phenolic composites [32], and pineapple leaffiber/polypropylene composites [33].

The improvement in tensile properties of the composites mightbe attributed to several reasons. Firstly, similar hydrophilic charac-ter of seaweed and TPSA led to good compatibility between themwhich promote good adhesion of the materials. According to Phan

R. Jumaidin et al. / International Journal of Biological Macromolecules 99 (2017) 265–273 269

a) tens

eiinwmoasistftaif

suKpstaath

TS

*

Fig. 4. Tensile properties of TPSA/seaweed composites (

t al., combination of compatible materials often led to significantmprovement in the mechanical properties, while the incompat-ble materials often led to inferior properties [34]. Secondly, theew hydrogen bond formation between the TPSA and the seaweedaste (as shown in FT-IR results) resulted in the difficulty of theobility of the polymer chains, hence, increasing the resistance

f the material to deformation. Prachayawarakorn et al., [35] alsossociates the improvement in tensile strength of thermoplastictarch/cotton fiber composites with the increase of hydrogen bond-ng shown in FT-IR spectra. Finally, the residual carrageenan in theeaweed waste might form a good network with starch and agar inhe matrix which results to reinforcement of the matrix. It is knownrom literature that carrageenan film tend to show more rigid struc-ure with higher strength than the starch film [36]. This finding is ingreement with previous works [7,37,38] which reported increasen the tensile strength and modulus of thermoplastic starch matrixollowing the incorporation of carrageenan.

This study shows improvement in the tensile properties ofeaweed composites compared to the previous studies whichtilize synthetic polymer as the composite’s matrix. Chitra andumar reported significant decrease in the tensile strength ofolypropylene composites following the addition brown and redeaweed [20]. Bulota and Budtova also reported decrease in theensile strength of poly(lactic) acid (PLA) composites following theddition of red, green, and brown algae [18]. Despite the biodegrad-

bility of PLA as a polymer matrix, the hydrophobic behavior ofhis material has led to poor filler-matrix compatibility with theydrophilic seaweed. Decrease in tensile strength of polymer com-

able 2ummary of the analysis of variance (ANOVA) of mechanical properties.

Variables df Tensile strength Tensile modulus Elongat

Mixture 4 0.00* 0.00* 0.00*

Note: Significantly difference at p ≤ 0.05.

ile strength (b) tensile modulus (c) elongation at break.

posites following the addition of seaweed were also reported inother studies [21,39,40].

3.3. Flexural properties

The flexural strength and modulus of TPSA/seaweed compositewere shown in Fig. 5a and b. Analysis of variance (ANOVA) of theflexural properties (Table 2) indicates that there is a statistically sig-nificant difference (p < 0.05) between the mean flexural strengthand modulus from one level of composites to another. In gen-eral, the flexural test results follow similar trend with tensile testswhere 30 wt.% filler shows the highest flexural strength. Signifi-cant improvement (p < 0.05) was evidence in the flexural propertiesof the composite when incorporated with seaweed. The flexuralstrength increase by 50.6% with addition of 30 wt.% filler while themodulus increase by 45.9% at 40 wt.% filler loading. Improvement inthe flexural properties of the composites might as well be attributedto similar reasons mentioned in the tensile test results. Generally,higher strength and modulus was shown by flexural test than ten-sile test, this finding is in consistent with the literature [41,42].A study on using Ascophyllum nodosum seaweed as bio filler forpolypropylene composite also reported similar finding of increasedflexural strength and modulus with increasing filler content whereaddition of 30 wt.% seaweed shows the highest strength [39]. Theauthors attributed the improvement in the flexural properties to

the ductile and spiral orientation of the seaweed fiber. Anotherstudy by Lee et al., reported significant increase in the flexuralmodulus of poly(butylene succinate) (PBS) matrix following theaddition of red algae fiber [43].

ion Flexural strength Flexural modulus Impact strength

0.00* 0.00* 0.02*

270 R. Jumaidin et al. / International Journal of Biological Macromolecules 99 (2017) 265–273

osites

3

fiwispc3J2lcrno

3

taoispnmibbtu

m

Fig. 5. Flexural and impact properties of TPSA/seaweed comp

.4. Impact properties

Fig. 5c shows the impact strength of the composites with variousller content. Analyses of variance (ANOVA) of the impact strengthere shown in Table 2. Since the P-value is less than 0.05, there

s a statistically significant difference between the mean impacttrength from one level of composites to another. In general, incor-oration of seaweed has led to increase in the impact strength ofomposites up to 20 wt.% filler content and gradually decrease at0 and 40 wt.% filler content. Similar findings were reported byang et al., where incorporation of brown and green seaweed up to0 wt.% has led to increase in the impact strength of the polypropy-

ene composites [44]. Improvement in impact strength of polymeromposites following the addition of green seaweed were alsoeported by Hassan et al. [30]. However, the impact strength of theeat matrix was not shown in this study, hence, the improvementf the polymer matrix with addition of seaweed is not visible.

