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Polymer Degradation and Stability 96 (2011) 2181e2188

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Polymer Degradation and Stability

journal homepage: www.elsevier .com/locate /polydegstab

Preparation and characterization of oxidized sesbania gum and evaluationof its warp sizing performance for fine cotton yarns

Ding Shena,b, Man Xuec, Lei Zhanga, Huijuan Liud, Lin Gaod, Yuanchen Cuia,b,*aCollege of Chemistry and Chemical Engineering, Henan University, Kaifeng 475004, ChinabKey Laboratory of Ministry of Education for Special Functional Materials, Henan University, Kaifeng 475004, ChinacDepartment of Natural Science, Kaifeng Institute of Education, Kaifeng 475001, ChinadHenan Institute of Technology, Zhengzhou 450007, China

a r t i c l e i n f o

Article history:Received 24 June 2011Received in revised form5 September 2011Accepted 17 September 2011Available online 22 September 2011

Keywords:Oxidized sesbania gumPreparationCharacterizationWarp sizing performance

* Corresponding author. Key Laboratory of MinisFunctional Materials, Henan University, Kaifeng 47503881358.

E-mail address: yuanchencui@126.com (Y. Cui).

0141-3910/$ e see front matter � 2011 Elsevier Ltd. Adoi:10.1016/j.polymdegradstab.2011.09.007

a b s t r a c t

Sesbania gum (SG) was oxidized by sodium hypochlorite. Resultant oxidized sesbania gum (OSG) wascharacterized by means of Fourier transformation infrared spectrometry, scanning electron microscopy,and high resolution transmission electron microscopy. The thermal stability of OSG was analyzed bymeans of thermal analysis and the apparent viscosity of its slurry was also measured by rotaryviscometer. Moreover, the effect of OSG slurry as a warp sizing agent on the physico-mechanical prop-erties of fine cotton yarns was investigated. It was found that fine cotton yarns sized with OSG hadincreased tensile strength and decreased elongation at break than the untreated ones. Besides, the finecotton yarns treated with the OSG slurry had obviously decreased hairiness index and slightly increasedabrasion resistance, and OSG slurry had good adhesion. In one word, as-synthesized OSG slurry may findpromising application as a novel high-performance warp sizing agent for fine cotton yarns.

� 2011 Elsevier Ltd. All rights reserved.

1. Introduction

Sesbania gum (SG), a polysaccharide, is a unique natural poly-mer produced in China. The ratio of galactose unit to mannose unitin SG molecule is 1:2 [1], as seen in its chemical structure sche-matically depicted in Fig. 1 [2]. When SG is dispersed in water atroom temperature, it can be divided into two parts, i.e., water-soluble part and water-insoluble part. The major water-solublecomponent in sesbania gum is galactomannan gum which is ofsignificance in industry [3]. This is why various modified sesbaniagums are currently applied in industry for wastewater treatment[4], flocculating treatment [5], papermaking [6], cigarette paperfabrication [7], catalyst fabrication [8], and so on.

The chemical components of sesbania gum are similar to starch.In recent years, starches and their derivatives occupy an importantposition in many industries and tremendous deals of research andtechnical work are related to them [9e13]. Polyvinyl alcohols (PVA),starches and acrylic copolymers are commonly used warp sizingagents; and in particular, starches and their derivatives with good

try of Education for Special04, China. Tel./fax: þ86 378

ll rights reserved.

biodegradability and low cost are widely used as warp sizing agentsin textile industry. Hebeish [14] studied the sizeability of starchusing gamma radiation. Mostafa [15e17] synthesized a series ofwarp sizing agents via hydrolysis of poly(acrylamide)-graftedstarch copolymer, poly(methacrylic acid)-grafted starch andcarboxyl-containing starch and their hydrolyzed derivatives.Resultant warp sizing agents were found to possess good warpsizing performance for cotton yarns. Abdel-Hafiz [18] oxidizedmaize starch to generate derivatives as the warp sizing agents forcotton textiles. Teli et al. [19]suggested that germinated maizestarch could be used in textile printing. Zhu [20] reported thatstarch mono-phosphorylation was able to enhance the stability ofstarch/PVA blend paste for warp sizing. Liu et al. [21] studied theeffect of highmolecular weight polyacrylamide on the properties ofoxidized cassava starch. In addition, carboxymethyl cellulose wasalso studied as amatrix for preparing warp sizing agents. Mohamedet al. [22] synthesized novel warp sizing agents and finishingadditives by using carboxymethyl cellulose as the starting material.Hebeish et al. [23] investigated the flocculation behavior and warpsizing performance of carboxymethyl cellulose (CMC) and starch-based hybrids.

