"A Ship is always safe at the shore - but that is NOT what it is built for”
- Albert Einstein
FABRIC SOFTENERS

A Softener is a chemical that alters the fabric hand making it more pleasing to the touch. The more pleasing feel is a combination of a smooth sensation, characteristic of silk, and of the material being less stiff. The softened fabric is fluffier and has better drape.

Functions of softeners:


  • Increase aesthetics (drape and silkiness),

  • Improve abrasion resistance,

  • Increase tearing strength,

  • Reduce sewing thread breakage and

  • Reduce needle cutting when the garment is sewn.
Because of these functional reasons, softener chemicals are included in nearly every finish formulation applied to fabrics.

How softeners alters the handle of textile materials


  • Softeners act as fiber lubricants and reduce the coefficient of friction between fibers, yarns, and between a fabric and an object (an abrasive object or a person's hand). Whenever yarns slide past each other more easily, the fabric will be more pliable and have better drape.

  • Tearing resistance, reduced abrasion and improved sewing characteristics are also related to lower coefficients of friction.

  • Fabric tearing is a function of breaking yarns, one at a time, when tearing forces are applied to the fabric. Softeners allow yarns to slide past each other more easily therefore several yarns can bunch up at the point of tear. More fiber mass is brought to bear and the force required to break the bunch is greater than the force required to break a single yarn.

  • Sewing problems are caused by the friction of a needle rapidly moving through the fabric. Friction will cause the needle to become hot and soften thermoplastic finishes on the fibers.

Points of Concern

There are some important points to consider when selecting the appropriate material as a softener.
Viscosity: The viscosity of softener materials range from water like (machine oil) to semisolids (waxes). All are capable of reducing coefficient of friction and therefore are effective in overcoming sewing problems, improving tear, and improving abrasion resistance. However the lower viscosity oils are the ones that impart the soft silky feel and improve drape.
Color: Some softener materials are dark in color to begin with while others become dark when exposed to heat, light, oxygen, ozone, oxides of nitrogen or other airborne gases. These might not be a problem on dark shades but they are to be avoided for pastel shades and whites.
Odor: Some softeners develop odor with age. Fat based softeners develop a rancid odor (associated with aged fats) and should be avoided whenever possible.
Bleeding: Some lubricants are good solvents for surface dyes. Disperse dyes, as a class, are particularly prone to dissolve in softener materials. Color from darker yarns will migrate (bleed) to stain adjacent lighter yarns like might be found in a striped pattern.
Spotting: The volatility of softeners is also important. Softener materials that have low smoke points will condense and drip back onto the fabric causing unsightly spots. Smoke from heated oils and waxes are droplets of oil suspended in air. These droplets will condense when they come in contact with cooler surfaces and eventually drip.
Soiling: Cationic softeners tend to attract soils making them harder to remove. This tendency must be compensated for by the use of soil release finishes.
Light fastness: Certain softeners will diminish the light fastness of some direct and reactive dyes. This tendency must be checked out and compensated for.

Desirable properties of softener


  • Good compatibility with chemicals

  • Stable to high temperature, no volatile by water and water vapor

  • No effect on fastness

  • No change of shade of color and no yellowing

  • Low forming, stable to shearing, no deposit on rollers

  • Regular and complete bath exhaust

  • Non-toxic, non-caustic, non-corrosive

  • Easily biodegradable

  • Dermatologically harmless

  • Easy handling (liquid and stable) and no restriction of transport and storage

Raw Materials for Softeners

Hydrocarbon radicals having a total of 8 to 20 carbons are the most effective molecular group used in textile softeners. Commercially, there are two main sources of raw material supply that are inexpensive and available in large quantities:

  1. Fat derived Raw Materials: obtained from animal and vegetable fats and oils

      1. Fatty acids

      2. Fatty acids monoesters

      3. Fatty acids ethoxylates

      4. Fatty amines

      5. Fatty alcohols

  2. Petrochemical derived Raw Materials: based on crude oil and natural gas

      1. Long chain hydrocarbons

      2. Short chain hydrocarbons

      3. Long chain alcohols

      4. Alkyl aromatics

      5. Ethylene, propylene oxides

      6. amines

Softener Classifications

Softeners are divided into four major chemical categories describing the ionic nature of the molecule,

