Properties and Biodegradability of Thermoplastic Starch Obtained … · 2019. 7. 30. · ResearchArticle Properties and Biodegradability of Thermoplastic Starch Obtained from Granular

Research ArticleProperties and Biodegradability of Thermoplastic StarchObtained from Granular Starches Grafted with Polycaprolactone

Z B Cuevas-Carballo S Duarte-Aranda and G Cancheacute-Escamilla

Centro de Investigacion Cientıfica de Yucatan AC Calle 43 No 130 Col Chuburna de Hidalgo 97205 Merida YUC Mexico

Correspondence should be addressed to G Canche-Escamilla gcanchecicymx

Received 28 April 2017 Accepted 25 May 2017 Published 6 July 2017

Academic Editor Marta Fernandez-Garcıa

Copyright copy 2017 Z B Cuevas-Carballo et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

Granular starches grafted with polycaprolactone (St-g-PCL) were obtained using N-methylimidazole (NMI) as a catalyst Theeffect of the starchmonomer ratio and catalyst content was studied to obtain different levels of grafted PCL The highest graftingpercentage (76) and addition (43) were achieved for reactions with a starchmonomer ratio of 5050 and 25 catalyst Thegrafting of PCL on the starch granule was verified by the emergence of the carbonyl group in the FTIR spectra and the increaseddiameter of the grafted starch granuleThermoplastic starch fromungrafted starch (TPS) and grafted starch (TPGS)was obtained bymixing ungrafted or grafted starch granules with water glycerol or sorbitol in a mixer TPS and TPGS behave as plastic materialsand their mechanical properties depend on the type of plasticizer used Materials with glycerol as the plasticizer exhibited lessrigidity The presence of starch-g-PCL results in a dramatic increase in the elongation of the thermoplastic material The starchpresent in the TPS or TPGS was completely biodegraded while the grafted PCL was partially biodegraded after the enzymaticdegradation of the materials

1 Introduction

Biodegradable polymers represent a solution to the problemsof contamination caused by conventional synthetic polymers[1ndash5] Starch is a completely biodegradable polysaccharidesynthesized by a large number of plants and is inexpensive [26ndash9] Its use in the production of biodegradablematerials cansimultaneously reduce the dependence on petroleum and theproblemof plastic waste [4 10ndash12] However there are limitedways of using starch in its granular form to obtain thermo-plastic materials by conventional processing techniques suchas extrusion or injection [13ndash17] Poor mechanical propertiesare obtained due to the thermal decomposition of granularstarch before melting occurs to the high water absorptionand poor interaction with other materials [6 11 13 18] Toovercome the shortcomings of thermoplastic-based starchthe starch has been plasticized [7 12 15 17] or modified bygrafting nondegradable monomers such as styrene [19] andmethyl methacrylate [8 20] to the backbone [21] as a wayof obtaining a material that can be processed by extrusion

or injection However in the last case the grafted starchesobtained are partially biodegradable [22]

Other methods used for the chemical modification ofstarch have included grafting of chains of biodegradablepolyesters such as polycaprolactone (PCL) [2 23] andpoly(L-lactide) (PLLA) [13] by reactions of their hydroxylgroups or through ring-opening graft polymerization ofmonomers with starch as the initiation site of polymeriza-tion In these studies graft efficiency close to the 60 wasobtained the mechanical properties were improved anda completely biodegradable copolymer was obtained Thestarch-g-polyester copolymers have been used as compatibi-lizers in blends of starch with other polymers [13]

There is limited information on the use of granulesstarches grafted with biodegradable polyesters to obtainthermoplastic grafted starches (TPGS) by using plasticizersalthough the granule starch has been modified either phys-ically or chemically in various ways and graft copolymer-ization has been extensively studied which opens up newresearch possibilities

HindawiInternational Journal of Polymer ScienceVolume 2017 Article ID 3975692 13 pageshttpsdoiorg10115520173975692

2 International Journal of Polymer Science

Table 1 Formulations used in grafting reactions of polycaprolactone on starch granules

Materials St-g-PCL1 St-g-PCL2 St-g-PCL3 St-g-PCL4 St-g-PCL5 St-g-PCL6 St-g-PCL7Starch [g] 5 5 5 5 5 100 100-Caprolactone (120576-CL) [g] 5 5 5 25 75 100 50N-Methylimidazole (NMI) [g] 0625 125 1875 125 125 25 25

This paper investigates thermoplastic grafted starches(TPGS) and considers two processes used to obtain themThefirst one is the reaction process for obtaining granular graftedstarch with biodegradable polyester (polycaprolactone PCL)and the second process involves obtaining thermoplasticstarches (TPGS) from grafted starch In the first processthe ratio between the starch and the monomer was studiedand the influence of the amount of catalyst used on thegrafting parameters was investigated In the second processthe influence of both the ratio between the amount of graftedstarch and plasticizer used and the type of plasticizer onthe properties and enzymatic degradation of the TPGS wasstudied

2 Materials and Methods

21 Grafting Copolymerization Corn starch was purchasedfrom Unilever Manufacturera S de RL de CV -caprolactone monomer (120576-CL) with 97 purity and catalystN-methylimidazole (NMI) were of reagent grade and werepurchased from Sigma-Aldrich Quımica S de RL de CVStarch particles were grafted according to a method reportedin the literature [23] The procedure was as follows starch(dry basis) 120576-CL monomer and catalyst NMI were placedinto a glass reactor equipped with a mechanical stirrer anda condenser The reactor was placed in a glycerin bath at150∘C and the mixture was stirred for a certain amountof time The polymerization yield was determined gravi-metrically In Table 1 the formulations used for obtainingpolycaprolactone-grafted starch are shown

22 Determination of Grafting Parameters Extraction withtoluene was conducted to dissolve remains of the 120576-CL monomer catalyst and ungrafted polymer chains(homopolymer) After toluene extraction the material wasdried under vacuum to a constant weight Grafting param-eters are determined from the weights before and after theextraction [3 24] using the following equations

Graft () = [PCL grafted weightStarch weight

] times 100

= [119908if minus 119908st119908st ] times 100Addition ()= [ PCL grafted weight

Total weight copolymer St-g-PCL] times 100

= [119908if minus 119908st119908if ] times 100

Grafting Efficiency ()= [ PCL grafted weight

PCL formed weight] times 100

= [ 119908if minus 119908st119908hp + (119908if minus 119908st)] times 100(1)

where 119908if is the weight of the product obtained after extrac-tion (the insoluble fraction) in grams (g) 119908st is the weightof starch loaded in the reaction in grams (g) and 119908hp is theweight of the homopolymer formed in the reaction in grams(g)

23 Characterization of Grafted Granule Starch The mor-phology of the particles was observed using a JEOL 6360LVSEM scanning electron microscope The particles were cov-ered with a gold surface layer to improve contrastThe size ofthe grafted and ungrafted starch granules was analysed witha Coulter Counter LS100Q after the granules were dispersedin deionized water FTIR analysis of starch and graftedstarch was performed in a Nicolet 870 Fourier transforminfrared spectrophotometer in a wavenumber range from4000 to 400 cmminus1 with 16 scans and a resolution of 4 cmminus1X-ray diffractograms were recorded on a Siemens D-5000diffractometer with a Cu-K120572 radiation source (wavelength120582 = 15418 A) The samples were exposed to the X-ray beamwith the X-ray generator running at 34 kV and 25mAand a step time of 6 sec and step size of 004∘ were usedTGA thermograms were obtained on a Perkin Elmer TGA-7thermogravimetric balance in a temperature range from 40to 700∘C with a heating rate of 10∘Cmin and in nitrogenatmosphere

24 Preparation and Characterization of the ThermoplasticStarch Thermoplastic materials with grafted (TPGS) andungrafted (TPS) granular starch were obtained with glycerolor sorbitol added as plasticizersThe ratio of starch (or graftedstarch) to water to glycerolsorbitol was 502525 or 501535The ungrafted or grafted granule starch was first blendedwithwater using a mixer and stored overnight Subsequently itwas mixed with glycerol or sorbitol and stored overnightThemixtures were manually fed into a Brabender Plasticordermixer for 10min at 150∘C with a rotation speed of 40 rpmTheblendsweremolded at 150∘C in aCarver Laboratory pressunder a force of 10000 lbs to obtain samples for mechanicalexperiments

Tensile tests for TPS and TPGS were conducted with aShimadzu AGS-X universal machine by following the ASTMD638-14 method [25] The analyses were performed after

