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| Diagram of the basic Silicone molecule |
Silicone ingredients are among the most
maligned, most demonized, of all hair care ingredients. They have been so thoroughly (and
effectively) attacked by beauty bloggers and natural care websites that some
pet shampoo manufacturers will deny using them or have stopped saying that they
use them.
A quick chemistry lesson: While
silicon is a natural element, silicones are not natural. All silicones are synthesized and man
made. What makes silicones
so interesting and infinitely variable is that they are polymeric. Polymers are long chained molecules complexes of repeating links.
Silicones have a backbone of repeating silicon-oxygen (Si-O) links. Varying the
length of the polymer chain allows
chemists to create a wide variety of properties. Silicone polymers are further complexed
by the attachment of other components to the basic repeating silicon-oxygen
backbone, such as vinyl, phenyl, or methyl groups. This allows nearly infinite variation. Silicones can be fluids, resins, gums,
or rubbers. In hair care, most of
the silicones are liquid.(1)
TYPES
OF SILICONES IN HAIR CARE
DIMETHICONE – Also referred to as Polydimethylsiloxane (PDMS), dimethicone oils
are the most commonly found silicones in pet grooming products. Dimethicone is
one of the most often used conditioning ingredients in 2-in-1 shampoos, aka,
conditioning shampoos. An
often-cited study by Kazuyuki Yahagi in 1992 clearly demonstrated the
superiority of Dimethicone to other conditioners in reducing combing forces. (2) The Wacker Company, a leading silicone supplier, has
determined that a two percent silicone ingredient in a two-in-one conditioning
shampoo can reduce the dry combing force by 75 percent. (3)
Dimethicones
are available as low, medium and high viscosity fluids. High viscosity dimethicone fluids are better suited to add sheen and manageability to hair care
products than lower viscosities. They are among the most commonly used
conditioning additives. Here are
the features of high viscosity dimethicones as presented by Clearco, another
major silicone supplier: • High Viscosity • Excellent Lubrication • Low Surface Tension: High Spreadability •Provides a soft, emollient feel to skin • Prevents stickiness in skin care products • Compatible with a wide range of solvents • Hydrophobic: water repellent • Inert- improves stability and shelf-life of formulations • Increase body & shine
in hair care products • Seal-in moisture: prevent hair damage.(4)
DIMETHICONOL - Dimethiconol is a mixture of siloxane polymers
referred to as polydimethylsiloxane terminated with hydroxyl (-OH) groups.
Dimethiconol can be combined with other molecules, such as the amino acids
(arginine, cysteine and methionine) or fatty acids (behenic acid, stearic fatty
acids from meadowfoam seed oil) or other compounds to form derivatives of
Dimethiconol that are useful as cosmetic ingredients(5) An example would be Dimethiconol
Panthenol. Dimethiconols have
superior lubricity and conditioning effects. They are often utilized as blends with cyclomethicones or
other substances to offer solutions to formulating difficulties that might be
experienced with dimethicones. The
silicone industry is very solutions oriented and is constantly developing new ingredients
designed to solve or avoid problems faced in using older ingredients.
DIMETHICONE COPOLYOLS – This family of
silicones that is made from a process of ethoxylation of Dimethicone with
polyoxyethylene and/or polyoxypropylene in order to create a water-soluble
silicone. These substances can be
identified by having PEG and/or PPG in the ingredient INCI name, such as PEG-8
Dimethicone, PEG/PPG-20/23 Dimethicone. The number represents the number of
moles of ethylene oxide or propylene oxide attached to the polymer. The higher the number of moles, the
greater the solubility. (6) In
shampoos and conditioners, the water soluble feature makes for easier
formulation, but there is considerably less conditioning effect as more is
rinsed off. Because they are nonionic and compatible with anionic detergent
surfactants, the Copolyols are a good choice for conditioning shampoos. Some Dimethicone Copolyols are also
emulsifiers and surfactants in personal care products.
PHENYL DIMETHICONE – This type of silicone
is unique for its high refractive index, which translates into the ability to
create high gloss and incredible shine.(7) In grooming products, it is found in
leave-in sprays, hair serums, and “silk drops.”
