thermal properties and chemical changes in blend melt spinning of cellulose acetate butyrate and a...

Thermal Properties and Chemical Changes in Blend MeltSpinning of Cellulose Acetate Butyrate and a NovelCationic Dyeable Copolyester

Bin Chen, Leilan Zhong, Lixia Gu

State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Donghua University, Shanghai201620, People’s Republic of China

Received 13 March 2009; accepted 23 June 2009DOI 10.1002/app.30984Published online 20 January 2010 in Wiley InterScience (www.interscience.wiley.com).

ABSTRACT: A novel cationic dyeable copolyester (MCDP)containing purified terephthalate acid (PTA), ethylene glycol (EG),2-methyl-1,3-propanediol (MPD), and sodium-5-sulfo-isophthalate(SIP) was synthesized via direct esterification method. The chemi-cal structure of modified cationic dyeable polyester (MCPD) wasconfirmed by FTIR and 1H-NMR. The thermal properties ofMCDP and cellulose acetate butyrate (CAB) blends with differentblend ratios were investigated by DSC. The results revealed thatMCDP and CAB were immiscible polymer blends, and the glasstransition temperature of CAB in blend fibers was higher than thatof CAB in blend chips because of the strengthening hydrogen

bonding. The chemical changes of MCDP and CAB in blend meltspinning were analyzed. It was found that the thermal hydrolysisreaction of ester side groups of CAB occurred in blend melt spin-ning, which resulted in that the acid gas was produced and thehydroxyl group content of CAB was increased. Furthermore, themoisture absorption of blend fibers was improved about threetimes than pure MCDP fiber even after washing 30 times. VC 2010Wiley Periodicals, Inc. J Appl PolymSci 116: 2487–2495, 2010

Key words: copolyester; cellulose acetate butyrate; fiber;blend melt spinning

INTRODUCTION

Poly(ethylene terephthalate) (PET) fiber has manyoutstanding properties for textile and clothing appli-cations. Despite the great success, it exhibits limita-tions in certain properties such as dyeability, mois-ture absorption, pilling resistance, and etc. Manycopolymers, in which a small amount of a thirdcomponent is added to PET in an effort to improveon the properties of PET resins, have been investi-gated for fiber applications.1–3 Sodium sulfonate-con-taining PET is known for long time and was origi-nally commercialized by DuPont as textile fiberswith improved dyeability to cationic dyes, but it alsolimited by the high melt viscosity resulted from theionic aggregates effect of sodium-5-sulfo-isophthalate(SIP).4,5 Therefore, we synthesized a novel cationicdyeable copolyester (MCDP) by adding 2-methyl-1,3-propanediol (MPD) into sulfonate-containingPET. MPD, as a smallest branched aliphatic diol, canreduce the crystallizability of modified polyestereffectively.6 Shwartz and coworkers7 revealed thatthe modified polyester containing MPD has wellspinnability and commercial values. No prior studies

of both MPD and SIP added to PET could be found.In our work, we found that MPD can reduce theionic aggregates of SIP8,9 and further enhance thedyeability of modified polyester fiber because of theirregular molecular structure of MPD. More detailsabout synthesis, characterization, and dyeability ofMCDP will be introduced elsewhere.In this article, we report a modification method by

using of cellulose acetate butyrate (CAB) to improvethe moisture absorption of MCDP. It is well knownthat CAB is one of the most important thermoplasticcellulose esters derived from natural polymers.10 Inthe last few years, various studies11–15 have beenperformed on the blends of CAB with other poly-mers in general attempt to use the high glass transi-tion temperature (Tg) or the molecular stiffness ofCAB,16 to compensate the weakness of other poly-mers, and to develop materials with friendly envi-ronmental conditions. For these studies, all of thearticles were interested in the miscibility, thermalproperty, crystallizability and super-molecular struc-ture of the blends. However, CAB often discolorsand suffers loss of physical properties due to thepoor thermal stability during melt processing.17 Thechemical changes of CAB in blend melt processwhich affect on the performance of blends havereceived very little attention. Therefore, the purposeof this article is to study the thermal properties andchemical changes in blend melt spinning. On the

Correspondence to: L. Gu ([email protected]).