International Journal of Polymer Science 3

Table 2 Effect of reaction conditions on the grafting parameters

Code Starchmonomer relation Catalyst (g) Monomer (g) Graft () Addition () Grafting efficiency ()St-g-PCL1 5050 0625 (125) 5 13 11 28St-g-PCL2 5050 125 (25) 5 68 40 88St-g-PCL3 5050 1875 (375) 5 64 39 72St-g-PCL4 7525 125 (25) 25 42 30 92St-g-PCL5 2575 125 (25) 75 21 18 22St-g-PCL6 5050 25 (25) 100 76 43 72St-g-PCL7 7525 25 (25) 50 35 26 50

equilibrating the samples according to the ASTM D618-13standard [26] for 2 days at temperatures of 23 plusmn 2∘C and atrelative humidities of 50 plusmn 5 and at a crosshead speed of5mmmin The specimens (type IV) were cut from the 1mmhot-pressed molded sheets using a die cutting machine TheJEOL 6360LV examines the failure surface of the thermoplas-tic starch aftermechanical tests the samples were coated withgold film before examination to improve the contrast Thestorage moduli and tan 120575 curves of samples were obtained ona Perkin Elmer DMA-7 mechanical dynamic analyser with aparallel platedisc mode at 1Hz at a heating rate of 5∘Cminand at a temperature range of minus100 to 50∘C The samples(10mm in diameter) were cut from the 1mm hot-pressedmolded sheetsThermogravimetric analysis of TPS andTPGSwas performed with a Perkin Elmer TG-7 thermogravimetricbalance at a heating rate of 10∘Cmin and a temperaturerange of 40 to 700∘C under nitrogen atmosphere XRDmeasurements were performed in a Siemens D-5000 diffrac-tometer with a Cu-K120572 radiation source (wavelength 120582 =15418 A) and a step time of 6 sec and a step size of 004∘

25 Enzymatic Degradation The enzymatic degradation wasperformed according to the methods reported in the lit-erature [11 22] using 120572-amylase from Bacillus licheniformisand glucoamylase from Aspergillus niger both purchasedfrom Sigma-Aldrich Incubations were carried out at 37∘Cin 25mL 01M acetate buffer (pH 50) containing 50 120583L ofMerthiolate to prevent microbial growth The concentrationof the enzymes was 75UmL of 120572-amylase and 15UmL ofglucoamylase The samples were of size 1mm times 75mm times75mm After a certain time the samples were filtered andthe solids were washed with distilled water and then driedto constant weight The solids obtained after enzymatichydrolysis were observed using a JEOL 6360LV SEM scan-ning electron microscope and characterized by FTIR andthermogravimetric analysis using the same conditions as inthe characterization of the thermoplastic starches

3 Results and Discussion

31 Characterization of GraftedGranule Starch Table 2 showsthe grafting parameters obtained after the extraction withtoluene Grafting reactions with different amounts of catalystwere carried out while maintaining a constant amount ofstarch and monomer It is observed that an increase inthe amount of catalyst (125 to 25) tends to increase

the grafting parameters However similar graft values wereobtained for reactionswith higher amounts of catalyst 25 and375 (St-g-PCL2 and St-g-PCL3) which can be attributedto the lower diffusion of the caprolactone in the reactionmedium As the concentration of catalyst increases thereis a higher reaction rate and a higher viscosity of thereaction medium [23] The lower grafting efficiency obtainedwith 375 of catalyst in comparison with 25 of catalystconfirms this assumption To obtain different levels of graftedpolycaprolactone in subsequent materials reactions wereperformed by varying the percentage of the monomer whilekeeping both the amount of catalyst (25 by weight) and theamount of starch constant Higher grafting parameter valueswere observed for a low amount of monomer comparedwith a high amount of monomer (St-g-PCL4 and St-g-PCL5) which is attributed to the homopolymerization beingthe principal reaction at high levels of caprolactone Toobtain enough material for making thermoplastic starchesthe reactions were scaled (St-g-PCL6 and St-g-PCL7) andthey showed similar grafting parameters to their counterparts(St-g-PCL2 and St-g-PCL4)

Figure 1 shows SEM micrographs of the grafted starchgranules It can be observed that the granular starchesmaintained their integrity and their surfaces were modifiedby the grafted aliphatic polyester chains Starch particlesare covered with a layer of polycaprolactone and a markedincrease in the average size was observed The increase ofthe granular size was confirmed in Figure 1(d) where thesize distribution curves for the starch and grafted starch areshown Average sizes of 14 120583m and 25120583m were obtained forthe ungrafted and grafted starch respectively These resultsare similar to those reported in the literature [20 21]

The grafting of polycaprolactone onto starch granules wasconfirmed by FTIR and XRD spectra Figure 2(a) displaysinfrared (IR) spectra of the starch PCL and grafted starchwith polycaprolactone The IR spectrum of the starch showsa broad bandbetween 3700 and 3000 cmminus1which is attributedto the stretching of the hydroxyl group (ndashOH) present inthe anhydroglucose unit also a peak at 1645 cmminus1 due to thebending of the same group is observed [27] In addition thespectrum exhibits two signals at 2930 cmminus1 and 2890 cmminus1which correspond to the asymmetric and symmetric stretch-ing of methylene group (ndashCH

2) respectively [28] The PCL

spectrum has an intense peak at 1730 cmminus1 which cor-responds to the stretching of the carbonyl group (C=O)


10 휇m

(a)

10 휇m

(b)

10 휇m

(c)

0 20 40 60 80 100

StarchSt-g-PCL 26 additionSt-g-PCL 43 addition

Volu

me (

)

Diameter (휇m)

PCL()

Mean diameter(휇m) SD

0

26

43

1367

2359

2522

826

1293

1325

(d)

Figure 1 SEM micrographs of (a) granular starch (b) granular starch with 30 of PCL (c) granular starch with 40 of PCL and (d) theparticle size distributions for grafted and ungrafted granule starch

4000 3500 3000 1800 1600 1400 1200 1000 800

St-g-PCL 26 addition


Polycaprolactone

Starch

Tran

smitt

ance

(ua

)

(OndashH)

Wavenumber (cmminus1)

3700ndash3000 cmminus1 1645 cmminus1 (OndashH)

2930 y 2890 cmminus1 (CndashH)

1730 cmminus1 (C=O)

1734 cmminus1 (C=O)

1736 cmminus1 (C=O)

(a)

10

10

20

20

30

30

40

40

50

50

60

60

0

1000

2000

3000

4000

15000

16000

10001200

600800

200400

0

Inte

nsity

(mA

)

Inte

nsity

(mA

)

StarchPCL

St-g-PCL 26St-g-PCL 43

2휃 (∘)

2휃 (∘)

(b)

Figure 2 FTIR spectra (a) and XRD diffractograms (b) of starch PCL and grafted starch with PCL


100 200 300 400 500 600 7000

20

40

60

80

100Re

sidua

l mas

s (

)


Temperature (∘C)

(a)

100 200 300 400 500 600 700

D (r

esid

ual m

ass)

D(T

)


Temperature (∘C)

(b)

Figure 3 TGA (a) and DTGA (b) thermograms of starch and grafted starch with different content of PCL

of the polyester [3 23] moreover characteristic stretchingsignals from the ndashCH

2group can be observed at 2950 cmminus1

and 2900 cmminus1 The spectra for the grafted starch show thestarch signals and the appearance of the signal due to thecarbonyl group of polycaprolactone (PCL) which confirmsthe grafting of polymer on the starch chains Additionallythe signal intensifies with increasing addition of PCL andexhibits a slight displacement towards higher values It hasbeen reported that the ester groups (C=O) absorb energy at1740ndash1715 cmminus1 when they are associated with carbon-carbondouble bonds (C=C) or aromatic hydrocarbons [28ndash31]

Figure 2(b) shows the XRD diffractograms of the starchthe PCL and the grafted starch with PCL It can be observedin the starch diffractogram peaks at 2120579 = 153 174 and231∘ which are typical for corn starch [32 33] The PCLdiffractogram shows two main diffraction peaks at 2120579 = 213and 236∘ [34] In grafted starch an increase in the intensity ofthe diffraction patterns occurs which is ascribed to a highercrystalline structure In addition to the peaks associated withstarch new signals appear at 202 and 228∘ attributed to thePCL grafted on the starch surface moreover an increase inthe peaks height is observed with a greater amount of graftedpolymer It has been reported that low crystallinity may bepromoted by the decrease of the hydrogen bonds during thegrafting process due to the formation of esters and that thegrafted polymer chains are too short to form crystals [23]

In the TGA (Figure 3(a)) and DTGA (Figure 3(b))thermograms a decrease in the initial weight loss for graftedstarch was observed which indicated a lower hydrophiliccharacter due to the presence of the PCL Two decompositionzones are observed in the range of 180ndash350∘C the first isattributed to PCL degradation and the second proves thatboth polymers are thermally decomposed in the range of250ndash350∘C with a maximum decomposition temperature(DTmax) of 331∘C

32 Characterization of Thermoplastic Starch and Thermo-plastic Grafted Starch While obtaining thermoplastic starch(TPS) and thermoplastic grafted starch (TPGS) the starchand starch grafted granules lost their granular structure dueto the presence of plasticizers (water glycerol or sorbitol) theheat and the high shear stress conditions in the mixer It hasbeen reported in the literature that this happens due to therupture of the granular starchwith a decrease in the hydrogenbonds andmelting of the starch due to the decrease of its melttemperature by the presence of the plasticizer [4 35]

