Chemical Modification of Silk Fibers with Ethylene Glycol Dimethacrylate

20Journal of Dong Hua University (Eng. Ed.) Vol. 19 No.1 (2002)Chemical Modification of Silk Fibers with Ethylene GlycolDimethacrylateCHEN Guo-qiang(陈国强) *Silk Research Instiue, Suzhou University, Suzhou ,215021ZHOU Xiang(周翔)College of Chemistry and Chenmical Eninering; Dong Hua Unvrsity, Shanghai , 200051Sillk fibers have been grafted with ethylene glycolpaper the effect of gafting sik fibers with ethylene glycoldimethacrylate ( EGDMA) and characteristics of thedimethacrylate(EGDMA) on the characteritics of the grafted onesgrafted silk fibers were analyzed in relation to the grafthas been studied under various graft yield conditions based on theyield on the basis of the tensile properties, dyeingresult of the dyeing behaviour, tensile properties, fiber durabilitybehaviour, durability during laundering and solubility ofduring laundering and fiber solubility in NaOH solution. Thesethe specimen in NaOH solution. The amount of the acidstudies may provide an important basis about the improvement ofdye absorbed by the fibers decreased with increasingthe current techniques of chemical mdifcation.graft yield, while the value of rating for washing fastnesson silk fibers was almost unchanged by the graftExperimenttreatment. The breaking loads of the fiber were almostunchanged whereas rigidity of the fibers increased afterlMaterials and reagentsgraft treatment. Graft treatnent enhanced silk fiberThe degummed silk fiber (21/22D) was used as gratingdurability during laundering and in Na0H solution.substrate. The EGDMA monomer, purchased from Suzhou AnliKeywords : Silk fibers, Chemical Modification, Ethylene glycolChemicals Company Ltd., was used without further purification.dimethacrylate.The dyestuff used were Carbolan Red 3B (C.1. Acid Red 139)and Weakly Acid Brliant Blue R (C.I. Acid Blue 62). Otherreagents used were of laboratory -reagent grade.Introduction2 Grafting procedureA measured amount of silk fibers was immersed in alcobolSilk pssesses many outstanding advantages such as goodaqucous solution (alcohol/water: 1/7) at necessary pH ( adjusteddyeability，moisture absorption and excellent fabric hand, inwith 2 mL/L formic acid)， containing 1.85% potassiumnstriking contrast with the synthetic fbers and fabric. However, silkpersulfate(KPS) on the weight of BGDMA, and 80% EGDMAcharacteristics including photoyellowing, wrinkle recovery, rut(owf) . The materialto-liquor ratio of 1:30 was maintained. Thresistance during laundering, and color fatness should be furthertemperature was raised to the desired value (50- 90C) and thenimproved.maintained for required time in constant temperature and vibrationalIn recent years a considerable amountof work has beenwater bath kettle. At the end of the reaction silk fiber was soakedcarnied out on chemical modification techniques onto silk with theior 30min at 60C with water containing 0.5g/L non ionicwide variety of vinyl monomers, epoxides1.2], and otheemulsifying agent OS, then rinsed with water at least three timesmodifying agents available. These techniques promise to band dried at 105C for 2 h. Samples were placed in a dehumidiferpowerful methods for substantial modifying fiber properties as wellover silica gel before measurements. Then the samples wereIs improving their textile performances. Among the vinylweighed and measured.monomers, methyl methacrylate ( MMA )b3J，methacrylamide3 Test methods(MAA )4，2- hydroxyethylmethacrylate ( HEMA )[s],The graft yield， G， was calculated according to themethacrylonitrile ( MAN)l6]，and styrene ( St)l7] have beenfolloextensively studied.