【Transaction Manufacture,Characterization ...

1. Introduction

Serious global environmental problems such asmarine plastic litter and global warming areattracting increasing attention. The problems causedby processing and wasting petroleum-derived plasticsare of major concern. To solve this issue, themanufacture of bio-based plastics derived fromnatural resources has been investigated, because suchplastics are biodegradable and readily reproduced.

Polysaccharides consisting of glucose with α- orβ-glucoside linkages are one of the expected rawresources for bio-based plastics. Cellulose is the mostabundant polysaccharide, and comprises linear β-1,4-glucan. Cellulose triacetate (CTA) is a well-knowncellulose derivative that is widely used in opticalmaterials owing to its extraordinary transparencyand excellent heat resistance.[1‒3] The thermal andmechanical properties of other cellulose ester

derivatives have already been reported.[4,5] However,owing to the poor thermal fluidity caused by rigidmainchain structures, a plasticizer is required whenheat-molding CTA-based materials.[6,7] Otherwise, anorganic solvent is adopted for manufacturing thematerials. Therefore, there is a demand for otherpolysaccharide - based materials with goodthermoformability.

Paramylon is a linear β-1,3-glucan that isphotosynthesized by Euglena.[8] In our previous study,we fabricated fully substituted paramylon esters withvarious numbers of carbon atoms and ester groups.[9]Paramylon esters with C2-C6 alkyl side chains arecrystalline polymers with melting temperatures of114 to 281 ̊C. In particular, those with C3-C5 alkylside-chains have good thermal fluidity, which allowsthem to form self-standing films. Such films can bemanufactured by melt - quenching, and havecomparable tensile properties to generally used

【Transaction】

# corresponding author: Tadahisa Iwata (E-mail: [email protected])

Abstract: Paramylon̶a β-1,3-glucan photoproduced by Euglena̶is a promising raw material for bio-basedplastics. Three kinds of paramylon ester derivatives̶paramylon propionate (PaPr), paramylon butyrate(PaBu), and paramylon valerate (PaVa)̶were synthesized to manufacture melt-spun fibers. The meltprocessing temperatures were determined by combining differential scanning calorimetry (DSC) and a meltflow test. The molecular orientation, crystallinity, and tensile properties of the melt-spun fibers wereinvestigated using a polarized optical microscope (POM), wide-angle X-ray diffraction (WAXD), and tensiletesting, respectively. The POM revealed that the PaPr molecular chains were aligned along the spinningdirection, despite variation in the take-up rate. However, WAXD confirmed that crystallization only occurredin PaPr fibers spun at a higher take-up rate of over 108 m/min, suggesting that crystallization is induced byhigh shearing force. This phenomenon seems to be due to the rigid mainchain structure consisting of pyranoserings. With further annealing of the PaPr fibers, the tensile strength increased with an increase in crystallinity.These tendencies were also observed in the PaBu and PaVa melt-spun fibers. The melt-spun fibers ofparamylon ester derivatives were manufactured from powders without any additives.

(Received 16 December, 2019; Accepted 17 February, 2020)

J. Fiber Sci. Technol., 76(5), 151-160 (2020)doi 10.2115/fiberst.2020-0018©2020 The Society of Fiber Science and Technology, Japan

Manufacture, Characterization, and Structure Analysisof Melt-Spun Fibers Derived from Paramylon Esters

Hongyi Gan＊1, Taizo Kabe＊1,2, and Tadahisa Iwata＊1,#＊1Science of Polymeric Materials, Graduate School of Agricultural and Life Sciences, The University of Tokyo,

1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan＊2Materials Structure Group I, The Research and Utilization Division, Japan Synchrotron Radiation Research Institute (JASRI),

1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan

Journal of Fiber Science and Technology (JFST), Vol.76, No. 5 (2020) 151

plastics such as polyethylene (PE) and polypropylene(PP). Besides, Shibakami et al. have reported the use ofshort- and long-chain mixed esters of paramylon,which have precisely controllable physical properties.[10‒13]

Plastic materials are required for the formation offilms and the manufacture of other forms such asfibers and molded articles. Therefore, the fabricationof fibers by melt spinning paramylon propionate(PaPr, C3), paramylon butyrate (PaBu, C4), andparamylon valerate (PaVa, C5) has been considered.