Journal ofAppliedPolymerScience,Vol. 116, 2487–2495 (2010)VC 2010 Wiley Periodicals, Inc.

basis of the experimental results, the mechanism ofchemical changes of CAB during blend melt spin-ning is discussed. Meanwhile, the moisture absorp-tion of MCDP fiber is well improved by blendingwith CAB.

EXPERIMENTAL

Materials

MCDP copolyester was synthesized via purified ter-ephthalate acid (PTA; Yizheng Chemical Fibers Corp.,China), ethylene glycol (EG; Yangzi PetrochemicalCorp., China), MPD (Lyondell Chemical Corp., USA),and SIP (Yangzhou Huitong Corp., China).

CAB was purchased from Acros Chemical Corp.,USA. The butyryl and acetryl were 35–39 wt % and12–15 wt %, respectively.

Synthesis of MCDP copolyester

MCDP copolyester was synthesized by direct esteri-fication method. The esterification of PTA, EG, andMPD (feed molar ratio: diacids/diols ¼ 1/1.4;MPD/EG ¼ 10/90) was reacted at 180–240�C for1.5–2 h in the presence of antimony triacetate as cat-alyst, water being removed by distillation at atmos-pheric pressure. Then the SIP (feed molar ratio: SIP/PTA ¼ 3/97) was added to esterification productbefore condensation reaction. The subsequent poly-condensation was carried out at 260–275�C for 1–1.5h under a vacuum of less than 1 torr. Finally, MCDPcopolyester was obtained. The intrinsic viscosity ofMCDP was 0.486 dL/g as measured at 25�C usingphenol/tetrachloroethane (3 : 2, w/w) as a mixingsolvent.

Preparation of MCDP/CAB blend fibers

First, MCDP and CAB were mixed with a certainproportion and dried under vacuum at 110�C for 12h. The blends were extruded and chipped by usingThermo Hakke EUROLAB-16 corotating twin-screwextruder. The temperature, the rotation rate, and theprocessing period were 250�C, 85 rmp, and 2 min,respectively. Different component samples are codedin Table I.

Then, the MCDP/CAB blend chips were dried byheating under vacuum at 110�C for 12 h. The blendmelt spinning experiment was performed using ABEspinning equipment. All the MCDP/CAB blendchips, along with MCDP and CAB chips, were spunwith the same temperature settings; the temperaturezones 1, 2, 3, and 4 (spinneret) in the spinningequipment were 265, 295, 300, and 280�C, respec-tively. Unfortunately, the MCDP/CAB blend fila-ments, except for the C5 and C10 blend filaments,

were hardly wound onto a bobbin at any given take-up velocity due to the immiscible of MCDP andCAB. Only the as-spun fibers extruded fromthe spinneret can be obtained. The C5 and C10filaments were subjected to the posting-spinningdrawing experiments by using Barmag two-stagedrawing equipment with total draw ratio R ¼ 4, thefirst and second stage temperature settings of two-stage drawing equipment were 80 and 160�C,respectively.

Measurement and characterization

FTIR analysis was done on Nicolet 8700 IR spec-trometer. All the spectra were collected in transmit-tance through KBr pellet.The characterization of MCDP was determined by

1H-NMR spectrometer (using Bruker Avance400).The MCDP sample was dissolved in a mixture ofdeutero-chloroform/deutero-trifluoroacetic acid (3 :1, v/v), and tetramethylsilane was used as an inter-nal standard. The structure of CAB was analyzedby 13C-NMR. The CAB sample was dissolved indeutero-chloroform. The center peak of deutero-chloroform was used as an internal standard.The thermal properties were investigated with a

PerkinElmer Diamond DSC under a N2 atmosphere.Every sample was heated from 40 to 300�C at a heat-ing rate of 20�C/min.Pyrolysis-Gas Chromatography/Mass Spectrome-

try (py-GCMS) studies were carried out via usingShimadzu GC/MS-QP2010 system with a pyrolysisunit (Frontier Laboratories Ltd.). The sample waspyrolyzed at 300�C. The products were separated ona DB-5MS column and identified through compari-son of their EIþ mass spectra with Nist 107, Wiley,and NBS electronic libraries.Thermogravimetric/infrared spectroscopic (TG-IR)

analysis was performed using a Netzsch TG 209F1in conjunction with a Nicolet 8700 spectrometer.Each sample was accurately weighted 5.0 mg. Thetemperature was raised with 20�C/min from 40 to300�C and held at 300�C. The volatile gaseous prod-ucts were identified by IR spectrophotometer andrecorded at each 5-min intervals.