中国煤化工x 100/w(1)Very litle work has been reported on the use ofTYHCNMHGmoulifunctional monomers during grafting of silk fibers(8,9]. In this where W2 1s the weignt of une grautea sample; Wi, the weight of#To whom crrespondence should be adressedReceived Dec. 6,2001Journal of Dong Hua University (Eng. Ed.) Vol. 19 No.1 (2002)21the original sample.polymer, which can be accomplished in many ways. The chemicalTensile tests of single silk flaments were made with a fiberinitiation technique inevitably needs initiators for this purpose. Thestrength tester (YG003) at 30C and 65% RH. The strain rateinitiators decompose on heating into free radicals that are capablewas 30 mm/ min and the gauge length was 25 mm. Machine strainof abstracting the H atom from the backbone polymer, creating sitewas within experimental eror. Breaking load and rigidity, whichfor the growth of a graft chain.are defined as the values of the tensile strength and initial modulusIn grafting systems like the one in this study, it is inevitablemultiplied by the cross-sectional area of the fiber werethat the homopolymer of the grafted monomer is formned in thedetermined 10.The values presented are the average of ten tests.graft polymerization medium. The common method for theDyeing was carried out at 9sC for 40 min and the dyebathremoval of the homopolymer from the fber is extraction of thewas adjusted to pH 4.5 using acetic acid (0.4mL/L), keeping ahomopolymer with an appropriate solvent. In the studiesmaterial-to-liquor ratio of 1:50. The initial dye concentration wasconcerming the grafting of vinyl monomers, the major solvents1% (owf). The dyed sample was taken out and rinsed well withused for the extraction of the homopolymer are acetene11.121] anddisilled water.benzene . 13.14) There was no decrease in the gaied sample weightThe colour measurement of the dyed samples was performedafter the sample was Soxhlet-extracted with acetone and benzeneunder Des iluminant at 10P observed through an Ultra Scan XErespectively for8 h. The increase in weight in the original samplespectophotometer. The reflectance values at maximum absorptionincluded two parts of graft polymer and homopolymer, but thewavelength were converted into K/S values.homopolymer may be very litle. It is believed that theThe fastness testing was caried out according to Chinesepolymerization reaction is mainly a grafting process. So, we tookNational Standard GB3923 - 83.the increase in weight in the original sarmple afer the graftingThe fibers were laundered for several times according to theprocedure as graft yield.method like GB/T 8629 method 4A (eqv ISO 6330) by placingEffect of reaction temperature and timethe fibers in a bag made of cotton fabric and using a washing-on graft yieldmachine.Fig.1 shows the effect of reaction temperature and time onThe surface morphology of silk samples was exarnined bythe gating. It can be seen clearly that the graft yield increasesscanning elecron microscopy(DXS10- A).with the increase of temperature up to 80C and beyond this limit itAlkali solubility was determined by the fllwing method.decreases. The inial increasing trend can be ascribed to a greaterSilk fibers (grafed as well as control samples)(0.2 g) was treatedactivation. As pointed out by Arai and Negishil15.16] in a similarwith 10 mL0.5 mol/L NaOH at 65C for 60 min. The fibers weresystem (methyl methacrylate grafing silk)， the mobility of thefiltered and washed with dild water, then washed twice withgrafted polyner chain end was controlled by the segmental mobilityaqueous acetic acid ，and finally washed several times withof the backbone polymer. Owing to the high stability of silk fiberdilled water. They were then dried at 110C and weighed. Thebackbone chains, the mobility of the graft copolymer radicalspercentage loss in weight of the silk gave the alkali solubility .would be greatly restricted. As a consequence, increasing thetemperature will thus increase the mobility of