In this guide, we outline what silicone is.
We also look at how sustainable silicone is, and whether it might be safe for human use (mainly from the perspective of using it for food and beverage/kitchen products, and also for contact with humans, such as with baby bottle nipples and feeders).
Summary – What Is Silicone, & Is It Sustainable & Safe?
Silicone is a polymer with a silicon backbone that can take several forms, such as a fluid, a gel, a rubber or a resin
Silicone is not technically a plastic or a rubber, but, it does usually possess properties from both materials, such as the elasticity of rubbers, or the malleability of plastics (plus other properties, depending on how the silicone chemistry is altered to suit the end use or application)
Silicone is used across a wide range of applications, with two examples of common everyday uses being as a sealant or glue around the house, and as a rubber in lids and containers for food and beverages. Baby bottle nipples and baby feeders are further examples
Silicone might be seen as slightly more sustainable than plastic in some ways. But, most silicones are still made with methyl group attached, and methyl groups generally originate from crude oil.
In addition, many silicones can’t or aren’t recycled via regular municipal recycling systems (at the very least, silicones tend to have a low recycling rate).
So, silicone doesn’t appear to be the most sustainable material in some ways, and certainly has some of the same sustainability concerns as plastic.
There are differing reports on just how safe silicone is for human health. Major organisations often indicate it is safe in the current exposure levels in society. Individual companies that sell silicone products can also indicate it doesn’t have the same leaching issues (of BPA, BPS, etc) or toxicity issues that plastic might have. However, other research and analysis suggests that the safety of silicone is still questionable in some ways, especially when it is exposed to very high temperatures, or oil and substances with a high fat content
Some conclusions about silicone say that we should be cautious about using it, especially silicones that come into contact with us, or our food. At the very least, we might research the silicone brand and material we intend on buying and using to know exactly what we are getting.
We might look at using alternative materials to silicone where possible – such as glass, metals like stainless steel, ceramics, and so on
Re-usable silicone that has a long life span and is re-used many times, may be more beneficial than other materials in some instances
But, it’s also hard to get a true gauge on silicone’s actual sustainability score as there aren’t any comprehensive life cycle assessments (that measure different sustainability indicators) done on it that we could find
Apart from food grade silicone and 100% pure platinum grade silicone, there are new silicone products emerging that are claiming to be made from 100% natural chemicals, as well as being recyclable, and BPA, BPS, phthalate, lead, latex and leachate/toxics free. So, these products may be might favorable from a sustainability and human health point of view – depending on the specific product.
One of the problems with food grade silicone for example is that there isn’t uniform regulations or standards for sustainability, health, and so on. So, each individual company may have to prove or certify the claims they are making about their material or product
*Always do your own research on the individual silicone product, and investigate these claims for yourself for each individual type of silicone, product and company (as they can differ). Also, note that there are many different types of silicone that have to meet different legislative regulations, such as medical grade vs food grade silicone – so, understand the type of silicone you are using and understand the relevant safety regulations and approvals yourself. There’s also special silicones like 100% pure platinum grade silicone. This guide is a general guide, and not expert or professional advice.
Difference Between Silicon, & Silicone
Apart from the ‘e’, the difference is:
- Silicon is one natural element that makes up the synthetic material silicone (so, silicon is one part of silicone)
- Silicon is a naturally occuring chemical element that makes up silicone, along with other elements such as oxygen, and carbon and hydrogen
- … [silicon is a naturally occurring chemical element, whereas silicone is a synthetic substance]
What Is Silicone? (What Is It Made Of Chemically?)
Explaining what silicone is from a scientific or chemistry perspective can get very complicated and technical.
So, here are a few of the more simple and shorter explanations:
Silicones have unique properties amongst polymers because of the simultaneous presence of organic groups attached to a chain of inorganic atoms … Silicones are synthetic polymers with a silicon-oxygen backbone similar to that in silicon dioxide (silica), but with organic groups attached to the silicon atoms by C-Si bonds. The silicone chain exposes organic groups to the outside. Silicone is, at it’s core, a silicon compound (essentialchemicalindustry.org)
Silicone is a synthetic polymer made up of silicon, oxygen and other elements, most typically carbon and hydrogen (livescience.com)
Silicones are inorganic polymers, that is, there are no carbon atoms in the backbone chain. The backbone [of silicone] is a chain of alternating silicon and oxygen atoms. Each silicone has two groups attached to it, and these can be any organic groups (pslc.ws)
Silicones, also known as polysiloxanes, are polymers that include any synthetic compound made up of repeating units of siloxane, which is a chain of alternating silicon atoms and oxygen atoms, combined with carbon, hydrogen, and sometimes other elements (en.wikipedia.org)
Types & Forms Of Silicone
From a general perspective, silicones we use mainly come in the form of:
- and resins
From a chemistry perspective, the types of silicones we use most commonly are:
- Silane, siloxan, and poly(diphenylsiloxane)
- The most widely used silicones are those which have methyl groups along the backbone
What Is Silicone Used For?