Figure 4 shows the effect of the grafted polymer andthe plasticizer on the mechanical properties of thermoplasticstarch For TPS the stress-deformation curves for bothplasticizers show that the stress increases continuously withstrain without yield until fracture which is typically referredto as plastic behavior based on the elongation at break ForTPSwith sorbitol (Figure 4(b)) the stress increases comparedto TPSwith glycerol and the elongation decreases It has beenshown that themacroscopic behavior of the TPSwith sorbitolshows considerable variations depending on the amount ofsorbitol added indicating that there are two types of behaviorin starch containingmaterials plasticized by sorbitol At a lowamount of plasticizer (lt27) the materials were shown tobe brittle whereas when the amount of sorbitol increased(gt27) it fulfilled the function of a plasticizer and thematerials had a plastic mechanical behavior [36] The TPGShas lower mechanical properties compared to TPS The PCLgraft results inmaterials with lower Youngrsquosmoduli and stressbut with higher elongation A strain at break greater than300 was obtained for TPGS with 43 of PCL and 25of glycerol or sorbitol plasticizers It is reported that thePCL polymer possesses an important elongation at break andmedium modulus [5] In the TPGS with 26 of PCL wheresorbitol was used as the plasticizer an increase in Youngrsquosmodulus stress and elongation at break was obtained in


0

0

50

50

100

100

150

150

200

200

250

250

300

300

0

1

2

3St

ress

(MPa

)

Stre

ss (M

Pa)

Strain ()

Strain ()

000002004006008010

PCL glyTPS 0 25TPS 0 35TPGS 26 25

TPGS 26 35TPGS 43 25TPGS 43 35

(a)

0 50 100 150 200 250 3000

1

2

3

Stre

ss (M

Pa)

Stre

ss (M

Pa)

Strain ()

Strain ()0 50 100 150 200 250 300

000002004006008010

PCL sorTPS 0 25TPS 0 35TPGS 26 25


(b)

Figure 4 Effect of grafted polymer and plasticizers on the mechanical properties of thermoplastic starch with the formulations of 502525and 501535 (a) starch or grafted starchglycerol and (b) starch or grafted starchsorbitol

comparison with the materials obtained with glycerol Forboth plasticizers where TPGSwas obtainedwith 43 of PCLthe mechanical properties were similar

Figure 5 shows the fracture surface of the specimenafter the tensile test Disintegration of the granules wasobserved due to the action of plasticizers during high shearmixing A rough surface was observed for the TPS (Figures5(a) and 5(b)) and as the amount of grafted polymer wasincreased a smooth surface with greater homogeneity wasobtained (Figures 5(c)ndash5(f)) Some authors have reportedthat roughness can refer to materials with semicrystallinebehavior [12 14]

Figure 6 shows the effect of the grafted PCL and theplasticizers on the storage modulus and the tan 120575 curvesof TPS and TPGS The TPS with glycerol as the plasticizershowed two reductions in the storage modulus (Figure 6(a))this occurred in a range from minus65 to minus23∘C and minus12 to 12∘Cwith two maxima in the tan 120575 curve (Figure 6(b)) at minus41 and14∘C In the storage modulus curve from TPS with sorbitolas the plasticizer (Figure 6(a)) a decrease between minus27 and18∘C is observedwithmaximumat 7∘C (Figure 6(b)) Peaks oftan 120575 have been reported to be related to polymer relaxationsdue to primary (such as glass transition temperature Tg)and secondary transitions [15 37] For plasticized starchwith glycerol the position of the transition towards highertemperatures is associated with the Tg of a phase with highstarch content while the signal towards lower temperaturesrefers to the Tg of a plasticizer-rich phase [9 15] On the otherhand the single peak for TPS with sorbitol as the plasticizerindicates that a more homogeneous material was obtained[15]

For the TPGS plasticized with glycerol a lower storagemodulus was obtained in comparison with TPS and very

pronounced reductions by one order of magnitude areobserved in themodulus curves for TPGSwith 43of graftedPCL (Figure 6(a)) This decrease can be attributed to themore flexible TPGS material compared to TPS due to thehigher plasticization of the ungrafted starch matrix and thelow Tg (minus60∘C) of PCL and it is in accordance with themechanical properties of these materials In the tan 120575 curvesa shoulder is observed at minus35∘C in all the TPGS sampleswith glycerol (Figure 6(b)) It has been reported that thisshoulder corresponds to an overlap of the Tg of PCL andto the secondary relaxation of the plasticized starch [5] Thepeak associated with the glass transition of the plasticizedstarch can be clearly observed and this temperature dependson the PCL content in the starch-g-PCL fraction At a PCLcontent of 43 the transition shows a maximum at 15∘C(Figure 6(b))

The TPGS samples plasticized with sorbitol have a highermodulus than the TPGS samples plasticized with glyceroland only one decrease is observed in themodulus curves (Fig-ure 6(a)) Moreover one transition is observed for all of thesematerials For the smallest addition of PCL the maximumtransition values are observed at 38∘C However for higheradditions of polymer the maximum value decreased to minus3∘C(Figure 6(b)) This is consistent with the data presented inthe mechanical tests where a larger amount of PCL in TPGSresults in a more plastic behavior

Figure 7 shows the loss of mass due to thermal degrada-tion of thermoplastic starch and thermoplastic grafted starchwhich is obtained by TG analysis The thermogravimetriccurve of TPS with glycerol as the plasticizer (Figure 7(a))shows the occurrence of a mass loss process below 260∘Cbetween 260 and 315∘C and above 315∘C The first mass losswas attributed to a loss of moisture and plasticizer and the


50 휇m

(a)

50 휇m

(b)

50 휇m

(c)

50 휇m

(d)

50 휇m

(e)

50 휇m

(f)

Figure 5 SEM micrographs of rupture zones of TPS with glycerol (a) or sorbitol (b) SEM micrographs of rupture zones of TPGS with 26of PCL with glycerol (c) or sorbitol (d) and TPGS with 43 of PCL with glycerol (e) or sorbitol (f)

latter to the degradation of the starch and char formation[16 20] The maximum decomposition temperature (DTmax)of TPS with glycerol was observed as two peaks in the DTGAcurves (Figure 7(b)) at 306 and 335∘C due to the differentdegradation rates of the polymers composing the starch(amylose and amylopectin) [16] For TPGS with glycerol asthe plasticizer the second step occurs at a low temperaturecompared with TPS due to the thermal degradation of thestarch-g-PCL in addition a large mass loss is observed in therange of 43ndash338∘C (50) This behavior is more prominentfor thematerial with a higher amount of PCL (43 addition)and two peaks were observed at 317 and 334∘C Other authorshave observed similar signs [38] The thermal degradation

of the ungrafted starch in the TPGS is observed at the samerange temperature of the starch

The TPS and TPGS with sorbitol as the plasticizer(Figure 7(a)) had a higher thermal stability than thematerialsplasticized with glycerol which could be due to a betterinteraction between the sorbitol and the starch chainsSome authors have attributed this better interaction to themolecular weight of this plasticizer [12 17] In this case thethermal degradation of the ungrafted and PCL-grafted starchis observed at the same zone and only the peaks (DTmax) at335 315 and 309∘C are attributed to TPS TPGS with 26of PCL and TPGS with 43 of PCL respectively The lowerDTmax for TPGS compared to TPS could occur because the


TPS 25 glyTPS 25 sor

Stor

age m

odul

us (P

a)

minus100 minus80 minus60 minus40 minus20 0 20 40 60 80Temperature (∘C)

108

107

106

PCL plasticizer

TPGS 26 25 gly

TPGS 26 25 sorTPGS 43 25 glyTPGS 43 25 sor

(a)


Tan훿


PCL plasticizer

TPGS 26 25 gly


(b)

Figure 6 Storage modulus (a) and Tan 120575 (b) curves of TPS and TPGS with glycerol or sorbitol as the plasticizer

100 200 300 400 500 600 7000

20

40

60

80

100

Resid

ual m

ass (

)

Temperature (∘C)


PCL plasticizer

TPGS 26 25 gly


(a)

100 200 300 400 500 600 700

D (r

esid

ual m

ass)

D(T

)

Temperature (∘C)


PCL plasticizer

TPGS 26 25 gly


(b)

Figure 7 TGA (a) and DTGA (b) curves of TPS and TPGS with glycerol or sorbitol The ratio of starch or grafted starchwaterglycerol orsorbitol of 502525 was used

degradation products of caprolactone increase the rate ofdegradation of starch

Figure 8 shows the X-ray diffractograms of the TPS andTPGS plasticized with glycerol or sorbitol In the TPS withglycerol (Figure 8(a)) the crystallinity of starch was modifiedand the B-type and V-type crystallinities are formed [3940] The B-type crystallinity in starch materials that containglycerol as plasticizer is represented by the crystals forming

some outer chains of the branched polymer of the starch(amylopectin) of smaller size with a maximum at 1696∘ [3941ndash44] The V-type crystallinity is related to the process ofrecrystallization of the linear polymer of the starch (amylose)due to the type of processing to obtain the thermoplasticstarch and is represented with the maxima at 1296ndash1976∘[39 41 43] The TPGS with PCL and glycerol (Figure 8(a))exhibits two different patterns The first pattern is for the


0 10 20 30 40 50 60

Inte

nsity

(ua

)

2휃 (∘)

PCL glyTPS 25TPGS 26 25TPGS 43 25

(a)

0 10 20 30 40 50 60

TPS 25

Inte

nsity

(ua

)

2휃 (∘)

PCL sor

TPGS 26 25TPGS 43 25

(b)