TABLE ISample Code of Different CAB/MCDP Weight Ratio

No. CAB (wt %) MCDP (wt %) Sample code

1 0 100 MCDP2 5 95 C53 10 90 C104 15 85 C155 30 70 C306 50 50 C507 100 0 CAB

2488 CHEN, ZHONG, AND GU

Journal of Applied Polymer Science DOI 10.1002/app

All the samples were sputter coated with a thinlayer of gold for scanning electron microscopic(SEM) observations via using a HITACHI S3000NSEM.

Moisture absorption of blend fibers was measuredafter deoiling and drying. The fiber was kept at25�C, 65% RH for 48 h, and weighted (w1/g). Thenafter balancing at 100�C for 48 h in vacuum bakingoven, it was again weighed (w2/g). Moisture absorp-tion (M) can be calculated according to thisformula18:

Mð%Þ ¼ w1 � w2

w1� 100% (1)

The dyeability of blend fibers was carried outusing a laboratory scale dyeing machine (Atlas Linit-est Plus). One gram of the sample was placed in a2% owf Cationic Red GRL dyebath of a liquor ratio50 : 1 and was dyed at 100�C for 1 h. The commer-cial cationic dyeable polyester fiber (CDP; SIP con-tent: 3 mol %) was also dyed at same condition forcomparison. The dye uptake value was determinedby the absorbance of each dyebath solution beforeand after the dyeing via using a PerkinElmerLambda 35 UV/visible scanning spectrophotometer.The dye uptake (D) was calculated by the followequation,19 where A0 and A are the absorbance ofthe dyebath before and after dyeing, respectively.

Dð%Þ ¼ A0 � A

A0� 100% (2)

Mechanical properties of blend fibers were deter-mined by using Shimadzu AGS-500ND universalmaterial testing machine. Length between two hold-

ing jigs was 200 mm and drop rate was 200 mm/min at room temperature.

RESULTS AND DISCUSSION

Characterization of MCDP copolyester

The FTIR spectra of the MCDP and PET are shownin Figure 1. Most absorption bands of MCDP weresimilar to the PET homopolymer, as well as a certainabsorption bands belong to MCDP. Particularly, theabsorption peaks at 624 cm�1 and 755 cm�1 wereattributed to benzene ring of SIP units, and at 1390cm�1 was attributed to free methyl of MPD units.The FTIR analysis indicates that the MPD and SIPwere polymerized into MCDP copolyester.The 1H-NMR spectra of MCDP can also confirm

the results above (Fig. 2). The chemical shifts of pro-tons of SIP were H1 (9.02 ppm) and H2 (8.93 ppm),and those of MPD appeared at H5 (4.88 ppm), H6

(2.65 ppm) and H7 (1.29 ppm), respectively. Thechemical compositions of MCDP were determinedfrom the relative integration areas of these protonpeaks. The calculated results were listed in Table II.It shows that the SIP unit content in MCDP wasvery close to the SIP feed ratio, whereas the MPDunit content was a slighter rich than MPD in thefeed ratio. This result might come mainly from thefollowing reason.20,21 MPD has a relatively high boil-ing point ) (212�C) than that of EG (197�C).

Thermal properties changes in blend meltspinning of CAB and MCDP

The moisture absorption of MCDP fiber is very poordue to lacking of hydrophilic groups. To deal with

Figure 1 The FTIR spectra of PET and MCDP.

Figure 2 1H-NMR spectra of MCDP. The peaks in 1H-NMR spectra coded were represented different hydrogenin MCDP molecular structure.

NOVEL CATIONIC DYEABLE COPOLYESTER 2489


this problem, the CAB was added into the MCDPfiber via using blend melt spinning. Surprisingly,the moisture absorption of MCDP/CAB blend fiberwas well improved even adding a small amount ofCAB. Moreover, it was interesting to find that thegas acid smell escaped in actual MCDP/CAB blendmelt spinning process. These phenomenons implythat some chemical changes occurred in the blendmelt spinning. For this concern, we first investigatedthe thermal properties changes of MCDP/CABblend chips and their as-spun fibers via using DSCanalysis. The as-spun fibers extruded from spinneretwere quickly submerged in ice-water to prevent fur-ther chemical changes during cooling process. Allthe results have been summarized in Table III.

