Polypropylene and PVDF

Materials ·

Polypropylene (PP) and polyvinylidene fluoride (PVDF) are thermoplastic pump materials offering exceptional chemical resistance to acids, alkalis, and solvents at a fraction of the cost of exotic metal alloys, used for wetted-end components in chemical dosing, electroplating, and semiconductor process pumps where metals would rapidly corrode.

History

Polypropylene was discovered by Giulio Natta at Politecnico di Milano, Italy in 1954 using Ziegler-Natta catalysis, earning Natta the Nobel Prize in Chemistry in 1963 alongside Karl Ziegler. The first commercial polypropylene pump casings appeared in Germany in the early 1960s, replacing glass-lined steel in acid circulation service. PVDF was developed by Pennwalt Corporation (later Arkema) in 1948 and introduced commercially as Kynar in 1960. PVDF pump components gained widespread adoption in the 1980s as semiconductor wet process cleaning required ultra-pure, metal-ion-free fluid contact materials.

Key Properties

  • PP density: 0.9 g/cm3 — lightest common pump casing material
  • PP tensile strength: 30 to 40 MPa; service temperature -20 to +90 degrees C continuous
  • PVDF density: 1.75 to 1.78 g/cm3; tensile strength: 50 to 55 MPa
  • PVDF service temperature: -40 to +140 degrees C — superior to PP for hot acid service
  • PVDF: very low extractables — ultra-pure semiconductor grade available from multiple suppliers
  • Both materials offer excellent UV and radiation resistance compared to most thermoplastics

Corrosion and Chemical Resistance

  • PP: resistant to most dilute and concentrated inorganic acids, alkalis, alcohols, and many solvents below 80 degrees C
  • PP: attacked by aromatic hydrocarbons, chlorinated solvents, and concentrated oxidizing acids
  • PVDF: resistant to most inorganic acids including HF, HCl, and H2SO4, halogens, and oxidizing agents up to 140 degrees C
  • PVDF: attacked by fuming sulfuric acid, ketones, and strong alkalis at elevated temperature
  • Neither material is suitable for concentrated nitric acid above 65 degrees C

Grades and Standards

  • PP homopolymer (PPH) and PP-natural food grade: ISO 15494 for industrial piping and pump systems
  • PVDF standard grade: ASTM D3222; semiconductor grade: Kynar 740 and Solef 6008
  • SEMI F57 standard covers PVDF and PP purity requirements for semiconductor process chemicals

Applications

  • Chemical dosing and metering pumps for acid-base water treatment
  • Electroplating bath circulation pumps in hydrochloric and sulfuric acid service
  • Swimming pool and spa chemical dosing pump casings
  • Semiconductor wet bench recirculation and chemical delivery pumps (PVDF grade)
  • Laboratory chemical transfer pumps for corrosive reagents
  • Hydrofluoric acid handling pumps (PVDF only — all metals corrode immediately)

Advantages

  • Extremely broad chemical resistance at low material cost (PP) or moderate cost (PVDF)
  • Lightweight construction — enables portable and floor-mounted pump designs
  • Non-contaminating — no metallic ion release into the process fluid
  • Easy field repair — thermoplastic components can be solvent-welded or heat-fused
  • Transparent and translucent options available for visual flow inspection in some grades

Limitations

  • Low mechanical strength limits maximum operating pressure (typically 6 to 10 bar)
  • Poor thermal stability above service temperature limits — creep and deformation risk
  • PP cannot be used with aromatic solvents; PVDF attacked by certain ketones at elevated temperature
  • UV degradation of unstabilized PP — specify UV-stabilized or carbon-black grades for outdoor use
  • Not suitable for high-speed, high-flow applications due to hydraulic efficiency limitations

Selection Criteria

  • Choose PP for dilute acid and base chemical dosing pumps operating below 80 degrees C and 6 bar
  • Choose PVDF for elevated temperature acid service, HF handling, or ultra-pure semiconductor applications
  • Specify semiconductor-grade PVDF (Kynar 740 or Solef equivalent) for sub-10 ppb extractables requirement
  • Verify chemical compatibility against manufacturer resistance tables for your specific solvent mixture and temperature
  • Pair with PTFE diaphragms and check valves for a fully corrosion-proof pump assembly

Top 10 Manufacturers

  • 1. IWAKI Co. Ltd. (Japan) — ~16% of PP/PVDF pump market; chemical resistance pumps in both PP and PVDF
  • 2. Grundfos A/S (Denmark) — ~12%; Alldos brand PP dosing pumps for water treatment systems
  • 3. Finish Thompson Inc. (USA) — ~8%; PP and PVDF centrifugal drum and sump pump casings
  • 4. Vanton Pump and Equipment (USA) — ~7%; solid PP centrifugal pump casings for acid service
  • 5. Argal Pumps (Italy) — ~6%; PVDF centrifugal and magnetic drive pumps for strong acids
  • 6. Lutz-JESCO GmbH (Germany) — ~6%; PP dosing pump heads for water and wastewater treatment
  • 7. Blue-White Industries (USA) — ~5%; PP peristaltic metering pumps for chemical dosing
  • 8. Sethco Division (USA) — ~5%; PP and PVDF sump pump product lines for chemical tanks
  • 9. Tapflo AB (Sweden) — ~4%; PP air-operated double-diaphragm pumps for chemical transfer
  • 10. Liquiflo Equipment (USA) — ~4%; PVDF gear pumps for aggressive solvents and acids