In the present study, the melt spinnabilities ofPaPr, PaBu, and PaVa were determined by meltspinning the polymers into fibers. In the case of PaPrin particular, the take-up rate during spinning wasadjusted and the obtained fibers were subsequentlyannealed, with the aim of controlling the crystallinityof the fibers. By combining wide-angle X-raydiffraction (WAXD) and tensile testing, it was possibleto determine the relationship between thecrystallinity and the tensile properties of the PaPrfibers.

2. Materials and methods

2.1 MaterialsParamylon was purchased from the Euglena Co.

(Tokyo, Japan). Trifluoroacetic anhydride (TFAA),propionic acid, butyric acid, and valeric acid werepurchased from Wako Pure Chemicals (Tokyo, Japan),and were used without further purification.2.2 Synthesis of the paramylon esters

Paramylon propionate (PaPr, n = 3), paramylonbutyrate (PaBu, n = 4), and paramylon valerate (PaVa,n = 5) were synthesized using trifluoroaceticanhydride (TFAA) and the corresponding carboxylicacids, as shown in Fig. 1. The representative

procedure for the synthesis of PaPr was as follows. Apremixed solution of TFAA (80 mL) and propionicacid (40 mL) was stirred at 50 ̊C for 5 min, thenimmediately added to a flask containing pre-driedparamylon (2 g). The solution was stirred at 50 ̊C for1.0 h. After cooling to room temperature of 25 ̊C, thesolution was poured into a mixture of water andmethanol (1.5 L). The resulting precipitate was thenfiltered and washed with methanol, dissolved inchloroform (100 mL), and reprecipitated in a mixtureof methanol and water (1.5 L). Finally, the precipitatewas washed with methanol, filtered, and dried in vacuoto yield solid paramylon propionate (PaPr). The otherparamylon esters were produced using the sameprocedure, except with the appropriate carboxylicacid (40 mL) instead of propionic acid. The yields (%)of the obtained PaPr, PaBu, and PaVa were 76%, 88%,and 80%, respectively. The degree of substitution (DS)of the paramylon esters was determined by protonnuclear magnetic resonance (1H-NMR), and each had aDS of 3.2.3 Differential scanning calorimetry (DSC) analysisof PaPr, PaBu, and PaVa powdersDifferential scanning calorimetry ( DSC )

thermograms of PaPr, PaBu, and PaVa powders wererecorded on a DSC 8500 system (Perkin Elmer) undera nitrogen atmosphere to determine their meltingbehaviors. The measurements were performed using2‒4-mg samples on a DSC pan. The samples were firstheated from 30 ̊C to 250 ̊C at a rate of 20 ̊C/min asthe first run, then cooled from 250 ̊C to -50 ̊C at arate of 200 ̊C/min. Finally, they were scanned whilstheating from -50 ̊C to 250 ̊C at a rate of 20 ̊C/min asa second run.2.4 Melt flow test

The samples were tested in powder form. Themelt flow tests were conducted using a CFT-500EX

Fig. 1 Scheme illustrating the synthesis of paramylon propionate (PaPr), Paramylon butyrate(PaBu), and paramylon valerate (PaVa).

152 Journal of Fiber Science and Technology (JFST), Vol.76, No. 5 (2020)

Flowtester (Shimadzu, Japan) to determine theprocess temperatures combined with the DSC results.The non-isothermal mode was used starting from30 ̊C at a rate of 5 ̊C/min. A constant load of10 kilogram-force (kgf) was applied to each sample,and the diameter and effective length of the die wereboth 1.0 mm. The melting temperatures were definedby the offset method at 5.0 mm, and the temperaturesat the start of flow were recorded. Fig. 2 is aschematic diagram describing the melt flow test. Theoffset temperature at 5.0 mm is the temperature atwhich the polymer in the heated barrel can beextruded 5.0 mm from the die.

