Choosing a Material for Plastic Chemical Tanks

Plastic chemical tanks are used for holding and storing harsh and corrosive chemicals in a variety of applications across many industries. Plastics are versatile, inexpensive to manufacture, and chemically adaptable—properties that have led to the replacement of expensive stainless steel tanks throughout manufacturing processes for biomedical, pharmaceutical, and semiconductor industries. Because some plastics can react with different chemicals, heat, or pressure, tanks must be designed using materials specifically tailored for the chemicals and processes they need to hold.

Industries for Plastic Chemical Tanks

Biomedical and Pharmaceutical

You will often find plastic chemical tanks used in the biomedical and pharmaceutical industries, where they are employed to store, drain, and mix chemical compounds. The tanks need to be composed of materials that will not interact with or leach into the compounds they are holding. Tanks for pharmaceutical and biomedical use are often constructed using rigorously tested USP Class VI Certified plastics to ensure biocompatibility and prevent toxic interactions with the chemicals in use.

Semiconductor

Plastic chemical tanks used in the semiconductor industry must be highly resistant to corrosion and safe for sterile use in clean rooms. They are useful in harsh environments for the manufacture of circuitry and electronic components for semiconductor equipment. The tanks must be constructed of durable and highly inert plastics to withstand the hot gas, aggressive chemicals, and high-pressure used in the industry, as well as avoid corrosion and a reaction with the materials being used.

Common Materials Used in Plastic Tanks

Depending on their intended use, plastic tanks must be carefully constructed to tolerate various volatile circumstances without risk of corrosion or leaching. As such, a number of different plastic materials are used in their construction.

  • Polypropylene is a versatile semi-crystalline material that is highly chemically resistant at low temperatures, but can be less stable at very high temperatures.
  • Polyvinylidene difluoride, or PVDF, is a strong fluropolymer that has high chemical resistance, but is less stable at high temperatures.
  • High Density Polyethylene, or HDPE, is an opaque semi-crystalline thermoplastic that is highly chemical resistant and impact resistant at low temperatures.
  • PVC, or polyvinyl chloride, comes in both rigid and flexible varieties. It is highly resistant to corrosion and has fair to good chemical resistance.

Properties of Each Material

Each plastic material has physical and chemical properties that help determine which is best for a given chemical or application. When choosing a material, consider the tensile strength, dielectric strength, and maximum operating temperature of each material to ensure that the ideal material is being used in each circumstance. Below is a short list of the important physical properties of each of the plastics commonly used in plastic tanks:

Polypropylene

  • Tensile Strength (MPa): 33
  • Dielectric Strength (MV/m): 28
  • Maximum Operating Temperature: (°C): 100

PVDF

  • Tensile Strength: 35
  • Dielectric Strength (MV/m): 13
  • Maximum Operating Temperature: (°C): 150

HDPE

  • Tensile Strength (MPa): 32
  • Dielectric Strength (MV/m): 22
  • Maximum Operating Temperature: 55

PVC

  • Tensile Strength (MPa): 20
  • Dielectric Strength (MV/m): 30
  • Maximum Operating Temperature: (°C): 50

Advantages and Disadvantages of Plastic Materials

Plastic Material Advantages Disadvantages
Polypropylene
  • Higher maximum operating temperature (100°C /210°F)
  • Better tensile strength than unmodified polypropylene copolymer
  • Higher heat deflection temperature (HDT) than unmodified polypropylene copolymer
  • Lower notched impact strength
  • Elongation at break
  • Higher brittle temperature (0°C/30°F) than unmodified polypropylene copolymer
PVDF
  • Highest tensile strength of all processable fluorocarbons
  • Good radiation resistance (better than other fluorocarbons)
  • Melt processable
  • Excellent abrasion resistance
  • Good general chemical resistance, although inferior to PTFE
  • Maximum use temperature 150°C (300°F)
  • Useful piezo-electric properties
  • High dissipation factor
  • Processing machinery must be clean and free of debris
  • Cannot blend with glass fibers, as boron will cause the material to decompose
  • Poor resistance to fuming acids
HDPE
  • Good low-temperature impact resistance
  • Excellent chemical resistance
  • Susceptible to stress cracking
  • Lower stiffness compared to Polypropylene
  • High mold shrinkage
  • Poor UV resistance
PVC
  • Higher tensile strength than PVC with higher levels of plasticization
  • Less flammable than PVC with higher levels of plasticization
  • Lower elongation at break than PVC with higher levels of plasticization
  • Lower low-temperature impact strength than PVC with higher levels of plasticization

Contact Plastic Design for Plastic Chemical Tanks

Plastic Design Inc. is proud to offer high-quality custom plastic tank designs using precise processes and procedures that are fully ISO 9001:2015 certified. We can manufacture products in high quantities that meet and exceed industry specifications, including Factory Mutual, Semi, NFPA, and OSHA. Our knowledgeable and experienced engineers are available to conduct on-site surveys and evaluations of your existing systems, so you can find the best solutions and modifications for your needs.

For more information on our custom plastic tank services and pricing, contact us or request a quote today!