.5. SEM

Fig. 6 shows the scanning electron micrograph of tensile frac-ure surface of TPSA matrix reinforced with seaweed. In general,

homogeneous structure with no apparent phase separation wasbserved in the composites suggesting good filler-matrix compat-bility. This finding might be attributed to several reasons. Firstly,eaweed has similar hydrophilic behavior with TPSA matrix, hence,roper adhesion between the two materials led to more homoge-ous surface. Secondly, seaweed, starch, agar, and glycerol wereelt-mixed together prior to hot pressing which led to better mix-

ng of the materials. Finally, the carrageenan in seaweed mighte melted during the melt-mixing process, hence, forming a sta-le mixture. Previous studies had shown that carrageenan is able

o form homogenous structure when mixed with starch and agarnder the application of heat [7,45].

Incorporation of seaweed was observed to promote the for-ation of more cleavage planes on the tensile fracture. Similar

(a) flexural strength (b) flexural modulus (c) impact strength.

cleavage planes were also reported in the fracture surface of starchfilm [46]. Increasing number of cleavage planes with incorpora-tion of seaweed suggesting stronger intermolecular bonding of thecomposites that resists deformation under loading before fracture[22]. The presence of crack was evidence at 40 wt.% filler suggest-ing the effect of matrix discontinuity upon high filler content. Apartfrom that, the presence of void was also observed in the compos-ites, which is more evidence at higher filler concentration. Similarfindings were also reported for incorporation of 60 wt.% flax anddate palm fiber into thermoplastic starch composites [41].

3.6. Thermal properties

Fig. 7 shows the TG and DTG curve of TPSA and TPSA/seaweedcomposites respectively. In general, the degradation step that occurbelow 100 ◦C were assigned to dehydration of loosely bound waterand low molecular weight compound [47]. The degradation stepsaround 130–250 ◦C can be assigned to evaporation of glycerol [41].Meanwhile, according to Prachayawarakorn et al., the degrada-tion occured at around 100–200 ◦C might as well be associatedto the evaporation of both water and glycerol [25]. The degrada-tion occured above 270 ◦C was associated with degradation of agar[6]. The temperature at which maximum degaradation occurred atapproximately 300 ◦C was due to the decomposition and depoly-merization of starch carbon chains [25,48].

For the TPSA/seaweed composites, the decomposition occuredat approximately 180–450 ◦C can be attributed to the degradationof both carbohydrate and protein [49]. The degradation occurred atapproximately 200–270 ◦C might also be associated to decompo-sition of hemicellulose and early stage of cellulose decomposition[50]. Moreover, the degradation at 270–370 ◦C were assigned todecomposition of lignin and final decomposition of cellulose [50].

The degradation above 500 ◦C might be associated to carbonatedecomposition in seaweed which led to char formation [50]. Thefinal decomposition stage for the composites were assigned to oxi-dation of the remaining char formed [49].

R. Jumaidin et al. / International Journal of Biological Macromolecules 99 (2017) 265–273 271

F : (a) Tc

tcTfile

ocswTt

ig. 6. SEM investigation of tensile fracture surface of TPSA/seaweed compositesomposites and (e) void in TPSA/seaweed composites.

Incorporation of seaweed (0–40 wt.%) was observed to decreasehe initial decomposition temperature of TPSA which can be asso-iated to lower initial decomposition temperature of seaweed thanPSA. Similar finding was reported for thermoplastic starch rein-orced with kapok fiber [25]. Nevertheless, the TG curve shows thatncreased in seaweed content have led to decreased in the weightoss of the composites at temperature above 300 ◦C, suggestingnhanced thermal stability of the composites.

Meanwhile, the DTG curve allows more visible transformationf the composites degradation characteristics. The first peak in DTGurve of the composites (maximum decomposition) were slightly

hifted to lower temperature following the incorporation of sea-eed which is in agreement with the results shown by the TG curve.

he weight loss following the maximum decomposition stage ofhe composites was decreased following the addition of seaweed,

PSA matrix (b) 10% seaweed (c) 20% seaweed (d) 30% seaweed (d) 40% seaweed

suggesting the dominant role of starch and agar at this stage. Simi-lar findings were reported for thermoplastic starch reinforced withjute and kapok fiber [25]. Moreover, at temperature range above500 ◦C, new degradation peak was evidence in the compositeswhich is not visible in TPSA curve. Increased in seaweed contentfrom 10 to 40 wt.% has increase the degradation rate at this stage,suggesting seaweed is mainly responsible for this decompositionstage. This degradation peak might be associated with carbonatedecomposition in the composites which is not present in TPSA.