2.5 Melt spinningMelt spinning was performed using a system

comprising a melt indexer (IMC-19F8, Imoto, Japan)and a customized spinning apparatus. Paramylonesters in powder form were used for melt spinning.For the melt indexer, the diameter and L/D ratio ofthe die were 1.0 mm and 2, respectively. The polymerwas first placed in the indexer (which was set to theprocessing temperature), melted for 3 min, thenextruded at a rate of 0.5 mm/s (the descent speed ofthe extruded bar). The initial part of the extrudedpolymer was quenched in air and pasted on a roller,which was part of the spinning apparatus. Thedistance between the die and the roller was set at 40mm. The take-up rate of the spinning apparatus couldbe varied between 50 and 500 rpm. In the presentstudy, four take-up rates were established: 50, 100, 300,and 500 rpm. The diameter of the roller was 114.5 mm.Therefore, the calculated take-up rates of 50, 100, 300,and 500 rpm corresponded to 18, 36, 108, and180 m/min, respectively.2.6 Gel permeation chromatography (GPC)

The number- and weight-average molecular

weights (Mn and Mw), and the polydispersity indexvalues (Mw/Mn) were estimated by GPC using a RID-20A refractive index detector (Shimadzu) inchloroform at 40 ̊C. Shodex columns (K-806 M, K-802)were used at a flow rate of 0.8 mL/min, and acalibration curve was constructed using polystyrene(PS) standards (Shodex).2.7 Annealing treatment of the melt-spun fibers

To investigate the influence of crystallinity, thePaPr fibers were fixed and further annealed in athermostatic oven at 150 ̊C for 30 min.2.8 Polarized optical microscope ( POM )investigationsAn ECLIPSE E 600 polarized optical microscope

(Nikon, Japan) equipped with a DFC 450 charge-coupled device camera (Leica) was used to determinethe orientation and diameters of the fibers. Themagnification was set at 10 times. A sensitive colorplate was inserted during the examination.2.9 WAXD analysis of the melt-spun fibers

Two-dimensional WAXD measurements of thefibers were obtained using a MicroMax-007 HFsystem (Rigaku MicroMax-007 HF) operating at 40 kVand 30 mA with Cu Kα radiation (λ = 0.15418 nm).Each X-ray fiber pattern was recorded on an imagingplate (Fujifilm Corp.; 2540 × 2540 pixels, 50 × 50 µm2

pixel-1), and read using a RAXIA-Di system (RigakuCorp.). The sample-to-detector distance was set atapproximately 83 mm. The sample holder and thedetector were set in a vacuum chamber. Siliconpowder was used as a standard sample, and themeasurements were obtained at room temperature.Two - dimensional fiber pattern analysis andconversion to a one-dimensional powder pattern wasperformed using 2DP software (Rigaku Corp.). Someof the measurements were also carried out usingbeamlines BL40B2 and BL03XU of the SPring-8(Harima, Japan) at a wavelength of 0.1 nm.2.10 Tensile tests on the melt-spun fibers

The tensile tests were performed at roomtemperature using an EZ-test machine (Shimadzu,Japan) equipped with a 10 N load cell. The crossheadtension speed was 10 mm/min, and the initial gaugelength was 10 mm. The fibers were assumed to becylindrical, and their diameters were measured usingthe POM mentioned in section 2.8. Approximately fivespecimens of the melt-spun fibers were used for eachmeasurement, and the data were averaged for eachfiber.

Fig. 2 Schematic diagram of melt flow test.


