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How to choose the right plastic material (PP vs FRP vs PVC) for industrial fabrication projects?

Choosing the appropriate type of plastic for industrial manufacturing like chemical storage, exhaust pipes, or water treatment, is one of the most important aspects of safety, durability, and cost. Three different types of plastics will meet these functions: polypropylene (PP) , fiber-reinforced plastics (FRP) , and polyvinyl chloride (PVC) . Each type of material provides both advantages and disadvantages.

 

Through this guide, you will find an in-depth comparison of the three materials to assist engineers and manufacturers with their selections based on the specific needs of each individual project.

 

Understanding the Core Materials

 

To properly initiate a comparison, we first need to define these three materials at their base level.

 

Polypropylene (PP) is a thermoplastic polymer that possesses several advantageous properties, including lightweight, high melting point (as compared to other commodity plastics), and has exceptional chemical resistance. It is considered semi-crystalline and provides a good combination of strength and flexibility when constructing.

 

Fiber-Reinforced Plastic (FRP), otherwise known as Glass-Reinforced Plastic (GRP), is a composite material consisting of a polymer matrix (the resin) and fibres used as reinforcement. The resin typically is a thermoset plastic such as Polyurethane or Vinyl Ester, while the reinforcement is most often glass fibre. The combination of these two components provides a unique property of FRP, which is its ability to have strength equivalent to that of steel while having a fraction of the weight.

 

Polyvinyl Chloride (PVC) is an amorphous thermoplastic that has natural flame retardant properties, good resistance to chemicals, great rigidity and strength across the full range of possible industrial applications. The rigid form of PVC (unplasticised) is the preferred type of PVC for use in industrial fabrication due to its ability to maintain structural integrity.

Material Properties: A Detailed Comparison

 

Analysis of the Key Physical Properties of the Three Materials

 

Weight and Performance: When it comes to lightweight materials, PP reigns supreme making handling and installation easier than ever before. As such, for applications that need high load capacities or need to extend over large distances, FRP has the best strength to weight ratio and is therefore optimal for these types of uses. PVC has good stiffness for smaller self-supporting structures but is weightier than both PP and FRP.

 

Temperature Limits: Operating temperature is usually one of the determining factors when selecting a product. Standard PVC will begin to soften, deform, and lose its shape at approximately 60 degrees Celsius (140 degrees), while PP can withstand continous use at temperatures between 80 degrees Celsius (176 degrees) and 100 degrees Celsius (212 degrees) making it ideal for use with hot process liquids. If fabricated using the correct high temperature resin, FRP can perform at temperatures well above 100 degrees Celsius (212 degrees).

 

Chemical Compatibility: All three products have good corrosion resistance; however, the type of chemical will greatly affect the performance of each. PP has exceptional resistance to a broad range of acids, alkalis and organic solvents. PVC has many similar resistances; however, certain solvents and aromatics will not be compatible with PVC. It can be stressed that the chemical resistance of an FRP is completely dependent upon the type of resin used; however, by using vinyl ester or epoxy type resins, a FRP can be created to withstand highly aggressive media that would typically corrode PP and PVC.

 

Ease of Repair and Fabrication: The ease of fabrication and repair of both PP and PVC is a large differentiator. Both PP and PVC are thermoplastics, and as such, are able to be fabricated using thermal welding and also have a high machinability factor. Both PP and PVC can be repaired easily if damage occurs.

 

When to Choose Which Material

 

The type of decision matrix directly relates to the specific characteristics of the application. 

 

Use PP (Polypropylene) When:

 

Chemical handling is a primary concern: PP is frequently found to be the best all-around example as well as the least expensive for tanks and ductwork that are designed for handling strong acids (such as HCl or H2SO4) and bases (for example, NaOH).

 

Moderate temperatures: PP is recommended for process streams that consistently stay within an operating range of 60 °C to 100 °C, as PP will remain functional while PVC would not and FRP may be severely over-specified.

 

Custom fabrication and repairability: Welding is relatively simple and would allow for custom modifications to be created or provide ease of repair for many years.

 

Very high levels of purity: BPA free and can be formulated to meet food grade specifications; therefore, it is appropriate for use in pharmaceutical or food processing applications.

 

Cost: PP provides exceptional value in terms of overall performance at competitive costs relative to other materials.

 

Typical Applications for PP include:

 

  • Chemical Storage Tanks (acidic and alkaline) 
  • Electroplating and Metal Finishing Lines 
  • Fume Ductwork for Laboratory Exhaust 
  • Food and Beverage Processing Equipment 
  • Semiconductor Wet Benches

 

When FRP should be chosen:

 

  • When a lot of Strength is Required: FRP has higher strength than other materials when using very large amounts of materials (storage tanks, pressure vessels and scrubbers) that need to handle heavy loads.
  • When a Very High-Temperature Environment Exists: If the operating temperature is greater than 100°C, there are a few options for the specification of an FRP material (properly specified FRP Systems are about the only option of the 3 materials).
  • When Large Scale Equipment is Required: Composite manufacturing allows for the creation of very large containers without the use of thermoplastic sheets.
  • When you have Specific Chemical Resistance Requirements: Custom FRP resin systems can be manufactured for unique chemical environments, whereas standard thermoplastics may not fit the bill.

