Heathrow Scientific PTFE Octagonal Stir Bar with Pivot Ring - 120547 Series | Alnico Magnet, Pack of 10, Autoclavable

Cheap magnetic stir bars spin out under load, crack their PTFE coating over time, and lose magnetic strength after repeated use — forcing researchers to stop runs, fish out the bar, and start over. The Heathrow Scientific PTFE Octagonal Pivot Ring Magnetic Stir Bar series is built around Alnico magnet cores — one of the strongest permanent magnet materials available — sintered to reduce decoupling spin-outs, then encapsulated in chemical-resistant PTFE that protects both the magnet and the solution from contamination. The octagonal cross-section creates turbulent mixing with better coupling characteristics than smooth cylindrical bars, and the center pivot ring reduces friction against the vessel bottom for quieter, more stable operation at high speeds.

Available in six sizes from 10×5mm through 35×9mm, each sold in packs of 10, these bars cover the full range of laboratory vessel sizes — from small vials and test tubes to 3L beakers and flasks. Autoclavable at standard cycles. Compatible with all Heathrow Scientific stirrer platforms and standard magnetic stirrers from other manufacturers.

Features and Benefits

• Alnico Magnet Core — Maximum Coupling Strength: Alnico (Aluminum-Nickel-Cobalt) is among the strongest permanent magnet alloys available for stir bar applications — maintaining superior magnetic coupling at high stirring speeds and in larger vessels where weaker magnets lose traction and spin out.

• Sintered Manufacturing — Reduced Spin-Out Rate: The sintered magnet core production process creates a more uniform magnetic field distribution than cast magnet alternatives — significantly reducing the decoupling spin-outs that interrupt runs and waste time in high-speed mixing applications.

• PTFE Encapsulation — Chemical Resistance to 250°C: Full PTFE coating protects the magnet from chemical attack and prevents contamination of the stirred solution. PTFE withstands temperatures up to 250°C — compatible with both ambient and heated stirring applications.

• Octagonal Cross-Section for Enhanced Turbulence: The eight flat faces create more aggressive fluid turbulence per revolution compared to smooth cylindrical bars — producing faster mixing and better suspension of particulates in solution without requiring higher speeds.

• Center Pivot Ring — Low-Friction Stable Rotation: The raised center ring elevates the bar slightly off the vessel floor, reducing friction and wobble during rotation — resulting in quieter operation, more stable high-speed spinning, and less vessel bottom abrasion over time.

• Autoclavable — Steam Sterilization Compatible: Withstands standard autoclave cycles (121°C, 15 psi, 20 min) for sterile applications in cell culture, microbiology, and pharmaceutical research requiring sterile mixing conditions.

Specifications

Laboratory Applications

• High-Speed Buffer & Reagent Preparation: Use in beakers and flasks up to 3L where maximum coupling strength is needed to maintain speed through viscosity changes as solutes dissolve and solution density changes.

• Heated Stirring Applications: Temperature tolerance up to 250°C makes these bars compatible with hot plate stirrers for applications requiring simultaneous heating and mixing — including titrations, dissolution testing, and reflux reactions.

• Sterile Cell Culture & Microbiology: Autoclave before use to maintain sterile conditions in cell culture media preparation, microbial growth media formulation, and other applications requiring contamination-free mixing.

• Particulate Suspension Mixing: The octagonal cross-section's turbulent mixing pattern is particularly effective for keeping particulates, precipitates, and dense solids in suspension during mixing — reducing settling time and improving mixing uniformity.

Frequently Asked Questions

What size stir bar should I use for my vessel?
As a general guide: 10mm bars for vials and tubes under 50mL; 20–25mm bars for 100–500mL beakers and flasks; 28–30mm bars for 500mL–1L vessels; 35mm bars for 1–3L vessels. The bar should be roughly 1/3 to 1/2 the diameter of the vessel's flat bottom for optimal coupling.

What is the difference between the Octagonal Pivot Ring bars and the Smooth bars?
The Octagonal Pivot Ring bars (120547–120552) use the octagonal cross-section for higher turbulence and the pivot ring for low-friction rotation — ideal for flat-bottom beakers and standard vessels. The Smooth bars (120894–120897) have a cylindrical profile optimized for concave-bottom glassware where the rounded bar shape maintains better contact with the curved vessel floor.

Can these stir bars be used with heated stirrers?
Yes. PTFE encapsulation is stable up to 250°C, making these bars fully compatible with hot plate magnetic stirrers. The Alnico magnet core retains its magnetic properties across the temperature ranges encountered in standard heated stirring protocols.

Are these stir bars compatible with induction stirrers?
Yes. Alnico-core PTFE stir bars are compatible with the Heathrow Scientific Magnetic Induction Stirrer (120584/120585) and all standard magnetic stirrer platforms from other manufacturers.

Quality Assurance

Heathrow Scientific PTFE stir bars are manufactured with sintered Alnico cores and full PTFE encapsulation under rigorous quality standards. Each production lot is inspected for coating integrity and dimensional consistency to ensure reliable coupling performance and contamination-free use.

Academic and Institutional Pricing

LabSupplies.com offers tiered quantity pricing for academic and research institutions. As an authorized dealer, we ship directly from USA inventory.