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Research ArticleComparative Study on Properties of Polylactic AcidNanocomposites with Cellulose and Chitin Nanofibers Extractedfrom Different Raw Materials

Jingjing Li1 Jian Li1 Dejun Feng1 Jingfeng Zhao1 Jingrong Sun1 and Dagang Li2

1College of Forestry Northwest AampF University Yangling China2College of Materials Science and Engineering Nanjing Forestry University Nanjing China

Correspondence should be addressed to Dagang Li 396420748qqcom

Received 15 May 2017 Revised 17 September 2017 Accepted 16 October 2017 Published 20 November 2017

Academic Editor Mangala Joshi

Copyright copy 2017 Jingjing Li et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Polylactic acid (PLA) was reinforced with ultralong cellulose and chitin nanofibers extracted from four rawmaterials by extrusionThe mechanical rheological thermal and viscoelastic performances of four nanocomposites were comparatively studied in detailThe results showed that fibrillation of poplar was much easier than that of cotton and fibrillation of crab shell was relatively hard ascompared to prawn shell The poplar CNFsPLA composite exhibited the best mechanical properties among four nanocompositesdue to the highest aspect ratio of nanofibers while both the cotton CNFsPLA composite and the crab shell CHNFsPLA compositehad low mechanical strength due to the relatively low aspect ratio FE-SEM images showed that the ultralong nanofibers wereuniformly dispersed in PLAmatrix for all four samples with the water preblending methodThe CTE values of the nanocompositeswith 40wt nanofibers extracted from poplar cotton crab shell and prawn shell were 695 times 10minus6 Kminus1 796 times 10minus6 Kminus1 772 times10minus6 Kminus1 and 753 times 10minus6 Kminus1 respectively All the results indicated that the aspect ratio of the nanofibers has a great influence onthe performance of the composites irrespective of the composites prepared by cellulose or chitin

1 Introduction

Polylactic acid (PLA) is a renewable biocompatible andbiodegradable polymer and it is one of the most widely usedbioplastics [1] Due to the excellent modulus and tensilestrength and high transparency comparable to petroleum-based polymers PLA is a good alternative for the conven-tional synthetic polymers in different applications especiallyin packaging [2] Nevertheless the properties of PLA such asthermal stability and impact toughness are inferior to thoseof conventional polymers used for thermoplastic applications[3] To overcome the mentioned drawbacks and broaden theapplication areas of PLA considerable researches have beencarried out to develop and study modified PLA PLA-basedcopolymers and PLA-based composites [4]

Cellulose nanofibers (CNFs) and chitin nanofibers(CHNFs) have attracted the attention of researches as addi-tives in the green nanocomposites field because they are

biodegradable and renewable polymers with good mechan-ical properties CNFs have highly ordered crystalline regionsalternating with disordered amorphous domains [5] Thecrystalline regions of CNFs have a high Youngrsquos modulusof 138GPa [6] and a very low thermal expansion coefficient(10minus7 Kminus1 in the longitudinal direction) [7] As the secondmost abundant natural polysaccharide after cellulose chitinis the major structural component of cell walls in fungi andyeast the exoskeleton of arthropods andmollusk shells [8] Itis reported that the longitudinal modulus and the transversemodulus of chitin nanocrystals are 150GPa and 15GParespectively [9] Because of these distinctive propertiesCNFsCHNFs have been used in a wide range of applicationssuch as optically transparent materials reinforced polymernanocomposites biomimetic foams multifunctional fiberstemplates for chiral nematic mesoporous materials andconductive materials [10]

HindawiJournal of NanomaterialsVolume 2017 Article ID 7193263 11 pageshttpsdoiorg10115520177193263

2 Journal of Nanomaterials

Cellulose nanomaterials have been extensively used asan additive to improve the thermal mechanical and barrierproperties of PLA [11ndash17] However most of the literaturehas focused on the NCC or MCC (microcrystal cellulose)reinforced PLA composites There is a lack of study on theCNFs with high aspect ratio reinforced PLA composites dueto the dispersion problem of the ultralong CNFs In additionchitin nanofibers are mainly used in other polymers such aspoly (caprolactone) chitosan PVA PMMA and starch [14]while the research on chitin nanofibers reinforced PLA is veryrare [18]

Although CNFs and CHNFs have great potential as rein-forcements the uniform dispersion in polymer matrix is themajor challenge It is well known that materials in nanosizehave a strong tendency to aggregate In addition the stronghydrogen bonds form when cellulose and chitin are driedleading to the aggregation problem To overcome the disper-sion and compatibility difficulties cellulosechitin nanofibershave been subjected to physical treatments and chemicalmodification [19] However the mechanical properties ofthe prepared nanocomposites are not remarkably improveddue to the damaged molecular structure of nanofibers bychemical modification

Until now the preparation of CNFsCHNFs reinforcedpolymer composites is mainly focused on the methodsof solvent casting freeze-drying and electrospinning Thedevelopment of more flexible and viable processing tech-niques for industrial applications is needed to promote thecommercialization of nanofibers-based composites Amongthe processing techniques the melt-compounding process isthemost potential technique since the final product preparedby this technique can be easily shaped [13] However there areonly very few studies on the nanocomposite prepared by themelt-compounding technique especially in the case of chitinnanofibers [20 21]

In this study four different CNFsCHNFs reinforced PLAcomposites were prepared using the extrusion process TheCNFsCHNFs were extracted from the raw materials ofpoplar flour cotton crab shell and prawn shell All theisolated CNFsCHNFs showed network structure and highaspect ratio The effects of fiber morphology on the mechan-ical thermal and viscoelastic properties of the preparednanocomposites were comparatively investigated to evaluatethe reinforcing effect of CNFs and CHNFs To solve the dis-persion problem of ultralong CNFsCHNFs in PLA matrixthe PLA powders were premixed with the CNFsCHNFswater slurry followed by freeze-drying before the nanocom-posites were extruded This process is a time-saving andenvironmentally friendly method due to the absence ofchemical reagent

2 Materials and Methods

21 Materials Polylactic acid (PLA) NatureWorks TM4032D was supplied by Nanjing Jufeng Advanced MaterialsCo Ltd (Nanjing China) The glass transition temperature(119879119892) and melting point (119879119898) were 55∘C and 180∘C respec-tively The melt flow index (MFI) was 6 g10min (190∘C

216 kg) The poplar flour with the size of 60ndash80mesh wasobtained from Nanjing Jufeng Advanced Materials Co Ltd(Nanjing China) Absorbent cotton medical grade waspurchased from Beijing Tianheng BohaoMedical EquipmentCo Ltd (Beijing China) Dried crab shell powder and prawnshell powder were obtained from Golden Shell BiochemicalCo Ltd (Zhejiang China) The other chemicals and dis-tilled water were purchased from Nanjing Chemical ReagentCompany and used without further purification in this study(Nanjing China)