3. Results and discussion

3.1 Thermal and melt-flow propertiesThe melting behaviors and the melt flow

properties of PaPr, PaBu, and PaVa were evaluatedby DSC analysis and melt flow tests, respectively. Fig.3 shows the DSC heat flow curves at the 1st and 2ndstages of heating. The glass transition temperatures,the crystallization temperatures, and the meltingtemperatures are summarized in Table 1. PaPr hadtwo melting temperatures (Tm1 and Tm2) in the 1 ststage of the heating process, which were alsoobserved in the DSC heat flow curves of a PaPrsolvent-cast film in our previous research.[9] The twomelting temperatures of PaPr indicate crystallinepolymorphism. Two melting peaks have also beenobserved for curdlan propionate.[14] Curdlan is amicrobial polysaccharide with the same chemicalstructure as paramylon but with a higher molecularweight.[15] Marubayashi et al. found that the lowermelting peak was attributable to a six-fold helicalstructure (form I), whereas the higher melting peakwas attributable to a five-fold helical structure (formII).[16] Only form II existed in the melt-spun PaPrfibers investigated in the present study, as proved byWAXD in section 3.3. By increasing the carbonnumber of the ester groups from PaPr to PaVa, the

melting temperature and glass transitiontemperature decreased from 220 to 170 ̊C, and from114 to 55 ̊C, respectively.

The stroke ‒ temperature and viscosity ‒temperature curves of PaPr, PaBu, and PaVaobtained from the melt flow test are shown in Fig. 4aand 4b, respectively. The flow-starting temperaturesand the melt flow temperatures determined by offsetat 5.00 mm are given in Table 1. The stroke at theflow-starting temperature was set as the referenceposition. The temperature at which there was 5-mmshift of the polymer from the reference position wasdefined as the offset temperature. In Fig. 4a, all thesamples exhibit a similar growth tendency in whichthe change of the stroke can be divided into tworegions. In the first region, the stroke increasesslightly between the glass transition temperature andthe melting temperature detected by DSC analysis,which represents the minor flow of the molecularchains under the constant load. In the second regionabove the melting temperature, the stroke increasesdrastically compared with region I, and is recognizedas the melt flow temperature of the polymer. Inaddition, the flow-starting temperatures of the threeparamylon esters are close to the meltingtemperatures from DSC analysis. Thus, the melt-flowbehaviors and temperatures from the melt-flow test

Glass transitiontemperature

(̊C)

Crystallizationtemperature

(̊C)

1st run meltingtemperature

(̊C)

2nd run meltingtemperature

(̊C)

Flow-startingtemperature

(̊C)

5 mm offsettemperature

(̊C)

PaPr 114 187 220 (Tm2) 215 218 232

PaBu 81 152 192 186 201 219

PaVa 55 129 170 160 183 200

Fig. 3 Differential scanning calorimetry (DSC) curves of paramylon propionate (PaPr),paramylon butyrate (PaBu), and paramylon valerate (PaVa) as powders.

Table 1 Differential scanning calorimetry (DSC) and melt flow test results.


are in good agreement with the thermal behaviorsfrom the DSC analysis. In addition, the viscosity-temperature curves shown in Fig. 4b reveal adecrease in viscosity with increasing temperature,which indicates that the plasticity of the polymersincreased at higher temperatures. The offset methodat 5.0 mm was adopted to determine the melt-flowtemperatures of the polymers from the results of themelt flow test. The calculated offset meltingtemperatures of PaPr, PaBu, and PaVa were 232, 219,and 200 ̊C, respectively. All the offset meltingtemperatures were 20‒30 ̊C higher than the meltingtemperatures from the DSC analysis, which alsoindicates that the melt-spinning process temperaturesshould be set above the offset melting temperaturesto ensure polymer molding. Therefore, the melt-spinning process temperatures of PaPr, PaBu, and

PaVa were established as 240, 220, and 220 ̊C,respectively.3.2 Melt spinning of PaPr, PaBu, and PaVa

