Creative Developments
(Cosmetics) Limited
The writer collects old books on cosmetic science; a
favourite quotation by a Professor Astbury from a book published in 1947 on
hair is “…. it would seem that practically everything has been done by now to
perfect the technique of permanent waving. Little remains to be known
….employing new chemicals may perhaps be a possibility, but the chemist, as
yet, has not taken a deep interest…..” He continues “…X-ray treatment may be used to break down the structure of the
hair and reform it and it is obvious that professional scientists rather than chemists
and hairdressers will be responsible for any future developments”. Fifty years
or more later one may be forgiven for assuming that practically everything has
now been done to perfect permanent waving and all other hair treatments yet a
review of the papers presented at the SCS Symposium in the Spring of ’98 and
the IFSCC Congress in the Autumn of 1998 shows that professional scientists are
still increasing our knowledge of the structure and processes of human hair and
that even chemists have a part to play in improving the products applied to it.
Papers presented at the IFSCC Congress can be divided
into those describing investigations into the structure of hair and the
mechanisms governing its growth and behaviour, those that describe hair
treatments and those that describe methods of measuring the effect of such
treatments. J.C.Garson [REF 1}studied the keratinisation process in the human
hair follicle using X-ray micro-diffraction. Human hair is keratin; a
macroprotein synthesised by the basal layer cells in the bulb. The hair fibre
contains two structures: a-keratin and amorphous keratin. In the a-structure,
molecules are organised into coils. Coils pair into dimers, forming a
coil-coiled structure stabilised by disulphide bridges. Two dimers form a
protofilament. Seven protofilaments form the hexagonal microfilament. This
structure is stabilised by favourable ionic interactions and the amorphous
keratin is responsible for cohesion between the microfilaments. Garson found
that molecular organisation appears progressively in the bulb and that the
formation of a-helices is completed inside the bulb while supramolecular
organisation appears only outside of the bulb and filament structure is
observed far from the bulb.
A paper by M. Breuer [Ref 2] described the mechanism
of diffusion in hair; cosmetic hair treatments act either by modifying the hair
surface, e.g. shampoos, hair conditioners, hair sprays, etc. or by altering the
interior fibre properties, e.g. permanent hair colorants, hair waving and
straightening agents, etc. All hair treatments are constrained by two
conditions; the processes can only take a limited time and have to be carried
out at a temperature that will be acceptable to the consumer. Breuer postulated
a migration mechanism whereby small molecules penetrate into the macromolecule
structure of the polymeric material that forms hair and suggested that if
changes in the dynamic rheological properties of hair could be induced
deposition rates could be enhanced.
The common theme linking the majority of new materials
introduced at the major cosmetic conferences through 1998 is improved
conditioning. Shampoos have changed from strong cleansers to be used weekly to
mild formulations for daily use. Some have simply reduced the active levels,
others have increased the amphoteric content and many have included
conditioning aids. Cationic polymers are commonly used as conditioning
additives. Used at 0.1% to 0.5% they form a complex within the shampoo that is
soluble in the large excess of anionic surfactant present. On dilution by application
to wet hair the polymer is precipitated and adsorbed onto the hair with
sufficient attraction to resist being lost at the rinse stage. In fact so
strong is the bond between anionic hair and the cationic polymer that they may
build up on the hair to an undesirable extent so ease of removal is also an
important attribute.
In describing conditioning polymers in today's
shampoos Dr. Peter Hössel [REF 3] compared the action of Luviquat Care with
other conditioning polymers. Luviquat Care is a branched copolymer of
vinylpyrrolidone and quaternised vinylimidazolium methyl sulfate with a
molecular weight of more than one million and is available from BASF. The
investigations were carried out on formulations that contained sodium laureth
sulfate / cocamidopropyl betaine and selected cationic polymers that are known
to be effective in shampoos: Polyquaternium-7, Polyquaternium-10, guar
hydroxypropyltrimonium chloride and Luviquat Care. Wet combability and other
characteristics were measured and it was possible to demonstrate the efficacy
of these conditioning polymers by means of zeta potential measurements and
Atomic Force Measurements.
When the hair is treated with the test shampoos
containing a cationic polymer, the zeta potential changes from -52 mV (virgin
hair) to higher values, but there is no change to positive values as in the
case of treatment with cationic formulations without anionic surfactant. This
indicates that a charge-neutral polymer/surfactant complex is adsorbed onto the
hair. Luviquat Care and Polyquaternium-10 were the only polymers whose residues
could be desorbed from the hair by rinsing with water/surfactant.
Polyquaternium-7 and the cationic guar gum could not
be desorbed completely from the hair. This suggests that shampoo formulations
containing these polymers tend to overcondition the hair and to cause build-up.
