Md. Abdul Hannan
Associate Prof. DUET
Concepts on soil and soiling
• Soil deposits on textile materials are usually of complex
• containing both oily and particulate matter.
• Particulate matter - microscopic solid or liquid matter suspended
in the Earth's atmosphere
• Particulate soil may be clay, soot or metal oxides.
• Street dirt contains several components such as peat moss,
cement, silica, Raolin clay, mineral oil, carbon black and iron
oxide. Oily soils are typically fatty materials secreted by the body.
Most common within this category is shirt collar dirt consisting of
skin cells, sebum and eccrine sweat.
• Various other substances that contribute to the soiling of textiles
include stains from oily liquids and food residues.
• Soot -mass of impure carbon particles
resulting from the incomplete combustion
• Clay is a fine-grained natural rock or soil
material that combines one or more clay
mineral with traces of metal oxides and
• Peat moss – one kind of soil conditioner
• a product which is added to soil to improve
the soil’s physical qualities, especially its
ability to provide nutrition for plants
• Carbon black - produced by the incomplete
combustion of heavy petroleum
• Oily soils are typically fatty materials secreted by the
body. Most common within this category is shirt collar
dirt consisting of skin cells, sebum and eccrine sweat.
• Sebum is a naturally occuring substance that is
produced by the sebaceous glands, which are found in
the skin and mucus membranes of mammals. The
primary function of sebum is to moisturize, lubricate
and protect skin and hair.
• Various other substances that contribute to the soiling
of textiles include stains from oily liquids and food
• A stain is a discoloration that can be clearly
distinguished from the surface, material, or
medium it is found upon. They are caused by
the chemical or physical interaction of two
• The mechanism of soiling is influenced by various factors
associated with the transport and adsorption of soil onto
• Electrostatic attractive forces are primarily responsible
for the deposition of air-borne particulate soil onto
curtains or upholstery.
• In contrast, shoe dirt ground into a carpet surface, or
soiling of a shirt collar or sofa by oily soil, arises from
direct contact, exacerbated by rubbing action.
• Finally cross transfer of soil or redeposition on the same
fabric may take place during laundering of textile items.
This last mechanism of soil transfer is referred to as wet
• Airborne particulate matter, which includes dust,
dirt, soot, smoke, and liquid droplets emitted into
the air, is small enough to be suspended in the
• Airborne particulates may be a complex mixture
of organic and inorganic substances. They can be
characterized by their physical attributes, which
influence their transport and deposition, and
their chemical composition, which influences
their effect on health.
• Irrespective of the method of soil transfer onto a textile, the
main cause of soiling is considered to be due to subsequent
adhesion of the soil onto the fibre surface.
• This is effected mostly by van der Waals forces, which operate
only over very short distances.
• The strength of this interactive force will depend on
1. The nature of the soil and of the substrate,
2. The area of contact between the two.
Example: Kissa  has shown that iron oxide adsorption on
• polyester and cotton fabric increases with greater applied
pressure; the soil particle is considered to deform under pressure
and conform to the shape of the textile surface.
Factors influencing Soiling
Natural fibers and regenerated cellulose rayons have high moisture regain and have
little tendency to accumulate static electricity. Even if static electricity is generated,
it is quickly dissipated to the atmosphere. Therefore, the problem of soiling and
soil removal is not very acute in the case of fibers having high moisture regain.
Synthetic fibers have low moisture regain, therefore they accumulate static electricity
which attracts dirt and dust from atmosphere.
When the moisture regain of the fibers drops below 4%, soiling increases rapidly.
Polyester has the lowest moisture regain (0.4%) among synthetic fibers; therefore it
attracts maximum soil. Since these fibers are hydrophobic, they do not swell in
water and the removal of soil from the fiber becomes difficult.
In the case of blends with cellulosic fibers, whatever soil is removed from the cellulosic
component during washing, gets redeposited on the synthetic fiber because the
synthetic fiber being oleophilic, attracts oily matter from the dirty wash waters.
• Electrostatic charge
Synthetic fibers accumulate static charge during manufacture and during wear. Charged fibers
attract soil from the atmosphere, positively charged fabric attracting more soil than the negatively
Fabric construction, yarn count, twist and the cross section of the fiber influence soiling.