22 Preparation of Poplar CNFs Based on our previouslyreported methods [22] the preparation procedure of poplarCNFs was mainly divided into chemical pretreatment andgrinding nanofibrillationAfter chemical treatment thewaterslurry with 1 wt CNFs was passed through a grinder(MKCA6-2 Masuko Sangyo Co Japan) for 20 times with thegrinding stone at 1800 rpm

23 Preparation of Cotton CNFs The preparation of cottonCNFs was conducted according to our previously reportedmethods [23] The extraction process of cotton CNFs wassimpler than that of poplar CNFs due to higher cellulosecontent in cotton

24 Preparation of CrabPrawn CHNFs Crabprawn shellsare composed of chitin and some other constituents such asproteins lipids calcium carbonate and pigmentsThe chem-ical treatment of crabprawn shell was conducted accordingto our previously reported methods [24] Finally a watersuspension with 1 wt CHNFs was passed through thegrinder for 20 times with the grinding stone at 1800 rpm

25 Preparation of NanofibersPLA Composites Beforethe extrusion process different contents of PLA powders(60ndash80mesh) were added to the 1 wt CNFsCHNFs waterslurry and were continuously stirred by a magnetic stirrerat 75∘C for 1 h After the water preblending process themixture slurry was dehydrated by vacuum filtration using aBuchner funnel and then was freeze-dried Subsequently thenanofibersPLAmixturewas fully broken using a blender andfed into a HAAKE MiniLab (HAAKE MiniLab II ThermoFisher Scientific Germany) for compounding The HAAKEMiniLab is a small twin screw extruder for laboratory useThe samples were extruded through a rectangular die withthe sectional dimension of 35 times 1mm2 The samples werecrushed into powder by a blender and then hot-pressed at170∘C for 5min with a press vulcanizer

26 Characterization

CelluloseChitin Nanofibers

FE-SEM The morphologies of four different nanofibers wereobserved using a field emission scanning electronmicroscope(HITACHI S-4860 HITACHI Japan) Prior to FE-SEMobservations the samples were kept in a vacuum oven at30∘Covernight and then coatedwith gold for 30ndash60 s to avoid

Journal of Nanomaterials 3

charging The acceleration voltage was 3 kV and the coatingcurrent was 10mA The width of nanofibers was measuredusing a microscope image analysis system Image-Pro Plus

CNFsCHNFs Reinforced PLA Composites

Rheological Properties The nanofibersPLA mixture was fedinto the HAAKE MiniLab for capillary rheological test Theextrusion temperature was set at 180∘C The rotating screwspeed was set from 10 rpm to 100 rpm After the rheologicalmeasurement themixture was extruded through the dieTherotating screw speed was fixed at 40 rpm in the extrusionprocess

FE-SEM The fracture surfaces of four different nanofi-bersPLA composites were observed by a FE-SEM Thenanocomposite samples were frozen in liquid nitrogen andthen quickly broken

Mechanical Properties The tensile and flexural propertiesof different nanofibersPLA composites were tested using auniversal materials testing machine (AG-10TA ShimadzuJapan) The tensile gauge length was fixed at 25mm at atensile speed of 1mmmin Each sample was prepared witha dumbbell shape and dimensions of 50mm length 3mmwidth and 3mm thickness The flexural properties weretested in bendingmode with the span of 40mm and the crosshead speed of 1mmmin following ASTM-D 790-2010 Theresults represent the average value of six specimens for eachformulation

The impact strength of different nanofibersPLA compos-ites was measured by an Izod impact test machine (QJBCXShanghai Qingji Instrumentation Technology Co China)according to ASTM D256-2010 Moreover at least fourreplications were tested for each measurement

Coefficient of Thermal Expansion (CTE) The CTE values ofdifferent nanofibersPLA composites were measured usinga thermal mechanical analyzer (TMA 401F1 NETZSCHGermany) to investigate the change in length with theincrease of temperature The samples were tested in tensionmode with a static load of 1 N and the dimension of 15mm times5mm times 1mmThe tests were performed over the temperaturerange from minus20 to 110∘C at a heating rate of 5∘Cmin

Dynamic Mechanical Analysis (DMA) Dynamic mechanicalanalysis of different nanofibersPLA composites was per-formed on a dynamic mechanical analyzer (DMA 242CNETZSCH Germany) Prior to the test the samples were cutinto strips with dimension of 32mm times 35mm times 1mm Thetests were carried out in a dual cantilever mode at a heatingrate of 3∘Cmin over the temperature range fromminus20 to 110∘C

3 Results and Discussion

31 CelluloseChitin Nanofibers

FE-SEM The SEM images of poplar CNFs cotton CNFscrab shell CHNFs and prawn shell CHNFs after the grindingtreatment are shown in Figure 1 A classical web-like network

structure is observed in all the nanofibers Moreover a verylong entangled cellulosic filament can be found The fibersof poplar CNFs in Figure 1(a) are highly uniform even overan extensive area with the average width of approximately30ndash80 nm The SEM observation also reveals that the lengthof most obtained poplar CNFs is a few microns Hence theaspect ratio of poplar CNFs is up to 500ndash2000 Comparedto poplar CNFs the morphology of cotton CNFs is verydifferent (Figure 1(b)) Although long and single-cellulosenanofiber can be clearly observed many large fiber bundlesare still present Therefore the grinder treatment is unableto fibrillate the cotton fibers into nanofibers with a uniformwidth because of the remaining strong hydrogen bondingwithin the adjacent cotton cellulose after the chemical purifi-cation [25] Figure 1(c) displays the morphology of crab shellCHNFs after removal of the protein and mineral matrixcomponents It can be noticed that crab shell could not beuniformly nanofibrillated as compared to the poplar CNFsThe widths of the fibers derived from crab shell are in arange from 120 to 200 nm The thick fibers correspondingto bundles of nanofibers of 10ndash20 nm in width were notsuccessfully fibrillated by the grinding treatment Comparedto crab shell the CHNFs extracted fromprawn shell using thesame treatment are relatively uniform over an extensive areaand the width of the nanofibers is 80ndash120 nm (Figure 1(d))Fibrillation of the prawn shell was relatively easy as comparedto crab shell due to the differences in the cuticle structureand fiber thickness Prawn is primarily made up of a fineexocuticle while crab shell is mainly composed of theendocuticle which has a much coarser matrix structure witha thicker fiber diameter than exocuticle [26]

Diameter Distribution Figure 2 presents the diameter distri-bution of four different nanofibers after the grinding treat-ment In Figure 2(a) the percentage of the poplar CNFs withthe width of 30ndash80 nm is about 65 The percentage of thecotton CNFs with the width of 120ndash500 nm is approximately80 (Figure 2(b)) These results show that cotton CNFshave much thicker fiber bundles as compared to the poplarCNFs It is very difficult for cotton to fibrillate into nanofiberswith a uniform width by the only grinding treatment Othermechanical processes are necessary to break the stronghydrogen bonding and individualize cotton fibers into muchfiner nanofibers For the crab shell CHNFs the percentagesof nanofibers with widths of 120ndash200 nm and 80ndash120 nm areabout 50 and 24 respectively (Figure 2(c)) In contrastthe percentages of prawn shell CHNFs with the widths of120ndash200 nm and 80ndash120 nm are 23 and 52 respectivelyThe data suggests that fibrillation of prawn shell is easier thanthat of crab shell