Figure 8 X-ray diffractograms of TPS and TPGS with (a) glycerol and (b) sorbitol The ratio of starch or grafted starchwaterplasticizer of502525 was used

26 of grafted PCL where two intense peaks are observed at204 and 2204∘The second pattern is presented for the otherTPGS samplewith 43of the grafted polymer which exhibitsonly a broad peak at 2044∘ These maximums are related tothe V-type crystallinity of TPS A change was also observedin the diffractograms in the height of the peak referring tothe PCL when the amount of PCL was greater the heightdecreased indicating a lower crystallinity in the materials

TPS and TPGS with sorbitol as the plasticizer (Fig-ure 8(b)) show a similar behavior compared to TPS withglycerol as the plasticizer In the TPS with sorbitol similarpeaks to those observed in the TPS with glycerol as theplasticizer are obtained For TPGS with the least amount ofgrafted polymers (26 of PCL) only three signals appear apeak at 136∘ a broad peak at 204∘ and a peak at 30∘ whichindicates good dispersion of the plasticizer in the mixturedue to the presence of the grafted polymerThe broad peak isan indication of the change in crystal from A-type to V-type[39] When the amount of grafted polymer increased (43PCL) strong signals were observed which likely indicates aretrogradation of the material and an overlapping betweenthe peaks from the grafted polymer and the plasticizer

Figure 9 shows the percentage of weight loss of the TPSand TPGS after enzymatic degradation by 48 hours It canbe seen that the percentage of weight loss is above 95 forall materials evaluated TPGS with 43 of grafted PCL hadlower weight loss percentages (95-96) compared to thelesser amount of grafted polymer (97-98) and nongraftedthermoplastic starches (98-99) which is in agreement withthe different rates of enzymatic degradation of starch andPCL with the enzymes used in this workThe starch-formingpolymers amylose and amylopectin are readily hydrolysed

25 gly 35 gly 25 sor 35 sor0

20

40

60

80

100

Wei

ght l

oss o

f TPS

()

TPS26 PCL43 PCL

Figure 9 Weight loss of TPS and TPGS after enzymatic degrada-tion

by enzymes [45] The amylase initiates the breakdown ofthe amylose glucoside linkage 1ndash4 [22 45ndash47] while theglucoamylase attacks the 1ndash6 linkages of amylopectin reduc-ing the size of the starch chains These smaller chains aresolubilized in the aqueous phase and this is recorded as aweight loss [22 45] On the other hand these enzymes alsoattack the CndashO bonds of the ester groups of the PCL whichresults in the rupture of the polymer chains The remainingsolid residue after enzymatic degradation corresponds to


(a) (b)

(c) (d)

(b㰀)

(d㰀)

1000 휇m

1000 휇m

100 휇m

100 휇m 50 휇m

50 휇m

Figure 10 Images of TPGSfilms before enzymatic degradation (a) 26 PCL25 gly and (c) 43 PCL25 gly SEMmicrographs of residues obtainedafter enzymatic degradation (b) 26 PCL 25 gly and (d) 43 PCL 25 gly

PCL chains with hydroxyl or acid group as chain ends Thereare no notable changes in the weight loss due to the type ofplasticizer used

Figure 10 shows SEM micrographs of the residuesobtained after TPGS biodegradation After biodegradationthe TPGS films were disintegrated and the micrographs ofthe residues of TPGS with the least PCL (26 Figures 10(b)and 10(b1015840)) show a surface eroded from the inside to thesurface this behavior suggests the formation of a starch-g-polycaprolactone layer on the surface of the materials Whenthe PCL is present in the largest amount in the TPGS (43Figures 10(d) and 10(d1015840)) a rough surface is observed dueto the minor plasticization for the starch-g-PCL with highcontent of PCL When high starch contents are presentgreater accessibility to the phase formed by this materialis obtained which is reflected with higher percentages ofdegradation [45]

Figure 11 displays infrared spectra of the residues of TPGSafter enzymatic degradation All the biodegraded materialsshow a decrease in the broad band corresponding to thehydroxyl groups (ndashOH) of starch this could be due to thesolubilization in the aqueous medium of the degraded starchchains as well as the plasticizer In addition the band at1160 cmminus1 corresponding to the glucosidic bonds ndashCndashOndashCndash[46] shows a decrease in the intensity confirming starchdegradation The intense peak at 1736 cmminus1 that correspondsto the stretching of the carbonyl group (C=O) present inthe PCL confirms the presence of the grafted polymer in the

4000 3500 3000 1800 1600 1400 1200 1000

PCL

Starch

Tran

smitt

ance

(ua

)


TPGS 43 PCL 25 gly

TPGS 43 PCL 25 sor

Figure 11 FTIR spectra of starch and PCL and the residues after theTPGS enzymatic biodegradation

residues obtained after the enzymatic hydrolysisThis is morenotorious for the TPGS obtained using glycerol as plasticizer

Figure 12 shows the thermal degradation of the TPGSand the residues obtained after enzymatic hydrolysis Thepresence of three mass loss processes for the TPGS can beobserved which are best defined in the DTGA curves Forthe residues of TPGS grafted with PCL (Figures 12(a) and12(b)) after enzymatic hydrolysis two mass loss processes are


0

20

40

60

80

100

TPGS 43 PCL 25 glyTPGS 43 PCL 25 gly deg

D (r

esid

ual m

ass)

D(T

)

Resid

ual m

ass (

)

100 200 300 400 500 600 700

Temperature (∘C)

100 200 300 400 500 600 700Temperature (∘C)

(a)

0

20

40

60

80

100

D (r

esid

ual m

ass)

D(T

)

Resid

ual m

ass (

)

TPGS 43 PCL 25 sorTPGS 43 PCL 25 sor deg

100 200 300 400 500 600 700Temperature (∘C)

100 200 300 400 500 600 700

Temperature (∘C)

(b)

Figure 12 TGA and DTGA curves of TPGS before degradation and residues obtained after enzymatic hydrolysis (a) TPGS 43 PCL 25 glyand (b) TPGS 43 PCL 25 sor

observed and the main maximum decomposition temper-ature (DTmax) shows a shift towards higher temperaturesattributed to the polymer grafted (PCL) confirming thebiodegradation of the starch chains The similar decomposi-tion in the range between 50 and 300∘C of the TPGS obtainedusing sorbitol and the residues obtained after its enzymaticdegradation indicates the presence of starch or plasticizer inthese residues due to the lower degradation of the starch-g-PCL at high PCL content

4 Conclusions

Granular starch with grafted PCL was obtained and thepolymer grafting was verified by different physicochemicaltechniques Modifying the concentration of catalyst or thestarchmonomer ratio resulted in different levels of thegrafted polymer The grafted chains produced changes in thesurface of these particles and resulted in more hydrophobicmaterials

Thermoplastic grafted starches (TPGS) were obtainedwith glycerol and sorbitol as the plasticizers The mechan-ical properties of thermoplastic starch can be modified bythe use of grafted polymers The use of rubbery polymers(PCL) increases the flexibility of thermoplastic grafted starch(TPGS) compared to thermoplastic starch (TPS) and itenables the preparation of a wide range of materials by mod-ifying the ratio of starch120576-caprolactone in the grafted poly-mer Enzymatic hydrolysis of starch in TPS and TPGS usingamylolytic enzymes shows that thermoplastics were almostcompletely biodegraded The residues obtained from thePCL-grafted TPGS after enzymatic degradation are mainlyPCL chains indicating the higher rate of starch degradation

Conflicts of Interest

The authors declare that they have no conflicts of interestregarding the publication of this paper

Acknowledgments

The authors wish to thank the National Council of Scienceand Technology inMexico (CONACyT) for financial supportof the PhD thesis of Z B Cuevas-Carballo The X-raydiffraction analysis was performed at theNational Laboratoryof Nano and Biomaterials (financed by Fomix-Yucatan andCONACyT) CINVESTAV-IPN Merida Unit The authorsalso thank Dr Patricia Quintana for access to LANNBIO andM C Daniel Aguilar for technical support in obtaining thediffractograms

References

[1] A C Correa V B Carmona J A Simao L H Cappar-elli Mattoso and J M Marconcini ldquoBiodegradable blendsof urea plasticized thermoplastic starch (UTPS) and poly(120576-caprolactone) (PCL) Morphological rheological thermal andmechanical propertiesrdquo Carbohydrate Polymers vol 167 pp177ndash184 2017

[2] A Zerroukhi T Jeanmaire C Raveyre and A Ainser ldquoSyn-thesis and characterization of hydrophobically modified starchby ring opening polymerization using imidazole as catalystrdquoStarchStaerke vol 64 no 8 pp 613ndash620 2012

[3] L Chen Y Ni X Bian et al ldquoA novel approach to graftingpolymerization of 120576-caprolactone onto starch granulesrdquo Carbo-hydrate Polymers vol 60 no 1 pp 103ndash109 2005


[4] B Ghanbarzadeh and H Almasi BiodegradationLife of ScienceInTech Rijeka119908 Croatia 2013

[5] L Averous L Moro P Dole and C Fringant ldquoProperties ofthermoplastic blends starch-polycaprolactonerdquo Polymer vol41 no 11 pp 4157ndash4167 2000

