The term "phenolic" is used to refer to a few different substances made with phenol, an organic compound. It can describe a type of resin used to create various consumer items and is the name given to a class of plant-based chemical compounds. It can also refer to carbolic acid, an organic material that has been used in various medical and cleaning products.
Resin
Phenolic resin is made by combining phenol and an aldehyde. When these organic compounds are mixed, and both pressure and heat are applied, it causes polymerization, which is a chemical reaction that can be used to mold solids. Since it is both versatile and durable, this resin is used to make a wide variety of consumer and industrial products.
A range of goods, from billiard balls to kitchen gadgets, and automotive parts to construction adhesives, are made with phenolic resins. The material is often used to create consumer fittings, such as the plugs on electronic devices, handles for pots and pans, and screw-tops on most bottles. Its affordability and the ease with which it is molded can make it an ideal choice for many applications.
Bakelite®
Resin may be made by mixing simple phenol with any number of aldehydes, but the combination made with formaldehyde — known as phenolic formaldehyde resin (PF) — is the most widely used. It was the first synthesized resin, and was marketed under the brand name Bakelite®. Soon after, because it was cheap to make and admired for its beauty, this substance was used to make many household objects, including jewelry, radios, musical instrument components, and cameras. While the heyday of items made with it was from 1920 to 1940, this malleable material is still used to make board game pieces, gun parts, and even heat shields on rockets.
Use as a Binder and Insulator
The combination of phenol and formaldehyde is also frequently used as an agent to bind together composite woods, including chipboard and plywood. While it can be somewhat brittle when used in this way, it produces very little smoke if it catches on fire, and, at high grades, can resist temperatures up to 370°F (185°C). In construction, phenolic foam made from these compounds is often used as insulation, usually in the form of rigid sheets. This type of insulation is often chosen for its ease of installation, affordability, and thermal mass — it's ability to moderate temperature fluctuations.
As a Laminate
Sheets of paper, glass fabric, and certain kinds of cloth, like linen and cotton, can be treated with phenolic resin, then pressed and heated to form hard, laminated plastic sheets. This composite laminate is heat-resistant, strong, and waterproof. The flat plates are easily shaped or carved and frequently used on tables, counter tops, and even as pick guards on guitars.
Phenols in Organic Chemistry
Any member within the class of organic phenols may be termed a phenolic compound. Compounds in this class are simple hydrocarbon groups, similar to alcohols. Phenolics are varied and found in a range of natural things — from capsaicin, the heat agent in chili peppers, to neurotransmitters in the brain, like dopamine.
Natural Compounds in Plant Antioxidants
Phenols are found in many plants, including fruits and vegetables. While the study of these substances is ongoing, it is known that their antioxidant properties — found in wine, berries, and many types of tea — may protect cells from damage and death. These substances are also found in other foods, such as olive oil, and in certain dietary nutrients, like vitamin E.
Carbolic Acid
Carbolic acid is another name for phenol or phenic acid, and is a natural substance that is solid, white, and crystalline. It was originally derived from coal tar, and has been used in soaps, cosmetics, and cleaning agents. Through the 19th and part of the 20th centuries, this mild acid was used medicinally, particularly as an antiseptic and topical anesthetic in and around the mouth. It is toxic, however, and can cause chemical burns to the skin, so its use has been largely discontinued in favor of safer alternatives.
You may not have ever heard of phenolic acid, but you’ve likely encountered it countless times in products that you use every day. Indeed, phenolic acid is a common component of many products — one of the most widely distributed non-flavonoid plant compounds, in fact. With a wide range of applications, unparalleled versatility, and stable composition, this compound is a key resource for commercial manufacturing, but two of the most common types of phenolic acid — hydroxybenzoic and hydroxycinnamic acids — are also naturally found in many foods.
How Is Phenolic Acid Made?
To ask how phenolic acid is “made” might be slightly misleading. It is a naturally occurring compound that can be found in all food groups. It is especially present in foods such as the following:
- Legumes
- Cereal
- Vegetables and fruits
- Oilseeds
- Beverages
- Herbs
In addition to its naturally occurring form, there are chemical synthetizations that are not naturally found. In its manufactured form, it can be practically identical to its natural counterpart, classified as water-soluble, and typically sold commercially in bulk for use in consumer products.
What Is Phenolic Acid Used In?
So what commercial products is phenolic acid so commonly used in? Phenolic acid has a wide range of uses in manufacturing, including in the making of products such as the following:
- Household products
- Surgical antiseptic
- Slimicide
- Electrical manufacturing
- Marine technology
- Fire safety technology
- Throat numbing sprays
These are just a few of the myriad uses that phenolic is commonly manufactured for. Additionally, it is frequently used in the construction industry as an adhesive for materials such as plywood, molding, and insulation. Phenolic acid is particularly attractive for this application because of its superior thermal stability. It remains intact even in extreme temperature highs and lows.
Another industry that relies heavily on the use of phenolic acid is plastic manufacturing. Phenolic acid is used to make plastics because of its resistance to weak acids. This makes it a highly durable option, and its aforementioned thermal stability make it ideal for use in electrical wiring, mechanical parts, and auto accessories, too.
Risks of Exposure to Phenolic Acid
Though it is highly versatile, affordable, and naturally occurring, phenolic acid can pose risks to users. According to the Center for Disease Control, exposure to phenols can cause irritation — especially to a person’s throat, nose, skin, and eyes. Additional symptoms such as the following may also occur:
- Weight loss
- Exhaustion
- Weakness
- Aches and pain
- Damage to liver or kidney
- Burns on the skin
- Tremors and convulsions
- Twitching
The greater the concentration or longer the period of exposure is, the more severe a person’s symptoms are likely to be. In some cases, exposure to phenolic acid is also linked to certain cancers. It’s important to note that most of this risk comes from exposure that occurs during the processing of phenolic acid — for example, in the petroleum industry or during the manufacture of nylon. Phenolic acid fumes from these processes can be particularly harmful, putting people at risk of injury is exposure is extensive.
Benefits of Phenolic Acid
With all of these risks, you might not think that phenolic acid offers any benefits, but it actually can! Phenolic acid is especially beneficial when consumed via nutritious foods such as fruits and vegetables. In this form, a person is exposed to phenolic acid in its purest form, and it can act as a potent antioxidant, offering an array of health benefits. These benefits come from phenolic acid’s ability to penetrate the walls of your intestinal tract and mitigate cell damage that’s been inflicted by free radicals.
For this reason, phenolic acid is commonly cited as an important agent in anti-aging, antioxidant, and anti-inflammatory responses. If you aren’t able to get sufficient levels of phenolic acid from your diet alone, there are plenty of supplements available that can substantially boost your phenolic acid intake. Many of these supplements are marketed as generic anti-inflammatory vitamins, so it’s important to check the label and ensure it features sufficient phenolic acid levels.
Alternatives to Phenolic Acid
Though phenolic acids found in foods have the potential to offer a wide range of health benefits, these compounds still pose a risk when found in other forms. Many manufacturers have begun to seek out alternatives to phenolic acid for this reason, and some of the options are as follows:
- Lignin
- Tannin
- Cardanol
- Hydroxymethylfurfural
- glyoxal
Though some of these compounds may be less risky than phenolic acid, it’s possible that they carry unique risks of their own. Phenolic acid will likely continue to be the substance of choice for manufacturing and plastic production.