32 CNFsCHNFs Reinforced PLA Composites

Rheological Properties Figure 3 presents the capillary rheo-logical curves in terms of the viscosity and shear stress offour nanofibers (40wt)PLA composite melts as functionsof shear rate All samples show a shear-thinning behaviorwithout a plateau region and a less frequency-dependencybehavior especially at lower frequencies The shear-thinning


1 m

(a)

1 m

(b)

1 m

(c)

1 m

(d)

Figure 1 FE-SEMmicrographs of the nanofibers extracted from original (a) poplar (b) cotton (c) crab shell and (d) prawn shell

behavior can be attributed to disentanglement and orien-tation of nanofibers and PLA chains in the flow directionreducing the viscous resistance In addition the viscosityand shear stress of four composites are much higher thanthose of the pure PLA suggesting a network formationwith the addition of cellulosechitin nanofibers Nanofiberswill disturb the normal flow of the matrix melt and hinderthe mobility of chain segments of polymers It can also benoticed that the viscosity and shear stress of the poplarCNFsPLA composite are highest among four samples andthe corresponding values of the cottonPLA composite arethe lowest According to the SEM images in Figure 1 poplarCNFs have higher aspect ratio more refined structure andlarger specific surface area than other nanofibers extractedfrom cotton and crabprawn shell Consequently muchstronger CNFPLA interactions and restriction to PLA chainmobility are generated leading to the relatively high viscosityand shear stress It was reported that in addition to theinterfacial interactions through molecular entanglement andmechanical interlocking between nanofibers and the polymermatrix [27] CNFs may have electrostatic attractions withPLA as well [28 29] The cottoncrab shell nanofibers aremore easily aligned anddistributed along the direction of flowdue to the relatively low aspect ratio Hence the probability offiberfiber collisions ismuch less than that of the poplar CNFscomposite leading to the lower viscosity and shear stress ofthe nanocomposites

Mechanical Properties Generally mechanical properties arethe key factors in determining the reinforcing effect ofnanofibers for PLA The effect of nanofiber content on thetensile flexural and impact properties of four nanofibersPLA composites is presented in Figure 4The tensile strengthof PLA is increased slightly with the addition of 10 wtnanofibers due to the high stiffness of the nanofiber itself Asshown in Figure 4(a) the tensile strength of nanocompositesincreases with increasing nanofiber content up to 30wtHowever it can be noticed that the tensile strength of the40wt nanofiberPLA composite is lower than that of the30wt nanofiberPLA compositeThe decrease in the tensilestrength indicates that nanofibersrsquo aggregation and poordispersion will occur in the composite with high content ofnanofibers Different from the tensile strength Youngrsquos mod-ulus bending strength (MOR) bending modulus (MOE)and impact toughness of four nanocomposites increaserapidly with increasing the loading of nanofibers The dra-matic improvement can be attributed to the excellent disper-sion and improved interfacial interaction between nanofibersand PLA chains Excellent dispersion of nanofibers leadsto the formation of a network structure which leads tosignificant improvement in mechanical strength Howeverwhen the content of nanofiber is fixed four composites showdifferent mechanical propertiesThe poplar CNFsPLA com-posite exhibits the best mechanical properties and the prawnshell CHNFsPLA composite shows the second highest


Width of nanofibers (nm)

Poplar cellulose nanofiber

200ndash500120ndash20080ndash12030ndash8010ndash305ndash100

10

20

30

40

50

60

70

Rate

()

(a)

Cotton cellulose nanofiber

Width of nanofibers (nm)200ndash500120ndash20080ndash12030ndash8010ndash305ndash10

0

10

20

30

40

50

60

Rate

()

(b)

Crab shell chitin nanofiber


0

10

20

30

40

50

60

Rate

()

(c)

Prawn shell chitin nanofiber


0

10

20

30

40

50

60

Rate

()

(d)

Figure 2 Diameter distribution of the nanofibers extracted from original (a) poplar (b) cotton (c) crab shell and (d) prawn shell

mechanical strength among four nanocomposites Themechanical properties of cotton CNFsPLA composite andthe crab shell CHNFsPLA composite are the worst Theexcellent mechanical performance of the poplar CNFsPLAcomposite is ascribed to the highest aspect ratio of poplarCNFs So it can be concluded that the aspect ratio ofnanofibers is the main reason for different mechanicalproperties of the nanocomposites whether raw material iscellulose or chitin Rowell and coworkers reported that a highaspect ratio is very important in fiber reinforced compositesas it indicates potential strength properties [30] Stark andRowlands reported that aspect ratio rather than particlesize has the greatest effect on strength and stiffness [31]The mechanical properties of the fiberpolymer compositesare determined by several factors such as nature of thereinforcement fiber fiber aspect ratio fiber-matrix interfacialadhesion and also the fiber orientation in the composites[32] Except for the factor of fiber aspect ratio the interfacialadhesion and fiber dispersion are also very important factors

to influence the reinforcing effect of fibersThe improvementsof mechanical properties demonstrate that homogeneousdispersion of CNFsCHNFs could be achieved by usingthe water preblending method Furthermore the excellentimpact toughness of the nanocomposites could be obtaineddue to the ultralong CNFsCHNFs If the nanofibers areuniformly dispersed in the matrix the refined nanofibersnetwork structure can absorb a large amount of energy in theprocess of fracture leading to a great improvement in impactstrength of the nanocomposite

FE-SEM FE-SEM micrographs of fractured surfaces of fourdifferent nanofibers reinforced PLA composites are presentedin Figure 5 Homogeneous dispersion of nanofibers in PLAmatrix could be achieved for all four samples with the waterpreblending method It is observed that lots of ultralong andrefined nanofibers are distributed uniformly and compactlyon the fracture surface of the nanocomposite in the formof a ldquospider webrdquo without aggregation The cellulosechitin


Shear rate (Ｍminus1)400350300250200150100500

200

400

600

800

1000

1200

14001600

Cotton CNFsCrab shell CHNFsPrawn shell CHNFs

Poplar CNFsPure PLA

Visc

osity

(Pamiddot

s)

(a)


40000

60000

80000

100000

120000

Shea

r stre

ss (P

a)


Poplar CNFsPure PLA

(b)

Figure 3 The viscosity and shear stress of four nanofibersPLA composites as functions of shear rate

nanofibers in the composites have the same entangledstructure as the nanofibers which means that the networkstructure of the nanofibers is stable and unaltered even afterthe water preblending and extrusion processes The roughfracture surface suggests that large plastic deformation hasoccurred in the process of the fracture instead of the brittlefracture mode for the neat PLAThe fiber bundles disruptionand delamination take more energy as compared to fiberfracture leading to the prolonged crack propagation beforefailure This mechanism is responsible for high toughnessin the nanofiberPLA composite For the water pretreatmentmethod hydrophilic nanofiber and hydrophobic PLA fiberscan be uniformly dispersed in aqueous suspension [33]During the preblending process nanofibers are adsorbed onPLA fiber and entangled to form a net shape Therefore theformed electrostatic repulsion and steric hindrance betweennanofibers and PLA result in the uniform dispersion ofcellulosechitin nanofibers