To our surprise, no report is currently available about SG ormodified SG as matrix of warp sizing agents for making yarns,though warp sizing agents have been applied in industry for lots ofyears. The main shortcomings of native sesbania gums are their

O

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1 OO

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16

Fig. 1. Chemical structure of sesbania gum.

D. Shen et al. / Polymer Degradation and Stability 96 (2011) 2181e21882182

large molecular size and instability of the viscous solutionunder varying temperature for a particular end-use. Therefore, weintend to fabricate novel warp sizing agents by making use ofsodi.um hypochlorite to oxidize SG in the present research.As-prepared oxidized SG was then used as a warp sizing agentfor fine cotton yarns, and its physico-mechanical properties suchas tensile strength, elongation at break, hairiness index, andabrasion resistance were investigated in relation to warp sizingperformance.

2. Experimental

2.1. Materials

Commercial sesbania gum (apparent viscosity ¼ 2000 mPa s;numbereaveragemolecular weight¼ 2.0� 105) was obtained fromLankao Vegetable Gum Factory (Kaifeng, China). Polyvinyl alcohol(trade name: PVA205; alcoholysis degree ¼ 88%; degreepolymerization ¼ 500) was commercially obtained from KurarayTrading (Shanghai) Co., Ltd (Shanghai, China). Potato esterifiedstarch (trade name: PR-Su) was supplied by Emsland-Starke Co., Ltd(Lower Saxony, Germany). Light cotton fabric (14.5 tex) sampleswere provided by Zhengzhou No. 3 Textile Co., Ltd (Zhengzhou,China). Analytical grade sodium hypochlorite and anhydrous ethylalcohol were supplied by Deen Agents Co., Ltd (Tianjin, China).Distilled water prepared at our lab was used as a solvent and forrinsing as well.

2.2. Preparation of oxidized sesbania gum

Unless otherwise stated, the oxidation process was conducted asfollows. Briefly, 2.0 g of sesbania gumwas placed in a 250mL three-neck round bottom flask equipped with a thermometer,a condenser and a dropping funnel, and dispersed with a certainamount of anhydrous ethyl alcohol at ambient temperature, fol-lowed by mixing with 200 mL of distilled water. Then 4 mL ofsodium hypochlorite solution (mass fraction of active chlorine:10%) was added into the flask from the dropping funnel; resultantreactant mixture was heated in a thermostatic water-bath undermagnetic stirring until pre-set temperature (40 �C) was reached.After the reactant mixture was stirred for about 15 min, theaqueous solution of sodium hypochlorite was slowly dripped intothe flask also from the dropping funnel to allow oxidation reactionfor 1 h. Target product, OSG slurry, was precipitated by methanoland dried at 80 �C in an oven for 24 h. Resultant dried OSG samplewas then used for characterization.

2.3. Structural characterizations

An Avatar360 Fourier transformation infrared (FTIR) spectrometer(Nicolet Company, USA) was performed to record the FTIR spectra ofSG and OSG (SG and OSG samples were mixed with KBr and pressedinto pellets, respectively.); FTIR spectrawere recorded within awave-number range of 400e4000 cm�1. An EXSTAR6000 thermal analysissystem(SeikoCompany, Japan)wasperformed toevaluate the thermalstability of SG and OSG, withwhich thermogravimetric analysis (TGA)and differential thermal analysis were carried out in N2 fromtemperature to 900 �C at a heating rate of 10 �C/min. Themorphologyof SG and OSG samples was observed using a JSM5600LV scanningelectron microscope (SEM; JEOL Co., Ltd., Japan; beam voltage 20 kV).The samples for SEM analysis were obtained by pasting a smallamount of SG or OSG powder onto copper slices with conductive tapeinassociationwith follow-up ionplatingofAufilm. Themicrostructureof OSG was analyzed with a JEM-2010 high resolution transmissionelectron microscope (HRTEM; JEOL Co., Ltd., Japan) at an acceleratingvoltage of 200 kV, with which a proper amount of OSG slurry wasdispersed in distilled water, dripped onto carbon coated copper grid,and dried in atmosphere to generate samples for TEM analysis.

