Polypropylene (PP) is one of the most widely used thermoplastic polymers in the filtration industry. Known for its excellent chemical resistance, low cost, and versatility, polypropylene plays a critical role across a broad spectrum of filtration applications—from water treatment to chemical processing.
Material Properties of Polypropylene
Polypropylene is a semi-crystalline thermoplastic polymer belonging to the polyolefin family. It is synthesized through the polymerization of propylene monomers and is available in various grades, including homopolymer and copolymer types. For filtration applications, the key properties of polypropylene include:
Naturally repels water, making it suitable for filtering non-aqueous solutions or for applications requiring hydrophobic media (can also be treated to become hydrophilic).
Approximately 0.90 g/cm³, making it one of the lightest commercial plastics.
Offers good mechanical stability under pressure.
Prevents swelling and degradation in wet environments.
Food grade Polypropylene felt filter bags are safe for use in food, beverage, and pharmaceutical applications.
Operating Temperature Range
Polypropylene has a moderately high melting point among thermoplastics:
Up to 80°C in continuous use.
Below 0°C (32°F), the material can become more rigid and susceptible to cracking under mechanical stress.
In high-temperature applications beyond the 80°C limit, materials such as Nylon or Polyester maybe considered. Please contact sales if your application requires higher thermal resistance.
Chemical Compatibility
One of the standout features of polypropylene is its broad chemical resistance, especially against corrosive and acidic solutions. It is resistant to:
Excellent compatibility with most inorganic and organic acids.
Strong resistance to caustic solutions and sodium/potassium hydroxide.
Good resistance to many alcohols, esters, and ketones (though limited with strong oxidizers and chlorinated hydrocarbons).
Not suitable for strong oxidizing chemicals like nitric acid or concentrated hydrogen peroxide.
Polypropylene’s chemical compatibility makes it ideal for aggressive chemical filtration environments where metals or other polymers may degrade.
Filtration Applications of Polypropylene
Polypropylene is used in both filter media and filter housing components. Below are the major applications in filtration:
Water & Wastewater Filtration
Sediment removal in pre-filtration steps
Municipal and industrial water treatment
Borehole water
Suitable for potable water due to food grade media
Food & Beverage Industry
Clarification and pre-filtration of liquids such as juices, syrups, and process water
Dairy, brewery, and beverage filtration where chemical safety is critical
Chemical Processing
Filtration of corrosive fluids like acids, alkalis and solvents
Polypropylene’s combination of mechanical stability, chemical resistance, and cost-effectiveness makes it a cornerstone material in the filtration industry. While it has limitations in high-temperature or highly oxidative environments, it remains an optimal choice for a vast array of filtration applications, from simple sediment removal to chemically aggressive process streams.
For engineers, system designers, and procurement professionals, polypropylene offers a versatile and reliable solution, particularly where affordability and chemical robustness are required.