Seen the DSC results of blend chips in Table III,CAB and MCDP have their own Tg in the blend chips,which was similar to the Tg of pure CAB and pureMCDP. The Tm’s of MCDP in the blend chips keptconstant with composition. The measured DHm’s ofMCDP were decreased as MCDP content reduced, asshown in Figure 3. It was found a good linear rela-tionship with an R2 value of 0.9874. The Tm’s of CABblend chips were increased slightly and the measuredDHm’s of CAB were increased with rising CAB con-tent (Fig. 3). It is easily noticed that the measuredDHm’ s of MCDP or CAB were affected by the weightfraction significantly. If the DHm were corrected toinclude the weight fraction using the formula:

DH�m ¼ DHm

w(3)

where w is the weight fraction. The results showthat the corrected DHm*’s of MCDP were tend toidentical, whereas the corrected DHm*’s of CAB werestill differ markedly. It can be assumed that theinteraction between of CAB and MCDP were verypoor, and the MCDP component attains the samelevel of crystallinity regardless of the amount ofCAB. The different corrected DHm*’s value of CAB,which might be explained that the original crystalli-zation structure of CAB in blend chips was signifi-cantly affected by the chemical reaction occurred inheating process.

For the DSC results of as-spun fibers, it can beclearly seen that Tg’s of CAB in as-spun fibers werealways higher than that of CAB in blend chips, and

TABLE IIFeed Molar Ratio and Relative Ratio Calculated

from 1H-NMR

Feed molarratio

Relative ratiocalculated from 1H-NMR

MPD/EG 10/90 10.83/89.17SIP/PTA 3/97 2.96/97.04

TABLEIII

Measu

redTg,Tm,andDH

mvalue,andCalculatedDH

m*andTgValueforBlendch

ipsandAs-Spunfibers

Sam

ple

code

Blendch

ips

As-sp

unfibers

MCDP

CAB

MCDP

CAB

Tgcalb

(�C)

Tg

(�C)

Tm

(�C)

DH

m

(J/g)

DH

m*a

(J/g)

Tg

(�C)

Tm

(�C)

DH

m

(J/g)

DH

m*(J/g)

Tg

(�C)

Tm

(�C)

DH

m*

(J/g)

Tg

(�C)

Tm

(�C)

MCDP

74.6

212.9

1.24

1.24

//

//

74.6

212.2

0.56

//

/C5

74.3

212.5

1.18

1.31

128.2

168.1

0.25

5.01

74.1

212.4

0.61

129.0

/77.7

C10

75.1

212.7

1.13

1.25

128.2

168.3

0.79

7.16

73.2

212.8

0.59

129.5

/80.7

C15

74.5

212.2

1.17

1.38

128.5

168.3

1.07

7.94

74.6

212.9

0.51

132.2

/83.8

C30

74.2

212.9

0.95

1.35

128.1

168.7

3.07

10.24

73.5

212.6

0.65

132.6

/93.0

C50

74.6

212.9

0.66

1.32

127.9

168.8

6.14

12.29

74.8

212.9

0.57

133.0

/105.3

CAB

//

//

128.6

168.8

13.32

13.32

//

/135.9

//

aDH

m*valueis

correctedto

includetheweightfractionin

blends.

bTgcalvalueis

calculatedbyFoxeq

uation.



the Tg’s of CAB in as-spun fibers were increasedwith CAB content rising. In contrast, the Tg’s ofMCDP in as-spun fibers were still constant. It is evi-dent that the CAB occurred chemical changes inblend melt spinning, which perhaps enhanced theintermolecular hydrogen bonding among thehydroxyl groups in CAB. Furthermore, the Tg’s ofCAB in as-spun fibers were seriously increased bythe strong hydroxyl bonding. In the DSC scan of as-spun fibers, the melting peak of CAB totally disap-peared in as-spun fibers, indicating that no furthercrystallization took place in CAB during heating.The Tm’s and corrected DHm*’s of MCDP in as-spunfibers still maintain constant with composition.