2.4. Evaluation of apparent viscosity and viscosity stability

The apparent viscosity of OSG was evaluated with an NDJ-1rotary viscometer (Shanghai Changji Geology Instrument Co., Ltd.,Shanghai, China) in a two-step manner. At the first step, theapparent viscosity of 1% OSG slurry (mass fraction; solvent:distilledwater) wasmeasured at 40 �C, 50 �C, 60 �C, 70 �C, 80 �C and90 �C, respectively. The OSG slurry was then held at 90 �C for 1 h,followed by the second step of measurement of apparent viscosityat 90 �C, 80 �C, 70 �C, 60 �C, 50 �C and 40 �C, respectively. Theviscosity stability of the OSG slurry was examined by heating at95 �C for up to 7 h in connectionwithmeasuring viscosity every 1 h.The viscosity stability is calculated as Zhu et al. [24]:

Vs ¼�1� Vmax � Vmin

V

�� 100

Where V is the apparent viscosity of the slurry; Vmax and Vmin arethe maximum and minimum viscosity measured in 7 h of viscositystability test.

2.5. Adhesion of OSG slurry

The adhesion of OSG slurry was estimated by making use ofroving-impregnation method. Briefly, 2500 mL of 1% OSG slurry

4000 3500 3000 2500 2000 1500 1000 50010

15

20

25

30

Tran

smitt

ance

(%)

Wavenumbers(cm-1)

SG

OSG

Fig. 2. FTIR spectra of SG and OSG.

D. Shen et al. / Polymer Degradation and Stability 96 (2011) 2181e2188 2183

was placed in a beaker and heated to 95 �C with a thermostaticwater-bath under mechanical stirring. After the OSG slurry waskept at 95 �C for 1 h, rovings softly entwined with a speciallydesigned metal rack were immersed into the slurry and kept for5 min. At the end of immersion, the rovings were taken out of theslurry and vertically hung in atmosphere to allow drying. As-driedrovings were kept at 20 �C for 24 h (relative humidity 65%) beforebeing used for evaluation of mechanical properties. The adhesion ofthe ready-to-use rovings was measured with a HD026 fabricstrength tester (Nantong Hongda Experimental InstrumentsCompany Ltd., Nantong, China) at a sample gauge length of 100mmand rate of 50 mm/min.

2.6. Warp sizing of OSG slurry for fine cotton yarns

Fine cotton yarns were fabricated with a GA391 single yarnsizing machine (vertical; Tongyuan Electrical InstrumentsCompany Ltd., Jiangyin, China). They were impregnated at 25 �Cwith 1% OSG slurry, 1% PVA205 liquor, and 1% PR-Su solution,respectively. Resultant impregnated cotton yarns were squeezedand dried in an electric oven at 100 �C for 5 min. Before the warpsizing performance was evaluated, the sized and non-sized fabricsamples were conditioned at a temperature of 20 �C and relativehumidity of 65% for at least 24 h (YG751B constant temperature/humidity cabinet; Ningbo Textile Instrument Factory, Ningbo,China).

2.7. Mechanical properties of sized fine cotton yarns

2.7.1. Tensile strength and elongation at breakThe tensile strength and elongation at break of fine cotton yarns

and the sized ones were determined with a YG061 electronic singleyarn sizing machine (Laizhou Electrical Instruments Company Ltd.,Laizhou, China) at a sample gauge length of 500 mm, rate of500 mm/min, temperature of 20 �C, relative humidity of 65%, andcorrection factor of 1, in orientation stretching mode (the lightcotton fabric samples and the sized ones had a linear density of14.5 tex). Ten repeat measurements were carried out. The averagedtensile strength and elongation at break of the ten repeat tests arereported in this article.

2.7.2. Hairiness indexThe hairiness index of sized fine cotton yarns (14.5 tex) was

estimated with a YG171B-1 hairiness yarn meter (Laizhou ElectricalInstruments Company Ltd., Laizhou, China) at a rate of 30 m/min,temperature of 20 �C, relatively humidity of 65%, and segmentlength of 10 m. Ten repeat measurements were carried out. Theaveraged hariness index of the ten repeat tests is reported in thisarticle.