[6] F J Aranda-Garcıa R Gonzalez-Nunez C F Jasso-Gastineland E Mendizabal ldquoWater absorption and thermomechani-cal characterization of extruded starchpoly(lactic acid)agavebagasse fiber bioplastic compositesrdquo International Journal ofPolymer Science vol 2015 Article ID 343294 7 pages 2015

[7] G A Arboleda C E Montilla H S Villada and G AVarona ldquoObtaining a flexible film elaborated from cassavathermoplastic starch and polylactic acidrdquo International Journalof Polymer Science vol 2015 Article ID 627268 9 pages 2015

[8] M-C Li J K Lee and U R Cho ldquoSynthesis characteriza-tion and enzymatic degradation of starch-grafted poly(methylmethacrylate) copolymer filmsrdquo Journal of Applied PolymerScience vol 125 no 1 pp 405ndash414 2012

[9] PM Forssell J MMikkila G KMoates and R Parker ldquoPhaseand glass transition behaviour of concentrated barley starch-glycerol-water mixtures a model for thermoplastic starchrdquoCarbohydrate Polymers vol 34 no 4 pp 275ndash282 1998

[10] Q Shi CChen LGao L JiaoHXu andWGuo ldquoPhysical anddegradation properties of binary or ternary blends composed ofpoly (lactic acid) thermoplastic starch and GMA grafted POErdquoPolymer Degradation and Stability vol 96 no 1 pp 175ndash1822011

[11] M Vikman S H D Hulleman M Van Der Zee P Myllarinenand H Feil ldquoMorphology and enzymatic degradation of ther-moplastic starch-polycaprolactone blendsrdquo Journal of AppliedPolymer Science vol 74 no 11 pp 2594ndash2604 1999

[12] J Castano R Bouza S Rodrıguez-Llamazares C Carrasco andR V B Vinicius ldquoProcessing and characterization of starch-based materials from pehuen seeds (Araucaria araucana (Mol)K Koch)rdquo Carbohydrate Polymers vol 88 no 1 pp 299ndash3072012

[13] L Chen X Qiu M Deng et al ldquoThe starch grafted poly(l-lactide) and the physical properties of its blending compositesrdquoPolymer vol 46 no 15 pp 5723ndash5729 2005

[14] X Y Zhou Y F Cui D M Jia and D Xie ldquoEffect of acomplex plasticizer on the structure and properties of thethermoplastic PVAstarch blendsrdquoPolymer - Plastics Technologyand Engineering vol 48 no 5 pp 489ndash495 2009

[15] H Schmitt A Guidez K Prashantha J Soulestin M FLacrampe and P Krawczak ldquoStudies on the effect of storagetime and plasticizers on the structural variations in thermoplas-tic starchrdquo Carbohydrate Polymers vol 115 pp 364ndash372 2015

[16] J F Mano D Koniarova and R L Reis ldquoThermal propertiesof thermoplastic starchsynthetic polymer blendswith potentialbiomedical applicabilityrdquo Journal of Materials Science Materialsin Medicine vol 14 no 2 pp 127ndash135 2003

[17] X Qiao Z Tang and K Sun ldquoPlasticization of corn starch bypolyol mixturesrdquoCarbohydrate Polymers vol 83 no 2 pp 659ndash664 2011

[18] J Ren H Fu T Ren and W Yuan ldquoPreparation characteriza-tion and properties of binary and ternary blends with thermo-plastic starch poly(lactic acid) and poly(butylene adipate-co-terephthalate)rdquo Carbohydrate Polymers vol 77 no 3 pp 576ndash582 2009

[19] K Kaewtatip V Tanrattanakul K M Szecsenyi J Pavlicevicand J Budinski-Simendic ldquoThermal properties and mor-phology of cassava starch grafted with different content of

polystyrenerdquo Journal of Thermal Analysis and Calorimetry vol102 no 3 pp 1035ndash1041 2010

[20] G Canche-Escamilla M Canche-Canche S Duarte-ArandaM Caceres-Farfan and R Borges-Argaez ldquoMechanical prop-erties and biodegradation of thermoplastic starches obtainedfromgrafted starcheswith acrylicsrdquoCarbohydrate Polymers vol86 no 4 pp 1501ndash1508 2011

[21] D Rutot P Degee R Narayan and P Dubois ldquoAliphaticpolyester-grafted starch composites by in situ ring openingpolymerizationrdquo Composite Interfaces vol 7 no 3 pp 215ndash2252000

[22] C S Tena-Salcido F J Rodrıguez-Gonzalez M L Mendez-Hernandez and J CContreras-Esquivel ldquoEffect ofmorphologyon the biodegradation of thermoplastic starch in LDPETPSblendsrdquo Polymer Bulletin vol 60 no 5 pp 677ndash688 2008

[23] L Najemi T Jeanmaire A Zerroukhi and M RaihaneldquoOrganic catalyst for ring opening polymerization of 120576-capro-lactone in bulk Route to starch-graft-polycaprolactonerdquo StarchStaerke vol 62 no 3-4 pp 147ndash154 2010

[24] M Vera-Pacheco H Vazquez-Torres and G Canche-Escamilla ldquoPreparation and characterization of hydrogelsobtained by grafting of acrylonitrile onto cassava starch byceric ion initiationrdquo Journal of Applied Polymer Science vol 47no 1 pp 53ndash59 1993

[25] ASTM in Proceedings of the D638-14 Standard test methodfor tensile properties of plastics ASTM International WestConshohocken PA USA 2014

[26] ASTM in Proceedings of the D618-13 Standard practice forconditioning plastics for testing ASTM International WestConshohocken PA USA 2013

[27] M V Moreno-Chulim F Barahona-Perez and G Canche-Escamilla ldquoBiodegradation of starch and acrylic-grafted starchby Aspergillus nigerrdquo Journal of Applied Polymer Science vol 89no 10 pp 2764ndash2770 2003

[28] N B Colthup L H Daly and S E Wiberley Introduction toInfrared And Raman Spectroscopy Elsevier Cambridge MAUSA 3rd edition 1990

[29] W L Walton and R B Hughes ldquoInfrared identification offumarates andmaleatesrdquoAnalytical Chemistry vol 28 no 9 pp1388ndash1391 1956

[30] A R Katritzky JM Lagowski and J A T Beard ldquoThe infra-redspectra of esters-I Methyl ethyl n- and i-propyl and n- i- ands-butyl estersrdquo Spectrochimica Acta vol 16 no 8 pp 954ndash9631960

[31] J LMateos R Cetina E Olivera and SMeza ldquoThe intensity ofthe carbonyl band in the infrared spectra of methyl benzoatesrdquoJournal of Organic Chemistry vol 26 no 7 pp 2494ndash2498 1961

[32] X Xie Q Liu and S W Cui ldquoStudies on the granular structureof resistant starches (type 4) from normal high amylose andwaxy corn starch citratesrdquo Food Research International vol 39no 3 pp 332ndash341 2006

[33] M G Casarrubias-Castillo G Mendez-Montealvo S LRodrıguez-Ambriz M M Sanchez-Rivera and L A Bello-Perez ldquoStructural and rheological differences between fruit andcereal starchesrdquo Agrociencia vol 46 no 5 pp 455ndash466 2012

[34] S Agarwal and C Speyerer ldquoDegradable blends of semi-crystalline and amorphous branched poly(caprolactone) effectof microstructure on blend propertiesrdquo Polymer vol 51 no 5pp 1024ndash1032 2010

[35] J Fang and P Fowler ldquoThe use of starch and its derivativesas biopolymer sources of packaging materialsrdquo Journal of FoodAgriculture and Environment vol 1 pp 82ndash84 2003


[36] S Gaudin D Lourdin D Le Botlan J L Ilari and P ColonnaldquoPlasticisation and mobility in starch-sorbitol filmsrdquo Journal ofCereal Science vol 29 no 3 pp 273ndash284 1999

[37] B Wunderlich Thermal Analysis of Polymeric MaterialsSpringer Science Business Media Berlin Germany 2005

[38] O Persenaire M Alexandre P Degee and P DuboisldquoMechanisms and kinetics of thermal degradation of poly(120576-caprolactone)rdquo Biomacromolecules vol 2 no 1 pp 288ndash2942001

[39] J J G Van Soest and P Essers ldquoInfluence of amylose-amylopectin ratio on properties of extruded starch plasticsheetsrdquo Journal of Macromolecular Science - Pure and AppliedChemistry vol 34 no 9 pp 1665ndash1689 1997

[40] J J G Van Soest S H D Hulleman D De Wit and J FG Vliegenthart ldquoCrystallinity in starch bioplasticsrdquo IndustrialCrops and Products vol 5 no 1 pp 11ndash22 1996

[41] J J G Van Soest K Benes D DeWit and J F G VliegenthartldquoThe influence of starch molecular mass on the properties ofextruded thermoplastic starchrdquo Polymer vol 37 no 16 pp3543ndash3552 1996

[42] J J G Van Soest D De Wit and J F G VliegenthartldquoMechanical properties of thermoplastic waxy maize starchrdquoJournal of Applied Polymer Science vol 61 no 11 pp 1927ndash19371996

