Softening finishesSoftening finishes are among the most important oftextile chemical after treatments.
INTRODUCTION• With chemical softeners, textiles can achieve an agreeable, soft hand (supple, pliant, sleek and fluffy), some smoothness, more flexibility and better drape and pliability.• To achieve the desired quality of fabric handle or softness• Chemicals used to impart the desired softness in fabric is termed as SOFTNERS
INTRODUCTION• The hand of a fabric is a subjective sensation felt by the skin when a textile fabric is touched with – the finger tips and gently compressed.• The perceived softness of a textile is the combination of several measurable physical phenomena such as1. elasticity,2. compressibility3. and smoothness.• During preparation, textiles can become embrittled because – natural oils and waxes or fibre preparations are removed.
INTRODUCTION• Finishing with softeners can overcome this deficiency and even improve on the original suppleness. Other properties improved by softeners include 1. the feeling of added fullness, 2. antistatic properties 3. and sewability.• Disadvantages sometimes seen with chemical softeners include – Reduced crockfastness, – yellowing of white goods, – changes in hue of dyed goods – and fabric structure slippage.
Mechanisms of the softening effect• Softeners provide their main effects Basic Mechanism » on the surface of the fibres. •Softeners provide their main effects on the surface of the• Small softener molecules, in addition, fibres. penetrate the fibre and provide an internal plasticisation of the fibre forming polymer •Softeners orient themselves by reducing of the glass transition temperature toward the fibre creating a new surface consisting of Tg. molecular chains that provide• The physical arrangement of the usual the characteristic softening and lubricity. softener molecules on the fibre surface is important and shown in Fig . – It depends on the ionic nature of the softener molecule •Small softener molecules – and the relative hydrophobicity of the fibre penetrate the fibre and surface. provide plasticisation of fibre forming polymer
Most softeners consist of molecules with both ahydrophobic and a hydrophilic part
Cationic softenersMechanisms of the softening effect• orient themselves with their positively charged ends toward – the partially negatively charged fibre (zeta potential), – creating a new surface of hydrophobic• carbon chains that provide the characteristic excellent softening and lubricity seen – with cationic softeners.
Anionic softenersMechanisms of the softening effect• orient themselves with their negatively charged ends – repelled away from the negatively charged fibre surface.• This leads to higher hydrophilicity, – but less softening than with cationic softners
non-ionic softeners• The orientation of non- ionic softeners depends on the – nature of the fibre surface,• with the hydrophilic portion of the softener being attracted to – Hydrophilic surfaces• and the hydrophobic portion being attracted to – hydrophobic surfaces.
Desirable Properties of Softners1. Compatible with other chemicals2. Easy to handle3. Good exhaustion properties4. Stable to high temperature5. No effect on shade or fastness6. Non toxic, biodegradable, non corrosive
Product types and theirchemistryMost softeners consist of molecules with both ahydrophobicand a hydrophilic part.Therefore, they can be classified assurfactants (surface active agents)and are to be found concentrated at the fibresurfaces.
Product types and their chemistry• Most softeners have a low water solubility. Therefore softening products are usually sold as – oil in water emulsions containing 20–30 % solids.• The softener molecules typically contain a long – Alkyl group, – sometimes branched, of more than 16 and up to 22 carbon atoms, – but most have 18 corresponding to the stearyl residue.• Exceptions to this molecular structure are the special categories of silicones, paraffins and polyethylene softeners.• About one-third of the softeners used in the textile industry are – Silicone based.
Types of SoftenersDepending on charge on parent molecule.
Cationic softeners• typical cationic softener structures, for example,• N,N-distearyl- N,N-dimethyl ammonium chloride (DSDMAC).• Cationic softeners have the best softness and are reasonably durable to laundering.• They can be applied by – exhaustion to all fibres – from a high liquor to goods ratio bath – and they provide a hydrophobic surface – and poor rewetting properties, because their hydrophobic groups are oriented away from the fibre surface.• They are usually not compatible – with anionic products (precipitation of insoluble adducts).• Cationic softeners attract soil, may cause – yellowing upon exposure to high temperatures – and may adversely affect the lightfastness of direct and reactive dyes.• Inherent ecological disadvantages of many conventional (unmodified) quaternary ammonium compounds (quaternaries) are fish toxicity and poor biodegradability.
