PVDF Kynar Properties: Mechanical, Thermal & Chemical

PVDF (polyvinylidene fluoride) / Kynar properties combine what most fluoropolymers sacrifice: rigidity and chemical inertness in the same material. With a tensile strength of 7,000 psi and a flexural modulus approaching 290,000 psi, PVDF is three to five times stiffer than unfilled PTFE while still resisting mineral acids, halogens, and oxidizing environments at temperatures up to 300°F (149°C). This page documents the full property profile — mechanical, thermal, chemical, electrical, and fire behavior — with comparison data against PTFE where relevant.

At a Glance

• Tensile strength 7,000 psi — substantially higher than PTFE (~2,000–3,000 psi)
• Flexural modulus 290,000 psi — rigid, suitable for unsupported structural panels
• Continuous use temperature 300°F (149°C); short-term excursions to ~330°F
• Resists HCl, H₂SO₄, HF, HNO₃, Cl₂, Br₂, and most oxidizing acids
• UL 94 V-0 flame rating inherently — no additives required
• Density 1.78 g/cc; low coefficient of friction ~0.20
• Piezoelectric behavior is intrinsic but typically irrelevant for structural parts

Mechanical Properties

Tensile and Compressive Strength

PVDF's tensile strength of 7,000 psi (48 MPa) is the property that most distinguishes it from PTFE. Unfilled PTFE typically measures 2,000–3,500 psi in tension, which limits unsupported panel thickness and wall thicknesses of tanks or vessels. PVDF allows thinner, lighter-weight fabrications with equivalent structural integrity. Compressive strength is approximately 8,000 psi (55 MPa), making PVDF well suited for loaded bearing surfaces and clamp blocks.

Stiffness vs PTFE: The Key Structural Difference

The practical implication: a PVDF tank wall or manifold block can carry loads that would cause a PTFE equivalent to cold-flow over time. For structural chemical-processing components, the choice between PVDF and PTFE is rarely close once load-bearing is required. PVDF is the working fluoropolymer for fabricated assemblies; PTFE is the choice for seals, liners, and applications where its superior chemical breadth justifies tolerating its poor mechanical properties. For unsupported chemical tanks, PVDF is the structurally sound choice; PTFE is typically restricted to liners, seals, and thin-section components where its superior chemical breadth justifies tolerating its mechanical weakness.

Creep and Fatigue Behavior

Under sustained load, PVDF exhibits far lower creep than PTFE. This is particularly important for bolted-flange assemblies, where PTFE gaskets and liners require regular torque re-checks due to cold flow. PVDF bolted components retain their clamping load more reliably over time. Fatigue resistance is adequate for most industrial cycling applications, though PVDF is not specified for high-cycle dynamic fatigue without application-specific testing.

Impact Strength Considerations

PVDF's notched Izod impact strength of 3.0–4.0 ft·lb/in is moderate — sufficient for most chemical-processing structural applications but not exceptional. At lower temperatures, impact resistance decreases as the material approaches its Tg (-37°C / -35°F). For applications subject to impact loading at low temperature, Kynar Flex copolymer grades offer better impact resistance due to their lower crystallinity and higher ductility. Standard PVDF homopolymer is adequate for normal industrial handling and thermal-cycling service.

Thermal Properties

Continuous and Intermittent Temperature Limits

PVDF is rated for continuous use at 300°F (149°C). This is lower than PTFE's continuous rating (~500°F / 260°C) but adequate for the vast majority of chemical-processing streams, which operate below 200°F in practice. Intermittent excursions to 320–330°F are tolerated for short durations; sustained operation above the continuous limit accelerates degradation and dimensional change.

Thermal Expansion Considerations

PVDF's CTE is significant — roughly 7–8 × 10⁻⁵ in/in/°F — and must be accounted for in designs that span large temperature ranges or are constrained between rigid supports. A 48-inch panel experiencing a 100°F temperature rise will expand approximately 0.34 inches. Expansion joints, slip-fit holes, and allowance in mounting hardware are engineering necessities in thermally cycled PVDF assemblies.