[43] J J G Van Soest Starch Plastics Structure-Property Relation-ships Universiteit Utrecht Netherlands

[44] S H D Hulleman F H P Janssen and H Feil ldquoThe role ofwater during plasticization of native starchesrdquo Polymer vol 39no 10 pp 2043ndash2048 1998

[45] M A Araujo A M Cunha and M Mota ldquoEnzymaticdegradation of starch-based thermoplastic compounds usedin protheses identification of the degradation products insolutionrdquo Biomaterials vol 25 no 13 pp 2687ndash2693 2004

[46] H S Azevedo and R L Reis Understanding the enzymaticdegradation of biodegradable polymers and strategies to controltheir degradation rate Biodegradable systems in tissue engineer-ing and regenerative medicine CRC Press 177201 Boca RatonFla USA 2005

[47] Y Dumoulin L H Cartilier and M A Mateescu ldquoCross-linked amylose tablets containing 120572-amylase an enzymatically-controlled drug release systemrdquo Journal of Controlled Releasevol 60 no 2-3 pp 161ndash167 1999

Submit your manuscripts athttpswwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of



CeramicsJournal of


CompositesJournal of

NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of



Table 1 Formulations used in grafting reactions of polycaprolactone on starch granules

Materials St-g-PCL1 St-g-PCL2 St-g-PCL3 St-g-PCL4 St-g-PCL5 St-g-PCL6 St-g-PCL7Starch [g] 5 5 5 5 5 100 100-Caprolactone (120576-CL) [g] 5 5 5 25 75 100 50N-Methylimidazole (NMI) [g] 0625 125 1875 125 125 25 25

This paper investigates thermoplastic grafted starches(TPGS) and considers two processes used to obtain themThefirst one is the reaction process for obtaining granular graftedstarch with biodegradable polyester (polycaprolactone PCL)and the second process involves obtaining thermoplasticstarches (TPGS) from grafted starch In the first processthe ratio between the starch and the monomer was studiedand the influence of the amount of catalyst used on thegrafting parameters was investigated In the second processthe influence of both the ratio between the amount of graftedstarch and plasticizer used and the type of plasticizer onthe properties and enzymatic degradation of the TPGS wasstudied

2 Materials and Methods

21 Grafting Copolymerization Corn starch was purchasedfrom Unilever Manufacturera S de RL de CV -caprolactone monomer (120576-CL) with 97 purity and catalystN-methylimidazole (NMI) were of reagent grade and werepurchased from Sigma-Aldrich Quımica S de RL de CVStarch particles were grafted according to a method reportedin the literature [23] The procedure was as follows starch(dry basis) 120576-CL monomer and catalyst NMI were placedinto a glass reactor equipped with a mechanical stirrer anda condenser The reactor was placed in a glycerin bath at150∘C and the mixture was stirred for a certain amountof time The polymerization yield was determined gravi-metrically In Table 1 the formulations used for obtainingpolycaprolactone-grafted starch are shown

22 Determination of Grafting Parameters Extraction withtoluene was conducted to dissolve remains of the 120576-CL monomer catalyst and ungrafted polymer chains(homopolymer) After toluene extraction the material wasdried under vacuum to a constant weight Grafting param-eters are determined from the weights before and after theextraction [3 24] using the following equations

Graft () = [PCL grafted weightStarch weight

] times 100

= [119908if minus 119908st119908st ] times 100Addition ()= [ PCL grafted weight

Total weight copolymer St-g-PCL] times 100

= [119908if minus 119908st119908if ] times 100

Grafting Efficiency ()= [ PCL grafted weight

PCL formed weight] times 100

= [ 119908if minus 119908st119908hp + (119908if minus 119908st)] times 100(1)

where 119908if is the weight of the product obtained after extrac-tion (the insoluble fraction) in grams (g) 119908st is the weightof starch loaded in the reaction in grams (g) and 119908hp is theweight of the homopolymer formed in the reaction in grams(g)

23 Characterization of Grafted Granule Starch The mor-phology of the particles was observed using a JEOL 6360LVSEM scanning electron microscope The particles were cov-ered with a gold surface layer to improve contrastThe size ofthe grafted and ungrafted starch granules was analysed witha Coulter Counter LS100Q after the granules were dispersedin deionized water FTIR analysis of starch and graftedstarch was performed in a Nicolet 870 Fourier transforminfrared spectrophotometer in a wavenumber range from4000 to 400 cmminus1 with 16 scans and a resolution of 4 cmminus1X-ray diffractograms were recorded on a Siemens D-5000diffractometer with a Cu-K120572 radiation source (wavelength120582 = 15418 A) The samples were exposed to the X-ray beamwith the X-ray generator running at 34 kV and 25mAand a step time of 6 sec and step size of 004∘ were usedTGA thermograms were obtained on a Perkin Elmer TGA-7thermogravimetric balance in a temperature range from 40to 700∘C with a heating rate of 10∘Cmin and in nitrogenatmosphere

24 Preparation and Characterization of the ThermoplasticStarch Thermoplastic materials with grafted (TPGS) andungrafted (TPS) granular starch were obtained with glycerolor sorbitol added as plasticizersThe ratio of starch (or graftedstarch) to water to glycerolsorbitol was 502525 or 501535The ungrafted or grafted granule starch was first blendedwithwater using a mixer and stored overnight Subsequently itwas mixed with glycerol or sorbitol and stored overnightThemixtures were manually fed into a Brabender Plasticordermixer for 10min at 150∘C with a rotation speed of 40 rpmTheblendsweremolded at 150∘C in aCarver Laboratory pressunder a force of 10000 lbs to obtain samples for mechanicalexperiments

Tensile tests for TPS and TPGS were conducted with aShimadzu AGS-X universal machine by following the ASTMD638-14 method [25] The analyses were performed after














10 휇m

(a)

10 휇m

(b)

10 휇m

(c)

0 20 40 60 80 100


Volu

me (

)

Diameter (휇m)

PCL()


0

26

43

1367

2359

2522

826

1293

1325

(d)


4000 3500 3000 1800 1600 1400 1200 1000 800



Polycaprolactone

Starch

Tran

smitt

ance

(ua

)

(OndashH)




1730 cmminus1 (C=O)

1734 cmminus1 (C=O)

1736 cmminus1 (C=O)

(a)

10

10

20

20

30

30

40

40

50

50

60

60

0

1000

2000

3000

4000

15000

16000

10001200

600800

200400

0

Inte

nsity

(mA

)

Inte

nsity

(mA

)

StarchPCL


2휃 (∘)

2휃 (∘)

(b)



100 200 300 400 500 600 7000

20

40

60

80

100Re

sidua

l mas

s (

)


Temperature (∘C)

(a)

100 200 300 400 500 600 700

D (r

esid

ual m

ass)

D(T

)


Temperature (∘C)

(b)










0

0

50

50

100

100

150

150

200

200

250

250

300

300

0

1

2

3St

ress

(MPa

)

Stre

ss (M

Pa)

Strain ()

Strain ()

000002004006008010



(a)

0 50 100 150 200 250 3000

1

2

3

Stre

ss (M

Pa)

Stre

ss (M

Pa)

Strain ()

Strain ()0 50 100 150 200 250 300

000002004006008010



(b)










50 휇m

(a)

50 휇m

(b)

50 휇m

(c)

50 휇m

(d)

50 휇m

(e)

50 휇m

(f)







Stor

age m

odul

us (P

a)


108

107

106

PCL plasticizer

TPGS 26 25 gly


(a)


Tan훿


PCL plasticizer

TPGS 26 25 gly


(b)


100 200 300 400 500 600 7000

20

40

60

80

100

Resid

ual m

ass (

)

Temperature (∘C)


PCL plasticizer

TPGS 26 25 gly


(a)

100 200 300 400 500 600 700

D (r

esid

ual m

ass)

D(T

)

Temperature (∘C)


PCL plasticizer

TPGS 26 25 gly


(b)






0 10 20 30 40 50 60

Inte

nsity

(ua

)

2휃 (∘)


(a)

0 10 20 30 40 50 60

TPS 25

Inte

nsity

(ua

)

2휃 (∘)

PCL sor


(b)






20

40

60

80

100

Wei

ght l

oss o

f TPS

()

TPS26 PCL43 PCL




(a) (b)

(c) (d)

(b㰀)

(d㰀)

1000 휇m

1000 휇m

100 휇m

100 휇m 50 휇m

50 휇m





4000 3500 3000 1800 1600 1400 1200 1000

PCL

Starch

Tran

smitt

ance

(ua

)


TPGS 43 PCL 25 gly

TPGS 43 PCL 25 sor





0

20

40

60

80

100


D (r

esid

ual m

ass)

D(T

)

Resid

ual m

ass (

)

100 200 300 400 500 600 700

Temperature (∘C)

100 200 300 400 500 600 700Temperature (∘C)

(a)

0

20

40

60

80

100

D (r

esid

ual m

ass)

D(T

)

Resid

ual m

ass (

)


100 200 300 400 500 600 700Temperature (∘C)

100 200 300 400 500 600 700

Temperature (∘C)

(b)



4 Conclusions





Acknowledgments


References


























































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of















10 휇m

(a)

10 휇m

(b)

10 휇m

(c)