  1. Anionic,

  2. Cationic

  3. Nonionic

  4. Amphoteric

Anionic Softeners

Anionic softeners and/or surfactant molecules have a negative charge on the molecule which come from either a carboxylate group (-COO-), a sulfate group (-OSO3-) or a phosphate group (-PO4-). Sulfates and sulfonates make up the bulk of the anionic softeners.
Properties of Anionic Softeners
Anionic softeners impart pliability and flexibility without making the fabric feel silky. They are used extensively on fabrics to be mechanically finished, e.g. napped, and sheared or Sanforized. A good napping lubricant, for example, provides lubrication between the fabric and the napping wires yet at the same time provides a certain amount of cohesiveness between fibers. If the fibers are too slippery, the napping wires will overly damage the yarn.
Advantages

  • Most anionic softeners show good stability towards heat & some are resistant to yellowing.

  • Anionic softeners do not interfere with finishes to be foamed, in fact like defoamers and are deleterious for foam finishing.

  • Anionic softeners have good rewetting properties and are preferred for those fabrics that must adsorb water such as bath towels.

  • Cheaper compared to other types

  • In case of white finishes, it has been used.
Disadvantages

  • The degree of softness with anionic softeners is inferior when compared with cationic softeners and some nonionic softeners.

  • Anionic softeners have limited durability to laundering and dry-cleaning.

  • Anionic softeners will not exhaust from a bath, they must be physically deposited on the fabric.

  • Anionic softeners tend to be sensitive to water hardness and to electrolytes in finish baths.

  • Anionic softeners are incompatible in some finish baths containing cationically stabilized emulsions.

Cationic Softeners

Cationic softeners are ionic molecules that have a positive charge on the large part of the molecule. The important ones are based on nitrogen, either in the form of an amine or in the form of a quaternary ammonium salt. The amine becomes positively charged at acidic pHs and therefore functions as a cationic material at pH below 7. Quaternary ammonium salts (hereafter referred to as QUATS), retain their cationic nature at all pHs.
An important quality of cationic softeners is that they exhaust from water onto all fibers. Cationics are highly efficient softeners. The ionic attraction causes complete exhaustion from baths and the orientation on the fiber surfaces allows a monolayer to-be as effective as having more lubricant piled on-top.
Figure Adsorption on Fiber Surface

  1. Amine Functional Cationic Softeners

They exhaust and become excellent softeners under acidic conditions. The cationic charge on a given hydrophobe is proportional to the number of amino groups, therefore the attraction of the cationic portion to the fiber surface increases as the number of amine groups’ increase.

    1. Primary Fatty Amines

    2. Difatty Amines

    3. Fatty Diamines

    4. Cationic Amine Salts:

  1. Fatty Aminoesters


  2. Fatty Amidoamides


  3. Quaternary Ammonium Salts

Quaternary ammonium salts are extremely important fatty acid derivatives. The quat's cationic charge is permanent, being maintained at all pHs. In addition to imparting softness, quats reduce the static charge on synthetic fabrics and inhibit the growth of bacteria. Quats are therefore used as antistats and germicides as well as softeners. Cationics containing two C18 fatty tails attached to the nitrogen impart very soft, fluffy hand to textile products.

      1. Synthesis of Monofatty Quats

      1. Synthesis of Difatty Quats

      2. Synthesis of Imidazoline Quats
Advantages

  • Cationic softeners impart very soft, fluffy, silky hand to most all fabrics at very low levels of add-on.

  • Cationics will exhaust from dyebaths and laundry rinse baths making them very efficient materials to use.

  • Cationics will exhaust from acidic solutions.

  • Cationics improve tear resistance, abrasion resistance and fabric sewability.

  • Cationics also improve antistatic properties of synthetic fibers.