The DSC results in Table III also demonstrate thatall the as-spun fibers existed obvious two Tg. If CABis completely miscible with MCDP, we could calcu-late the theoretical single Tg value by Fox equation22

as follows:

1

TgBlend¼ wCAB

TgCABþ wMCDP

Pba

TgMCDP(4)

where w is the weight fraction, the subscripts‘‘blend’’, ‘‘CAB,’’ and ‘‘MCDP’’ indicating value ofthe blend fibers, CAB and MCDP fibers, respec-tively. However, neither the Tg’s of CAB nor the Tg’sof MCDP obtained from DSC had a tendency to thecalculated Tg’s value or depend on composition ofblends, which suggests that CAB was immisciblewith MCDP.

From above discussion, the conclusion can bedrawn that the interaction between MCDP and CABwere poor due to the immiscible blends; the thermalproperties of CAB were changed markedly by the

chemical reaction occurred in blend melt spinning,whereas that of MCDP were seldom affected.

The chemical changes in blend meltspinning of MCDP/CAB

To gain insight with regard to the chemical changesin blend melt spinning, the gaseous products ofCAB were analyzed by using py-GCMS at 300�C(simulating the spinning temperature). Figure 4shows that the volatile gaseous products of CAB atthe spinning temperature were butyric acid, butyricanhydride, acetic acid, and unknown complex com-pound. The majority of the products were butyricacid and butyric anhydride, which accounted for94% of all. This result might come mainly from thereasons as follows. On the one hand, the content ofbutyrate in CAB is higher than that of acetate inCAB. One the other hand, butyrate having moremethylene units than acetate, the electron density ofthe oxygen atom in the butyrate is greater than thatof acetate. The ester bond in butyrate is more favor-ably to react, which results in a relatively high con-tent of butyric acid and butyric anhydride in gase-ous products.To probe the chemical changes further, The CAB

was extracted from C5 blend chip and C5 blendfiber by dissolving in acetone, and then examinedby the 13C-NMR spectra, respectively. Compared

Figure 3 The plot of relationship between DHm and con-tent for MCDP and CAB. [Color figure can be viewed inthe online issue, which is available at www.interscience.wiley.com.]

Figure 4 (a) Chromatograms obtained from CAB; (b) EImass spectrum, molecular structure, name and relativeintensity of volatile pyrolysis gaseous products of CAB.



Figure 5(b) with Figure 5(a) spectra, it can be foundthat no peaks disappeared or new peaks emerged,especially in the region 60–110 ppm, which repre-sents the carbon atoms in anhydroglucose units,indicating that the backbone of CAB kept stable inblend melt spinning. From the carbonyl carbonregion 180–170 ppm for acetate and butyrate,23,24 itis obviously noted that the content of butyrate washigher than that of acetate of CAB in blend chip,whereas the content of butyrate was lower than thatof acetate of CAB in blend fiber, proving that mostof chemical reaction occurred on butyrate ester sidegroups.

The hydroxyl groups of CAB and MCDP extractedfrom C5 blend chip and C5 blend fiber were alsoexamined by using FTIR spectra, respectively. Seenin Figure 6, CAB in blend chip exhibited an appa-rently single peak with the maximum 3462.7 cm�1,which may be assigned actually to a mixture of ab-sorbance free and from intramolecularly hydrogen

bonded hydroxyl groups.25 After blend melt spin-ning, the hydroxyl absorption peak of CAB in blendfiber was shifted to low wavenumbers at 3447.8cm�1 which can be associated with intermolecularhydrogen bonding.25 The new peak displayed at3750.1 cm�1 due to moisture uptake, becoming pro-nounced with the increase of hydroxyl content ofCAB. The hydroxyl absorption peaks of MCDP inblend chip and blend fiber were centered at 3432.0cm�1 and 3432.2 cm�1, and seldom be changedbefore and after melt spinning. It can be easilyexplained that the ester bond in MCDP was rela-tively stable compared with CAB due to the conjuga-tion effect of benzene ring.Based on the above study, it can be assumed that

the chemical reaction of CAB occurred in blend meltspinning was the thermal hydrolysis reaction, whichresults in that the acid gas was produced and thehydroxyl group content of CAB was increased. Seenin Figure 7(a), the CAB backbone is composed ofrepeat glucose unit. Every glucose unit contains ran-dom acetate ester, butyrate ester, and hydroxylgroups. As an example for butyrate ester, the pro-posed mechanism of the thermal hydrolysis reactionof CAB in blend melt spinning is shown in Figure7(b). It is easy to understand that the blend chipsalways contain water moisture due to the hydrophi-licity of hydroxyl groups in CAB. Under the blendmelt spinning condition, the carbonyl carbon reactmore favorably with water molecular which lead tothe chemical scission of ester bond in CAB. Finally,the ester bond scission created carboxyl acid andhydroxyl groups.

