Plasticizers in Cosmetic
A plasticizer is a substance which when added to a material,
usually a plastic, makes it flexible, resilient and easier to
They are colorless, odorless liquids produced by a simple
chemical reaction, where by molecules of water are eliminated
from petrochemical products.
They are not just additives. They are major components that
determine the physical properties of polymer products.
Plasticizers are relatively low molecular weight
materials which have a capacity to alter the
physical properties of a polymer to render it more
useful as film forming agents.
The polymers used as film forming agents are
relatively brittle in nature at room temperature
The function of plasticizer is to make the
polymer more pliable and soft and thereby
enhancing the flexibility and plasticity to the
They modify the physical and mechanical
Plasticizer are added in order to reduce the glass
transition temperature, this addition of the
plasticizer facilitates the thermal stability of the
The intensity of particle coalescence and the
quality of the resulting final film so formed
entirely depends on the type and the
concentration of plasticizer added to the coating
The efficiency of a plasticizer is intensely related
to its chemical structure and the extent and rate
of interaction with the polymeric material present
in the formulation.
Physicochemical properties of the films mainly
A plasticizer or softener is a substance incorporated in a
material (usually a plastic) to increase the flexibility,
elongation, workability, dispensability.
It may reduce the melt viscosity, lower temperature of second
order transition or lower the elastic modulus of the product.
A Plasticizer is a distinct polymer additive.
There are more than 300 different types of plasticizers
available . The most commonly used plasticizers are ester like
phthalates, adipates and trimellitates.
IDEAL PROPERTIES OF PLASTICIZERS:
• It should be flexible resilient and easier to handle.
• It should be non volatile with high boiling point.
• It should not come out from materials to which it is added.
• Plasticizers used for internal purpose should be non toxic.
• Lower the tensile strength and softening temperature, of the
polymeric materials to which it is added.
• Polar with a high Mol. Wt. ester type organic compounds.
• Reduce internal friction between polymer chain.
• It should reduce the brittleness, improve flow,
flexibility, and increase toughness, shear strength, and
impart resistance to the polymeric film coating.
• It should lower the glass transition temperature of
the polymeric film coating. It should reduce the
viscosity of materials to which it is added.
• it should impart permanent properties such as liability,
shock resistance, hand drop.
• The main role of the plasticizer is to improve mechanical
properties of the polymers by increasing flexibility, decreasing
tensile strength and lowering the second order transition
GLASS TRANSITION TEMPERATURE(Tg):
• The temperature at which the glassy polymer becomes rubbery
on heating and rubbery polymer reverts to glassy on cooling is
called the glass transition temperature.
• Polymer in rubbery state are very viscous liquids with
relatively high freedom of rotation round the carbon-carbon
bonds in the backbone with in the constraint of tetrahedral
• The temperature is high enough so that most bonds capable of
overcoming potential energy barrier against rotation. This
rotational freedom results in very flexible chains.
10% plasticizer 20%plasticizer
Acetyl triethyl citrate
Acetyl tributyl citrate
Tg of unplasticized
film is 55ºc
Tg of Eudragit RS 30D(ºc)
GLASS TRASITION TEMPERATURE OF EUDRAGIT RS 30 D POLYMERIC FILMS
Why do we need plasticizers?
Almost all the film forming agents or polymers are
brittle in nature do to their complex structure.
Most commonly used polymers are the cellulose
derivatives or cellulose related compounds like
HPMC, MC, EC, Nitrocellulose, HPMCP etc.
These polymers are widely used as film forming
materials as they:-
Produce transparent films
Produce intact films
They have lower values for water vapor
They have lower values for oxygen
They can be structurally modified to
achieve sustained release ,like HPMC can
be converted to HPMCP for enteric
But due to presence of multiple polymeric
strands within a single molecule of polymer
makes them brittle. 11
When such a material is applied as a film coat
on to tablet a smooth film is not be obtained.
This condition necessitates the addition of
plasticizers to the coating/Film forming
The addition of plasticizers to polymeric
material causes them to diffuse within the
polymers and cause polymer deformation and
coalescence into homogeneous films.
The effectiveness of plasticizers on polymeric
dispersion depends upon polymer
compatibility and the permanence of
Effect of Plasticizers
• Easy melt
• Improve flexibility
• Increase Softness and Flexibility.
• Improve Process ability.
• Alters Softening point, Tensile Strength,
Elongation at break & Impact.
Mechanism of action
The mechanism of action of plasticizers is
defined as to interpose between every individual
strand of polymer and thereby causing
breakdown of polymer -polymer interactions.