  • They are compatible with most resin finishes.

  • They are good for fabrics to be napped or sueded.
b. Disadvantages

  • They are incompatible with anionic auxiliary chemicals.

  • They have poor resistance to yellowing.

  • They may change dye shade or affect light fastness of some dyes.

  • They retain chlorine from bleach baths.

  • They adversely affect soiling and soil removal and may impart unwanted water repellency to some fabrics.

C. Nonionic Softeners

They are not very good softener, however it can be used with any composition of the bath as they are nonionic. Now a days one of its class silicone softeners have been used extensively.
Nonionic softeners can be divided into three subcategories,

    • ethylene oxide derivatives,

    • hydrocarbon waxes based on paraffin or polyethylene.

    • Silicones
Dispersions with anionic, nonionic and cationic character are made by selecting appropriate auxiliary emulsifier. Selecting an emulsion with the proper ionic character is important otherwise the finishing bath will become unstable and break out.
Silicone Chemistry
Silicones are Polysiloxane Polymers and fall under the class of materials known as organometallics. The element silicon is considered a metal and is found in abundance in nature as silica, SiO2. Silicon resembles carbon in that it is tetravalent and forms covalent bond with other elements. Simple tetravalent compounds are called silanes. Silicon forms a stable covalent bond with carbon leading to a class of materials known as organosilanes

  1. Formation of Organofunctional Reactive Silanes
Compound Name
[I] Dimethylchlorosilane
[II] Methylchlorosilane
[III] Methylhydrogendichlorosilane
[IV] Trimethylchlorosilane

Silicone Softeners

Four varieties of silicone polymers have found use as textile softeners. One variety is based on

    • Dimethyl Fluids

    • Methylhydrogen Fluids

    • Amino Functional Silicones

    • Epoxy Functional Silicones
a. Dimethyl Fluids
Dimethyl fluids are made from dimethyldichloro silane. Fluids are water clear and do not discolor with heat or age. They impart soft silky hands to fabrics. In addition to softening, dimethyl fluids render fabrics somewhat water repellent; however, being fluids, they are not durable.
Figure Orientation of Dimethyl Fluids on Fiber Surface.
b. Methylhydrogen Fluids
Methylhydrogendichlorosilane offers a route for making a linear polysiloxane These offer a way of improving durability.
c. Amino Functional Silicones
Amino functional silicones are made by incorporation the appropriate organofunctional chlorosilane to the reaction mix. Amino functional silicones become cationic at acid pHs and exhaust from aqueous baths.
d. Epoxy Functional Silicones
Epoxy functional groups can be incorporated into silicone polymers by incorporating the appropriate group into the silicone polymer back boneThese softeners are more durable to repeated laundering.
Advantages

  • Silicones are water clear oils that are stable to heat and light and do not discolor fabric.

  • They produce a slick silky hand and are preferred for white goods. They improve tear and abrasion resistance and are excellent for improving sewing properties of fabrics.

  • Amino functional silicones improve DP performance of cotton goods.

  • Epoxy functionals are more durable.
Disadvantages

  • The silicones are water repellent which make them unsuitable as towel softeners.

  • Silicones are expensive compared with fatty softeners.

  • Amino functional silicone discolors with heat and aging.

  • They may interfere with redyeing when salvaging off quality goods.

Amphoteric softener

Amphoteric softener have long alkyl chain which contain both acidic and basic group and their nature depends on pH. At
Low pH: cationic
pH 7: nonionic
high pH: anionic
They are expensive and used in novelty products in specialist application. Generally they are not used in textile industry but cosmetic industry.
The products are based on

  • Substituted amino acids: R-+NH2CH2CH2COO-

  • Sulphobetains: R3N+ (CH2)n-SO3-

  • Betains: R CONH-C3H6N+(CH3)2CH2COO-

  • Imidazolines

Trade name of softener

BASF

    • Basosoft EUK (cationic)

    • Basosoft FA535 (cationic but mixed with silicone softener)

    • Siligen FA210 (normal silicone)
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