Types of Plastics That Resist Petrol and Hydrocarbons
When dealing with petrol and hydrocarbons, selecting the right type of plastic is crucial to ensure longevity and performance. This article explores various plastics that are notably resistant to petrol, including polypropylene (PP), polyethylene (PE), polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), and nylon polyamide. Understanding the characteristics of these plastics can help you make informed decisions in a wide range of applications.
Polypropylene (PP) - A Versatile Option
One of the plastics that stand out for their excellent resistance to petrol is polypropylene (PP). This versatile plastic is widely used in various applications due to its good chemical resistance, which extends to petrol. Its versatility makes it an ideal choice for many industries, where robust and durable materials are required.
Other High-Resistance Plastics
Polyethylene (PE)
Both low-density polyethylene (LDPE) and high-density polyethylene (HDPE) are known for their resistance to petrol. These types of polyethylene are frequently used for containers and tanks, offering reliable performance in petrol-related applications. HDPE, in particular, is a popular choice for making plastic gas cans and barrels due to its insulation and protective properties.
Polytetrafluoroethylene (PTFE) - The Gold Standard
PTFE, more commonly known as Teflon, is renowned for its exceptional chemical resistance and thermal stability. It is almost completely unaffected by petrol, making it an ideal choice for applications where prolonged exposure to petrol is expected. This makes PTFE a key material in the manufacturing of many crucial automotive and industrial components.
Polyvinyl Chloride (PVC)
While PTFE and HDPE offer the highest resistance, some formulations of PVC can also withstand petrol exposure. Though not as resistant as the other mentioned plastics, PVC can serve as a viable alternative in less stringent applications. Its affordability and availability make it a common choice for many industries.
Nylon Polyamide - A Balanced Choice
Nylon polyamides have shown good resistance to petroleum products, although they may absorb some hydrocarbons. Certain grades of nylon can maintain their integrity when exposed to petrol, making it a balanced choice for applications that require both performance and cost-effectiveness.
Application Considerations
When selecting a plastic for applications involving petrol, it's crucial to consider several factors, including temperature, pressure, and exposure duration. These factors can significantly affect the material's performance over time. For instance, in automotive applications, nylon polyamides are used for intake manifolds due to their good petrol resistance. In contrast, for making gas cans and barrels, high-density polyethylene (HDPE) is a common choice due to its insulation and protection against the heat from the petrol.
Advanced Techniques for Enhanced Resistance
For applications where the highest level of resistance is required, advanced techniques can be employed. For example, multi-layer walls can be used, with a very thin layer of EVAL sandwiched between layers of HDPE. Another effective method is treated HDPE, where the container is exposed to a fluorine gas, forming a very thin layer of fluorocarbon that petrol cannot penetrate.
Examples in Use
In Australia, jerry cans for petrol are generally made from high-density polyethylene (HDPE). Similarly, fuel tanks in small petrol engines are typically made of HDPE for their excellent resistance to petrol and their ability to insulate the contents from external heat. Polypropylene too is gas-proof and can be used in similar applications.
Additionally, the oil permeability of HDPE is addressed by the presence of gasoline, which is a non-polar halo-carbon with a high hydrogen content. This characteristic can affect the performance of most polyolefins. However, nylon can work but is expensive and difficult to mold large parts using blow molding techniques. In such cases, advanced methods such as using multi-layer walls or treated HDPE can be employed to achieve the desired level of protection.
Overall, the selection of the right plastic for petrol resistance depends on specific application needs and environmental conditions. Understanding the characteristics of different plastics, such as polypropylene, polyethylene, PTFE, PVC, and nylon, can help in making informed decisions that ensure the longevity and performance of the materials used in petrol-related applications.