AMINE-FUNCTIONALIZED SILICONES – Usually labeled as
Amodimethicone or Trimethylsilylamodimethicone,
this family of silicones has been modified to be more substantive to the
hair. They have been made more
cationic and have a positive ion charge that is strongly attracted to the
negative charge that exists on the surface of the hair wet shaft. Since the sites on the hair shaft where
there is cuticle damage carry a
stronger negative charge, the cationic conditioner deposits more conditioner
molecules to these sites, very effectively filling in the spaces of the hair
cuticle. This makes
amine-functionalized silicones well-suited for conditioning treatments, and
allows formulators to maximize the conditioning ability of a product with a
lesser quantity of silicone ingredients.(8) Since canine hair is often more porous
and more negatively charged, especially curly coats and soft undercoat, amine-
functionalized silicones are a good fit for dog grooming products. These silicones have also been
engineered to resist build up, as the molecules do not layer or attach to themselves(9)(10)
CYCLOMETHICONES – This silicone family is made of
cyclic, rather than linear molecular chains. There are three types of cyclomethicones, Cyclotetrasiloxane
(D4), Cyclopentasiloxane (D5) and Cyclohexasiloxane (D6). The cyclomethicones
are known as “volatile” silicones.
Due to their volatility (varying rates of evaporation), low
surface tensions (high spreadability), and non-greasy feel, Cyclomethicones are
used as base fluids, carrying agents and wetting agents in a wide range of
personal care products, including hair products. Because they evaporate rather quickly, they are most often
found in combination with other silicones, such as Dimethicone or Dimethiconol,
which they deliver to the substrate (hair or skin). They are also the diluents for hair serums and silk drops
products. All three types of
cyclomethicones are approved as safe for cosmetic use in the U.S., E.U, and
Canada, although some animal studies have raised potential health issues in
regards to D4, and D4 is also under investigation as an environmental hazard in
the EU and Canada. (12)(13)(14)
Unfortunately, the issues raised by
studies of D4 cyclomethicone have been used by fear mongers to indict the
entire body of silicone cosmetic ingredients. We will review these issues in greater depth in Part II of
the series on Silicones: A Quest for Truth – Safety Issues & Environmental
Concerns. Stay tuned!
QUATERNIZED SILICONES (Silicone
Quats) – In
studying the action of how silicones act on the hair, cosmetic scientists
observed that Amodimethicone had greater affinity to hair when formulated along
with Cetrimonium Chloride, a popular quaternized conditioner (quat). Silicone suppliers began offering the
two ingredients in a blended emulsion.
Never satisfied to leave well-enough alone, the next step for silicone
chemists was to create a polymer where the two could be combined in a single
molecule. Voila! Silicone Quats were born and have become popular players in
human hair care. This latest
generation of silicones offers the best ever substantivity to hair and resistance
to breakage(15_)
PROTEIN/SILICONE COPOLYMERS – Hydrolyzed Wheat
Protein PG-Propyl Silanetriol and Cystine Bis-PG-
Propyl Silanetriol are advanced copolymers of proteins and silicone that offer
proven protection against cuticle damage caused by common hairstyling practices
such as blow drying, combing and styling. Due to their complex polymeric structure,
these polymers cross-link on drying to form a conditioning and protective
network that offers functional benefits to hair care products. (16)
The protection created by the cross-linkage is
referred to as “heat activated” conditioning benefits. The incorporation of natural protein
structures into the silicone polymer molecule is the trend of creating more
“natural” silicone ingredients to meet the powerful market demand in the human
beauty industry. While silicone
quats and protein/silicone copolymer ingredients are rare in grooming products,
the competitive nature of the industry will ultimately result in the
utilization of these newer, more sophisticated conditioning ingredients.
BENEFITS
OF SILICONES IN GROOMING PRODUCTS
Here is my view of the
benefits of Silicones in pet grooming products:
·
Improves straightening effect by smoothing hair cuticle.
·
Helps hair resist humidity and re-curl.
·
Aids detangling and brush out.
·
Facilitates deshedding by adding slip to hair and reducing static cling
in the coat.
·
Protects hair from thermal damage from heat drying.
·
Allows hair to be dried and shaped with less heat application,
·
Adds shine and glow to all coat types.
·
Provides conditioning without over softening.
·
Creates a breathable film that seals in essential moisture to hair
cortex and prevents moisture loss.
·
Protects hair cuticle from damage by brushing and combing.