the graft copolymerResults and Discussionradicals greatly. Furthermore, at a higher temperature， thediffusion of the monomer to silk fber is also enhanced. As a resultThe graft copolymerization reaction onto textile fibers isthe initial increasing trend can be seen.carried out through generation of free radical sites on the backbone504540巴35- + 50"C吕30-60C! 25-★70'C2(- *-80'C;1-*- 85'C中国煤化工1(230TYHCNMHGTime/ minFig.1 Effer of graft temperature on graft yield22Journal of Dong Hua University (Eng. Ed.) Vol. 19 No.1 (2002)However, when the temperature is more than 80C, the3 Dyeing propertiescombination rates of radicals will increase and, as a result, theThe color appearance of dyed fibers is better expressed ingraft yield will decrease. The increase in temperature will haveterms of K/S values, obtained by reflectance measurements.several efects: 1) enhancement of the ease of free madicalThese values are related to the amount of dye absorbed and are aformation; 2) increase in the mobility of monomer and initiator;direct measure of bue, intensity, and depth of shade of dyed3) higher rate of polymerization in solution phase than that in fibersamples.phase, so, change of the balance of competition between graftK/S values of silk fbers grafted with EGDMA werecopolymerization and homopolymerization, etc.calculated on the basis of reflectance measurements at 520 nm andOa the other hand, from Fig.1 it can be seen that, with the640 nm respectively. Results obtained are listed in Table 1. Slightincrease of reaction time, graft yields increase up to 30 min anddecrease of the K/S for the gafted silk fibers was observed. Thethen become rclatively constant wih a futher increase of reactionresults demonstrating the difference in dyeing appear to have madeime. Similar trend has been reported in the system of acrylonitrilea considerable contribution to the decreased internaction dyeing sitesgrafting to silk fiber.tn] The phenomena may be explained asand acessibility because of graft cross linking between the silkfollows: with the increase of reaction time, the concentration offber molecules and EGDMA.monomer decreases. On the other hand,as the graftTable 1 K/S values of silk fbers grafted with EGDMApolymerization is going on and the number of the grafted branchesincreases to be relatively constant. Since the surface of the fiber isK/SGrat yield (%)-covered by the graft polymer chains, it is difficult that new activeC.I. Acid Red 139C.1. Acid Blue 62graft site forms. When the grafting reaction reaches saturation graftyield, the value of the graft yield will remain unchanged.Ungrafted 015.419.60 .Tensile properties12.514.6218.2322.513.5117.92In Fig.2 and Fig. 3, the breaking loads and rigidity of the32.913.1217.38grafted silk fibers are plotted against graft yield. The value of thebreaking load was almost unchanged. But the rigidity increasedwith the increase in the graft yield. This indicates that high creaseThe wash fastness properties of grafted dyed as well asungrafted dyed fibers are presented in Tab.2. It can be scen fromresistance can be expected from grafted silk fibers.the table that the graft does not alter the fastness properties of dyed10「samples. The fatness of grafted dyed fibers is comparable withthat of ungrafted dyed ones.Table 2 Color fastness of grafted silk fibers dyed6上Wshing (Rating)Grat yield (%)&1C.I. Acid Red 139 C.I. Acid Blue 6224.03.510203040Graft yield (%)32.9 .Fig. 2 Breaking loads as a function of graft yield4 Laundering durability12 [Silk fibers include a bundle of fibrils that are bound together0tby a hydrogen bonding mechanism. The hydrogen bonding isreadily dissociated when the fbers are swollen in water.8'Therefore, if a mechanical stress is imposed on the wet sik fbers,the fibers are easily tom into fibris, and the durability of fibersagainst laundering is diminished The occurrence of abrasion onthe中国煤化工ering will subatalaly lowerCNMHCjibers. In Tab.3, a retention0ratio小, wuinmby upi.