The tertiary structure of the polymer is modified
into more porous, flexible and with less cohesive
Plasticizers soften and swell the polymer (latex
spheres) which aids in overcoming their
resistance to deformation.
As a result the plasticized polymer would deform
at a lower tensile force as compared to without
plasticizer. This enhances the polymer -
This effect in turn enhances the film elongation
This interaction to a greater extend depends
upon the glass transition temperature of
polymers. Glass transition temperature, Tg is the
temperature at which hard glassy polymer is
converted into a rubbery material.
All polymers have higher glass transition
temperatures and addition of plasticizers reduces
the glass transition temperature.
As plasticizers usually possess relatively long alkyl chains,
they have the effect of screening the polymer chains from
each other, thereby preventing them from re-forming the
chain-chain interactions which give the unplasticized polymer
Lubricity Theory: Plasticizer acts as a lubricant,
reducing intermolecular friction between polymer
molecules responsible for rigidity of the polymer.
Gel Theory: Polymers are formed by an internal
Free Volume Theory: Plasticizer lowers the glass
transition temperature (Tg) of the polymer.
Mechanistic Theory: Plasticizer molecules are not
bound permanently to the polymer molecules form.
A “dry” polymer, a resin without plasticizer, is rigid
because friction exists between its chains, binding them
into a network.
When the polymer is heated in order to be plasticized, the
binding is weakened and the smaller plasticizer molecules
are able to slip in between the chains.
When the polymer cools, the plasticizer molecules act as a
lubricant between the chains, allowing them to “slip.”
The plasticizer molecules break up the polymer-polymer
interaction by getting in between the chains and
“obscuring” these interaction sites from the polymer
THE FREE VOLUME THEORY:
• The free volume of a polymer can be described as the “empty
internal space” available for the movement of the polymer
chains.The free volume of a polymer greatly increases when it
reaches the glass transition temperature.
• At the glass transition temperature, the molecular motion
begins to occur, which corresponds to an increase in the free
volume of the polymer.
• These plasticizer molecules are having low glass transition
temperature than the polymer, so that Tg of the resulting
mixture will be lower.
Assumes the rigidity of the resin (pure
polymer) arises from “intermolecular
Plasticizer molecules are introduced on
At room temperature, these molecules
act as lubricants for the polymer chains.
Resin-resin interactions occur at
“centers of attachment.”
Plasticizer molecules break these
interactions and masks the centers from
each other, preventing re-formation.
This theory is not sufficient to describe
interaction– should be combined with
Free volume: “internal space” available
in the polymer for the chains to move.
This volume increases sharply at the
glass transition temperature, Tg.
Plasticizer is meant to decrease the
glass transition temperature, imparting
increased flexibility to polymer at room
TYPES OF PLASTICIZERS
These are two types
Majority of plasticizers are Organic Esters.
According to technique of Plasticization
Not physically bound to
polymer & can evaporate,
migrate or exude from
Group constituting a part
of a basic polymer chain,
which may incorporate
• A rigid polymer may be internally plasticized by chemically
modifying the polymer or monomer so that flexibility polymer is
• The process by which Tg of rigid polyvinylchloride is lowered
through copolymerization, is called internal plasticization.
• These are high boiling liquids, non volatile and having low vapor
• They must soluble in polymer and reduce the Tg of polymer below
room temperature rendering it softer and flexible
• They acts as lubricants between the polymer chains, facilitating
slippage of chain under stress.
Types of Plasticizer (I)
Internal vs. External
Internal plasticization occurs via
Copolymerization is one type of internal
External plasticization occurs via
External is the most common: cost, ease
Conventionally classified as
Sufficient level of
compatibility to be used
give desirable effect.
directly interact with
Limited compatibility & can
exude if used alone.
Incorporate with primary
Also called as chemical plasticizers, when added to
polymer, will cause the properties of elongation and softness
of the polymer to be increased.
Also called as plasticizing oils. They are not used
alone but when combined with primary plasticizers will
enhance the plasticizing performance of the primary
Types of Plasticizer (II)
Primary vs. Secondary
Primary Plasticizer affects resin
Secondary is a “Plasticizer-
plasticizer”: used to increase the
effectiveness of the primary
Types of Plasticizers
• Primary – These are highly compatible
with PVC and can be used alone.
– Phthalates – Di-Octyl Phthalate (DOP), Di Iso
Octyl Phthalate (DIOP)
– Phosphates – Tricresyl Phosphate (TCP),
Types of Plasticizers
• Secondary – These are less compatible
with resin & and are usually employed
together with primary plasticizers.
