Tillie Doyle
Teflon pans are made by first melting and casting aluminium into slabs, which are then thinned out and punch-cut into the desired shape. The aluminium is then treated with sodium hydroxide to dilate its pores so that it can bind with coatings. An enamel coating is sprayed on the exterior of the pan and cured in an oven. The interior of the pan is then sprayed with a coat of primer before the PTFE coating is applied, giving the pan its non-stick properties. The PTFE coating is then baked at a high temperature to ensure it sticks to the aluminium.
| Characteristics | Values |
|---|---|
| Material | PTFE (Teflon is a brand name of PTFE) |
| PTFE Synthesis | The process begins with the synthesis of Calcium Fluoride, Sulphuric Acid and Chloroform to create the TFE monomer |
| Polymerization | The TFE monomer is polymerized using a solution of ammonium persulphate, borax and water, agitated at 80 degrees Celsius for an hour |
| PTFE Coating | The PTFE coating is applied by spraying it onto the aluminum surface |
| Baking | The coated pan is baked at a high temperature (370-385°C) to ensure the coating sticks |
| Number of PTFE Layers | One to seven layers of PTFE are sprayed or rolled on |
| Layer Thickness | The number and thickness of layers determine the quality of the non-stick coating |
| Primer | The interior of the pan is sprayed with a coat of primer before the PTFE coating |
| Enamel Coating | An enamel coating is sprayed on the exterior of the pan and cured in an oven |
| Aluminum | Aluminum is melted, cast into slabs, thinned out, and punch-cut into the desired shape |
| Aluminum Treatment | The aluminum is treated with sodium hydroxide to dilate its pores so it can bind with coatings |
| Thermoset Plastics | Thermoset plastics are used for the handle of the pan due to their resistance to high heat |
| PFOA | PFOA was previously used in PTFE processing but is now being phased out due to toxicity concerns |
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What You'll Learn
PTFE is synthetised from Calcium Fluoride, Sulphuric Acid and Chloroform
Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene, commonly known by the brand name Teflon. It is a fluorocarbon solid, consisting wholly of carbon and fluorine. PTFE is hydrophobic, meaning that neither water nor water-containing substances can wet its surface. This is due to the low electric polarizability of fluorine. PTFE also has one of the lowest coefficients of friction of any solid.
PTFE is synthesised from calcium fluoride (fluorspar), sulphuric acid, and chloroform. The reaction of fluorspar (CaF2) with sulphuric acid yields hydrofluoric acid. This reaction can be represented by the following chemical equation:
CaF2 + H2SO4 → CaSO4 + 2HF
The resulting hydrofluoric acid then reacts with chloroform to produce monochlorodifluoromethane, as shown in the equation below:
CHCl3 + 2HF → CHClF2 + 2HCl
PTFE is manufactured commercially through two major processes, leading to different forms of the polymer. One process results in a "granular" polymer, while the other produces a dispersion of polymers with smaller particle sizes and lower molecular weights. The reactions in the second process are carried out at temperatures up to 90°C.
PTFE is used in various applications, including non-stick coatings for cookware, waterproof clothing, and industrial pipe linings. It is valued for its chemical inertness, high heat resistance, and low friction.
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Molten metal is poured into moulds
The creation of a Teflon pan begins with aluminium, which is melted down and cast into slabs. These slabs are then thinned out and punch-cut into the desired shape of the pan. The aluminium is then treated with sodium hydroxide to dilate the pores, allowing the metal to bind with the coatings that will be applied to its surface.
The aluminium is then cast into a furnace to create molten metal, which is poured into moulds to form the base of the pan. This process is typically carried out by a robotic ladle, which pours the molten metal into the moulds. Workers and machines then cut off any excess metal to further shape the pan.
The temperature is then adjusted to cool the metal, which requires a significant amount of energy. This is followed by another energy-intensive process as the pans are moved to a coating system via a conveyor belt.
The pans are then spun around by a rotating machine to ensure an even coating layer. An enamel coating is sprayed onto the exterior of the pan and then cured in an oven. After curing, the interior of the pan is sprayed with a coat of primer before the PTFE coating is applied, giving the Teflon pan its unique non-stick properties.
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Pans are coated with PTFE
PTFE, or polytetrafluoroethylene, is a synthetic fluoropolymer that forms the non-stick coating on Teflon pans. It is created through the synthesis of Calcium Fluoride, Sulphuric Acid, and Chloroform to create the TFE monomer, which is then polymerized using various methods. The process of manufacturing PTFE involves excluding the addition of perfluorooctanoic acid (PFOA) due to its toxicity and negative impact on hormonal balance.