Silicone is used across a range of industries:
Silicones are used in many industries including … electronics, paints, construction and food … (essentialchemicalindustry.org)
[Silicone is used in the medical field, in personal care items, kitchenware, cookware coatings (because of non stick properties) food and beverage containers, lubricant for automotive parts, and more] (livescience.com)
Silicone can be used to make malleable rubber-like items, hard resins, and spreadable fluids … Silicone is often used for baby nipples, cookware, bakeware, utensils, and toys. Silicones are also used for insulation, sealants, adhesives, lubricants, gaskets, filters, medical applications (e.g., tubing), and casing for electrical components (lifewithoutplastic.com)
Features & Properties Of Silicone
Silicone can have a range of properties and features depending on how it’s chemistry is altered (to suit an end use or application):
- Properties such as solubility in organic solvents, water-repellence and flexibility can be altered by substituting other organic groups for the methyl groups.
- For example, silicones with phenyl groups are more flexible polymers than those with methyl groups.
- They are also better lubricants and are superior solvents for organic compounds.
Silicone in general has:
- Low toxicity and high heat resistance. It also provides good electrical insulation (livescience.com)
- … many plastic-like properties: flexibility, malleability, clarity, temperature resistance, water resistance … it is a unique plastic because it is much more temperature resistant and durable than most plastics and has a low reactivity with chemicals. And while water resistant, it is also highly gas permeable, making it useful for medical or industrial applications where air flow is required. It’s also easy-to-clean, non-stick, and non-staining, making it popular for cookware and kitchen utensils (lifewithoutplastic.com)
Silicone elastomers specifically have:
- … high temperature resistance, excellent environmental resistance, low compression set, low level of flammable components, high physiological inertness, poor abrasion, poor oil/petroleum resistance (silicone.co.uk)
Silicone bags can be:
- … lightweight, flexible, stretchy, washable, waterproof
Silicone bakeware can be:
- Highly functional, and can handle hot and cold temperatures
- Microwave and dishwasher safe
- Non stick – can skip greasing
Ecolunchboxes.com notes that silicone may be the answer to food container lids that don’t leak, and don’t leach chemicals like plastic might.
What About The Properties Of Food Grade Silicone Specifically?
It depends on the company and the individual food silicone product (specifically, how they make their silicone).
But some select silicone food grade products might have the following properties, or features …
- Not a “100% natural” material like rubber
- Is a non-toxic polymer mostly made from silica (sand).
- Can withstand heating and freezing without leaching or off-gassing, hazardous chemicals – unlike plastics, which contaminate food in these environments.
- It is also odor- and stain-resistant, hypoallergenic, and because of it’s smooth surface, very easy to clean.
- For these reasons, and because it is soft life rubber and does not break, it is the perfect material for eco-friendly and non-toxic baby products in particular
Food grade silicone made by some companies might be:
- Highly resistant to damage
- Highly resistant to degradation from high temperatures
- Doesn’t harden, crack, peel, crumble, dry out, rot or become brittle over time
- Non-toxic and odorless – contains no BPA, latex, lead, or phthalates
- May be 100% recycled at select locations
- Considered a non-hazardous waste
– stasherbag.com [note, Stasherbag does a specific type of food grade silicone called platinum food grade silicone – Stasher products are made of 100% pure platinum grade silicone — a standard even higher than food grade silicone, passing all U.S. safety requirements and even tougher European standards]
Some benefits of food grade silicone, and tips for choosing and using silicone dishes can be found at https://clearandwell.com/is-silicone-toxic/
Is Silicone A Plastic? What’s The Difference?
Silicone is not technically a plastic, but has several close similarities (different sources refer to it as a plastic because of this), as well as some differences.
The specific differences are:
… most plastics have a polymer backbone of hydrogen and carbon, [but] silicones have a backbone made of silicon and oxygen, and hydrocarbon side groups (lifewithoutplastic.com)
Silicone is something of a hybrid between a synthetic rubber and a synthetic plastic polymer (lifewithoutplastic.com)
The key difference from the common carbon-based plastics … is that silicones have a backbone made of silicon … while most plastics have a polymer backbone of hydrogen and carbon, silicones have a backbone made of silicon and oxygen, and hydrocarbon side groups – all of which gives them plastic-like characteristics (lifewithoutplastic.com)
[silicone is not plastic, and is closer to the rubber family than plastic]
Is Silicone A Rubber?
Like the plastic section above, silicone is not technically a rubber, but displays close similarities:
The correct way to describe silicone might be an ‘elastomer’, that displays elastic properties [like rubber] (silicone.co.uk)
Read more on silicone and synthetic rubbers in these resources:
Is Silicone Sustainable?
