“Thread-locking fluid”的意思、由来-开放百科全书

词条

Thread-locking fluid

释义

History
Properties
Application and care
References
External links

Thread-locking fluid or threadlocker is a thin, single-component adhesive, applied to the threads of fasteners such as screws and bolts to prevent loosening, leakage, and corrosion.

Most thread-locking formulas are methacrylate-based and rely on the electrochemical activity of a metal substrate to cause polymerization of the fluid. Thread-locking fluid is thixotropic, which allows it to flow well over time, yet still resist shocks and vibrations. It can be permanent or removable; in the latter case, it can be removed with heat, for example. Typically, brands are color-coded to indicate strength and whether they can be removed.

History

Thread-locking fluid was developed by American professor Vernon K. Krieble in 1953. His company, American Sealants, founded the Loctite brand.^[1] An early version of the compound was patented in 1960.^[2]

Properties

Typically, thread-locking fluids are methacrylate-based, and cure anaerobically. Thread-locking fluid is a thixotropic fluid: under shear stress, it exhibits a time-dependent decrease in viscosity. This allows it to flow well over time, yet still resist short-duration shearing, as in vibration or shock.

Thread-locking fluid is typically sold in small containers, in amounts from 5 millilitres (about one teaspoon) to {{convert|250|mL|USoz}}. Threadlocker is also sold in sticks and in tape form, similar to Teflon tape.

Typical properties of thread-locking fluids ^[3]
Type	Typical color code	Torque to break free{{br(3/8-16 size bolt)	Torque to continue turning	Temperature range
Low strength	purple}} Purple	62 in-lb (7 N⋅m)	27 in-lb (3 N⋅m)	−54 to 149 °C
Medium strength	blue}} Blue	115 in-lb (12 N⋅m)	53 in-lb (6 N⋅m)	−54 to 149 °C
Medium strength surface insensitive	blue}} Blue	180 in-lb (20 N⋅m)	62 in-lb (7 N⋅m)	−54 to 149 °C
High strength	red}} Red	230 in-lb (25 N⋅m)	225 in-lb (25 N⋅m)	−54 to 149 °C
High temperature	red}} Red	180 in-lb (20 N⋅m)	270 in-lb (30 N⋅m)	−54 to 232 °C
Penetrating	green}} Green	90 in-lb (10 N⋅m)	310 in-lb (35 N⋅m)	−54 to 149 °C

Application and care

Thread-locking fluid may be applied before or after assembly, depending on the type. Threadlockers are available in varieties of "permanent", "removable", and "low-strength" formulas. Many brands color-code the container and the fluid itself to indicate the degree of permanency. The low-strength types prevent loosening under vibration, but may still be readily disassembled. Removable types resist higher amounts of vibration, but may still be disassembled with hand or power tools. The strongest permanent threadlockers are rated at {{convert|3000|psi|MPa|abbr=on}} in shear strength. The applied torque required to loosen a permanently threadlocked fastener may exceed the yield strength of the fastener itself, such that attempting disassembly by force may twist off the stem of the fastener. However, high-strength permanent threadlockers become potentially removable by heating the assembly, typically to 230{{nbsp}}°C (450{{nbsp}}°F).

Working temperatures for threadlocked fasteners are typically limited to 150{{nbsp}}°C (300{{nbsp}}°F), which is below the softening point of the methacrylate polymer.

Above this temperature, the material softens and strength reduces.

Because thread locking adhesives typically rely on the electrochemical activity of a metal substrate to form a bond, surfaces must be clean to develop the full bonding strength. In the case of less electrochemically active metals such as the normally oxided surface of aluminium, an additional step of priming is required for full strength results.^[4]

Lock washers, locknuts, jam nuts, and safety wire may be used in conjunction with thread-locking fluid to prevent loosening of bolted joints.

Because electrochemical activity is one of the two triggers that cause polymerization of the threadlocker fluid, care must be taken to avoid contaminating the entire container of threadlocker with threadlocker that has had contact with metal, otherwise the material in the container may polymerize.^[5]

References

1. ^The Loctite Story by Kenneth W. Butterworth. New York: Newcomen Society of the United States, 1988.
2. ^{{cite patent| country = US| number = 3043820| title = Anaerobic curing sealant composition having extended shelf stability}}
3. ^{{ cite web | title = Devcon Permatex Product Selector | url = http://www.devcon.com | accessdate = 2009-11-13 }}
4. ^{{ cite web | title = Hernon Introduces a New Surface Insensitive Thread Locking Adhesive | work = ThomasNet Industrial Newsroom | date = June 26, 2002 | url = http://news.thomasnet.com/fullstory/12347 | accessdate = 2009-07-06 }}
5. ^{{ cite web | title = Permatex Medium Strength BLUE Threadlocker Gel Technical Data Sheet | url = http://www.permatex.com/documents/tds/Automotive/24010.pdf | accessdate = 2009-11-16 | deadurl = yes | archiveurl = https://web.archive.org/web/20110102195950/http://permatex.com/documents/tds/Automotive/24010.pdf | archivedate = 2011-01-02 | df = }}

External links

{{ cite web | last = Allen | first = Mike | title = How to Secure Bolts Using Threadlocker: Auto Clinic | work = Popular Mechanics | date = September 2009 | url = http://www.popularmechanics.com/cars/how-to/a1172/4208687/ }}
Current Loctite Threadlockers
Threadlocker

4 : Adhesives|Acrylate polymers|Non-Newtonian fluids|Screws

随便看

开放百科全书收录14589846条英语、德语、日语等多语种百科知识，基本涵盖了大多数领域的百科知识，是一部内容自由、开放的电子版国际百科全书。