What Are Born2Bond Retaining Anaerobic Adhesives and How Do They Work?
Born2Bond Retaining anaerobic adhesives from Bostik are single-component solutions designed to bond all types of cylindrical assemblies while sealing metal joints to eliminate fretting corrosion. They cure in the absence of air and achieve 100% surface-to-surface contact, producing a cohesive, durable connection capable of withstanding vibration, extreme temperatures, and chemical substances.
Unlike purely mechanical retaining methods, these adhesives offer a cost-effective alternative or supplement to pressed fits, keys, and shrink fits — reinforcing or even replacing machined elements in applications where fretting corrosion or loosening under dynamic load is a failure mode.
What Applications Are Best Suited for Born2Bond Retaining Adhesives?
The Born2Bond retaining line is formulated for high-power-transmission assemblies where dynamic loads and vibration are constant threats. Documented typical applications include:
- Gear manufacturing
- Machine engineering and bearing assembly
- Drive shafts and conveyor belts
- Centrifuges and turbines
The adhesives are suitable for both active and passive metals, expanding compatibility across steel, aluminum, brass, and zinc substrates commonly found in rotating equipment.
How Do the Four Born2Bond Retaining Grades Compare?
Bostik offers four grades — RA-38, RA-41, RA-48, and RA-60 — differentiated by viscosity, gap-fill capability, strength, and temperature tolerance. Selecting the correct grade depends on joint clearance, required shear strength, and operating temperature.
- RA-38: High strength, 2,000–3,000 mPa.s viscosity, 0.008 in (0.2 mm) gap fill, 3,626 psi compressive shear on steel (ISO 10123), −67 to 356°F (−55 to 180°C), green.
- RA-41: Medium strength, 400–800 mPa.s viscosity, 0.004 in (0.1 mm) gap fill, 870 psi compressive shear on steel (ISO 10123), −67 to 302°F (−55 to 150°C), yellow.
- RA-48: High strength, 400–600 mPa.s viscosity, 0.006 in (0.15 mm) gap fill, 3,771 psi compressive shear on steel (ISO 10123), −67 to 356°F (−55 to 180°C), green.
- RA-60: High strength, paste viscosity, 0.020 in (0.5 mm) gap fill, 2,611 psi compressive shear on steel (ISO 10123), −67 to 302°F (−55 to 150°C), grey.
RA-48 delivers the highest measured shear strength at 3,771 psi, making it the strongest grade in the line for tight-clearance steel joints. RA-60’s paste format and 0.020 in gap-fill capability address larger or worn clearances where liquid grades would drain before cure.
Why Does Gap Fill Matter When Selecting a Retaining Adhesive?
Gap fill directly governs whether an anaerobic adhesive will bridge the annular clearance between a shaft and bore. If the clearance exceeds the adhesive’s rated gap fill, incomplete cure and reduced joint strength result. RA-60’s 0.020 in (0.5 mm) gap fill is 2.5× greater than RA-38’s 0.008 in and 5× greater than RA-41’s 0.004 in, making it the preferred choice for loose-tolerance or field-repair applications.
For precision bearing assemblies with tight tolerances, RA-41 or RA-48’s lower viscosity (400–800 mPa.s) allows easier application into confined spaces without overflow or mess.
How Does Temperature Range Affect Grade Selection?
Two of the four grades — RA-38 and RA-48 — are rated to 356°F (180°C), while RA-41 and RA-60 top out at 302°F (150°C). For turbine or centrifuge applications where operating temperatures approach or exceed 300°F, specifying RA-38 or RA-48 avoids premature adhesive degradation and loss of joint integrity. All four grades share a lower service limit of −67°F (−55°C), covering most industrial cold-climate installations.
How Do Born2Bond Retaining Adhesives Prevent Fretting Corrosion?
Fretting corrosion occurs when micro-motion between press-fitted or keyed metal surfaces generates iron oxide debris, accelerating wear and fatigue cracking. Born2Bond retaining adhesives fill 100% of the metal-to-metal interface, eliminating the micro-motion that initiates fretting. The sealed joint also blocks oxygen and moisture ingress, preventing the oxidation pathway entirely — an outcome that mechanical fits alone cannot guarantee.
Summary
- Born2Bond Retaining adhesives are single-component anaerobic adhesives achieving 100% surface contact to eliminate fretting corrosion in cylindrical assemblies.
- Four grades (RA-38, RA-41, RA-48, RA-60) span viscosities from 400 mPa.s liquid to paste and gap fills from 0.004 in to 0.020 in.
- Maximum compressive shear strength is 3,771 psi (ISO 10123) for RA-48 on steel; minimum is 870 psi for medium-strength RA-41.
- RA-38 and RA-48 tolerate up to 356°F (180°C); RA-41 and RA-60 are rated to 302°F (150°C).
- Typical applications include gear manufacturing, bearing assembly, drive shafts, conveyor belts, centrifuges, and turbines.
Products discussed in this episode
- Bostik Born2Bond RA-38 Retaining Adhesive – 50 ml Bottle
- Bostik Born2Bond RA-41 Retaining Adhesive – 50 ml Bottle
- BOSTIK Bostik Born2Bond RA-48 Retaining Adhesive – 50 ml Bottle
- Bostik Born2Bond RA-60 Retaining Adhesive – 50 ml Bottle
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