Figure 5 (a) 13C-NMR spectra of CAB extracted from C5blend chip; (b) 13C-NMR spectra of CAB extracted fromC5 blend fiber. The inset shows carbonyl carbon region of185�160 ppm.

Figure 6 The hydroxyl stretching region in the FTIRspectra of CAB and MCDP extracted from C5 blend chipand C5 blend fiber. The peak maximums are indicated.[Color figure can be viewed in the online issue, which isavailable at www.interscience.wiley.com.]



Because the most of gaseous products escaped inblend melt spinning were acid gas which containingcarbonyl group, the dynamic changes of the thermalhydrolysis reaction can be indirectly investigatedfrom the changes of carbonyl infrared absorbance at1783 cm�1 (coded as Acarbonyl) by using TG-IR analy-sis. From Figure 8, except for pure MCDP, the Acar-

bonyl of other samples were gradually increased withthe time extension, suggesting thermal hydrolysisreaction occurred on more and more ester groups inCAB. Compared the Acarbonyl of different blend sam-ples, it was found that the higher CAB content inblends, the stronger carbonyl absorbance. The ther-mal hydrolysis reaction was seriously affected bythe weight fraction. Figure 8 also clearly shows thatthe Acarbonyl increased sharply from 15 to 20 min,which indicates that the thermal hydrolysis reactionrate arrived at maximum. It was in good agreementwith the phenomena observed in actual MCDP/CABblend melt spinning. The spinning stability ofMCDP/CAB blends got worse while the spinningtime exceed 15 min, because the large number ofescaped acid gas were seriously decreased the stabil-ity of the blends melt flow.

Moisture absorption, mechanical properties,dyeability, and morphology of CAB/MCDPblend fibers

Figure 9(a,b) shows the SEM images of pure MCDPfiber and C5 blend fiber. To enhance contrast forimage analysis, both of the samples were treated bysubmerging in acetone, and the CAB phase wasetched due to dissolving in acetone. As seen in Fig-ure 9(a), the surface of pure MCDP fiber was stillsmooth after treated by acetone. In contrast, the sur-face of C5 blend fiber exhibited lots of microvoidsranged from 0.1 to 1 lm, proving the immiscible ofCAB and MCDP.The moisture absorption of C5 and C10 blend

fibers, as well as MCDP and CAB fibers, are shownin Table IV. Compared with the MCDP fiber, themoisture absorption of C5 blend fiber was improvedmore than three times. The theoretical estimate ofblend fiber’s moisture absorption value was calcu-lated from the moisture absorption of pure MCDPand pure CAB as the following formula:

Figure 7 (a) Structure of CAB; (b) a proposed mechanismof thermal hydrolysis reaction of CAB in blend meltspinning.

Figure 8 Carbonyl absorbencies of gaseous products ofCAB/MCDP blend chips with different time.

Figure 9 (a) SEM image of MCDP fiber treated with ace-tone; (b) SEM image of C5 fiber etched with acetone.



MTð%Þ ¼ MCAB

Xb

a

wCAB þMMCDP

Xb

a

wMCDP (5)

where MCAB is 4.75%, MMCDP is 0.56% measured inlaboratory. It is found that the actual moistureabsorption of blend fibers was much higher than thevalue of theoretical estimate. The reason might beexplained that the hydroxyl content of fiber wasincreased by the thermal hydrolysis of CAB, andfinally improved the moisture absorption of blendfibers.