From the SEM images it can be found that there aredistinct differences in the fiber diameter and length for foursamples The poplar CNFs in the PLA matrix are the mosthomogeneous having the lowest fiber diameter and highestlength These finer and longer fibers have higher resistanceto deformation under the vacuum applied and developgreater network strength The prawn shell CHNFsPLAsample is intermediate between the poplar sample and thecrab shellcotton samples as it contains some thicker fiberscompared to poplar CNFs but finer fibers compared to crabshellcotton nanofibers For the crab shellcotton nanofibersboth samples have some large fiber bundles thus the samplesare highly heterogeneousThis is because the strong hydrogenbonding between the nanofiber bundles makes it difficult toobtain thin and uniform nanofibers from crab shellcottonThe fiber bundles with low aspect ratio lead to relatively lowmechanical properties of the nanocomposites

Coefficient of Thermal Expansion (CTE) The reinforcementeffect of fibers can also be characterized to analyze thethermal expansion of plastics examined using the TMAAs reported thermal expansion has an inverse relationshipwith Youngrsquos modulus [33] The CTE values of four differentnanocomposites and sheets prepared by different raw mate-rials are presented in Figure 6 The CTE value of neat PLA isup to 180 times 10minus6 Kminus1 due to its amorphous flexible molecularchains (Figure 6(a)) The thermal expansion of PLA wasremarkably suppressed by the introduction of CHNFsCNFsThe CTE values of the composites with 40wt nanofibersextracted from poplar cotton crab shell and prawn shellare 695 times 10minus6 Kminus1 796 times 10minus6 Kminus1 772 times 10minus6 Kminus1 and753 times10minus6 Kminus1 respectively CNFsCHNFs with low CTEand high Youngrsquos modulus can effectively decrease the ther-mal expansion of PLA matrix due to the reinforcementeffect resulting from the suppression of the expansion forPLA matrix by the rigid three-dimensional nanostructuralnetworks of nanofibers at high temperature [34] On theother hand the reinforcement effect can be attributed to thehomogeneous dispersion of nanofibers in PLA matrix withthe water preblending method It can also be found thatthe poplar CNFsPLA composite shows the lowest thermalexpansion and the cotton CNFsPLA composite shows thehighest thermal expansion In addition it can be noticedthat the CTE value of the crab shell CHNFsPLA compositeis slightly lower than that of cotton CNFsPLA compositewhich is different from the result of mechanical proper-ties This phenomenon can be explained by the fact thatchitin nanofibers have higher thermal stability and highercrystallinity than cellulose nanofibers [14] Furthermore theCTE values of nanofibers sheets were measured in the sametemperature region From Figure 6(b) it can be seen thatCTE values of the sheetsmade from poplar cotton crab shelland prawn shell are 369 times 10minus6 Kminus1 457 times 10minus6 Kminus1 364 times


Nanofiber content ()50403020100

30

35

40

45

50

55

Tens

ile st

reng

th (M

Pa)

PoplarCottonCrab shell

Prawn shell

(a)


1500

2000

2500

3000

3500

4000

4500

Youn

grsquos m

odul

us (M

Pa)


Prawn shell

(b)


20

30

40

50

60

Flex

ural

stre

ngth

(MPa

)


Prawn shell

(c)


0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

Flex

ural

mod

ulus

(MPa

)


Prawn shell

(d)


0

5

10

15

20

25

30

35

40

45

50

Impa

ct to

ughn

ess (

Jm)


Prawn shell

(e)

Figure 4 The mechanical properties (a) tensile strength (b) Youngrsquos modulus (c) flexural strength (d) flexural modulus and (e) impacttoughness of four nanofibersPLA composites as functions of nanofiber content


10 m

(a)

10 m

(b)

10 m

(c)

10 m

(d)

Figure 5 The FE-SEM images of fracture surfaces for 40wt nanofibersPLA composites (a) poplar CNFs (b) cotton CNFs (c) crab shellCHNFs and (d) prawn shell CHNFs

Cotton Crab PrawnPoplarPLANanocomposite

0

20

40

60

80

100

120

140

160

180

CTE

(10minus6K

)

(a)Sheet

0

10

20

30

40

50

CTE

(10minus6K

)

Cotton Crab PrawnPoplar

(b)

Figure 6 CTE values of (a) nanofibersPLA composites and (b) nanofiber sheets

10minus6 Kminus1 and 321times 10minus6 Kminus1 respectively CHNFs sheets havelower thermal expansion than that of CNFs sheets Hence thecrab shell CHNFsPLA composite presents lower CTE valuethan the cotton CNFsPLA composite In addition it can benoticed that the CTE value of the crab shell CHNFs sheetis approximately equal to that of the poplar CNFs sheet butthe poplar CNFsPLA composite shows much lower thermalexpansion than that of crab shell CHNFsPLA composite

This result can be ascribed to the fact that poplar CNFshave much higher aspect ratio than the crab shell CHNFsleading to higher mechanical properties Therefore it can beconcluded that the aspect ratio of fibers has great influenceon the thermal expansion of the polymer matrix

DMA Dynamic mechanical test methods have been widelyemployed for investigating the structures and viscoelastic


Cotton CNFs

Crab shell CHNFs

Prawn shell CHNFs

Poplar CNFs

Pure PLA

Temperature (∘C)100806040200minus20

0

1000

2000

3000

4000

5000

6000

7000

8000

E

(MPa

)

(a)

Pure PLA

Cotton CNFs

Crab shell CHNFs

Poplar CNFs

Prawn shellCHNFs


00

01

02

03

04

05

06

Tg

(b)

Figure 7 Temperature dependence on (a) storage modulus (1198641015840) and (b) loss factor (tan 120575) of four nanofibersPLA composites at fiber contentof 40wt

behavior of polymeric materials to determine their stiff-ness and damping characteristics for various applicationsFigure 7 represents the plots of storage modulus (1198641015840) andloss factor (tan 120575) with respect to temperature for thefour nanofibersPLA composites In Figure 7(a) all thenanocomposites exhibit the storage modulus in the followingorder in the glassy region poplar CNFsPLA gt prawn shellCHNFsPLA gt crab shell CHNFsPLA gt cotton CNFsPLAThe storage modulus in the glassy state is primarily deter-mined by the strength of the intermolecular forces and theway of the polymer chains packed by fibers [35] High 1198641015840value can be attributed to the high interfacial adhesion andhigh aspect ratio of nanofibers which may be helpful tothe stress transfer in the nanofiber-matrix interface [36]tan 120575 is a dimensionless parameter that measures the ratioof loss modulus to storage modulus For fiberspolymercomposites the loss of energy mainly occurs on the interfaceof fibers and polymers thus high strength of compositesindicates the low energy loss and low tan 120575 [37] In contrastfour nanocomposites exhibit tan 120575 in the following order(Figure 7(b)) cotton CNFsPLA gt crab shell CHNFsPLAgt prawn shell CHNFsPLA gt poplar CNFs An increase intan 120575 among different composites indicates that the viscosityof the composite is improved The DMA results indicate thatthe aspect ratio of the nanofibers has a great influence onthe thermal and mechanical performance of the compositesirrespective of the composites prepared by cellulose or chitin

