Loctite blue

Loctite™ 242 is a thixotropic (gel state at rest, liquid state when agitated), acrylic-based liquid that cures into a solid in the absence of air, or in contact with metal. It is commonly used in the automotive industry. Hobbyists and bicycle manufacturers frequently also use them. E.g. Santa Cruz Bicycles. It is very useful in preventing bolts and nuts from loosening under vibration. E.g. derailleur pulley bolts.

Loctite™ 242's qualities, however, may be compromised by the presence of oil, grease or other contaminants. Enter the Loctite™ 243, an oil-resistant version of Loctite™ 242. While cleaning fasteners of oil and grease contaminants is a good practice, a threadlocking compound with oil-resistant characteristics makes for good insurance. In addition, Loctite™ 243 also possesses a slightly higher cure strength:


Break / Prevail Torque (inch - pounds)
Loctite™ 242        115 / 53
Loctite™ 243        180 / 62


Tips: to prevent clogging, avoid having the applicator nozzle come in contact with metal (e.g. bolt, nut, etc.). Spills and excess may be removed with acetone.

There is a price for the added insurance (of course): while the 50 ml bottle of Loctite™ 242 cost SGD$22 (US$14.41), the 10 ml bottle of Loctite™ 243 cost SGD$14.55 (US$9.54). This means Loctite™ 243 costs 3.3 times more than Loctite™ 242.

Loctite™ 242 Technical Data Sheet (PDF).
Loctite™ 243 Technical Data Sheet (PDF).

A characteristic of Loctite™ 243 that is not mentioned in the Data Sheet is its higher viscosity. In its uncured state, Loctite™ 242 behaves like a liquid, while Loctite™ 243 is more of a gel.