2.7.3. Abrasion resistanceThe abrasion resistance of sized fine cotton yarns (14.5 tex) was

evaluated using an LYF-20 multi-function textile abrasion tester(Shandong Research Institute of Textile Science, Qingdao, China) ata rotary rate of 60 rev/min. Abrasive paper of 400 mesh was usedfor the abrasion test. Ten repeat measurements were carried out.The averaged value of the ten repeat tests is reported in this article.

3. Results and discussion

3.1. Characterizations analyses

3.1.1. FTIR analysisFTIR analysis was carried out to compare the chemical structural

identity of purified sesbania gum and oxidized sesbania gum and to

explore their degradation behavior and intra-molecular interac-tions. The FTIR spectra of SG and OSG are shown in Fig. 2, where theknown composition of SG can be used for verification. In general,SG and OSG show almost the same FTIR spectra. The absorptionbands at 3413 cm�1 and 1390 cm�1 are assigned to the stretchingvibration of OeH group; and those at 2923 cm�1 and 1075 cm�1 areattributed to stretching vibration of CeH and CeO, respectively.Besides, the absorption bands at 1653 cm�1 and 1637 cm�1 may beattributed to H2O. This means that, although it is assumed that highmolecular weight SG is oxidized by sodium hypochlorite to yieldlow molecular weight OSG in association with formation of basiccomponents of mannose and galactose via breakage of be(1e4)eglycoside linkages and ae(1e6)eglycoside linkages (Fig. 3), no FTIRevidences are available about such oxidation-induced changes inchemical structure of SG.

3.1.2. Thermal analysisThe thermal stability of warp sizing agents has a great effect on

the warp sizing performance. The TG curves of SG and OSGmeasured in N2 are shown in Figs. 4 and 5. It is seen that SG andOSG have excellent thermal stability from room temperature to240 �C and 220 �C, respectively; but they become unstable andobviously lose weight above 240 �C and 220 �C, possibly due tovolatilization, dehydration, oxidation and other chemical reactionsthereat. In terms of thermal stability, OSG can be used as a qualifiedand efficient high-temperature sizing agent for fine cotton yarns.

3.1.3. SEM and HRTEM analysisFig. 6 shows the SEM images of SG and OSG. It can be seen that

both SG and OSG have a broad range of size distribution (approx-imately 10e100 mm). Though OSG seems to be smoother than SG,the former has a larger size and seemingly contains a fewmicrogel-like polymer segments. Such differences in the morphology of SGand OSGmay be attributed to external factors like temperature andhumidity as well as internal factors like dipole forces, in particular,hydrogen-bonding with ability to stiffen and strengthen polymermolecules (see Fig. 7).

The HRTEM image of the OSG slurry is illustrated in Fig. 8. It canbe seen that OSG slurry contains needle-like structurewith a lengthof up to 200 nm, which may favor the permeation of OSG slurryin fine cotton yarns, resulting in poor sizing quality and loomefficiency.

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+

sodium hypochlorite

Fig. 3. Schematic diagram showing possible oxidation process of SG.

D. Shen et al. / Polymer Degradation and Stability 96 (2011) 2181e21882184

3.2. Liquor viscosity

3.2.1. Apparent viscosityDue to its high viscosity, only SG solution with a low concen-

tration can be used for warp sizing of fine cotton yarns. Even so, 1%SG slurry still has a high viscosity of more than 2000mPa s, which is

200 400 600 800 10000

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100

Temperature( )

TG

(%)

-0.0012

-0.0010

-0.0008

-0.0006

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0.0000

0.0002

DT

G

240

Fig. 4. TG and DTG curves of SG.

unbeneficial for SG liquid to penetrate into the interior of cottonyarn, resulting in poor sizing quality and loom efficiency. Fig. 9shows the variation of apparent viscosity of 1% OSG slurry withtemperature; where curve a refers to temperature-rising process ofthe slurry from 40 �C to 90 �C, and curve b refers to temperature-declining process of the slurry from 90 �C to 40 �C after it was

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(%)

-0.0010

-0.0008

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G

Fig. 5. TG and DTG curves of OSG.

Fig. 6. SEM images of SG and OSG.