4 Conclusions

Polylactic acid (PLA) was reinforced with ultralong celluloseand chitin nanofibers extracted from four raw materialsby the extrusion molding The poplar CNFsPLA compos-ite exhibited the best mechanical properties among fournanocomposites while both the cottonCNFsPLA composite

and the crab shell CHNFsPLA composite had low mechan-ical strength Rheological measurement indicated that theviscosity and shear stress of the poplar CNFsPLA compositeare the highest among four samples and the correspondingvalues of the cottonPLA composite are the lowest FE-SEMimages showed that homogeneous dispersion of nanofibersin PLA matrix can be achieved with the water preblendingmethodThe CTE values of the nanocomposites with 40wtnanofibers extracted from poplar cotton crab shell andprawn shell were 695 times 10minus6 Kminus1 796 times 10minus6 Kminus1 772times 10minus6 Kminus1 and 753 times 10minus6 Kminus1 respectively The storagemodulus of four nanocomposites in the glassy region is listedin the following order poplar CNFsPLA gt prawn shellCHNFsPLA gt crab shell CHNFsPLA gt cotton CNFsPLAAll the results indicated that the aspect ratio of the nanofibershas a great influence on the performance of the compositesirrespective of the composites prepared by cellulose or chitin

Disclosure

Jingjing Li and Jian Li are co-first authors

Conflicts of Interest

The authors declare that there are no conflicts of interestregarding the publication of this manuscript

Authorsrsquo Contributions

Jingjing Li and Jian Li contributed equally to this work

Acknowledgments

This work is financially supported by PhD Start-up Fund ofNorthwest AampF University (Z109021613)


References

[1] I Armentano N Bitinis E Fortunati et al ldquoMultifunctionalnanostructured PLA materials for packaging and tissue engi-neeringrdquo Progress in Polymer Science vol 38 no 10-11 pp 1720ndash1747 2013

[2] M M Reddy S Vivekanandhan M Misra S K Bhatia andA K Mohanty ldquoBiobased plastics and bionanocompositescurrent status and future opportunitiesrdquo Progress in PolymerScience vol 38 no 10-11 pp 1653ndash1689 2013

[3] H Li and M A Huneault ldquoEffect of nucleation and plasticiza-tion on the crystallization of poly(lactic acid)rdquo Polymer Journalvol 48 no 23 pp 6855ndash6866 2007

[4] R Auras B Harte and S Selke ldquoAn overview of polylactides aspackaging materialsrdquo Macromolecular Bioscience vol 4 no 9pp 835ndash864 2004

[5] D Klemm BHeublein H P Fink andA Bohn ldquoCellulose fas-cinating biopolymer and sustainable rawmaterialrdquoAngewandteChemie vol 44 no 22 pp 3358ndash3393 2005

[6] I Sakurada Y Nukushina and T Ito ldquoExperimental determi-nation of the elastic modulus of crystalline regions in orientedpolymersrdquo Journal of Polymer Science vol 57 no 165 pp 651ndash660 1962

[7] T Nishino I Matsuda and K Hirao ldquoAll-cellulose compositerdquoMacromolecules vol 37 no 20 pp 7683ndash7687 2004

[8] J Jin P Hassanzadeh G Perotto et al ldquoA biomimetic compositefrom solution self-assembly of chitin nanofibers in a silk fibroinmatrixrdquo Advanced Materials vol 25 no 32 pp 4482ndash44872013

[9] J-B Zeng Y-S He S-L Li and Y-Z Wang ldquoChitin whiskersAn overviewrdquo Biomacromolecules vol 13 no 1 pp 1ndash11 2012

[10] W Chen K Abe K Uetani H Yu Y Liu and H Yano ldquoIndi-vidual cotton cellulose nanofibers pretreatment and fibrillationtechniquerdquo Cellulose vol 21 no 3 pp 1517ndash1528 2014

[11] P Dhar D Tarafder A Kumar and V Katiyar ldquoThermallyrecyclable polylactic acidcellulose nanocrystal films throughreactive extrusion processrdquo Polymer (United Kingdom) vol 87pp 268ndash282 2016

[12] A N Frone S Berlioz J-F Chailan and D M PanaitesculdquoMorphology and thermal properties of PLA-cellulosenanofibers compositesrdquo Carbohydrate Polymers vol 91 no 1pp 377ndash384 2013

[13] N Herrera A P Mathew and K Oksman ldquoPlasticizedpolylactic acidcellulose nanocomposites prepared using melt-extrusion and liquid feeding Mechanical thermal and opticalpropertiesrdquo Composites Science and Technology vol 106 pp149ndash155 2015

[14] N Herrera A M Salaberria A P Mathew and K OksmanldquoPlasticized polylactic acid nanocomposite films with celluloseand chitin nanocrystals prepared using extrusion and compres-sion molding with two cooling rates Effects on mechanicalthermal and optical propertiesrdquo Composites Part A AppliedScience and Manufacturing vol 83 pp 89ndash97 2016

[15] M Jonoobi J Harun A P Mathew and K Oksman ldquoMechani-cal properties of cellulose nanofiber (CNF) reinforced polylacticacid (PLA) prepared by twin screw extrusionrdquo CompositesScience and Technology vol 70 no 12 pp 1742ndash1747 2010

[16] M Kowalczyk E Piorkowska P Kulpinski and M PracellaldquoMechanical and thermal properties of PLA composites withcellulose nanofibers and standard size fibersrdquo Composites PartA Applied Science and Manufacturing vol 42 no 10 pp 1509ndash1514 2011

[17] L Suryanegara A N Nakagaito and H Yano ldquoThe effect ofcrystallization of PLA on the thermal and mechanical prop-erties of microfibrillated cellulose-reinforced PLA compositesrdquoComposites Science and Technology vol 69 no 7-8 pp 1187ndash1192 2009

[18] A N Nakagaito K Yamada S Ifuku M Morimoto and HSaimoto ldquoFabrication of chitin nanofiber-reinforced polylacticacid nanocomposites by an environmentally friendly processrdquoJournal of Biobased Materials and Bioenergy vol 7 no 1 pp152ndash156 2013

[19] L Tang B Huang N Yang et al ldquoOrganic solvent-free andefficient manufacture of functionalized cellulose nanocrystalsvia one-pot tandem reactionsrdquo Green Chemistry vol 15 no 9pp 2369ndash2373 2013