– Di Octyl Sebacate (DOS)
– Adipic Acid Polyesters
– Epoxidised oil.
Choice of plasticizer depends upon the properties
required in final product, the application technology
used to make it !!
Prize boundaries present for product process.
Stability in processing & service condition.
Compatibility & ease of mixing.
The measure of concentration of plasticizer require
to improve a specifies softness of the polymer.
Plasticizer efficiency increases as carbon number
of alcohol chain decreases.
Linear plasticizer is more efficient.
Plasticization in Cosmetics
Polymers used in cosmetics are generally
amorphous in nature.
Unfortunately Glass transition temperature of
most of the polymers are in excess of
conditions exposed for the cosmetic
Thus one needs to incorporate plasticizer
basically for two main reasons:-
1. Modification of polymer properties so as to
impart flexibility which reduces the Tg of
2. To facilitate the processing of dosage form at
substantial temperature conditions to protect
the integrity of active ingredient.
(A) LEACHING EFFECT-
The major trouble encountered during the
plasticizing of polymers is the leaching of the
plasticizer from the film.
This leaching effect of Plasticizer is dependent on
the type and concentration of dissolution medium.
This eventually results in drastic alteration of film
This tendency of plasticizers can be well
demonstrated from the In vitro dissolution studies
with cast films of Eudragit® RS/RL had leached
out the water-soluble plasticizers when the
Permanence is an attribute taken in
consideration as loss of plasticizer during storage
of plasticizers which in turn can hamper integrity
of coated tablets.
The mechanism by which permanence occurs is
said to be migration via diffusion process.
The molecular size and shape of the plasticizer
are highly important as small molecules migrate
faster than large ones. Also linear molecules
migrate faster than bulky, branched ones.
The highly solvating ones that produce an open
gel structure migrate at a faster rate.
Volatility was found to be one of the major cause.
Thus permanence due to leaching tendency of
plasticizers can be controlled by diffusion control.
This diffusion of plasticizer can be controlled by
incorporating a more non volatile plasticizer or
switching to a higher molecular weight plasticizer.
PLASTICIZERS IN FILM COATING:
The commonly used plasticizers can be categorized into three groups:
(a) Glycerol (glycerin);
(b) Propylene glycol;
s(c) Polyethylene glycols PEG (generally the 200–6000 grades).
2. Organic esters:
(a) Phthalate esters (diethyl, dibutyl);
(b) Dibutyl sebacete;
(c) Citrate esters (triethyl, acetyl triethyl, acetyl tributyl);
3. Oils/ glycerides:
(a) Castor oil;
(b) Acetylated monoglycerides;
(c) Fractionated coconut oil
TYPES OF PLASTICIZERS:
• Phosphate esters
• Esters of glycol and polyhydric alcohols
• Sebacate nad azelate esters
• Secondary plasticizers
Classification of plasticizers
Depending on their properties they can be
PEG 200-6000 grades.
Diethyl phthalate (DEP),
Dibutyl phthalate (DBP) and
Tributyl citrate (TBC)
Fractionated coconut oil
Newer Plasticizers – DBS (Dibutyl Sebacate).
Can be used for the very plasticizing effect in
both aqueous and solvent based pharmaceutical
Under this category both the hydrophilic as well 44
Properties of commonly used
These are hydrophilic substances and soluble in
In the conventional film coating the solid grades
of PEGs are used alone as hydrophilic
Rate of release of water soluble drugs
decreases with increase in the molecular weight
The PEG with molecular weight of 6000 and
above decreases plasticizing effect and 45
Most widely use as plasticizer.
Phthalates accounts 92% of all plasticizers.
A Phthalate ester derived from phthalic acid by an
Properties: Colorless Oily liquid ( like vegetable oil)
Ester odor, High boiling point, Inert and very stable over
• Both ortho-phthalic and terephthalic acids are used to react with
alcohol to produce phthalate esters
• Alcohol used in the range from methanol(c1 up to c17.)
• When added to vinyl, phthalate molecules are tightly bound up
between the long vinyl molecules, making them slip and slide
against each other without sacrificing strength.
• Migration is less
• Readily biodegradable
• Does not cause any harm to body.
(C) DEP- Di ethyl Phthalate.
Used both as a solvent and plasticizer.
Non toxic, non irritant.
DEP is used as a plasticizer in film coating of
tablets , beads and granules at a concentration of
10-30% W/W of polymers.