Once the PTFE is ready, it is applied to the pan's surface. The pan's metallic substrate is first roughened by abrasive blasting or a similar method, creating an irregular surface that promotes adhesion of the PTFE and resists abrasion. This process is crucial for ensuring the PTFE coating adheres properly to the pan.
After the surface is prepared, the PTFE coating is applied. One to seven layers of PTFE are sprayed or rolled onto the pan's surface. The number and thickness of these layers, as well as the quality of the material, determine the overall quality of the non-stick coating. A higher number of layers generally results in a better non-stick surface.
Finally, the PTFE-coated pan undergoes a baking process known as sintering. The pan is baked at a temperature of around 370-385°C (700-725°F) for about five minutes. This step ensures that the PTFE coating adheres firmly to the pan's surface, creating a durable non-stick finish.
It is important to note that PTFE-coated pans have specific care instructions. Using metallic utensils harder than the coating can scratch the surface. Therefore, it is recommended to use non-metallic utensils, such as those made of plastic or wood, to prevent scratching. Additionally, overheating PTFE-coated pans beyond approximately 260°C (500°F) can cause the coating to break down, releasing harmful compounds.
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The coating is baked on
The PTFE coating is applied to the pan through spraying or rolling. One to seven layers of PTFE may be applied, depending on the desired quality of the non-stick coating. The number of layers, their thickness, and the quality of the material all contribute to the effectiveness of the non-stick property.
Before the PTFE coating is applied, the aluminium surface of the pan undergoes preparation to enhance the adhesion of the coating. The metallic substrate is roughened through abrasive blasting, creating an irregular surface that promotes better adhesion of the PTFE. Additionally, the aluminium may be treated with sodium hydroxide to dilate its pores, further improving the binding process.
The baking process, or sintering, plays a crucial role in ensuring the durability and performance of the Teflon coating. It involves heating the coated pan at a specific temperature range for a short duration. This controlled application of thermal energy helps to strengthen the bond between the PTFE molecules and the aluminium surface, resulting in a non-stick coating that can withstand everyday cooking demands.
It is important to note that the PTFE coating has a limitation. When pans are overheated beyond approximately 260 °C (500 °F), the PTFE coating begins to break down, releasing harmful substances such as hydrofluoric acid and organofluorine compounds. Therefore, the baking process during manufacturing must be carefully controlled to avoid any potential negative effects on the performance and safety of the Teflon coating.
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Thermoset plastics are used for the handle
The manufacturing process of Teflon pans involves the use of high temperatures. Firstly, aluminum is melted and cast into slabs, which are then thinned out and punch-cut into the desired shape of the pan. The aluminum is then treated with sodium hydroxide to dilate its pores so that it can bind with coatings. An enamel coating is sprayed onto the exterior of the pan and cured in an oven. The interior of the pan is then sprayed with a coat of primer before the PTFE coating is applied, which gives the Teflon pan its non-stick properties. As this manufacturing process involves high temperatures and the application of coatings, the handle must be made from a material that can withstand these conditions without warping or melting.
Thermoset plastics are ideal for this purpose as they are resistant to heat and can maintain their shape even when exposed to high temperatures. This ensures that the handle of the Teflon pan remains intact and functional throughout the manufacturing process and during subsequent use.
The use of thermoset plastics for the handles of Teflon pans is an important consideration in the design and manufacturing process. By selecting a material that can withstand high temperatures without deformation, manufacturers can ensure the durability and functionality of the pan. This contributes to the overall quality and safety of the product, providing consumers with a reliable cooking utensil.
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Frequently asked questions
Teflon is a brand name of PTFE (polytetrafluoroethylene), a synthetic fluoropolymer used in various applications, including non-stick coatings for pans.
The manufacturing process of Teflon pans involves several steps. First, aluminum is melted and cast into slabs, which are then thinned out and punch-cut into the desired shape of the pan. The aluminum surface is treated with sodium hydroxide to dilate its pores, allowing it to bind with coatings. An enamel coating is sprayed onto the exterior of the pan and cured in an oven. After curing, the interior of the pan is sprayed with a primer before the PTFE coating is applied, giving it its non-stick properties. The PTFE coating is then baked at high temperatures to ensure it adheres to the aluminum.
There have been concerns raised about the potential negative effects of using PTFE-coated pans. The coating can begin to break down and release harmful chemicals if overheated beyond approximately 260°C (500°F). Additionally, the past use of PFOA (perfluorooctanoic acid) as an emulsifier in PTFE processing has been phased out due to environmental and health concerns, as it is a persistent organic pollutant with potential hormonal impacts.