[20] A M Salaberria J Labidi and S C M Fernandes ldquoChitinnanocrystals and nanofibers as nano-sized fillers into thermo-plastic starch-based biocomposites processed by melt-mixingrdquoChemical Engineering Journal vol 256 pp 356ndash364 2014

[21] R Rizvi B CochraneHNaguib andPC Lee ldquoFabrication andcharacterization of melt-blended polylactide-chitin compositesand their foamsrdquo Journal of Cellular Plastics vol 47 no 3 pp283ndash300 2011

[22] J Li D Li Z Song S Shang and Y Guo ldquoPreparation andproperties of wood plastic composite reinforced by ultralongcellulose nanofibersrdquo Polymer Composites vol 37 no 4 pp1206ndash1215 2016

[23] J Li Z Song D Li S Shang and Y Guo ldquoCotton cellu-lose nanofiber-reinforced high density polyethylene compositesprepared with two different pretreatment methodsrdquo IndustrialCrops and Products vol 59 pp 318ndash328 2014

[24] J Li Y Gao J Zhao J Sun and D Li ldquoHomogeneousdispersion of chitin nanofibers in polylactic acid with differentpretreatment methodsrdquo Cellulose vol 24 no 4 pp 1705ndash17152017

[25] W Chen Q Li Y Wang et al ldquoComparative study of aerogelsobtained fromdifferently prepared nanocellulose fibersrdquoChem-SusChem vol 7 no 1 pp 154ndash161 2014

[26] S Ifuku and H Saimoto ldquoChitin nanofibers Preparationsmodifications and applicationsrdquo Nanoscale vol 4 no 11 pp3308ndash3318 2012

[27] C Miao and W Y Hamad ldquoCellulose reinforced polymercomposites and nanocomposites a critical reviewrdquo Cellulosevol 20 no 5 pp 2221ndash2262 2013

[28] A N Frone S Berlioz J-F Chailan D M Panaitescu and DDonescu ldquoCellulose fiber-reinforced polylactic acidrdquo PolymerComposites vol 32 no 6 pp 976ndash985 2011

[29] P Qu Y Gao G-F Wu and L-P Zhang ldquoNanocomposites ofpoly(lactic acid) reinforced with cellulose nanofibrilsrdquo Biore-sources vol 5 no 3 pp 1811ndash1823 2010

[30] R M Rowell J S Han and J S Rowell ldquoCharacterizationand factors effecting fiber propertiesrdquo in Natural Polymers andAgrofibers Composites pp 115ndash134 2000

[31] N M Stark and R E Rowlands ldquoEffects of wood fiber char-acteristics on mechanical properties of woodpolypropylenecompositesrdquoWood and Fiber Science vol 35 no 2 pp 167ndash1742003

[32] J K Sameni S H Ahmad and S Zakaria ldquoEffects of processingparameters and graft-copoly(propylenemaleic anhydride) onmechanical properties of thermoplastic natural rubber com-posites reinforced with wood fibresrdquo Plastics Rubber andComposites vol 31 no 4 pp 162ndash166 2002


[33] A N Nakagaito and H Yano ldquoThe effect of fiber content on themechanical and thermal expansion properties of biocompositesbased on microfibrillated celluloserdquo Cellulose vol 15 no 4 pp555ndash559 2008

[34] H Yousefi M Faezipour S Hedjazi M M Mousavi Y Azusaand A H Heidari ldquoComparative study of paper and nanopaperproperties prepared from bacterial cellulose nanofibers andfibersground cellulose nanofibers of canola strawrdquo IndustrialCrops and Products vol 43 no 1 pp 732ndash737 2013

[35] L A Pothan Z Oommen and S Thomas ldquoDynamic mechan-ical analysis of banana fiber reinforced polyester compositesrdquoComposites Science and Technology vol 63 no 2 pp 283ndash2932003

[36] M M Andrade-Mahecha F M Pelissari D R Tapia-Blacidoand F CMenegalli ldquoAchira as a source of biodegradablemateri-als isolation and characterization of nanofibersrdquo CarbohydratePolymers vol 123 pp 406ndash415 2015

[37] P Zugenmaier ldquoMaterials of cellulose derivatives and fiber-reinforced cellulose-polypropylene composites Characteriza-tion and applicationrdquo Pure and Applied Chemistry vol 78 no10 pp 1843ndash1855 2006

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



Cellulose nanomaterials have been extensively used asan additive to improve the thermal mechanical and barrierproperties of PLA [11ndash17] However most of the literaturehas focused on the NCC or MCC (microcrystal cellulose)reinforced PLA composites There is a lack of study on theCNFs with high aspect ratio reinforced PLA composites dueto the dispersion problem of the ultralong CNFs In additionchitin nanofibers are mainly used in other polymers such aspoly (caprolactone) chitosan PVA PMMA and starch [14]while the research on chitin nanofibers reinforced PLA is veryrare [18]

Although CNFs and CHNFs have great potential as rein-forcements the uniform dispersion in polymer matrix is themajor challenge It is well known that materials in nanosizehave a strong tendency to aggregate In addition the stronghydrogen bonds form when cellulose and chitin are driedleading to the aggregation problem To overcome the disper-sion and compatibility difficulties cellulosechitin nanofibershave been subjected to physical treatments and chemicalmodification [19] However the mechanical properties ofthe prepared nanocomposites are not remarkably improveddue to the damaged molecular structure of nanofibers bychemical modification

Until now the preparation of CNFsCHNFs reinforcedpolymer composites is mainly focused on the methodsof solvent casting freeze-drying and electrospinning Thedevelopment of more flexible and viable processing tech-niques for industrial applications is needed to promote thecommercialization of nanofibers-based composites Amongthe processing techniques the melt-compounding process isthemost potential technique since the final product preparedby this technique can be easily shaped [13] However there areonly very few studies on the nanocomposite prepared by themelt-compounding technique especially in the case of chitinnanofibers [20 21]

In this study four different CNFsCHNFs reinforced PLAcomposites were prepared using the extrusion process TheCNFsCHNFs were extracted from the raw materials ofpoplar flour cotton crab shell and prawn shell All theisolated CNFsCHNFs showed network structure and highaspect ratio The effects of fiber morphology on the mechan-ical thermal and viscoelastic properties of the preparednanocomposites were comparatively investigated to evaluatethe reinforcing effect of CNFs and CHNFs To solve the dis-persion problem of ultralong CNFsCHNFs in PLA matrixthe PLA powders were premixed with the CNFsCHNFswater slurry followed by freeze-drying before the nanocom-posites were extruded This process is a time-saving andenvironmentally friendly method due to the absence ofchemical reagent

2 Materials and Methods

21 Materials Polylactic acid (PLA) NatureWorks TM4032D was supplied by Nanjing Jufeng Advanced MaterialsCo Ltd (Nanjing China) The glass transition temperature(119879119892) and melting point (119879119898) were 55∘C and 180∘C respec-tively The melt flow index (MFI) was 6 g10min (190∘C