Cationic softeners• Quaternary ammonium compounds are easily removed from waste water by adsorption and by precipitation with anionic compounds.• Quaternaries with ester groups, for example tri-ethanol amine esters, are biodegradable, through the hydrolysis of the ester group• The example of an ester quaternary in Fig. 3.2 is synthesised from tri-ethanol-amine,• esterified with a double molar amount of stearic acid and then quaternarised with di-methyl-sulfate.
Cationic Softeners1. Advantages 1. Dis-Advantages 2. Incompatible with anionic2. Soft, lofty, silky handle to auxiliaries including FBAs most fabrics at low levels of add-on 3. Free amine causes yellowing3. Substantive to most fibres and may change dye shade or affect light fastness4. Good lubricant properties and often have positive 4. May react with residual chlorine effect on wet fastness from bleach baths5. Improve tear strength, abrasion 5. Adversely affect soil removal resistance and sewability proporties,6. Improve antistatic properties 6. Can cause tendering of sulphur ( especially on synthetics) dyed fabrics
Anionic softeners• Anionic softeners are heat stable – at normal textile processing temperatures• And compatible with other components of – dye and bleach baths.• They can easily be • washed off • and provide strong antistatic effects • and good rewetting properties• because their anionic groups are oriented outward and are surrounded by a thick hydration layer
Sulfonates are, in contrast to sulfates, resistent to hydrolysis They are often used for special applications, such as medical textiles, or in combination with anionic fluorescent brightening agents(FBA). Disadvantages • Inferior in softness performance toAdvantages cationics, generally and sensitive to water• Compatible with FBAs hardness and electrolytes in the finish bath• Have good rewetting properties • Usually higher concentrations required and• Do not tender Sulphur-dyed goods even then cationic impart softer feel• Used extensively on mechanically • Limited durability to laundering and dryfinished fabrics mechanically finished e.g. cleaning • Not exhaust from bath (except onto wool andbrushed, sheared , sanforised nylon) and must be padded
Non-ionic softeners based on paraffin andpolyethylene• Polyethylene (Fig. 3.5) can be modified by air oxidation in the melt at high pressure to add – hydrophilic character (mainly carboxylic acid groups).• Emulsification in the presence of alkali will provide – higher quality, more stable products.
Perform well as lubricantsNon-ionic SoftenersAdvantages •Most have good non- yellowing properties and• They show high lubricity (reduced usually do not cause shade surface friction) change• that is not durable to dry cleaning,• they are stable to extreme pH •Compatible with cationic conditions and heat and anionic products• at normal textile processing conditions, including FBAs and do not• and are reasonably priced tender sulphur-dyed goods• and compatible with most textile chemicals. •Easily removed if reprocessing is necessaryDisadvantages•Handle generally poorest out of anionic, cationic and non- ionic•Usually have negative effect on wet fastness properties of dyes•Cannot easily be applied by exhaust
Ethoxylated non-ionic softeners• These polyglycol ethers are synthesised by the addition of ethylene oxide to fatty alcohols, carboxylic acids, esters, amides or amines (Fig. 3.5).• They are surfactants and often used as antistatic agents and as components of fibre spin finishes. Their main characteristics are relatively high substantivity and hydrophilicity, nonyellowing and sometimes a low softening effect and lubricity, and a potential for foaming during processing.
Silicone softeners Non-ionic and cationic examples of silicone softeners are shown in Fig They provide very high softness, special unique hand, high lubricity, good sewability, elastic resilience, crease recovery, abrasion resistance and tear strength. They show good temperature stability and durability, with a high degree of permanence for those products that form crosslinked films and a range of properties from hydrophobic to hydrophilic
Silicone softeners• Depending on their method of synthesis, silicone softeners can contain variable amounts of – volatile siloxane oligomers• Together with volatile emulsifiers these oligomers can cause – pollution problems in the waste air from tenter frames• In textile finishing, silicones are also used as 1. water repellents, 2. elastomeric finishes, 3. coatings 4. and as defoamers.
Silicone softeners• the high molecular flexibility of the silicone chain• is the reason for – the very low glass transition temperature – (about –100 °C) – and for their special softness.• They postulate that to a great extent the methyl groups of the OSi(CH3)2-structure – shield the oxygen atoms from outside contact• Therefore the surface of fibres finished with – Poly-di-methyl-siloxane is mostly non-polar and hydrophobic• In the case of cellulose, wool, silk and polyamide fibres, there are strong hydrogen bonds between• the hydroxyl or amino groups of the fibres• and the amino groups of the modified silicones (Fig. 3.7, upper figure)..
