Study on Poly Ethylene Terephthalate Fabric to Improve Its Hydrophilic Character Using Poly Vinyl Alcohol

Abstract

The advent of synthetic yarns dawned a new era in the textileworld. Poly(ethylene terephthalate) or PET or polyester is one of the mostimportant synthetic fibres due to its high strength, elasticity, abrasionresistance, durability, crease recovery and good resistance to chemical,biological and environmental degradations. They have scored over naturalfibres as regards their light weight and ease of care properties. A significantdrawback of polyester material is its hydrophobic nature. The PET fibres do notabsorb water as do natural fibres like cotton. The fabric worn next to skin shouldabsorb perspiration and facilitate heat exchange with the surroundings. Hencethere is a need for extensive investigation in improving hydrophilicity of PETfabric.It is rather difficult to modify the surface properties of polyestermaterial due to its crystalline structure and deficiency of reactive groups. Ofthe various methods suggested, alkali treatment is commercially viable. In thisstudy an attempt is made to improve hydrophilicity of polyester fabric byemploying concomitant effect of sodium hydroxide and poly(vinyl alcohol)on PET fabric by two methods. Poly(vinyl alcohol) or PVA, is a non-toxicsynthetic polymer with good physical and chemical properties and film-forming ability with relatively a simple structure of pendant hydroxyl groups.Modification of the PET fabric surface without involving hazardous organicsolvents and achieving permanent hydrophilic character is the advantage of thechosen method. ivIn the first method a single stage treatment of PET fabric with PVAin alkaline medium was carried out. The PET fabric was treated with asolution of Poly(vinyl alcohol) in alkaline medium at boiling temperature.The treated fabric was washed with hot water to remove physically held PVA.The moisture related properties of the fabric, tensile strength, spectralanalysis, thermal studies, dyeability of fabric with disperse dyes, basic dyesand reactive dyes were assessed. The PET fabrics treated with sodiumhydroxide alone, under similar experimental conditions, were taken as controlfabrics with which the performance of PVA treated PET fabrics werecompared. Experiments were carried out using ten different concentrations ofPVA and sodium hydroxide. Based on the performance of treated fabrics, thetreatment of PET fabric with 1.5% (w/v) PVA solution in 1 N sodiumhydroxide at boil were considered as the optimum condition.The permanency of the presence of PVA on PET was confirmed byspot test after successive washings. The PVA treated PET fabric tested with adrop of boric acid and a drop of iodine solution developed a blue colour,confirming the presence of PVA. The PVA treated fabric showed improvedwettability, moisture regain, water retention and wickability. The watercontact angle of the PVA treated, control and untreated PET fabrics werefound to be 67.31º, 116.75º and 124.24º, respectively. The dyeability of thefabric showed improvement with both disperse and reactive dyes. The SEMphotograph and ATR-FTIR spectra of the fabric revealed the presence ofPVA. Melting temperature and heat of fusion of the treated fabric decreasedas indicated in the DSC traces. Analysis of moisture related properties and vreactive dyeing of the fabric revealed that high molecular weight PVA wasgiving better results compared to low molecular weight PVA.In the second method, application of PVA on PET fabric using atwo stage process was carried out. PET fabric was first treated with 1 Nsodium hydroxide at boil for one hour. The sodium hydroxide treated fabricswere padded with PVA solution along with glutaraldehyde, magnesiumchloride and acetic acid by a 3-dip/3-nip process, dried at 100oC, cured at150° C for 3 minutes. The treated samples were soaped to remove physicallyheld PVA.To assess the effect of glutaraldehyde on polyvinyl alcohol fixation,PET fabrics were padded with different concentrations of glutaraldehyde,magnesium chloride(10gpl) and acetic acid (0.1%), dried at 100oC, cured at150° C for 3 minutes and washed. The treated PET fabric showed improvedwettability, water retention and wickability. The dyeability of PET fabric withreactive dye showed considerable improvement. This observationsubstantiates the presence of polar hydroxyl functional groups on the treatedfabric surface. The dyeability of fabric with disperse dye was hindered by thistreatment as indicated by a low K/S value. The tensile strength of the fabricwas found to increase after PVA treatment.The SEM photograph of treated fabric revealed the presence ofPVA. The ATR-FTIR spectra of the PVA treated PET fabric showed a broadband in the region 3435 cm-1 which revealed the presence of hydroxyl groups.Study of moisture related properties, dyeability and spectral analysis showed vithat high molecular weight PVA showed better binding with PET fabriccompared to low molecular weight PVA.The pre-treatment conditions were varied and the PET fabrics weretreated with varying concentrations of NaOH solutions. PVA was applied onthese control fabrics by pad dry cure method. Based on the performance oftreated fabrics it is clear that the optimum pre-treatment condition forapplying PVA on PET fabric is treatment with 1 N NaOH giving a weightloss of about 5.77 %.The PET fabric was given a commercial hydrophilic finish,Hydroperm RPU using pad dry cure method. The moisture related propertiesand dyeability of the finished fabric were assessed and compared with PVAtreated fabric. PVA treatment is giving improved hydrophilic character toPET fabric comparable to the commercial finish. One added advantage ofPVA treatment is that the treated PET fabric can be dyed using a reactivedye.A similar study was carried out on cotton and polyester/cottonblend fabrics using PVA and glutaraldehyde for investigating the possibilityof dyeing of polyester/cotton fabric using reactive dye in a single bath. It wasobserved that PVA treatment improves the dye uptake of polyester/cottonblend fabric.From the work carried out it could be concluded that treatment ofpolyester fabric with poly(vinyl alcohol) promises a new method to improveits hydrophilicity.