·
Stabilizes foaming in products to reduce rinsing time, (saves time,
conserves water)
·
Significantly decreases drying time of all coat types. (saves time,
conserves electricity)
WHAT’S
NOT TO LOVE - SILICONE MYTHS &
MISCONCEPTIONS
One
thing that struck me about truth and myths regarding cosmetic ingredients,
including silicones, is how much work and expense goes into supporting
manufacturers claims and how little it takes to create a negative myth. Hair breakage is a good
example. In the world of human
hair care products, when a company makes a claim that their product reduces
hair breakage or prevents hair breakage, they must be able to substantiate that
claim. Chemical suppliers such as
Dow Corning, Wacker, and Evonik do extensive testing at great expense to prove
the effects of their ingredients(9) (10)(15) A myth or
negative claim, however, costs nothing.
It only needs to be repeated.
A good indication that a negative claim is baseless myth, is finding the
same phrases being repeated on many websites or blogs.
Silicones
are occlusive - One such phrase is that silicones coat the hair
“much like plastic wrap”, “suffocating” it and causing it to dry out and
subsequently break. (17) This statement is offered over and over on lists
of ingredients to avoid. No evidence is offered, often no reference is made, or
the reference is a so-called “expert” who simply offers the assertion. An expert who may have been the
originator of this myth is Chrystn Nawrot, a Regional Educator for Phyto Hair
Care Products, who was quoted in Marie Clair Magazine in January 2006, “While silicone products are
great at preventing frizz and enhancing shine, do not apply them before
heat-styling, or they can fuse to your hair and have a "shrink wrap"
effect, sapping all the moisture from your strands.” (18)These experts often have allegiance to a company that is marketing a
“no silicone” approach. Phyto Hair
Care is such a company.
The claim that silicones are occlusive is simply false. One of the primary properties of
silicone fluids is that they form a permeable
layer on the hair and skin. This
means that silicones seal in moisture while allowing the skin to breathe.
Silicones build up and can’t be washed from hair - Let’s talk about
build up! This is one of the biggest complaints against silicones in hair
products, and it has some basis in fact.
Except for the Dimethicone Copolyols, most silicone ingredients are not
soluble in water. This had lead to the belief that silicones are not removed by
washing and will build up over time.
This is not exactly true.
The ability of a conditioning
ingredient to adhere to the surface of the hair is called its
“substantivity.” In order to
replace the natural sebum that has been removed during the cleansing process,
it is desirable to have ingredients which coat the hair shaft and resist being
rinsed off. Considerable research
and development has gone into creating conditioning ingredients that have
greater substantivity with less weight to the hair shaft.
Build-up occurs when
ingredients that are very substantive to the hair accumulate to the point of
causing negative effects. Under
normal use, most substantive ingredients are washed off with regular
shampoo. That is they WERE, until
the trend toward sulfate-free ultra mild shampoos and conditioner shampooing
(“co-washing”). Instead of blaming
the shampoos for not doing the job of removing residue, they blame the
conditioning ingredients for doing the job of adhering to the hair.
News Flash: Silicones
are not the only ingredients that can build up on the hair. Silicones get the blame, but any of the quaternized conditioning
ingredients (quats and polyquats), such as Cetrimonium Chloride and
Polyquaternium-10 will stick to the hair and have potential for build-up as
well. Although some beauty
bloggers make a big to-do over the fact that most silicones are not
water-soluble and blame this for build-up, the truth is that substantivity (to
hair) not solubility (in water) is more of a factor. The products that have the greatest potential for build-up
are styling products, not shampoos or conditioners.
Shampooing with a
well-formulated sulfate shampoo will generally remove any residue from previous
conditioning or styling efforts.
CONCLUSION:
We have seen that the chemistry of silicones allows for
continual invention and evolution of products. State-of-the-Art of silicone
technology continues to drive forward with the creation of new polymers that
have enhanced benefits and solve the problems of yesterday. The ingredients of
today are not the same as twenty years ago when silicones first entered the pet
grooming arena. Misconceptions and
misinformation remain stuck due to continued recycling over the Internet. Instead of covering up and hiding the
use of silicones in grooming products, we would encourage manufacturers to own
their silicones and join the effort to educate users.
In Part II of Silicones, the Quest
for Truth, we will review safety issues surrounding silicone ingredients,
including various health issues and environmental concerns. Do silicones cause cancer and birth
defects? Will they destroy the
planet? Stay tuned, we are “going
there.”
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