Silicone softeners on polar fibres.• These bonds act as an anchor for the silicone, which forms an evenly distributed film on the fibre surface.• Good water repellency and very soft hand are the result.• With an optimal content of amino side groups, the polysiloxane segments between the anchor sites are long enough to maintain their high flexibility.• This is the main reason for the softness and the lubricating effect of amino functional silicones on polar fibres.
Silicone softeners on non-polar fibres.• In the case of relatively non-polar fibres such as polyester, the hydrophobic segments of the silicone chains interact strongly with the hydrophobic fibre surface (Fig. 3.7, lower figure).• The positively charged amino side groups of the silicone chains repel each other and give rise to enhanced flexibility of the silicone chain loops.• This again is the reason for the specially soft hand of amino functional silicones on non-polar fibres.
Amino-functional siloxanes are one of the most important product in textile softeners•Their softening properties are unique and in practice they have been provedsuperior to other compounds•The siloxane backbones are modified by amino residues• SILICONE SOFTNERS SILICONE SOFTNERS• •silicon dioxide can be •Silicones are structurally bound with silicon dioxide considered as basis of the in form of organically modified quartz, and this is whole modern silicone the reason why they are called polysiloxanes chemistry •Silicone oils, silicone rubber and silicone resins• •Silicon is with 25.8% the are the three most important raw material groups of second most important which more than 2000 high quality products can be element of the earths made for many different application crust after oxygen• •However in nature silicon Silicones offer a large number of application is always in form of possibilities in the textile because of the varied compounds, primarily as nature of product properties silicon dioxide (sand) and •Silicones give a variety of finishing effects like silicates brilliancy, softness, volume and elasticity. They also improve the technological demands of sewability, soil and water repellence
The amino siloxane can vary in the nitrogen content and the chain length of the siloxane •These modifications influence the handle characteristics, the tendency to yellowing and the reactivity of the siloxane to the fibre •The degree of softness normally becomes higher with increasing nitrogen content The different sizes of particles have an important impact on application technical properties•The medium particle size of macro- Softners based on micro-emulsions penetrate into the interior of the fibre, so that a good core softness isemulsions is in the range of approx. 100 to achieved1000 nm •Softners of macro-emulsion formulation when applied•Of micro-emulsions the average size of accumulate more at the fibre surface, and soft,particle of emulsified silicone drop is voluminous and smooth handle effects are obtainedsmaller than 10 nm this means that thefluid drops are smaller than the wavelength A semi-micro emulsion has droplets of silicone oil thatof visible light, which can penetrate such are 10 to 100 times smaller than those in conventional macro-emulsionan emulsion without becoming defused •When semi-micro emulsion is applied to a textile substrate. Smaller droplets penetrate in structure easily •Giving more lubrication between yarns and fibers with increased suppleness & Drape properties of fabric •While macro-emulsion does not penetrate so well and deposits more onto the surface giving a softer surface feel to the fabric.
Silicon SOFTNERS• Silicone Softeners Disadvantages Advantages •Create water-repellency of some type,1. • Silky handle on all fibres making them unsuitable when2. • Water-clear oils - stable to absorbency is required heat and light •Cannot easily be removed for redyeing3. • Improve tear strength, •Expensive abrasion resistance, and excellent for improving sewing properties4. • Amino-functional silicones improve durable press performance of cotton goods5. • Non-yellowing at moderate temperatures
Selection of SoftenerYellowing Exhaustibility•Usually the more cationic, the more the –Normally cationic softeners aresoftener yellows recommended –Non-ionic can be used with cationic emulsifiersFastness Properties –Anionic on wool•Cationic softeners give better washfastness but they may have a negativeeffect of light fastness Effect on Seam Slippage•Non-ionic may have negative effect on wet •Silicones can adversely affectfastness slippage •Heat Stability and Smoke Point •May cause processing problem onShade Change drying•Non-ionic normally have less tendency to •Odourcause shade change. •Fabric odour may be produced by•Some cationic and anionic will cause softenershade change•Silicones have tendency to bloom shade