Following our previous article on heat-resistant plastics, today’s discussion will focus on acid resistance with 5 high-performance plastics.
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Why are plastics so widely used to store liquids and, more specifically, chemicals such as acids? The answer is simple: plastics are not only strong and lightweight but also highly resistant, particularly to acid chemical solutions. In fact, several families of plastics have been specially developed with chemical compatibility in mind, making them a preferred solution for storing corrosive liquids and even concentrated acids.
"Thanks to their light weight, advantageous chemical compatibility, and mechanical resistance, performance plastics are an ideal solution for storing corrosive liquids such as concentrated acids."
Michel Bergeron, Technical Advisor
Chemical compatibility refers to a material's ability, in this case plastic, to avoid degradation when in contact with chemicals, retaining its properties for a long period of time. While there are many chemical-resistant plastics, more specifically to acids, we chose to focus on the 5 most common types for the purpose of this article.
It's also important to note that many factors can influence a plastic’s resistance to acids, the most important being acid concentration, acid type, temperature, and length of exposure.
Often white in colour, polypropylene (PP) is a semi-crystalline thermoplastic polymer that is widely used in the manufacture of containers, bottles, and various storage items. It’s not only affordable and versatile but also lightweight and very durable. Thanks to its chemical inertia, it offers an advantageous acid compatibility. This is why it’s often used in the manufacture of chemical storage tanks.
Aside from a few high-concentration acids, PP can easily withstand a prolonged exposure to a wide variety of acidic chemicals. However, other "higher-end” plastics, such as PVDF or ECFTE, should be considered for applications where tanks operate at high temperatures.
To learn more about polypropylene or its various types, read our article: The Advantages and Applications of Polypropylene.
Better known under the trade name Teflon®, polytetrafluoroethylene (PTFE) is a high-profile fluoropolymer. This high-performance plastic is prized for its impressive thermal resistance to both cold and heat, offering a wide operating temperature range from -200 °C to 260 °C.
Being chemically inert, PTFE can withstand even the most corrosive environments, resisting most types of acids.To learn about the misconceptions and preconceived notions surrounding PTFE, check out our article: 4 Myths about Teflon.
3. PEEK (polyetheretherketone)
Polyetheretherketone is a semi-crystalline thermoplastic from the polyaryletherketone family. Recognized for its physical and mechanical properties, it’s used in the field of aerospace, the manufacturing sector, and the food industry. This hard and very rigid plastic is resistant to traction, chemical products, and high temperatures. It remains stable and retains its properties even when exposed to temperatures of up to 482 °F (250 °C).
Ethylene-chlorotrifluoroethylene is a fluoropolymer specially developed for the most corrosive environments. It has excellent resistance to dilute and high-concentration acids. It's mainly used in the chemical and pharmaceutical industries.
Polyvinylidene fluoride is a high-performance plastic used for very specific applications. It has impressive mechanical, physical and chemical properties, all of which are superior to other plastics of the fluoropolymer family. This advanced plastic also has high thermal resistance.
This expensive material is used mostly in demanding environments. It’s therefore often used in the manufacture of tanks and liners that can withstand concentrated acids and other highly corrosive chemicals stored at high temperatures.
As previously mentioned, while these 5 plastics are excellent choices for applications that require corrosion-resistant materials, it’s important to refer to their respective chart and data sheet in order to make the right choice. It’s also crucial to evaluate all the constraints to which the plastic will be exposed in order to ensure the best compatibility for the desired application.