To investigate the washing resistance property,the blend fibers were washed several times accord-ing to AATCC test method 124-2006.26 Each washingcycle was conducted in a commercial washingmachine set on a normal wash for 35 min. Themachine was filled with water at 35�C and about 4g/L detergent. Table V presents the moistureabsorption of C5 and C10 blend fibers with differentwashing times. Although the moisture absorption ofC5 and C10 blend fibers were slightly decreasedwith increasing the washing times, the decreaseextent was tend to the balance. After washing 30times, the moisture absorption of C5 and C10 blendfibers were still improved about three times com-pared with MCDP fiber.

The SEM image of C5 blend fiber unwashedshown in Figure 10(a) was clearly illustrated that theCAB domain existed on the fiber surface. However,the C5 blend fiber after washing 30 times wasbecame rough and appeared some microvoids onfiber surface displayed on Figure 10(b). These resultsindicate that partial CAB broke off from the fibersurface after washing, which is the possible reasonleading to the decrease of moisture absorption.

The dyeability of blend fibers is shown in TableVI. The dye uptake value of MCDP fiber is obvi-ously higher than CDP fiber with the same SIP con-tent. It might be explained that the crystallizabilityof polyester molecular chains was inhibited by theintroduction of MPD,6 which leads to the dyestuffmolecular can be easily diffused into the MCDP mo-lecular chains and combined with the SIP group.The dye uptake value of blend fibers was slightlydecreased as CAB content increased, but was stillclose to the MCDP fiber, suggesting that the dyeabil-ity of blend fibers was also very good. The theoreti-cal estimate dye uptake value of blend fiber was cal-culated using the following formula:

Figure 10 (a) SEM image of C5 fiber unwashed; (b) SEMimage of C5 fiber after 30 washed times.

TABLE IVMeasured and Calculated Moisture Absorption for

MCDP, CAB, and CAB/MCDP Blend Fibers

MCDP C5 C10 CAB

M (%) 0.56 1.88 2.03 4.75MT (%) 0.56 0.77 0.87 4.75

TABLE VMoisture Absorption of C5 and C10 Blend Fibers after

Different Washing Times

Washing times

M (%)

C5 C10

0 1.88 2.0310 1.79 1.9220 1.63 1.7830 1.58 1.72

TABLE VIMeasured and Calculated Dyeability for CDP, MCDP,

CAB, and CAB/MCDP Blend Fibers

CDP MCDP C5 C10 CAB

D (%) 78.6 91.5 91.1 89.7 52.6DT (%) / 91.5 89.6 87.6 52.6



DTð%Þ ¼ DCABwCAB þDMCDPwMCDP (6)

where DMCDP is 91.5%, DCAB is 52.6%. The resultclearly shows that the actual dye uptake value ofblend fibers was higher than the theoretical estimatevalue. It was probably explained as due to the phaseseparation structure of blend fibers, which is benefitto the dyestuff molecular diffuse to the inner struc-ture of blend fibers.

As seen from Table VII, the breaking elongation ofC5 and C10 blend fibers were almost same as pureMCDP fiber. The breaking strength of C5 and C10blend fibers were lower than pure MCDP fiber,but still above 1.5 cN/dtex. It illustrates that theblend fibers can also suitable for the requirementsof textile.

CONCLUSIONS

Novel cationic dyeable copolyester containing SIPand MPD was first synthesized by direct esterifica-tion method, which was supported from the evi-dence of the FTIR and 1H-NMR results. Moreover,the content of MPD units in MCDP was higher thanfeed molar ratio. The thermal hydrolysis reaction ofCAB occurred in CAB/MCDP blend melt spinning,mainly to the butyrate ester side groups ofCAB, which results in that the acid gas was pro-duced and the hydroxyl group content in CAB wasincreased. The changes of thermal properties ofCAB before and after blend melt spinning indicatethat the hydrogen bonding of CAB was significantlyincreased. Furthermore, the moisture absorptionof MCDP/CAB blend fibers was improved aboutthree times than MCDP fiber even after washing 30times. The blend fibers also have a good dyeabilitysimilar to the MCDP fiber, and the mechanical prop-

erties of blend fibers were suitable for the require-ments of textile.

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TABLE VIIMechanical Properties of CAB/MCDP Blend Fibers

MCDP C5 C10

Breaking strength (cN/dtex) 2.22 1.89 1.56Breaking elongation (%) 32.3 31.7 33.8



thermal properties and chemical changes in blend melt spinning of cellulose acetate butyrate and a...

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