0 20 40 60 80 100


Volu

me (

)

Diameter (휇m)

PCL()


0

26

43

1367

2359

2522

826

1293

1325

(d)


4000 3500 3000 1800 1600 1400 1200 1000 800



Polycaprolactone

Starch

Tran

smitt

ance

(ua

)

(OndashH)




1730 cmminus1 (C=O)

1734 cmminus1 (C=O)

1736 cmminus1 (C=O)

(a)

10

10

20

20

30

30

40

40

50

50

60

60

0

1000

2000

3000

4000

15000

16000

10001200

600800

200400

0

Inte

nsity

(mA

)

Inte

nsity

(mA

)

StarchPCL


2휃 (∘)

2휃 (∘)

(b)



100 200 300 400 500 600 7000

20

40

60

80

100Re

sidua

l mas

s (

)


Temperature (∘C)

(a)

100 200 300 400 500 600 700

D (r

esid

ual m

ass)

D(T

)


Temperature (∘C)

(b)










0

0

50

50

100

100

150

150

200

200

250

250

300

300

0

1

2

3St

ress

(MPa

)

Stre

ss (M

Pa)

Strain ()

Strain ()

000002004006008010



(a)

0 50 100 150 200 250 3000

1

2

3

Stre

ss (M

Pa)

Stre

ss (M

Pa)

Strain ()

Strain ()0 50 100 150 200 250 300

000002004006008010



(b)










50 휇m

(a)

50 휇m

(b)

50 휇m

(c)

50 휇m

(d)

50 휇m

(e)

50 휇m

(f)







Stor

age m

odul

us (P

a)


108

107

106

PCL plasticizer

TPGS 26 25 gly


(a)


Tan훿


PCL plasticizer

TPGS 26 25 gly


(b)


100 200 300 400 500 600 7000

20

40

60

80

100

Resid

ual m

ass (

)

Temperature (∘C)


PCL plasticizer

TPGS 26 25 gly


(a)

100 200 300 400 500 600 700

D (r

esid

ual m

ass)

D(T

)

Temperature (∘C)


PCL plasticizer

TPGS 26 25 gly


(b)






0 10 20 30 40 50 60

Inte

nsity

(ua

)

2휃 (∘)


(a)

0 10 20 30 40 50 60

TPS 25

Inte

nsity

(ua

)

2휃 (∘)

PCL sor


(b)






20

40

60

80

100

Wei

ght l

oss o

f TPS

()

TPS26 PCL43 PCL




(a) (b)

(c) (d)

(b㰀)

(d㰀)

1000 휇m

1000 휇m

100 휇m

100 휇m 50 휇m

50 휇m





4000 3500 3000 1800 1600 1400 1200 1000

PCL

Starch

Tran

smitt

ance

(ua

)


TPGS 43 PCL 25 gly

TPGS 43 PCL 25 sor





0

20

40

60

80

100


D (r

esid

ual m

ass)

D(T

)

Resid

ual m

ass (

)

100 200 300 400 500 600 700

Temperature (∘C)

100 200 300 400 500 600 700Temperature (∘C)

(a)

0

20

40

60

80

100

D (r

esid

ual m

ass)

D(T

)

Resid

ual m

ass (

)


100 200 300 400 500 600 700Temperature (∘C)

100 200 300 400 500 600 700

Temperature (∘C)

(b)



4 Conclusions





Acknowledgments


References


























































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of



10 휇m

(a)

10 휇m

(b)

10 휇m

(c)

0 20 40 60 80 100


Volu

me (

)

Diameter (휇m)

PCL()


0

26

43

1367

2359

2522

826

1293

1325

(d)


4000 3500 3000 1800 1600 1400 1200 1000 800



Polycaprolactone

Starch

Tran

smitt

ance

(ua

)

(OndashH)




1730 cmminus1 (C=O)

1734 cmminus1 (C=O)

1736 cmminus1 (C=O)

(a)

10

10

20

20

30

30

40

40

50

50

60

60

0

1000

2000

3000

4000

15000

16000

10001200

600800

200400

0

Inte

nsity

(mA

)

Inte

nsity

(mA

)

StarchPCL


2휃 (∘)

2휃 (∘)

(b)



100 200 300 400 500 600 7000

20

40

60

80

100Re

sidua

l mas

s (

)


Temperature (∘C)

(a)

100 200 300 400 500 600 700

D (r

esid

ual m

ass)

D(T

)


Temperature (∘C)

(b)










0

0

50

50

100

100

150

150

200

200

250

250

300

300

0

1

2

3St

ress

(MPa

)

Stre

ss (M

Pa)

Strain ()

Strain ()

000002004006008010



(a)

0 50 100 150 200 250 3000

1

2

3

Stre

ss (M

Pa)

Stre

ss (M

Pa)

Strain ()

Strain ()0 50 100 150 200 250 300

000002004006008010



(b)










50 휇m

(a)

50 휇m

(b)

50 휇m

(c)

50 휇m

(d)

50 휇m

(e)

50 휇m

(f)







Stor

age m

odul

us (P

a)


108

107

106

PCL plasticizer

TPGS 26 25 gly


(a)


Tan훿


PCL plasticizer

TPGS 26 25 gly


(b)


100 200 300 400 500 600 7000

20

40

60

80

100

Resid

ual m

ass (

)

Temperature (∘C)


PCL plasticizer

TPGS 26 25 gly


(a)

100 200 300 400 500 600 700

D (r

esid

ual m

ass)

D(T

)

Temperature (∘C)


PCL plasticizer

TPGS 26 25 gly


(b)






0 10 20 30 40 50 60

Inte

nsity

(ua

)

2휃 (∘)


(a)

0 10 20 30 40 50 60

TPS 25

Inte

nsity

(ua

)

2휃 (∘)

PCL sor


(b)






20

40

60

80

100

Wei

ght l

oss o

f TPS

()

TPS26 PCL43 PCL




(a) (b)

(c) (d)

(b㰀)

(d㰀)

1000 휇m

1000 휇m

100 휇m

100 휇m 50 휇m

50 휇m





4000 3500 3000 1800 1600 1400 1200 1000

PCL

Starch

Tran

smitt

ance

(ua

)


TPGS 43 PCL 25 gly

TPGS 43 PCL 25 sor





0

20

40

60

80

100


D (r

esid

ual m

ass)

D(T

)

Resid

ual m

ass (

)

100 200 300 400 500 600 700

Temperature (∘C)

100 200 300 400 500 600 700Temperature (∘C)

(a)

0

20

40

60

80

100

D (r

esid

ual m

ass)

D(T

)

Resid

ual m

ass (

)


100 200 300 400 500 600 700Temperature (∘C)

100 200 300 400 500 600 700

Temperature (∘C)

(b)



4 Conclusions





Acknowledgments


References


























































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of



100 200 300 400 500 600 7000

20

40

60

80

100Re

sidua

l mas

s (

)


Temperature (∘C)

(a)

100 200 300 400 500 600 700

D (r

esid

ual m

ass)

D(T

)


Temperature (∘C)

(b)










0

0

50

50

100

100

150

150

200

200

250

250

300

300

0

1

2

3St

ress

(MPa

)

Stre

ss (M

Pa)

Strain ()

Strain ()

000002004006008010



(a)

0 50 100 150 200 250 3000

1

2

3

Stre

ss (M

Pa)

Stre

ss (M

Pa)

Strain ()

Strain ()0 50 100 150 200 250 300

000002004006008010



(b)










50 휇m

(a)

50 휇m

(b)

50 휇m

(c)

50 휇m

(d)

50 휇m

(e)

50 휇m

(f)







Stor

age m

odul

us (P

a)


108

107

106

PCL plasticizer

TPGS 26 25 gly


(a)


Tan훿


PCL plasticizer

TPGS 26 25 gly


(b)


100 200 300 400 500 600 7000

20

40

60

80

100

Resid

ual m

ass (

)

Temperature (∘C)


PCL plasticizer

TPGS 26 25 gly


(a)

100 200 300 400 500 600 700

D (r

esid

ual m

ass)

D(T

)

Temperature (∘C)


PCL plasticizer

TPGS 26 25 gly


(b)






0 10 20 30 40 50 60

Inte

nsity

(ua

)

2휃 (∘)


(a)

0 10 20 30 40 50 60

TPS 25

Inte

nsity

(ua

)

2휃 (∘)

PCL sor


(b)






20

40

60

80

100

Wei

ght l

oss o

f TPS

()

TPS26 PCL43 PCL




(a) (b)

(c) (d)

(b㰀)

(d㰀)

1000 휇m

1000 휇m

100 휇m

100 휇m 50 휇m

50 휇m





4000 3500 3000 1800 1600 1400 1200 1000

PCL

Starch

Tran

smitt

ance

(ua

)


TPGS 43 PCL 25 gly

TPGS 43 PCL 25 sor





0

20

40

60

80

100


D (r

esid

ual m

ass)

D(T

)

Resid

ual m

ass (

)

100 200 300 400 500 600 700

Temperature (∘C)

100 200 300 400 500 600 700Temperature (∘C)

(a)

0

20

40

60

80

100

D (r

esid

ual m

ass)

D(T

)

Resid

ual m

ass (

)


