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Silicone has been on the market for a long time and in some cosmetic products

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what is silicone

Do you remember high school chemistry classes, when the teacher (blessed be) taught us funny phrases to remember the content of the subjects? That's when he didn't appeal to songs... Still, who among us knows how to differentiate an "amide" from a "cycloalkane"? To understand what silicone is, you don't need to have memorized any tricky phrases, you just need to pull a little bit of the content of the organic chemistry class into your memory. But let's help you with this task.

First, organic chemistry, in short, is about the compounds of carbon molecules and the study of their derivatives. Silicon is a semi-organic compound because it is not made primarily of carbon, but of silicon and oxygen, having the following general chemical formula: [R2SiO]n. However, as it binds to molecules that have carbon, it is not inorganic either.

In addition to having many medical applications, such as catheters, drainage tubes and prostheses for people who have had an accident, silicone is common in the composition of cosmetic products and in everyday utensils. Chemically speaking, it is inert (does not react spontaneously with other compounds), has physical stability combined with heat resistance, withstanding from -40°C to 316°C! This is because of its semi-organic quality.

In a three-dimensional format, that general chemical formula has the core silicon component and the carbon part is like a plastic film tube wrapping it. In industry, in the face of heat, carbon atoms are first burned and then silicon, which is one of the biggest components of glass (to make glass, for example, a temperature of up to 1500°C is reached).

Silicone in hair

Because it's flexible, it's easy to spread silicone evenly across the hair's surface. The shape of the silicone has spaces for gas molecules to penetrate, making the covering on the hair "breath", being light, emollient (softener) and silky to the touch, in addition to having a high index of light refraction, giving shine. For this reason, silicone is used as a conditioning agent in many products, including some shampoos, especially those "2 in 1".

Always remembering the difference between silicone and petrolatum, please understand that we are talking here about the first one, silicone that is good for the hair, which really conditions - whose main molecule is silicon, not petroleum. Petrolatums, in short, coat the hair strands not allowing nutrients to penetrate the fiber, and accumulate over time, stifling their health, so they are harmful. Oil-free silicone doesn't do this and can be used with more peace of mind by most people, with the exception of allergy sufferers, of course. The most common marketed variants are dimethicone, cyclomethicone and other "cones".

UFRJ researchers have discovered a plant-derived silicone, extracted from the acacia tree, but most of those currently sold have, in fact, petrolatum in their composition. Like petrolatum, it is odorless and tasteless, and depending on the organic groups (carbon molecules) it is attached to, it can range from fluid liquid (used in cosmetics) to silicone elastomer (elastic solid polymers such as rubbers), hence its large-scale use by industry.

Other applications

Contact lenses, fake "gel" nails, sunscreens and some special enamels are other beauty and health applications for this versatile compound, not to mention the famous plastic surgery implants. When silicone is not bringing more beauty to our daily lives, it is bringing comfort. Practical uses can be in the manufacture of fiberglass, resins, pigments and dyes, mold rubbers, sealants, polyurethane and, ufa... a thousand applications.

The health

The Cosmetic Ingredient Review, among other organizations, carried out extensive research and laboratory tests that prove the safety of using cyclomethicones in the concentrations of the products evaluated in the experiment.

In the international classification CMR (Carcinogenic, Mutagenic or Reprotoxic) are classified as type 3, that is, without evidence within the spectrum of studies for any of these three types of disease. Evidence from animal testing is insufficient to place them in category 2 (which should be considered as possible carcinogenic/mutagenic/reprotoxic). The Type 1 CMR classification is the most alarming.

We emphasize that couples trying to get pregnant, or women who are already pregnant, should seek medical advice.

Environment

As poly-dimethyl-siloxanes silicones are present in a variety of products, not just cosmetics, and are non-volatile (not evaporating into the atmosphere), certain amounts are taken along with the bath or industrial rinse water, which ends up deposit in the soil and water to be treated. This, in turn, can stay in a household septic tank or municipal tanks. In fact, this is common, as 17% of the world's product volume is used in processes that require rinsing.

The silicone that has been rinsed will bond to solid particles and will eventually break off from the water in the natural sedimentation process. They do not have significant Biological Oxygen Demand (BOD) to be catalyzed by aerobic bacteria, which is a testament to their non-toxicity. The viscous mass of sediments agglutinated by these microorganisms is later incinerated, becomes fertilizer or goes to landfills.

If this "sludge" is incinerated, the silicone converts to amorphous silica, and the ashes, if deposited in landfill, have no environmental impact. The same is true for use as fertilizer, which is degraded in soil catalysis, the same purpose as when placed in landfills.

Silicon does not bioaccumulate either, as the size of the molecules is too large to pass through the membranes of fish or even land-care animals such as earthworms.

If the silicone goes straight into the soil, for example, it breaks down into smaller particles (Me2 Si(OH)2) after a few weeks, which eventually oxidize, returning to the natural forms of silica, carbon dioxide and water, no affecting soil health, seed germination or plant growth. They also do not disturb insects or birds, even when exposed to large amounts (studies have followed the species' eggs from deposition to the life of the chicks).

Volatile (evaporating) methylsiloxanes are found in skin and hair cosmetics and antiperspirants such as vehicles or emollients. Most of this type of silicone has a cyclic structure, which is why they are called "cyclomethicone". Industrial emissions from volatile silicone are minimal, and so is the consumer level, which is evaporated. If they happen to mix with water, a part of it will eventually come off into the atmosphere, and breaks up by oxidation within 10 to 30 days. This entire process takes place in the troposphere, so there is no possibility of contaminating the stratosphere and consequently the ozone layer, not contributing to global warming.

As all these silicones have the same general structure (chains of silicone and oxygen atoms, and -methyl groups attached to the silicone), they dissolve following the same sequence, generating new compounds, less volatile, rich in silanol, soluble in water and less soluble in lipids. They continue to decompose more and more, being in the atmosphere, as in a cycle. As with Polydimethylsiloxane, the remaining particles from this oxidation are silica, carbon dioxide and water.

Looking at the current world context, however, an observation must be made. As most people use industrialized hygiene, cosmetics and cleaning products, and as the world population is in the billions, the global ecosystem may already be overloaded with this compound, which takes some time to biodegrade. The product itself is not as harmful as petroleum products, for example, but it is important to consume it conscientiously and with a light footprint, within the possibilities of each one.