• Smaller the denier, greater is the tendency to soil. A circular cross sectional fiber retains less soil
than one with an irregular cross section. Higher the twist in the yarn, greater the soil retention.
Fabric with protruding fibers assists soiling. Loosely woven and open knitted fabrics are more prone
to soiling than closely woven fabrics but removal of soil from loosely woven fabrics is easy. Fabrics
made from filament yarn do not get soiled as fast as those made from spun yarns.
Particle size of Soil
The smaller the size of the soil particles, grater is the soil retention by the fabric.
Electron microscopy techniques have shown
oily soil to be located within the interfibre
capillaries of yarns, on the surface of the yarn
and embedded in crevices formed between
adjacent fibres within the yarn.
Additionally, with cotton fibres soil may be
located within the lumen, crenulations and
secondary wall of the fibre.
Particularly in the case of damaged cotton, it
is known that through repeated laundering
and wear cycles sebum can wick rapidly into
the fine capillaries of the fibre and into the
cotton lumen. This degree of soiling, as found
on shirt collars for instance, is especially
difficult to remove during laundering.
• The success of any soil-release treatment is
intimately associated with the removal of soil
by detergent action.
• physico-chcmical action of cleaning a solid
surface by an aqueous Solution of surfactants .lt
is accomplished by a combination of effects
1. alteration of interfacial tensions and
2. emulsification of the removal of soil.
The composition of this finish is based acrylic and methacrylic acid
and ester copolymers.
An ester to acid ratio of 70:30 is typical. This ratio seems to provide
the proper blend of hydrophilicity and oleophobicity (hydrophilic-
lipophilic balance, HLB) required for a soil release finish.
HLB values of about 15 are favored.
Greater hydropilicity would strongly reduce durability to laundering.
The ease of incorporating different acrylic monomers into
copolymers has led to a wide variety of available finishes.
other carboxy polymers that have been used as soil-release finishes
include styrene-maleic anhydride copolymers and sodium
• Hydroxy-based finishes
One of the earliest soil-release materials was starch,
Other starch- and cellulose based products that have
been used as soil release agents include methyl
cellulose, ethyl cellulose, hydroxypropyl starch,
hydroxyethyl cellulose, hydroxypropylmethyl cellulose
and hydrolyzed cellulose acetates.
• With some expectations these finished lack the
laundering durability desired in finish expected to last
of a garment and must be applied in combination with
a binder or cross-linking agent.
• Ethoxy-based finishes
One important group of soil-release agents for polyester fibers is based on
condensation copolymers of terephthalic acid with ethylene glycol and
polyethylene glycol. The structure of this polyester –ether copolymer contains
blocks of polyethylene terephthalate and polyxyethylene terephthalate that
provide a structure that has regions of hydrophilicity interspersed with
hydrophobic regions that have a strong attraction for the polyester surface.
• These products can provide extremely durable soil-release properties for
polyester fabrics by either exhaust or pad applications with about 0.5% solids add-
on. It is possible to exhaust apply these products during the dyeing process.
• A modification of the condensation copolymer compounds involves incorporating
anionic character into the polymer chain by use of sulfonated monomers. High
soil-release performance, excellent softness and combinability with fluorocarbon
finishes may be achieved by special silicone/polyalkylene oxide copolymers
• Fluorine-based finishes
These unique polymers have the unusual property of being hydrophobic
and oleophobhic in air and hydrophilic and oil-releasing during laundering
process. This is called ‘dual-action’ mechanism. The hydrophilic blocks are
shielded by the fluorocarbon segments when dry, presenting a repellent
surface. After immersion in the wash bath, the hydrophilic blocks can swell
and actually reverse the interfacial characteristics of the surface, yielding
the hydrophilic surface necessary for oily soil release. Typically, these
modified fluoropolymers are pad applied to fabrics in combination with
the durable press crosslinking agents to increase the durability of the
finish. The higher cost of the fluorochemical soil release agents compared
to the acrylic copolymers is somewhat compensated by the low add-on
required for soil-release performance. Mixtures of both polymers types
provide a common compromise between efficiency and costs.