PaPr, PaBu, and PaVa all had good meltspinnability at the various process temperaturesdetermined in section 3.1, and Fig. 5a shows images ofthe obtained melt-spun fibers. Continuous meltspinning was achieved at take-up rates of 18, 36, 108,and 180 m/min. Using an optical microscope, theaverage diameters of the melt-spun fibers at take-uprates of 18, 36, 108, and 180 m/min were calculated tobe 0.144, 0.142, 0.096, and 0.052 mm, respectively.Fig. 5b shows 2-D X-ray fiber patterns of PaPr, PaBu,and PaVa at take-up rate of 108 m/min, which revealswell oriented and crystallized of crystallite. GPCmeasurements of the PaPr melt-spun fibers wereobtained to assess thermal decomposition during the

Fig. 4 (a) Stroke-temperature curves and (b) viscosity-temperature curves produced using datafrom the melt flow test. “Tg” and “Tm” in (a) were derived from the differential scanningcalorimetry (DSC) measurements.

Fig. 5 (a) Images and (b) 2-D X-ray fiber patterns of the paramylon propionate (PaPr), paramylonbutyrate (PaBu), and paramylon valerate (PaVa) melt-spun fibers. The fibers used for theX-ray fiber patterns were took-up at 108 m/min.


manufacturing process, and the results are providedin Table 2. Before melt-spinning, the PaPr powder hada weight-average molecular weight of 3.14 × 105; thisremained virtually unchanged in each of the fibersproduced at the various take-up rates. Moreover, thesubsequent annealing process did not reduce themolecular weight. This was advantageous becausethe process temperature was lower than the thermaldecomposition temperature, which is above 300 ̊C inthe case of PaPr.[9] The molecular weights of PaBuand PaVa also remain unchanged after melt spinning.It was also worth noting that the melt spinning ofPaPr, PaBu, and PaVa did not require any additives.Particularly in the case of PaPr, which has relativelyhigh glass transition and melting temperatures, melt-spinning of the paramylon esters provides a goodreference for further applications.3.3 Orientation and crystallinity of the PaPr fibers

The molecular orientation and crystallinity of thePaPr fibers were characterized using a POM andWAXD, respectively. The POM images of the PaPrfibers at various take-up rates were presented inFig. 6. In each pair of images, the fiber in the field ofview changes from dark to light, which indicatesbirefringence caused by alignment of the molecularchains. Fig. 7a shows 2-D fiber diffraction patterns ofthe PaPr fibers at various take-up rates obtained byWAXD. The fibers manufactured at the lower take-up rates of 18 and 36 m/min produced amorphouspatterns, despite the alignment of their molecularchains. In contrast, the fibers manufactured at therelatively high take-up rates of 108 and 180 m/minclearly show patterns of crystallization and crystalorientation. Considering that higher take-up rates

during melt-spinning correspond to greater loadsapplied to the melting resin, shearing occurs morereadily among the crystals, which inducescrystallization.

To promote crystallization, melt-spun fibers offixed length were heated above their glass transitiontemperature. Fig. 7b shows the 2-D fiber diffractionpatterns of the fibers formed at various take-up ratesafter annealing. Fig. 8 shows plots of intensity versus2θ for the PaPr fibers derived from the corresponding2-D fiber patterns. The degree of orientation values ofthe (100) crystal plane (the numbers in parenthesesare the Miller indices) and the degree ofcrystallization values calculated from the plots ofintensity versus 2θ are presented in Table 3. Thefibers produced at low take-up rates of 18 and36 m/min produced diffraction patterns thatsuggested orientation and crystallization, with highdegree of orientation values of 97% and 93%,respectively. The high degree of orientation values ofthe two fibers suggest that their molecular chainswere well aligned during melt-spinning. Moreover, allthe (100) crystal planes of the PaPr fibers mentionedin the present study were well-oriented, with degreeof orientation values above 90%. The plots of intensityversus 2θ reveal that, without annealing, the fibersmanufactured at high take-up rates of 108 and180 m/min had few crystalline peaks, and the degreeof crystallization values were relatively low (22% and23%, respectively). After annealing, there were morecrystalline peaks in the plots of intensity versus 2θthan in those of the unannealed fibers, and the peakswere of higher relative intensity, which suggests theprogression of crystallization. In addition, as shown inTable 3, the calculated degree of crystallization ofeach of the annealed fibers was relatively high(approximately 50%). Therefore, during melt spinning,fibers with highly aligned molecular chains can beobtained regardless of the take-up rate, although thepromotion of crystallization requires a relatively hightake-up rate. Annealing the fibers promotes furthercrystallization. It should be noted that all of the 2-Ddiffraction patterns of the melt-spun fibers presentedhere are the same as those of the correspondingthermally stretched films prepared in the previousstudy. As mentioned in the discussion of the DSCresults presented in section 3.1, PaPr can have twotypes of crystal structure. The mainchains of the melt-spun fibers only comprised the second crystal form(the five-fold helical structure) along the fiber axis.