Cryogenic Behavior

Unlike many thermoplastics, PVDF retains acceptable ductility at -40°F (-40°C) without becoming brittle. This makes it usable in refrigerated chemical environments without switching to a cryogenic-rated material. For service below -40°F, impact strength should be verified with application-specific testing.

Chemical Resistance

Exceptional Resistance Categories

PVDF's chemical resistance is defined by strong performance against:

• Mineral acids: HCl (all concentrations), H₂SO₄ (to 50–70%), HNO₃ (dilute to moderate), HF (in semiconductor-grade applications)
• Halogens: Cl₂ (gas and aqueous), Br₂, F₂ (dilute), chlorinated water, bleach solutions
• Oxidizing agents: H₂O₂, ozone, hypochlorite solutions
• Chlorinated solvents: methylene chloride, trichloroethylene (limited temperatures)
• Hydrocarbons: aliphatic and aromatic at room temperature
• UV radiation: excellent inherent UV resistance without additives

Known Limitations

PVDF is not universally inert. Key exceptions:

• Strong bases: Concentrated NaOH (caustic soda), KOH — attack PVDF, causing swelling and cracking. Do not use PVDF in caustic service above 10% concentration at elevated temperature.
• Polar solvents at elevated temperature: Acetone, DMF (dimethylformamide), DMSO, and NMP can swell or dissolve PVDF at elevated temperatures.
• Esters and ketones: Limited resistance; verify temperature and concentration carefully.
• Fuming sulfuric acid (oleum): Aggressively attacks PVDF.
• Certain amines: High-molecular-weight amines and strong organic amines attack PVDF. Verify specific compound and concentration before specifying.

For process streams with mixed chemistries that include both acids and strong bases (e.g., alternating acid and caustic clean-in-place cycles), evaluate the caustic step carefully. PVDF may be appropriate if caustic contact is dilute and brief, but a material with better caustic resistance — such as HDPE or polypropylene — may be required for the caustic-contact sections of the system.

Selected Chemical Resistance Table

Flame and Smoke Properties

UL 94 V-0 Rating

PVDF is inherently flame retardant without halogenated or phosphorus-based additives — the fluorine in the polymer backbone itself provides this behavior. The material achieves a UL 94 V-0 rating, the highest flammability resistance classification for plastics, meaning burning material self-extinguishes within 10 seconds after removal of the ignition source, with no flaming drips.

Low Smoke in Fire Scenarios

PVDF produces significantly less smoke than PVC and many other plastics when exposed to fire. This matters in enclosed facilities — semiconductor fabs, chemical plants, and data centers — where smoke damage to equipment can be as costly as direct fire damage. Comparing PVDF to PVC for duct, lining, or enclosure applications: PVC releases HCl gas and generates dense smoke; PVDF self-extinguishes and produces minimal corrosive combustion products.

Electrical Properties

PVDF's electrical properties are uncommon for a structural plastic. The material is piezoelectric (generating a voltage under mechanical stress) and pyroelectric (generating charge with temperature change). These effects are deliberately exploited in PVDF sensor films and transducers but are generally inconsequential for stock-shape structural applications.

The dielectric constant of 8–9 is considerably higher than PTFE (~2.1), which means PVDF is not a preferred choice for high-frequency RF applications where low dielectric loss is critical. For structural and chemical-processing parts, electrical properties are secondary.

Summary: Why Choose PVDF Over PTFE

For most engineers choosing between PVDF and PTFE for chemical-resistant fabricated parts, the decision matrix is straightforward:

• Choose PVDF when: The design requires structural integrity (panels, tanks, valve bodies, manifolds), weldability for leak-tight joints, dimensional stability under load, or resistance to halogens and mineral acids in a rigid form.
• Choose PTFE when: Chemical compatibility needs include strong bases (concentrated NaOH), temperature requirements exceed 300°F, or the application is a seal, liner, or gasket where PTFE's softness is an asset rather than a liability.

For a full side-by-side comparison, see the PTFE vs PVDF comparison guide. For grade-specific property data, see the PVDF grades page.

Request PVDF Stock Shapes

FedMat stocks PVDF / Kynar sheet and rod in standard sizes. Contact us with your dimensions, grade, and quantity for a fast quote.

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Frequently asked questions — Pvdf Kynar FAQ