D. Shen et al. / Polymer Degradation and Stability 96 (2011) 2181e2188 2185

kept at 90 �C for 1 h. The apparent viscosity of OSG slurry graduallydeclined with the increase of temperature from 40 �C to 90 �C. After1% OSG slurry was kept at 90 �C for 1 h, its apparent viscosity rosesignificantly with the decrease of temperature from 90 �C to 40 �C(right to left on x axle). It is likely that highmolecular weight chainsof SG are oxidized by sodium hypochlorite to yield low molecularweight chains, which contributes to enhance the flexibility ofmolecular chains and increase the softening point, thereby result-ing in sharply decreased apparent viscosity of OSG liquid. In themeantime, the entangled molecular chains of OSG slurry may berearranged and uncoiled after it was heated at 90 �C for 1 h. Asa result, the OSG slurry heated at 90 �C for 1 h possessed a lowerapparent viscosity than as-synthesized OSG slurry under varioustemperatures.

3.2.2. Viscosity stabilityNeedless to say, unstable warp sizing liquids are unfavorable for

fine cotton yarns, due to uneven warp sizing and generation ofa large amount of hairiness [20]. In other words, OSG slurry asa warp sizing agent of cotton yarns should have good viscosity

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Fig. 7. Possible structure

stability after being stored for different periods. As shown in Fig. 10,1% OSG slurry has a linearly-fitted apparent viscosity of about44.3 mPa s and a viscosity stability of 90.3%. This means that theOSG slurry possesses good viscosity stability and may be well usedfor the warp sizing of fine cotton yarns.

3.3. Adhesion

The adhesion of polymeric warp sizing agents to yarns surfacestrongly depends on the interaction between polymers and yarns,and adhesives can be used to increase the adhesion strength oftwo different structures by way of forming a composite, as inpolymerepolymer welding. Besides, chemical bonding helps torealize enhanced contact between warp sizing agent and yarns,thereby improving the physico-mechanical properties of the sizedfine cotton yarns. In this respect, it will be feasible to improve thephysico-mechanical properties of sized fine cotton yarns withoutreducing its wrinkle resistance if the cross-linking on the yarnssurface is reduced while that in its interior is maintained. Theadhesion of OSG slurry to 65/35 polyester/cotton blend (T/C)

H

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of cross-linked OSG.

Fig. 8. HRTEM image of OSG.

1 2 3 4 5 6 7

36

38

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46

48

50

52

54

Fig. 10. Variation of the apparent viscosity of 1% OSG slurry with storage time. Thestraight line refers to the variation of linearly-fitted apparent viscosity of the OSGslurry with storage time.

D. Shen et al. / Polymer Degradation and Stability 96 (2011) 2181e21882186

rovings and cotton rovings was measured and compared with thatof PVA205 and PR-Su under the same concentration of 1% (massfraction of warp sizing agent in 100 mL of solution). Relevantresults are listed in Fig. 11. It is seen that OSG slurry has a slightlyhigher adhesion to T/C than PVA205 and PR-Su, but it possessesmuch higher adhesion to cotton than PVA205 and PR-Su. It islikely that, Compared with PVA205 and PR-Su, the OSG slurry hassmaller particle size, which affects the penetration of the sizingliquor into the interior of the yarns. In addition, because oxidation-induced changes in chemical structure of SG, chemical bondingcould be increased between the two layers contribute to increasednumbers of bonds and greater physico-mechanical propertiesthereby establishing good contact area with the yarns. This indi-cates that as-synthesized OSG slurry may find promising appli-cation as a novel high-performance warp sizing agent for finecotton yarns.

40 50 60 70 80 9025

50

75

100

125

150

175

200

225

250

275

300

325

a

b

Fig. 9. Variation of the apparent viscosity of 1% OSG slurry with temperature. Curvea refers to temperature-rising process of the slurry from 40 �C to 90 �C, and curveb refers to temperature-declining process of the slurry from 90 �C to 40 �C after beingkept at 90 �C for 1 h (right to left on x axle).

3.4. Physico-mechanical properties of fine cotton yarns sizedwith 1% OSG slurry

As an interesting alternative to the conventional sizing process,the use of appropriate technologies makes it possible to apply OSGin the form of a sizing agent resistant to warp breakages. However,the prime consideration in determining the general utility ofa sizing agent is its mechanical behavior. Hence, textile companiesmay utilize the expected properties of OSG for warp sizing anddevelop suitable sizing agents. The physico-mechanical propertiesof pure OSG type were measured in combination with fine cottonyarns in order to obtain information on the warp sizing perfor-mance in comparison to standard size types.