In conclusion Hössel stated that only
cationic polymers with a very high molecular weight are effective as
conditioners in shampoos based on anionic surfactants. Surprisingly, they do
not need to have a high positive charge but molecular structure is important. A
branched polymer is more coiled than a linear polymer and therefore less
hydrated in water-based formulations. The polymer/surfactant complex is more
readily precipitated and deposited on the hair upon dilution of the shampoo and
a coiled polymer is less strongly adsorbed on hair than a straight polymer and
is therefore easier to desorb if necessary.
Increased build-up of ingredients from hair
conditioners is likely to be an even greater problem than from conditioning
shampoos. A paper by Solka [REF 4] described the measurement of deposition of
conditioner ingredients on hair by mass spectrometry and the table below shows
the results obtained from cycling tresses through one, ten and twenty cycles of
alternate shampooing and conditioning with three different conditioner
products. “The extent of build-up is surprising” said Solka, but he reminded
the delegates that although the tresses are air-dried between treatments, they
are not towel dried or combed or subjected to any of the abrasive forces that
might be expected during daily wear. Recent similar experiments on siloxane
polymers from 2-in-1 shampoo showed that drying and combing remove significant
amounts of this material.
Table: Deposition following sequential in vitro
shampoo-conditioner treatments
Formula A Formula
B Formula C
No. of cycles X1 X10 X20 X1 X10 X20 X1 X10 X20
Measured on tress, micrograms/gram hair
Cetyl alcohol 350 1670 1800 360 1300 900 260 530 460
Stearyl alcohol 300 800 1050 180 365 190 210 300 265
Paraffin wax - - - 270 450 350
- - -
Quat* 800 1700 1700 170 340 460 250 680 710
Siloxane* 90
290 820 110
120 130 100
260 520
Formula A quat = stearyloctyldimonium methosulfate,
siloxane = amodimethicone.
Formula B quat = cetrimonium chloride, siloxane =
dimethiconol.
Formula C quat = behenetrimonium chloride, siloxane =
amodimethicone.
All silicones are effective in reducing combing forces
on dry and wet hair and a very low level of silicone imparts a substantial
improvement in combing performance but there is a limit to the quantity that
can be deposited. Low concentrations of cationic polymers do not improve
combing but when present in a silicone emulsion they greatly reduce the forces
exerted on the hair when it is being combed. This synergy between silicone and
cationic guars can double the amount of silicone deposited and greatly improve
the efficacy of the system. The conditioning effect of silicone compounds in
shampoos and conditioners is dependent on high molecular weight and it is
essential to disperse the silicones uniformly within the product. The use of a
pre-formed silicone emulsion may overcome many of the problems of using high
molecular weight silicones in the formulation.
A patented mechanical emulsifying process was
described by M-D Larrey[REF 5] whereby
silicone emulsions with high molecular weight and controlled particle size may
be prepared. The principle of this process is based on phase inversion which requires
first preparing a water-in-silicone emulsion which will phase invert. The
particle size obtained during the preparation of the w/Si emulsion will control
the final particle size of the o/w emulsion. The process can be used to
emulsify any non water-soluble silicone derivatives; it is not limited by
viscosity and a silicone content of 80% by weight with a particle size of 30
microns is practical. The stability of the emulsion is based on a new
biopolymer, Rheozan® (proposed INCI name: succinoglycan gum) from Rhodia. This
is a polysaccharide obtained through fermentation of Agrobacterium tumefaciens
which is an effective stabiliser at 0.1%.
The importance of silicones in hair products is shown
in figures recently released by Dow Corning; the graph shows the percentages of
silicone types used in hair care products introduced in the USA in 1997.
Dow Corning stress the importance of selecting the
correct silicone for the product; the cyclomethicones are volatile and may be
added to shampoos to decrease drying time, or to silicone serums to dilute high
molecular weight silicones to improve their spreadability. Dimethicone
copolyols are non-ionic surfactants that increase the wetting of hair while
enhancing the foaming characteristics of shampoo and because of their
solubility, they may be used in clear systems. Phenyl trimethicone has a high
refractive index and gives added gloss to styling products while dimethicones
are low surface tension liquids which form monolayer films over the hair shaft,
imparting gloss, substantivity and soft feel. Dimethiconols are high molecular
weight silicone gums with excellent conditioning but need to be blended with a
cyclomethicone or dimethicone to make them suitable for application.