心日puud against graft yield:R = A:/Ao(2)Fig. 3 Rigidity as a function of graft yieldwhere Ao and A1 are respectively the breaking loads of theJournal of Dong Hua University (Eng. Ed.) Vol. 19 No.1 (2002)23ungrafted fibers and the EGDMA-grafted fiberScanning electron micrographs of silk fibers laundered for tenlaundered ten times. The value of R became almost great whentimes are shown in Fig.4 and Fig. 5. Serious damage can begnaft yield increase, indicating that damage to the fibers duringobserved on ungrafted fibers (Fig. 4), while a smooth surface waslaundering was reduced.retained and only slight damage was observed on the grafted silkfbers (Fig. 5). It is thought likely that EGDMA polymer chainsTable 3 Retention atio of grafted silk fiber afterlaundering for ten timescrosslinked with each other. Crosslinking between EGDMApolymer chains tended to generate a network structure on theGraft yield(%)12.522.532.9surface of silk fibers, with the crosslinking reducing the damage tothe silk fbers during laundering.R0.750.890.910.93 .8.0011 820002891h2Fig. 4 Surface of ungrafted slk fbersFig. 5 Surface of grafed silk fibers (graft yield 12.5%)fter laundering for ten timesafter laundering for ten times5 Alkali solubilityhydrolyze them, i.e., to split the complex molecule into simpleFig. 6 shows the relationship between the alkali solubility andderivatives by a process of hydrolytic fssion at the polypeptidegraft yield of the silk fibers grafted with EGDMA. The solubilitybonds. The result demonstrating the decrease in the alkali solubilityof the ungrated silk fiber in a 0.5 mol/L NaOH solution wasof grafted silk fibers appears to have made a considenable47%，when the graft yield increased, the solubility decreased.contribution to the new coslinks formed on the backbone whichThe principal action of aqueous solutions of alkalis on proteins is towere protected to withstand akali hydrolysis.。50。色45↑5 40乏35s30,25e 2015E 10另5510 15 202530 35Fig. 6 Solubility of silk fbers graied with EGDMAMean中国煤化工ye absorbed by the fibersConclusionsdecreavhile the value of rating forwashirYHC N M H Gost unchanged by the graftThe graft of BGDMA onto silk fbers is an effective methodtreatment.to modify silk. It can be used for weighting silk and lowering thedamage to silk during laundering and in NaOH solution.24Journal of Dong Hua University ( Eng. Ed.) Vol. 19 No.1 (2002)Universiy( English Editon) ,2001 ,18(3) ,75References[10]} Kawahara Y., Shioya M. and Takaku A.，JSDC, 1995, 11,382,[1] Shiozaki H. and Tanaka Y., Malcromol. Chem., 1971, 143, 25.HuangY., Zhao B., ZhengG., HeS.. and GaoJ, J. Appl.[2] Tanaka Y. and Shiozaki H., J. Polym. Sci. Polym. Chem. Ed.Polym. Sci., 1992, 45,7112, 2741[12] Mamauchi J., Yamaoko A.. Ikemoto K., and Matsui T., J.[3] Tsukada M. ,J. Appl. Pobm. Sci., 1988,35, 965Appl. Polym. Sci., 1991,43, 1197[4] Bianchi Svilokos A., Massafra M. R., and Beretta s., La Seta,[13] VarmaD. s. and Ray N. D., Angew. Makromol. Chem., 1973,1983,46, 4 (in Ialin)32, 81[5] TsukadaM., J. Seric. Sei., 1984,53, 380 (in Japanese)[14] E-Rafie M. H, K hali M. I.. and Hcbeish A., J. Appl.[6] Tsuikada M. and Shiozalki H.. J. Appl. Polymn. Sci., 1990,39,Polymn. Sci., 1975, 19, 16771289[I5] Arai K. and Negishi M., Seni-Gakaishi, 1967, 23, 595 (in[7] KakoT.. Katayama A.. and Kuroki N., J. Seric. Sci., 1977,Japanese)46, 103 (in Japanse)[16] Arai K, Ngishi M., Komine s. , and Takeda K, Appl. Polym.[8] KatoH., J. Serc. Sci.. 1986,55, 235, (in Japanese)[9] Chean Guqiang, Xing Teling, Zhou Xiang, Joumal of Dong Hua[17] Huang C. and Hu H.，Polymer Materials Science and Enginerring，1987 .2,59 (in Chinese)中国煤化工MYHCNMHG