100 200 300 400 500 600 700Temperature (∘C)

100 200 300 400 500 600 700

Temperature (∘C)

(b)



4 Conclusions





Acknowledgments


References


























































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of



0

0

50

50

100

100

150

150

200

200

250

250

300

300

0

1

2

3St

ress

(MPa

)

Stre

ss (M

Pa)

Strain ()

Strain ()

000002004006008010



(a)

0 50 100 150 200 250 3000

1

2

3

Stre

ss (M

Pa)

Stre

ss (M

Pa)

Strain ()

Strain ()0 50 100 150 200 250 300

000002004006008010



(b)










50 휇m

(a)

50 휇m

(b)

50 휇m

(c)

50 휇m

(d)

50 휇m

(e)

50 휇m

(f)







Stor

age m

odul

us (P

a)


108

107

106

PCL plasticizer

TPGS 26 25 gly


(a)


Tan훿


PCL plasticizer

TPGS 26 25 gly


(b)


100 200 300 400 500 600 7000

20

40

60

80

100

Resid

ual m

ass (

)

Temperature (∘C)


PCL plasticizer

TPGS 26 25 gly


(a)

100 200 300 400 500 600 700

D (r

esid

ual m

ass)

D(T

)

Temperature (∘C)


PCL plasticizer

TPGS 26 25 gly


(b)






0 10 20 30 40 50 60

Inte

nsity

(ua

)

2휃 (∘)


(a)

0 10 20 30 40 50 60

TPS 25

Inte

nsity

(ua

)

2휃 (∘)

PCL sor


(b)






20

40

60

80

100

Wei

ght l

oss o

f TPS

()

TPS26 PCL43 PCL




(a) (b)

(c) (d)

(b㰀)

(d㰀)

1000 휇m

1000 휇m

100 휇m

100 휇m 50 휇m

50 휇m





4000 3500 3000 1800 1600 1400 1200 1000

PCL

Starch

Tran

smitt

ance

(ua

)


TPGS 43 PCL 25 gly

TPGS 43 PCL 25 sor





0

20

40

60

80

100


D (r

esid

ual m

ass)

D(T

)

Resid

ual m

ass (

)

100 200 300 400 500 600 700

Temperature (∘C)

100 200 300 400 500 600 700Temperature (∘C)

(a)

0

20

40

60

80

100

D (r

esid

ual m

ass)

D(T

)

Resid

ual m

ass (

)


100 200 300 400 500 600 700Temperature (∘C)

100 200 300 400 500 600 700

Temperature (∘C)

(b)



4 Conclusions





Acknowledgments


References


























































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of



50 휇m

(a)

50 휇m

(b)

50 휇m

(c)

50 휇m

(d)

50 휇m

(e)

50 휇m

(f)







Stor

age m

odul

us (P

a)


108

107

106

PCL plasticizer

TPGS 26 25 gly


(a)


Tan훿


PCL plasticizer

TPGS 26 25 gly


(b)


100 200 300 400 500 600 7000

20

40

60

80

100

Resid

ual m

ass (

)

Temperature (∘C)


PCL plasticizer

TPGS 26 25 gly


(a)

100 200 300 400 500 600 700

D (r

esid

ual m

ass)

D(T

)

Temperature (∘C)


PCL plasticizer

TPGS 26 25 gly


(b)






0 10 20 30 40 50 60

Inte

nsity

(ua

)

2휃 (∘)


(a)

0 10 20 30 40 50 60

TPS 25

Inte

nsity

(ua

)

2휃 (∘)

PCL sor


(b)






20

40

60

80

100

Wei

ght l

oss o

f TPS

()

TPS26 PCL43 PCL




(a) (b)

(c) (d)

(b㰀)

(d㰀)

1000 휇m

1000 휇m

100 휇m

100 휇m 50 휇m

50 휇m





4000 3500 3000 1800 1600 1400 1200 1000

PCL

Starch

Tran

smitt

ance

(ua

)


TPGS 43 PCL 25 gly

TPGS 43 PCL 25 sor





0

20

40

60

80

100


D (r

esid

ual m

ass)

D(T

)

Resid

ual m

ass (

)

100 200 300 400 500 600 700

Temperature (∘C)

100 200 300 400 500 600 700Temperature (∘C)

(a)

0

20

40

60

80

100

D (r

esid

ual m

ass)

D(T

)

Resid

ual m

ass (

)


100 200 300 400 500 600 700Temperature (∘C)

100 200 300 400 500 600 700

Temperature (∘C)

(b)



4 Conclusions





Acknowledgments


References


























































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of




Stor

age m

odul

us (P

a)


108

107

106

PCL plasticizer

TPGS 26 25 gly


(a)


Tan훿


PCL plasticizer

TPGS 26 25 gly


(b)


100 200 300 400 500 600 7000

20

40

60

80

100

Resid

ual m

ass (

)

Temperature (∘C)


PCL plasticizer

TPGS 26 25 gly


(a)

100 200 300 400 500 600 700

D (r

esid

ual m

ass)

D(T

)

Temperature (∘C)


PCL plasticizer

TPGS 26 25 gly


(b)






0 10 20 30 40 50 60

Inte

nsity

(ua

)

2휃 (∘)


(a)

0 10 20 30 40 50 60

TPS 25

Inte

nsity

(ua

)

2휃 (∘)

PCL sor


(b)






20

40

60

80

100

Wei

ght l

oss o

f TPS

()

TPS26 PCL43 PCL




(a) (b)

(c) (d)

(b㰀)

(d㰀)

1000 휇m

1000 휇m

100 휇m

100 휇m 50 휇m

50 휇m





4000 3500 3000 1800 1600 1400 1200 1000

PCL

Starch

Tran

smitt

ance

(ua

)


TPGS 43 PCL 25 gly

TPGS 43 PCL 25 sor





0

20

40

60

80

100


D (r

esid

ual m

ass)

D(T

)

Resid

ual m

ass (

)

100 200 300 400 500 600 700

Temperature (∘C)

100 200 300 400 500 600 700Temperature (∘C)

(a)

0

20

40

60

80

100

D (r

esid

ual m

ass)

D(T

)

Resid

ual m

ass (

)


100 200 300 400 500 600 700Temperature (∘C)

100 200 300 400 500 600 700

Temperature (∘C)

(b)



4 Conclusions





Acknowledgments


References


























































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of



0 10 20 30 40 50 60

Inte

nsity

(ua

)

2휃 (∘)


(a)

0 10 20 30 40 50 60

TPS 25

Inte

nsity

(ua

)

2휃 (∘)

PCL sor


(b)






20

40

60

80

100

Wei

ght l

oss o

f TPS

()

TPS26 PCL43 PCL




(a) (b)

(c) (d)

(b㰀)

(d㰀)

1000 휇m

1000 휇m

100 휇m

100 휇m 50 휇m

50 휇m





4000 3500 3000 1800 1600 1400 1200 1000

PCL

Starch

Tran

smitt

ance

(ua

)


TPGS 43 PCL 25 gly

TPGS 43 PCL 25 sor





0

20

40

60

80

100


D (r

esid

ual m

ass)

D(T

)

Resid

ual m

ass (

)

100 200 300 400 500 600 700

Temperature (∘C)

100 200 300 400 500 600 700Temperature (∘C)

(a)

0

20

40

60

80

100

D (r

esid

ual m

ass)

D(T

)

Resid

ual m

ass (

)


100 200 300 400 500 600 700Temperature (∘C)

100 200 300 400 500 600 700

Temperature (∘C)

(b)



4 Conclusions





Acknowledgments


References


























































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of



(a) (b)

(c) (d)

(b㰀)

(d㰀)

1000 휇m

1000 휇m

100 휇m

100 휇m 50 휇m

50 휇m





4000 3500 3000 1800 1600 1400 1200 1000

PCL

Starch

Tran

smitt

ance

(ua

)


TPGS 43 PCL 25 gly

TPGS 43 PCL 25 sor





0

20

40

60

80

100


D (r

esid

ual m

ass)

D(T

)

Resid

ual m

ass (

)

100 200 300 400 500 600 700

Temperature (∘C)

100 200 300 400 500 600 700Temperature (∘C)

(a)

0

20

40

60

80

100

D (r

esid

ual m

ass)

D(T

)

Resid

ual m

ass (

)


100 200 300 400 500 600 700Temperature (∘C)

100 200 300 400 500 600 700

Temperature (∘C)

(b)



4 Conclusions





Acknowledgments


References


























































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of



0

20

40

60

80

100


D (r

esid

ual m

ass)

D(T

)

Resid

ual m

ass (

)

100 200 300 400 500 600 700

Temperature (∘C)

100 200 300 400 500 600 700Temperature (∘C)

(a)

0

20

40

60

80

100

D (r

esid

ual m

ass)

D(T

)

Resid

ual m

ass (

)


100 200 300 400 500 600 700Temperature (∘C)

100 200 300 400 500 600 700

Temperature (∘C)

(b)



4 Conclusions





Acknowledgments


References


























































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of
























































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of






















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of









CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Documents

Properties and Biodegradability of Thermoplastic Starch Obtained … · 2019. 7. 30. · ResearchArticle Properties and Biodegradability of Thermoplastic Starch Obtained from Granular