Mw × 105 Mw / Mn

PaPr_powder 3.14 2.10

PaPr_50 rpm 2.98 2.10

PaPr_100 rpm 3.01 2.17

PaPr_300 rpm 3.03 1.94

PaPr_500 rpm 3.17 2.09

PaPr_50 rpm_annealed 3.00 2.05




Table 2 Gel permeation chromatography (GPC)results of PaPr.


3.4 Tensile properties of the melt-spun fibersThe results of the tensile tests on the PaBu and

PaVa fibers at a take-up rate of 108 m/min, and thePaPr fibers at various take-up rates are presented inTable 3. At a take-up rate of 108 m/min, the tensilestrength of the PaPr fibers was 138 MPa, which wasmuch higher than the tensile strengths of the PaBu(28 MPa) and PaVa (58 MPa) fibers. The self-standingfilms of the three paramylon esters exhibited a similar

trend; the tensile strength decreased as the numberof carbon atoms in the substituted ester groupsincreased. Considering that increasing the length ofthe side-chain reduces the crystallinity of theparamylon esters, the differences in the tensileproperties between the films and fibers are asexpected.

The stress‒strain curves of the unannealed PaPrfibers manufactured at take-up rates of 18, 36, 108, and

Fig. 6 Polarized optical microscope (POM) images of paramylon propionate (PaPr) fibersmanufactured at take-up rates of 18, 36, 108, and 180 m/min.


180 m/min are presented in Fig. 9a. PaPr fibersproduced at the same take-up rates weresubsequently annealed to determine the influence ofcrystallinity, as shown in Fig. 9b. Table 3 summarizesthe tensile properties of the fibers. The tensilestrengths of the unannealed PaPr fibersmanufactured at take-up rates of 18, 36, 108, and180 m/min were 106, 112, 138, and 200 MPa,respectively (Fig. 9a). The highest tensile strength of200 MPa corresponded to the fibers manufactured ata maximum spinning rate of 180 m/min. The Young’smoduli of the fibers manufactured at take-up rates of18, 36, 108, and 180 m/min were 1.12, 1.16, 1.57, and1.94 GPa, respectively. The highest Young’s modulus

of 1.94 GPa also corresponded to the fibersmanufactured at a spinning rate of 180 m/min.Therefore, the tensile strength and Young’s modulusvalues of the fibers tended to increase with increasingtake-up rate, whereas the elongation at breakdecreased from 100% to 34%.

The tensile strengths of the annealed fibersmanufactured at take-up rates of 18, 36, 108, and180 m/min were 59, 103, 151, and 200 MPa,respectively. The Young’s moduli of the fibersmanufactured at take-up rates of 18, 36, 108, and180 m/min were 0.95, 1.19, 1.53, and 1.64 GPa,respectively. Therefore, there was an improvement intensile strength, especially in the fibers manufacturedat the higher take-up rates of 108 and 180 m/min.