216 kg) The poplar flour with the size of 60ndash80mesh wasobtained from Nanjing Jufeng Advanced Materials Co Ltd(Nanjing China) Absorbent cotton medical grade waspurchased from Beijing Tianheng BohaoMedical EquipmentCo Ltd (Beijing China) Dried crab shell powder and prawnshell powder were obtained from Golden Shell BiochemicalCo Ltd (Zhejiang China) The other chemicals and dis-tilled water were purchased from Nanjing Chemical ReagentCompany and used without further purification in this study(Nanjing China)

22 Preparation of Poplar CNFs Based on our previouslyreported methods [22] the preparation procedure of poplarCNFs was mainly divided into chemical pretreatment andgrinding nanofibrillationAfter chemical treatment thewaterslurry with 1 wt CNFs was passed through a grinder(MKCA6-2 Masuko Sangyo Co Japan) for 20 times with thegrinding stone at 1800 rpm

23 Preparation of Cotton CNFs The preparation of cottonCNFs was conducted according to our previously reportedmethods [23] The extraction process of cotton CNFs wassimpler than that of poplar CNFs due to higher cellulosecontent in cotton

24 Preparation of CrabPrawn CHNFs Crabprawn shellsare composed of chitin and some other constituents such asproteins lipids calcium carbonate and pigmentsThe chem-ical treatment of crabprawn shell was conducted accordingto our previously reported methods [24] Finally a watersuspension with 1 wt CHNFs was passed through thegrinder for 20 times with the grinding stone at 1800 rpm

25 Preparation of NanofibersPLA Composites Beforethe extrusion process different contents of PLA powders(60ndash80mesh) were added to the 1 wt CNFsCHNFs waterslurry and were continuously stirred by a magnetic stirrerat 75∘C for 1 h After the water preblending process themixture slurry was dehydrated by vacuum filtration using aBuchner funnel and then was freeze-dried Subsequently thenanofibersPLAmixturewas fully broken using a blender andfed into a HAAKE MiniLab (HAAKE MiniLab II ThermoFisher Scientific Germany) for compounding The HAAKEMiniLab is a small twin screw extruder for laboratory useThe samples were extruded through a rectangular die withthe sectional dimension of 35 times 1mm2 The samples werecrushed into powder by a blender and then hot-pressed at170∘C for 5min with a press vulcanizer

26 Characterization

CelluloseChitin Nanofibers

FE-SEM The morphologies of four different nanofibers wereobserved using a field emission scanning electronmicroscope(HITACHI S-4860 HITACHI Japan) Prior to FE-SEMobservations the samples were kept in a vacuum oven at30∘Covernight and then coatedwith gold for 30ndash60 s to avoid


















1 m

(a)

1 m

(b)

1 m

(c)

1 m

(d)








10

20

30

40

50

60

70

Rate

()

(a)



0

10

20

30

40

50

60

Rate

()

(b)



0

10

20

30

40

50

60

Rate

()

(c)



0

10

20

30

40

50

60

Rate

()

(d)







200

400

600

800

1000

1200

14001600


Poplar CNFsPure PLA

Visc

osity

(Pamiddot

s)

(a)


40000

60000

80000

100000

120000

Shea

r stre

ss (P

a)


Poplar CNFsPure PLA

(b)







30

35

40

45

50

55

Tens

ile st

reng

th (M

Pa)


Prawn shell

(a)


1500

2000

2500

3000

3500

4000

4500

Youn

grsquos m

odul

us (M

Pa)


Prawn shell

(b)


20

30

40

50

60

Flex

ural

stre

ngth

(MPa

)


Prawn shell

(c)


0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

Flex

ural

mod

ulus

(MPa

)


Prawn shell

(d)


0

5

10

15

20

25

30

35

40

45

50

Impa

ct to

ughn

ess (

Jm)


Prawn shell

(e)



10 m

(a)

10 m

(b)

10 m

(c)

10 m

(d)



0

20

40

60

80

100

120

140

160

180

CTE

(10minus6K

)

(a)Sheet

0

10

20

30

40

50

CTE

(10minus6K

)


(b)






Cotton CNFs

Crab shell CHNFs

Prawn shell CHNFs

Poplar CNFs

Pure PLA


0

1000

2000

3000

4000

5000

6000

7000

8000

E

(MPa

)

(a)

Pure PLA

Cotton CNFs

Crab shell CHNFs

Poplar CNFs

Prawn shellCHNFs


00

01

02

03

04

05

06

Tg

(b)



4 Conclusions



Disclosure






Acknowledgments



References














































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of



















1 m

(a)

1 m

(b)

1 m

(c)

1 m

(d)








10

20

30

40

50

60

70

Rate

()

(a)



0

10

20

30

40

50

60

Rate

()

(b)



0

10

20

30

40

50

60

Rate

()

(c)



0

10

20

30

40

50

60

Rate

()

(d)







200

400

600

800

1000

1200

14001600


Poplar CNFsPure PLA

Visc

osity

(Pamiddot

s)

(a)


40000

60000

80000

100000

120000

Shea

r stre

ss (P

a)


Poplar CNFsPure PLA

(b)







30

35

40

45

50

55

Tens

ile st

reng

th (M

Pa)


Prawn shell

(a)


1500

2000

2500

3000

3500

4000

4500

Youn

grsquos m

odul

us (M

Pa)


Prawn shell

(b)


20

30

40

50

60

Flex

ural

stre

ngth

(MPa

)


Prawn shell

(c)


0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

Flex

ural

mod

ulus

(MPa

)


Prawn shell

(d)


0

5

10

15

20

25

30

35

40

45

50

Impa

ct to

ughn

ess (

Jm)


Prawn shell

(e)



10 m

(a)

10 m

(b)

10 m

(c)

10 m

(d)



0

20

40

60

80

100

120

140

160

180

CTE

(10minus6K

)

(a)Sheet

0

10

20

30

40

50

CTE

(10minus6K

)


(b)






Cotton CNFs

Crab shell CHNFs

Prawn shell CHNFs

Poplar CNFs

Pure PLA


0

1000

2000

3000

4000

5000

6000

7000

8000

E

(MPa

)

(a)

Pure PLA

Cotton CNFs

Crab shell CHNFs

Poplar CNFs

Prawn shellCHNFs


00

01

02

03

04

05

06

Tg

(b)



4 Conclusions



Disclosure






Acknowledgments



References














































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of



1 m

(a)

1 m

(b)

1 m

(c)

1 m

(d)








10

20

30

40

50

60

70

Rate

()

(a)



0

10

20

30

40

50

60

Rate

()

(b)



0

10

20

30

40

50

60

Rate

()

(c)



0

10

20

30

40

50

60

Rate

()

(d)







200

400

600

800

1000

1200

14001600


Poplar CNFsPure PLA

Visc

osity

(Pamiddot

s)

(a)


40000

60000

80000

100000

120000

Shea

r stre

ss (P

a)


Poplar CNFsPure PLA

(b)







30

35

40

45

50

55

Tens

ile st

reng

th (M

Pa)