3.4.1. Tensile strength and elongation at breakThe tensile strength and elongation at break of the fine cotton

yarns treated with various warp sizing agents are listed in Fig. 12.

cba0

20

40

60

80

100

120

T/C

Adhe

sion

(N)

Sizing agents

Cotton

Fig. 11. Adhesion of various warp sizing agents ((a) OSG, (b) PVA205 and (c) PR-Su) toT/C and cotton.

a b c d0

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100

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400 Tensile strength (cN)

Samples

0

1

2

3

4

5

6 Elongation at break (%)

Fig. 12. Physico-mechanical properties of fine cotton yarns treated with different warpsizing agents (concentration 1%): (a) raw yarn, (b) treated with OSG, (c) treated withPVA205 and (d) treated with PR-Su. Curve refers to tensile strength and elongation atbreak (left to right on y axle).

a b c d0

20

40

60

80

100

Abra

sion

resi

stan

ce (c

ycle

s)

Samples

Fig. 14. Abrasion resistance of fine cotton yarns treated with various warp sizingagents (concentration 1%): (a) raw yarn, (b) treated with OSG, (c) treated with PVA205and (d) treated with PR-Su.

D. Shen et al. / Polymer Degradation and Stability 96 (2011) 2181e2188 2187

Obviously, the tensile strength of fine cotton yarns is increased andits elongation at break is reduced after being warp sized with thethree kinds of warp sizing agents, where OSG lies in between interms of the ability to increase the tensile strength and decrease theelongation at break of the cotton fabric. Cotton yarns are polymersthat have high resistance to deformationdthey undergo only lowelongations and have very high tensile strengths. Compared withPVA205 and PR-Su, the intermolecular interaction between OSGand yarns similarly protects the fine cotton yarns againstmechanical attack by weaving loom. As a result, as-synthesizedOSG slurry has promising application as a novel warp sizingagent for fine cotton yarns.

3.4.2. Hairiness index and abrasion resistanceHairiness index is usually used to show the level of homogeneity

of fine cotton yarns routinely obtained. The homogeneity is usuallydetected using hairiness lengths, with which yarns analysis are

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0

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25

30

35

40

45

Hai

rines

s in

dex

Hairiness length ( mm)

Raw yran Treated with OSG Treated with PVA205 Treated with PR-Su

Fig. 13. Hairiness index of fine cotton yarns treated with various warp sizing agents(concentration 1%).

usually carried out at hairiness lengths from 2 mm to 5 mm, and inparticular at 3 mm for 14.5 tex of fine cotton yarns. Fig. 13 lists thehairiness index of the cfine cotton yarns (14.5 tex) treated withvarious warp sizing agents. The fine cotton yarns treated with OSGat hairiness lengths from 2 mm to 5 mm have the smaller hairinessindex, which indicates that OSG may be a potential high-performance warp sizing agent for fine cotton yarns.

Intermolecular interactions like hydrogen bond are typicallyeasily adhered between the warp sizing agents and the innersurfaces of fine cotton yarns, and it may be essential that the finecotton yarns in contact with the warp sizing agents have goodabrasion resistance. Fig. 14 shows the abrasion resistance of the finecotton yarns treated with various warp sizing agents. It is seen thatthe fine cotton yarns treated with 1% OSG slurry possesses slightlyincreased abrasion resistance than the untreated one. OSG iscomparable to PVA205 but much less effective than PR-Su in termsof the ability to increase the abrasion resistance of the fine cottonyarns. This is contradictive to the data of hairiness index.

4. Conclusions

OSGwith significantlydecreased apparent viscositywas obtainedby oxidizing SGwith sodium hypochlorite. Resultant as-synthesizedOSG slurry (concentration 1%) as a warp sizing agent had goodadhesionandwas able to effectively increase the tensile strength anddecrease elongation at break of the fine cotton yarns. Besides, as-synthesized OSG slurry was also able to obviously decrease thehairiness index and slightly increase the abrasion resistance of thefine cotton yarns, showing promising application as a novel high-performance warp sizing agent for the fine cotton yarns.

Acknowledgments

The authors acknowledge the financial support provided bythe Education Bureau of Henan province (Grant No. 2008A540002)and the Science and Technology Bureau of Kaifeng City (GrantNo. 09112).

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