Generally, in flexible polymers such aspolyethylene (PE) and polypropylene (PP), increasingthe degree of crystallinity increases the tensilestrength. However, polysaccharides with rigidpyranose rings are different from such flexiblepolymers in terms of chain-folding, which suggestsdifferences in crystal behavior. Accordingly, it seemsthat the extent of molecular chain alignment in thePaPr fibers, rather than the degree of crystallization,had a major influence on the tensile properties.Considering that the shear force increases withincreasing take-up rate during melt spinning, themolecular chains of the fibers tend to align more.Therefore, fibers with highly aligned molecular chainshave greater tensile strength. Annealing does notappear to affect the alignment of the molecular chains,despite increased crystallization, because the

Fig. 7 2-D X-ray fiber diffraction patterns of paramylon propionate (PaPr) fibers (a) before and(b) after annealing.

Fig. 8 Plots of intensity versus 2θ of paramylonpropionate (PaPr) fibers manufactured at take-up rates of 18, 36, 108, and 180 m/min (both

annealed and unannealed).


unannealed fibers already exhibit good alignment ofthe molecular chains, as confirmed by examinationusing a POM. In summary, the tensile properties ofthe melt-spun fibers seem to be mainly affected bythe take-up rate during the manufacturing process.However, it should be noted that although theannealing process does not improve the tensileproperties drastically, heat treatment does stillimprove the thermal stability, because there isincreased crystallization.

4. Conclusions

The three paramylon ester derivativesinvestigated in the present study had favorablethermal fluidity at the melt processing temperaturesindicated by the results of DSC and the melt flowtests. Each of the paramylon esters was successfullymelt-spun at various take-up rates, without the needfor additives, and its molecular weight did not changesignificantly. All the melt-spun fibers had goodmolecular orientation, as demonstrated byexamination under a polarized optical microscope. By

Tensilestrength(MPa)

Elongation atbreak (%)

Young’smodulus(GPa)

Degree oforientation

(%)

Degree ofcrystallization

(%)

PaPr_18 m/min 106 ± 21 100 ± 31 1.12 ± 0.19 －－

PaPr_36 m/min 112 ± 13 58 ± 25 1.16 ± 0.18 －－

PaPr_108 m/min 138 ± 13 31 ± 6 1.57 ± 0.21 95 22

PaPr_180 m/min 157 ± 8 34 ± 10 1.94 ± 0.20 92 23

PaPr_18 m/min_annealed 59 ± 11 52 ± 11 0.95 ± 0.11 97 54




PaBu_108 m/min 28 ± 3 54 ± 17 0.48 ± 0.13 －a －a

PaVa_108 m/min 58 ± 14 25 ± 6 0.31 ± 0.06 －a －a

Table 3 Tensile and crystalline properties.

aNot calculated due to low crystallinity.

Fig. 9 Stress-strain curves of paramylon propionate (PaPr) fibers (a) before and (b) afterannealing.


adjusting the take-up rate, it was possible to processcrystalline or amorphous melt-spun fibers. This resultindicates that the crystalline behavior of paramylonester derivatives with rigid pyranose rings is differentfrom that of flexible polymers with chain-folding. Thepresent study proves that melt-spun fibers can bemanufactured from polysaccharide ester derivatives.Therefore, polysaccharide ester derivatives havepotential for use as biomass-based plastics with highthermal stability and favorable mechanical properties.

Acknowledgments

This work was performed as part of the“ Innovative Synthesis of High - PerformanceBioplastics from Polysaccharides” project supportedby JST ALCA, Japan (grant number JPMJAL1502),and by JSPS KAKENHI (Early-Career Scientists)(grant number JP19K 20486). The synchrotronradiation experiments were mostly performed usingthe BL40B2 beamline at SPring-8 (2019A1213). Someparts of the synchrotron experiments wereperformed using the BL03XU beamline at SPring-8with the approval of the Japan Synchrotron RadiationResearch Institute (JASRI) and the Advanced SoftMaterial Beamline Consortium (FSBL) (2017A1440,2018A7232, 2019A7234).

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