Prawn shell

(a)


1500

2000

2500

3000

3500

4000

4500

Youn

grsquos m

odul

us (M

Pa)


Prawn shell

(b)


20

30

40

50

60

Flex

ural

stre

ngth

(MPa

)


Prawn shell

(c)


0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

Flex

ural

mod

ulus

(MPa

)


Prawn shell

(d)


0

5

10

15

20

25

30

35

40

45

50

Impa

ct to

ughn

ess (

Jm)


Prawn shell

(e)



10 m

(a)

10 m

(b)

10 m

(c)

10 m

(d)



0

20

40

60

80

100

120

140

160

180

CTE

(10minus6K

)

(a)Sheet

0

10

20

30

40

50

CTE

(10minus6K

)


(b)






Cotton CNFs

Crab shell CHNFs

Prawn shell CHNFs

Poplar CNFs

Pure PLA


0

1000

2000

3000

4000

5000

6000

7000

8000

E

(MPa

)

(a)

Pure PLA

Cotton CNFs

Crab shell CHNFs

Poplar CNFs

Prawn shellCHNFs


00

01

02

03

04

05

06

Tg

(b)



4 Conclusions



Disclosure






Acknowledgments



References














































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of






10

20

30

40

50

60

70

Rate

()

(a)



0

10

20

30

40

50

60

Rate

()

(b)



0

10

20

30

40

50

60

Rate

()

(c)



0

10

20

30

40

50

60

Rate

()

(d)







200

400

600

800

1000

1200

14001600


Poplar CNFsPure PLA

Visc

osity

(Pamiddot

s)

(a)


40000

60000

80000

100000

120000

Shea

r stre

ss (P

a)


Poplar CNFsPure PLA

(b)







30

35

40

45

50

55

Tens

ile st

reng

th (M

Pa)


Prawn shell

(a)


1500

2000

2500

3000

3500

4000

4500

Youn

grsquos m

odul

us (M

Pa)


Prawn shell

(b)


20

30

40

50

60

Flex

ural

stre

ngth

(MPa

)


Prawn shell

(c)


0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

Flex

ural

mod

ulus

(MPa

)


Prawn shell

(d)


0

5

10

15

20

25

30

35

40

45

50

Impa

ct to

ughn

ess (

Jm)


Prawn shell

(e)



10 m

(a)

10 m

(b)

10 m

(c)

10 m

(d)



0

20

40

60

80

100

120

140

160

180

CTE

(10minus6K

)

(a)Sheet

0

10

20

30

40

50

CTE

(10minus6K

)


(b)






Cotton CNFs

Crab shell CHNFs

Prawn shell CHNFs

Poplar CNFs

Pure PLA


0

1000

2000

3000

4000

5000

6000

7000

8000

E

(MPa

)

(a)

Pure PLA

Cotton CNFs

Crab shell CHNFs

Poplar CNFs

Prawn shellCHNFs


00

01

02

03

04

05

06

Tg

(b)



4 Conclusions



Disclosure






Acknowledgments



References














































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of




200

400

600

800

1000

1200

14001600


Poplar CNFsPure PLA

Visc

osity

(Pamiddot

s)

(a)


40000

60000

80000

100000

120000

Shea

r stre

ss (P

a)


Poplar CNFsPure PLA

(b)







30

35

40

45

50

55

Tens

ile st

reng

th (M

Pa)


Prawn shell

(a)


1500

2000

2500

3000

3500

4000

4500

Youn

grsquos m

odul

us (M

Pa)


Prawn shell

(b)


20

30

40

50

60

Flex

ural

stre

ngth

(MPa

)


Prawn shell

(c)


0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

Flex

ural

mod

ulus

(MPa

)


Prawn shell

(d)


0

5

10

15

20

25

30

35

40

45

50

Impa

ct to

ughn

ess (

Jm)


Prawn shell

(e)



10 m

(a)

10 m

(b)

10 m

(c)

10 m

(d)



0

20

40

60

80

100

120

140

160

180

CTE

(10minus6K

)

(a)Sheet

0

10

20

30

40

50

CTE

(10minus6K

)


(b)






Cotton CNFs

Crab shell CHNFs

Prawn shell CHNFs

Poplar CNFs

Pure PLA


0

1000

2000

3000

4000

5000

6000

7000

8000

E

(MPa

)

(a)

Pure PLA

Cotton CNFs

Crab shell CHNFs

Poplar CNFs

Prawn shellCHNFs


00

01

02

03

04

05

06

Tg

(b)



4 Conclusions



Disclosure






Acknowledgments



References














































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of




30

35

40

45

50

55

Tens

ile st

reng

th (M

Pa)


Prawn shell

(a)


1500

2000

2500

3000

3500

4000

4500

Youn

grsquos m

odul

us (M

Pa)


Prawn shell

(b)


20

30

40

50

60

Flex

ural

stre

ngth

(MPa

)


Prawn shell

(c)


0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

Flex

ural

mod

ulus

(MPa

)


Prawn shell

(d)


0

5

10

15

20

25

30

35

40

45

50

Impa

ct to

ughn

ess (

Jm)


Prawn shell

(e)



10 m

(a)

10 m

(b)

10 m

(c)

10 m

(d)



0

20

40

60

80

100

120

140

160

180

CTE

(10minus6K

)

(a)Sheet

0

10

20

30

40

50

CTE

(10minus6K

)


(b)






Cotton CNFs

Crab shell CHNFs

Prawn shell CHNFs

Poplar CNFs

Pure PLA


0

1000

2000

3000

4000

5000

6000

7000

8000

E

(MPa

)

(a)

Pure PLA

Cotton CNFs

Crab shell CHNFs

Poplar CNFs

Prawn shellCHNFs


00

01

02

03

04

05

06

Tg

(b)



4 Conclusions



Disclosure






Acknowledgments



References














































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of



10 m

(a)

10 m

(b)

10 m

(c)

10 m

(d)



0

20

40

60

80

100

120

140

160

180

CTE

(10minus6K

)

(a)Sheet

0

10

20

30

40

50

CTE

(10minus6K

)


(b)






Cotton CNFs

Crab shell CHNFs

Prawn shell CHNFs

Poplar CNFs

Pure PLA


0

1000

2000

3000

4000

5000

6000

7000

8000

E

(MPa

)

(a)

Pure PLA

Cotton CNFs

Crab shell CHNFs

Poplar CNFs

Prawn shellCHNFs


00

01

02

03

04

05

06

Tg

(b)



4 Conclusions



Disclosure






Acknowledgments



References














































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of



Cotton CNFs

Crab shell CHNFs

Prawn shell CHNFs

Poplar CNFs

Pure PLA


0

1000

2000

3000

4000

5000

6000

7000

8000

E

(MPa

)

(a)

Pure PLA

Cotton CNFs

Crab shell CHNFs

Poplar CNFs

Prawn shellCHNFs


00

01

02

03

04

05

06

Tg

(b)



4 Conclusions



Disclosure






Acknowledgments



References














































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of



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


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