Char is the residual material following the pyrolysis process ofall volatile component in a material [51]. The char residue con-

tent of TPSA/seaweed composites was observed to increase withincorporation of seaweed where 40 wt.% seaweed composites showthe highest amount. This finding is in good agreement with theimprovement in thermal stability of the composites shown in TG

272 R. Jumaidin et al. / International Journal of Biological Macromolecules 99 (2017) 265–273

cocmtsss

3

bbcwbbl

tas7

TS

Fig. 7. TGA results of TPSA/seaweed composites (a) TG curve (b) DTG curve.

urve at temperature above 300 ◦C. Improved in thermal stabilityf the composites than TPSA might be attributed to large carbonateomposition in the seaweed which corresponds well in the ther-al degradation results of the composites [18]. Improvement in

hermal stability of polymer composites following the addition ofeaweed were also reported in previous studies for incorporation ofeaweed into polypropylene [20] and poly(lactic) acid [18]. Table 3ummarizes the TGA results.

.7. Soil burial

Weight loss of material can be taken as the main indicator for theiodegradation process by moisture and microorganism during soilurial period [15,52]. Fig. 8 shows the weight loss of TPSA/seaweedomposites after soil burial for 2 and 4 weeks respectively. Highereight losses in all composites were evidence after 4 weeks of

urial than 2 weeks. This results can be assigned to higher num-er of microorganism activity occurred at longer burial time which

ed to increase in the weight loss of the materials.In general, the introduction of seaweed into TPSA matrix has led

o increase in the weight loss of the composites, suggesting moreggressive biodegradation process in the material. Incorporation ofeaweed from 0 to 40 wt.% has increase the weight loss from 53 to5% and 70 to 89% after soil burial for 2 and 4 weeks, respectively.

able 3ummary of TGA results of TPSA/Seaweed composites.

Samples Ton Tmax Weight loss at Tmax Char at 900 ◦C(◦C) (◦C) (wt%) (wt%)

TPSA 266 306 80.61 8.99TPSA/10Sw 256 296 72.93 11.04TPSA/20Sw 253 291 73.87 11.68TPSA/30Sw 252 285 71.25 10.08TPSA/40Sw 249 281 67.09 15.93

Fig. 8. Weight loss of TPSA/seaweed composites after soil burial for 2 and 4 weeks.

This finding might be attributed to more hydrophilic behavior ofseaweed than TPSA which increased the hygroscopic characteris-tics of the composites and promotes the growth of microorganismsduring degradation and increases the weight loss of the materials[52]. This result suggests that the seaweed shows great efficiencyfor the acceleration of biodegradation process of biocomposites.Similar finding was reported in previous studies for incorporationof agar [52], carrageenan [7], and sodium alginate [5] into thermo-plastic starch matrix.

4. Conclusions

In this study, novel biocomposites derived from seaweed andTPSA have been produced at various filler content and their ther-mal and mechanical properties have been investigated. Similarhydrophilic nature of seaweed and TPSA resulted in great adhesionbetween the filler and the matrix. Higher number of intermolecularhydrogen bonding evidence in FT-IR results indicates good com-patibility between seaweed and TPSA. Significant improvement intensile, flexural, and impact properties of the composites were evi-dence with incorporation of seaweed. Increased in thermal stabilityof the composites were observed with increase in seaweed con-tent. Soil burial results show that addition of seaweed increases theweight loss of the materials, suggesting faster biodegradation pro-cess of the composites. These results support that Eucheuma cottoniiseaweed waste can be used as excellent filler in biocomposites dueto diversify characteristics ranging from strength reinforcement topromoting biodegradation of biocomposites.

Acknowledgements

The authors would like to thank Universiti Putra Malaysia forthe financial support provided through Universiti Putra MalaysiaGrant scheme (project code GP-IPS/2015/9457200) as well as toUniversiti Teknikal Malaysia Melaka and Ministry of Higher Educa-tion Malaysia for providing the scholarship award to the principalauthor in this project.

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Effect of seaweed on mechanical, thermal, and biodegradation properties of thermoplastic sugar palm starch/agar composites1 Introduction2 Materials and methodology2.1 Materials2.2 Sample preparation2.3 FT-IR analysis2.4 Scanning electron microscope (SEM)2.5 Tensile testing2.6 Flexural testing2.7 Impact testing2.8 Thermogravimetric analysis (TGA)2.9 Soil burial2.10 Statistical analysis

3 Results and discussion3.1 FT-IR3.2 Tensile properties3.3 Flexural properties3.4 Impact properties3.5 SEM3.6 Thermal properties3.7 Soil burial

4 ConclusionsAcknowledgementsReferences