On one hand, there can be some sustainable aspects to silicone:
[Silicone is made in part with silicon, which] … is the second most abundant element in the Earth’s crust, after oxygen (livescience.com)
[Some pure platinum food grade silicones are]… made from sand (silica) and carbon, natural resources (stasherbag.com)
[Some silicone products are food-grade silicone [that] is made without petroleum-based chemicals, BPA, BPS, or fillers] (stasherbag.com)
If disposed of at a landfill for incineration, the silicone (unlike plastic) is converted back into inorganic, harmless ingredients: amorphous silica, carbon dioxide, and water vapor (ecolunchboxes.com)
[Compared to plastics, silicone is longer lasting and endures extreme fluctuations in temperature without melting, cracking or otherwise degrading, and, it resists oxidative deterioration (normal aging) for decades on end … these things increase it’s product lifecycle] (clearandwell.com)
On the other hand, there are non sustainable aspects to silicone:
But, most silicones use methyl groups attached to the backbone. [Methyl groups are hydrocarbon groups, and, most hydrocarbons found on Earth naturally occur in crude oil] (en.wikipedia.org)
[Silicone does] contain silica, which is derived from sand, it also contains synthetic and chemical additives that come from fossil fuels (treehugger.com)
Silicone does not biodegrade or decompose (certainly not in our lifetimes). Silicones are very persistent in the environment (lifewithoutplastic.com)
Silicone compounds are pervasive in the environment. Particular silicone compounds, cyclic siloxanes D4 and D5, are air and water pollutants and have negative health effects on test animals (en.wikipedia.org)
Some silicone products can be recycled in regular recycling, while most silicone products need specialised privatised recycling (and have a low recycling rate)
Is Silicone Safe? (Toxicity, BPA, & Human Health Concerns)
Some major organisations indicate that silicone is safe with the current exposure levels in society.
- … the FDA considers normal use of undamaged silicone cookware and other items to be safe (healthline.com)
- Health Canada confirms … silicone does not react with food or drinks or produce any hazardous fumes (clearandwell.com)
But, some independent research and studies question this stance.
… there has not been a lot of research done to date on the health effects of silicone … [But, independent research and review of peer-reviewed scientific studies shows] they can leach certain synthetic chemicals at low levels, and the leaching is increased with fatty substances, such as oils [and food with fatty content] … silicone is not as inert, stable and chemically unreactive as many claim (lifewithoutplastic.com)
Some studies indicate even food grade silicone can leach siloxanes when exposed to very high heat, and fat (thetot.com)
… there haven’t really been many in-depth or subsequent studies into [silicone’s] long-term effects … [but there are] reasons to indicate that “we should begin to be cautious about silicone.” … One study tested the release of siloxanes from silicone nipples and bakeware into milk, baby formula and a simulant solution of alcohol and water [and, after 72 hours, there were results that raised some questions] (treehugger.com)
Kitchen and bakeware products made from silicone are often marketed on the basis that they’re safe. They’re non-toxic, inert, can be heated as well as frozen and do not release any odours into food when cooking … However, some concerns still linger around the safety of silicone. For example, there is concern that, when heated to high temperatures (above 149oC) silicone becomes less stable. It may also leach certain undesirable compounds known as siloxanes … Further studies are needed before we have a more complete picture of any health risks posed by silicone (ecoandbeyond.co)
Potential tips on dealing with silicone if you are worried about health concerns might be …
- Use [silicone] with caution, and if you can find an alternative, use it
- … use high quality, relatively stable [silicone] material, and leaching of chemicals from other plastics is of much greater concern
- … use high quality, food grade or medical grade silicone
- … other options are glass, ceramic and stainless steel options for cooking and baking
Basic tips for using silicone can be found at https://lifewithoutplastic.com/silicone/
- Try food safe/food grade silicone for plates, cups and mealtime travel gear (it is claimed to be non toxic and doesn’t leach or off gas)
- Glass and metal work well for baby bottles
- BPA substitutes can be hazardous to health – so watch out for BPS and similar substitutes
- Silicones do play a useful role as seals or gaskets in many reusable containers, but these do not generally come into contact with the food and are a tolerable use of the product.
Specific silicone food grade products from some companies are claimed to have the following features [so you may look for companies and products with similar claims and research if they are accurate for yourself]:
- No fillers or toxic products in Stasher bags — no BPA, BPS, lead, latex, or phthalates
- Food grade silicone is a non-toxic type of silicone that doesn’t contain any chemical fillers or byproducts, making it safe for use with food.
Prepol.com makes a good point about silicone safety and compliance:
- … manufacturers of silicone components must demonstrate – on an individual basis – the compliance of the finished product
- [this is because] there is no automatic universal ‘approval’ of all silicone products or manufacturers
- [in addition, bodies like the FDA in the case of the US, are responsible to protect the public from food hazards – where we are looking at silicone as a food grade product … so we can look at what these bodies have to say too]
Is Silicone Recyclable?
- Silicones are recyclable, but have a low recycling rate and are generally not recyclable through the average local recycling program … usually specialized private recycling companies downcycle silicone into oil
- [some companies offer recyclable silicone products, and even offer to recycle and repurpose it themselves ]
- While there is nothing about silicone chemically that would prevent it from being recycled, curbside recycling programs rarely accept it, and it can be difficult to find a silicone recycler to accept post-consumer products. This is because many consumers confuse polyurethane with silicone.