Its is insoluble in water, soluble in ethanol, ether
and orgainc solvents.
It is volatile in nature.
(D) DBP- Dibutyl Phthalate.
Also known as kodaflex DBP.
Very soluble in acetone, benzene, ethanol, ether
and soluble in water.
Is principally used as a plasticizer.
But it has limited compatibility with the cellulose
A) DI-2-ETHYLHEXYL PHTHALATE:
Also known as di-octyl phthalate.
It is considered as the industry standard.
It is phthalate ester of alcohol 2-ethylhexanol.
Posses reasonable plasticizing efficiency, fusion rate , viscosity
It is toxic
Primary use as plasticizer.
Insoluble in water, Boiling point: 386.9oc,Density:
0.9732 g/L, Molecular weight: 390.5618 g/mol.
Production: Phthalic anhydride with 2-ehaxenol:
C6H4(CO)2O + 2 C8H17OH → C6H4(CO2 C8H17)2 + H2O
Used in medical devices ,Toys, Pacifiers, Vinyl
Upholstery, Food containers, Table cloths, Shower
B) DIISODECYL PHTHALATE(DIDP) AND DIISONONYL
PHTHALATE (DINP) :
These are prepared from oxo alcohols of carbon c9 and c10
These are used for heat resistant electrical cards, leather for car
interiors and PVC flooring in concentration of 25 to 50%.
Adipates are prepared from alcohols in the c8 to c10 range.
They are having improved low temperature performance and low
They are highly volatile, having high migration rate and are high
Mixture of chemical compounds consisting of various
isononyl esters & phthalic acid.
Properties :Insoluble in H2O,Soluble in most organic
solvents, Boiling point: 250Density: 0.98g/cc, Molecular
weight: 418.6 g/mol.
Use in Replacing DEHP in toys when initially
determined to be carcinogenic.
Mixture of compounds derived from the esterification of
phthalic acid & isomeric decyl alcohol.
Properties: density:0.96g/cc, melting point: -50, boiling
point: 250-257c at 0.5KPa.
Uses in plastisol application, provides good initial
viscosities & excellent viscosity stability.
These include triethyl citrate, acetyl triethyl citrate, tributyl
citrate and acetyl tribuyl citrate
Tri butyl citrate is heat stable and does not discolour when
processed in compound resins.
These esters used in electrical coatings, food industry, hair
sprays and inks.
They show good compatibility with PVC.
They are having good low temperature performance, migration
resistance and improved fire retardency relative to phthalates.
Also known as Triethyl glycerin or glycerol
Used as both plasticizer and a solvent.
Its an hydrophilic plasticizers.
This plasticizer is suitable for both aqueous and
solvent based polymeric coating of tablets,
granules and beads in concentration of 10-35%
by weight of polymer.
Miscible with water as well as in ether, ethanol, 56
(F) TEC- Triethyl Citrate.
It is a citric acid ethyl esters.
Also known as Citroflex 2.
Its is principally used as plasticizer.
It is effectively used in aqueous based coating in
Oral sustained or enteric coated tablets .
Miscible with water.
SEBACATES & ADIPATES
Dibutyl Sebacate is an organic chemical , a dibutyl ester of
Properties: density: 0.94g/cc, boiling point:344.5c , melting
point:-10c, flash point: 178c.
Used in food packaging industry, in plastics used for medical
devices, and for pharmaceutical applications,
TRIMELLITATE PLASTICIZERS -
Synthesized using one mole of trimellitic anhydride and 3
moles of an alcohol. The third alkyl group, compared to
phthalates, contributes higher molecular weight (low
diffusivity);the third ester group contributes sufficient polarity
to enhance compatibility with PVC.
Tri (2-ethylhexyl) Trimellitate
FATTY ACID ESTERS
Esters of fatty acids & monocarboxylic acids can be
used as viscosities depressant for PVC pastes &
also as secondary plasticizers for plasticized PVC.
Present in liquid form.
Stearic acid esters are used as plasticizers &
processing agent for various plastics & also as
lubricants for PS.
These extend the life of PVC products considerably
They reduce migration, extraction & volatility.
In these adipates are generally used in mixture with
other plasticizer to increase plasticization & improve
low temp. Properties.
Epoxied plasticizer (soybean oil & linseed oil) are
used as stabilizing plasticizer offering properties of
migration resistance in PVC compounds.
• These are produced by reacting a dibasic carboxylic acids
with one or more glycols.
• These are manufactured in a wide range of viscosities. With
increasing viscosity, handling become more difficult.