Amodimethicones have polar amine groups with a strong
affinity for hair and they provide excellent dry and wet combing, along with
softness, shine and static control. A
useful guide to the use of silicones in personal care products has recently
been issued by Dow Corning on CD; be warned, it requires 100 MB of hard disk
space for optimum viewing. The McIntyre Group offers a helpful guide to
formulating amidoamine conditioners as well as guides to formulating with
sulfosuccinates and to preserving hair products. Witco supplies a wide range of
silicone derivatives through its OSi Specialties subsidiary and A&E Connock
has produced a comprehensive pocket guide to its wide range of silicone
compounds and their applications.
While there is much emphasis on improved conditioning
many consumers wish to add “body” to hair. The reduction in combing force is
frequently used to quantify conditioning effect but materials that add body to
hair may increase this measurement. This increase may be used as an indicator
of improved body and texture and of an ability to be more readily styled.
J.Jachowicz [REF 6] has suggested that treatments producing an increase of dry
combing forces can actually contribute to better style stabilisation through
increased inter fibre friction and consequently result in an enhancement of
hair body. The combing effects depend on the condition of the fibre surface,
with the polymer or surfactant modification resulting in combing reductions for
damaged hair characterised by high frictional forces.
The same polymers applied to intact hair, with low
surface energy and characterised by low combing forces, may produce an effect
opposite to conditioning, i.e. an increase in combing forces. The extent of
hair conditioning depends on the structure of the conditioning agent. In
investigating the relationship between molecular structure and conditioning and
styling properties of various polymers .Jachowicz found that cationic polymers
containing vinyl caprolactam demonstrated a lower tendency to decrease combing
forces when compared to vinyl pyrrolidone based materials or a low molecular
weight cationic surfactant, which was found to be the most effective
conditioning agent.
Following the success of 2-in-1 shampoos it was not
going to be long before a styling function was added to create a 3-in-1 product
despite the conflict between conditioning and styling properties. The Stepan
Co. claims a 3-in-1 shampoo where one product delivers styling, conditioning,
cleansing and foaming properties [REF 7]. This is achieved by using a
polymer-surfactant complex formed by the interaction of a high molecular
weight, methyl vinyl ether/maleic acid (MVE/MA) copolymer with cetrimonium
chloride (CTAC) delivered in a high foaming amphoteric/non-ionic surfactant
system based on cocamidopropyl betaine at 25% and 2.5% lauramide
monoethanolamide. These concentrations may be varied to optimise the effect
sought. Curl retention data suggests that the deposited MVE/MA-CTAC complex
forms a continuous film, rendering the surface of the hair cuticle hydrophobic
and thus preventing binding of water.
Increasing the strength of hair is a much sought after
attribute and many ingredients have been suggested over the years. Panthenol,
phytantriol and biotin have each stood the test of time and are well supported
by documentary evidence and the results of numerous trials. Ormagel seaweed
extracts, Assessa Ltda., are claimed to coat the hair with a protective film of
alginate and to hydrate the cuticle, making it softer and less brittle and
therefore less prone to damage and breakage. Also from seaweed, Bio-Energiser
from SECMA is said to increase hair volume and density while a mixture of sea
minerals and an extract of Rhodophycea is supplied as Bio-Extender to improve
the biomechanical properties of hair. Indena SpA supplies a three component
lotion for combating hair loss. It is based on a mixture of esculin, ximenynic
acid and lauric acid. The esculin is a coumarin isolated from Aesculus
hippocastanum (Horse chestnut) which stimulates microcirculation. Ximenynic
acid is an unsaturated fatty acid from either Ximenia africana or Santalum
album that, it is said, stimulates the microvasculakinetic activity of the
scalp and lauric acid is said to have a strong affinity for androgen receptors.
When applied in a suitable vehicle to subjects suffering from androgenic
alopecia evidence shows that it slows the rate of hair loss.
All references are to papers presented at the IFSCC
1998 Congress, Cannes, France.
REF 1 Study
of the keratinisation process in human hair follicle by X-ray microdiffraction;
F. Baltenneck et al, L’Oreal, France. IFSCC Cannes 1998
REF 2 Mechanism
of diffusion in hair; Miklos M. Breuer, University of Rhode Island, USA.
REF 3 Conditioning
polymers in today's shampoo formulations - efficacy, mechanism and test
methods; Dr. Peter Hössel et al, BASF AG, Germany
REF 4 Measurement
of deposition of conditioner ingredients on hair by mass spectrometry; Bruce H.
Solka and Rita Samaritano; Unilever H.P.C. U.S.A.
REF 5 Controlled
uptake of silicone polymers; Marie-Dominique Larrey et al; Rhodia Recherches, France
REF 6 Structure-property
relationships for polymeric hair conditioners; J.Jachowicz et al, International
Specialty Products, USA
REF 7 3-in-1
Multi-functional styling and conditioning shampoo technology; Branko Sajic and
Y. Kamesh Rao; Stepan Co. USA