 

FRP is well suited for the following:

 

  • Large Diameter Storage Tanks (above 50m³)
  • Scrubbers and Stack Liners
  • Piping for High-Temperature Corrosive Fluids
  • Structural Components (Grating and Walkways)
  • Chemical Process Vessels Operating at Pressure or Vacuum

 

Choose PVC When:

 

  • Budget Constraints Exist: PVC represents the lowest cost non-critical application for low temperature uses.
  • Fire Safety Is Critical: PVC’s natural flame resistance makes it an excellent choice when fire codes are vigorous, as in building materials and electrical conduit.
  • Low-Temperature/Live Applications: PVC will satisfy the requirements for small drain lines or tanks that will contain water or a gentle chemical at about room temperature.
  • Translucent Applications: Depending on formulation, PVC may be created to have higher levels of translucency than polypropylene, thus providing useful options when creating sight glasses; monitoring fluid level.

 

PVC’s Ideal Applications:

 

  • DWV (drain, waste, and vent) pipe.
  • Chemical drainage at low temperatures.
  • Water treatment chemical placing lines.
  • Electrical conduit.
  • Extraction hoods for non-corrosive fumes.

 

The Limits: When to Avoid Each Material

 

It is as crucial to know when you should not use a material as it is to know when you should use them.

 

Use PVC when: You cannot consistently exceed 60˚C and/or when you will not have chemicals that can attack PVC. Aromatic solvents, esters, and/or ketones are some examples of chemicals that can attack PVC. Other scenarios to avoid PVC are if your application will require high impact strength at low temperatures due to the fact that PVC will become brittle at that temperature.

 

Use PP when: You have an application that requires long-term exposure to UV light without utilizing UV-stabilized grades and the application will not require FRP to provide high structural strength. Also, while PP is tough, it is not appropriate for use under a high amount of pressure; only moderate amounts of pressure can be applied to PP.


Use FRP when: You have a project that has a very tight budget for constructing a small, simple project and you will require the ability to make repairs and modifications on-site and/or using simple tools multiple times. Constructing and repairing FRP requires special skills on both sides of the construction/repair process.

Decision Framework: A Step-by-Step Guide

To reach a final conclusion, complete these steps:

 

  1. Determining the Work Environment:
  • Chemical – Specify each of the chemicals being used, including concentrations and potential combinations/mixtures, and use a chart for determining chemical resistance.
  • Temperature – Find the maximum continuous and peak or surge temperature.
  • Pressure – Is the part under pressure, vacuum, or atmospheric?
  1. Establish Mechanical Requirements.
  • What are the physical dimensions? Larger structures are generally stronger if FRP is used.
  • Will the Structure support additional static loads (i.e. Agitators, Wind, Snow)?
  • Are there any impact/vibration issues?
  1. Establish Fabrication and Lifecycle Needs.
  • Is the item a custom building block or standard item? Custom built items are typically better suited to PP due to welding capabilities.
  • Do you have in-house capabilities for thermoplastic welding or would you need to engage out-sourced composite lamination?
  • What are the expected service life of each component and how will they be maintained? FRP has excellent serviceable longevity, PP potentially has excellent repairability.
  1. Analyze Total Cost of Ownership.

Don’t forget, in addition to material/replacement cost, you need to factor in labor for manufacturing/installation or other various production cost which will be incurred during that service life . For example: Even though an FRP Storage Tank has a higher initial capital outlay than a PVC Storage Tank, it may very well prove to be the more economical option over the life of the products.

 

Conclusion

 

There is no one-size-fits-all for plastic in industrial manufacturing. The best plastic will meet the requirements of your individual project.

PP is trusted for chemical resistance in moderately high temperatures (up to 100 degrees Celsius) because of its adaptability and durability, which help ensure that custom tanks or ductwork that hold aggressive chemicals can be both fabricated and repaired easily.

 

FRP is the high-performance composite material used for large-scale, high-temperature (up to 360 degrees Fahrenheit), high-strength applications where structural integrity, material size and thermal resistance are all critical factors.

 

PVC is an economical, low-temperature, and flame-retardant alternative for basic applications (with low-cost considerations), including water and/or industries with mild chemicals, at ambient temperatures.

You can confidently select the most appropriate material for your project by taking into consideration the possible exposure to each of these factors; the use of PP, FRP, or PVC will help ensure that your fabricated items are safe, efficient, and durable.