• The optimum viscosities of some acids are
adipates-5600 cps, glutarates-12000 cps.
ESTERS OF GLYCOLS AND POLYHYDRIC
• polyhydric alcohols are propylene glycol, glycerol,
polyethylene glycol and Esters of glycols are glyceryl
triacetate, tri ethyl citrate.
• These are water soluble and used in aqueous film coatings.
• They are also known as extenders.
• The majority of these plasticizers include chlorinated
paraffin's, which are hydrocarbons chlorinated to a level of 30-
• The fire retardency and viscosity increases with chlorine
• Other materials used are epoxidised soya bean oil and
epoxidised linseed oil.
• They acts as lubricants to pvc due to their epoxy content.
• Common esters in these family are tris-2
ethylhexyltrimellitate,L810TM, an ester of mixed c8 and c10
• Low volatility
• Low migration rate.
SEBACATE AND AZELATE ESTERS:
• Di-2-ethylhexyl sebacate (DOS) and di-2-ethylhexyl azelate
(DOZ) are the most common members of this group, but
Diisodecyl Sebacate (DIDS) is also used. They give superior low
temperature performance than adipates.
(B) DBS- Dibutyl Sebacate.
These are esters of n-butanol and saturated
Principally used as plasticizers in film coating.
For film coating as a plasticizer, DBS is used in
10-30% concentration by weight of polymer.
Insoluble in water but soluble in ethanol, mineral
Quite suitable for solvent based coating
Classification on basis of water
(A) Water soluble
(B) Water insoluble are
Water soluble plasticizers make solutions
whereas the insoluble plasticizers are
emulsified into dispersions.
With insoluble plasticizers, their dispersion is
described as a 3 phase systems containing
water phase, polymer phase and plasticizer
The rate and the extend of plasticizers uptake
by the colloidal polymers was explained by
conducting the effect of type and
concentrations of plasticizers on Aquacoat
and the plasticized films so formed were
characterised by HPLC. 67
Whereas the water insoluble plasticizers i.e.
DBS partitioned about 90% or more into the
polymer phase. And the rest form was present
as emulsified droplets.
Under such conditions when the plasticized
droplet containing coating dispersions are
sprayed onto the tablets they generate rough,
brittle and uneven films which potentially
alters mechanical properties and release
profile of drug from the coated dosage forms.
The rate of uptake of plasticizers by the
polymers is a function of plasticizing time. But
in case of water soluble plasticizers like
triacetin or TEC uptake is not affected by the
But for water insoluble plasticizers like DBS
incomplete plasticizing is observed even after
long plasticization time for ethylcellulose latex.
To overcome this undesired effect we carry
out an additional step called “Curing Step” .
Plasticizers play a very significant role on
mechanical properties, permeability of films and
release of drug from the coated products.
They do enhance flexibity and plasticity of films.
Therefore, the selection of a plasticizer for a film-
coating formulation is very important in the
process development and optimization of a
coated dosage form.
Curing conditions can facilitate the uniform
distribution of plasticizers.
Therefore, one needs to strike a balance between
the desired and undesired effects of the
plasticizer and optimize its concentration in the
Plasticizers are necessary for almost all polymers that are
currently used for film coating of tablets and beads.
Plasticizers reduce the brittleness, improves flow, impart
flexibility, and increase flexibility, and increase toughness,
strength, tear resistance of polymers.
Although there are many plasticizers used in chemical
industry, only a few plasticizers have been approved for
pharmaceutical applications due to environmental and human
health concerns attributed to plasticizers toxicity.
1. Harry R.G., Reiger M.M., Harry’s Cosmeticology, Chemical publishing company.
2. Balsam M.S., Sagarin E., Cosmetics: Science and Technology. Wiley Interscience.
3. Rao Y.M., Shayeda, Cosmeceuticals, Pharma Med Press. Hyderabad
4. Paye M., Basel A.O., Maibach H.I., Handbook of Cosmetic Science & Technology,
5. Sharma P.P., Cosmetics Formulation, Manufacturing and Quality control, Vandana
Publication Pvt. Ltd. Delhi
6. Poucher W.A., Butler H., Poucher’s Perfumes, Cosmetic & Soaps, Springer India Pvt.
7. Nanda S., Nanda A., Cosmetic Technology, Birla Publication, Delhi.
8. SCCS's Notes of Guidance for the Testing of Cosmetic Ingredients and their Safety
Evaluation, 7th Revision. European Commission.
9. Indian Pharmacopoeia 2014(7th edition), Ministry of Health and Family Welfare,
Govt. of India.