Thread Locking Adhesive Fasteners for Bolt Loosening Prevention

Engineering Solutions for Pre-Applied Thread Locking Screws, Vibration Resistance and Reliable Threaded Connections

Thread loosening is one of the most common failure modes in mechanical fastening systems, especially in applications exposed to:

• Vibration

• Shock loading

• Thermal cycling

• Dynamic forces

• Continuous operation

To improve connection reliability, many industries use thread locking adhesive fasteners, also known as:

• Pre-applied thread locker bolts

• Microencapsulated adhesive locking fasteners

• Chemical locking screws

• Anti-loosening fasteners

These specialized fasteners use an adhesive coating applied directly onto the thread surface before assembly. During installation, the microcapsules break and the adhesive chemically reacts and cures, creating additional resistance against loosening.

Juxin Fasteners provides customized pre-applied adhesive locking fastener solutions for global OEM customers in:

• Automotive

• Electric Vehicle (EV)

• Battery Pack

• Rail Transit

• Aerospace

• Electrical Cabinets

• HVAC

• Medical Equipment

• Construction

• Machinery

• Robotics

• Sheet Metal Fabrication

What Are Thread Locking Adhesive Fasteners?

Thread locking adhesive fasteners are bolts, screws, and studs with a pre-applied chemical locking coating on the threaded area.

Unlike traditional mechanical locking methods, adhesive locking works by:

1. Filling the gaps between threads

2. Increasing thread friction

3. Creating chemical bonding after curing

4. Improving resistance against vibration loosening

Common applications include:

• Automotive assembly bolts

• EV battery fastening systems

• Electronic equipment

• Industrial machinery

• Precision mechanical components

How Microencapsulated Thread Locking Adhesive Works

The adhesive coating contains microscopic capsules filled with locking compounds.

During tightening:

1. Thread contact pressure breaks the microcapsules

2. The adhesive components mix together

3. Chemical curing begins

4. The thread connection gains additional locking force

This process improves:

• Loosening torque

• Vibration resistance

• Assembly reliability

• Long-term fastening performance

Performance Requirements of Thread Locking Adhesive Fasteners

The effectiveness of pre-applied thread locking fasteners depends on several design parameters.

Important factors include:

• Adhesive coating length (Lb)

• Distance from thread end

• Bolt diameter

• Thread pitch

• Surface condition

• Friction coefficient

Adhesive Coating Length Design

The adhesive coating length must provide sufficient thread engagement.

Key parameters:

Lb

Length of adhesive coating area

A

Distance from adhesive area to thread end

Normally:

A = 2–3 thread pitches

d

Bolt outside diameter

p

Thread pitch

For example:

A typical:

M12 × 80 Grade 8.8 bolt

with:

• Friction coefficient: μ = 0.10–0.16

may require:

• Adhesive length: approximately 30 mm

• Thread distance: approximately 10 mm

Proper adhesive placement ensures stable locking performance.

How Thread Locking Adhesive Improves Loosening Resistance

The performance of adhesive locking can be evaluated by comparing:

• Tightening torque (MA)

• Loosening torque (MLB)

The ratio:

MLB / MA

is used to evaluate locking efficiency.

A higher ratio indicates stronger resistance against loosening.

Loosening Torque Performance Testing

For example:

An M10 bolt tightened under:

• Friction coefficient μ = 0.15

may achieve:

MLB / MA ≈ 0.77

with thread locking adhesive.

According to:

DIN 267-27 Thread Locking Requirements

the loosening torque ratio should achieve a specified performance level.

For M10 bolts:

Pre-applied adhesive locking can significantly improve loosening torque performance compared with untreated fasteners.

Factors Affecting Thread Locking Adhesive Performance

Although thread locking adhesive improves fastener reliability, several conditions can reduce its effectiveness.

1. High Temperature Effects

High-temperature environments can reduce adhesive performance.

Common applications affected include:

• Automotive engine systems

• Industrial machinery

• HVAC equipment

• Power equipment

At elevated temperatures:

• Adhesive strength may decrease

• Curing performance may change

• Loosening resistance may reduce

High Temperature Testing Method

A typical evaluation process includes:

1. Determine tightening torque according to bolt size and grade

2. Allow bolt assembly to stabilize

3. Place untreated and adhesive-treated fasteners in a 150°C environment

4. Maintain temperature exposure

5. Compare loosening torque performance

The adhesive solution is considered effective when:

MLB/MA remains higher than untreated fastener performance.

2. Surface Lubrication Effects

Surface contamination is one of the most important factors affecting adhesive bonding.

Lubricants may:

• Reduce adhesive contact

• Prevent chemical bonding

• Lower locking torque performance

Common contaminants include:

• Oil

• Grease

• Processing lubricants

• Anti-rust coatings

How to Solve Lubrication Compatibility Issues

Recommended manufacturing sequence:

1. Apply thread locking adhesive first

2. Complete curing process

3. Apply required surface treatment or lubrication afterward

This helps maintain:

• Adhesive bonding strength

• Required friction coefficient

• Corrosion protection

3. Insufficient Adhesive Length

Short adhesive coating length reduces:

• Number of bonded threads

• Contact area

• Loosening resistance

The adhesive length should normally cover sufficient thread engagement.

A commonly used engineering guideline:

Adhesive length ≥ 0.8d

where:

d = bolt diameter

Solutions for Short Adhesive Length Problems

Engineering solutions include:

• Increase adhesive coating length

• Optimize thread engagement

• Adjust bolt design

• Use suitable locking coating specifications

The final performance should always be verified through:

• Torque testing

• Loosening testing

• Environmental testing

Advantages of Pre-Applied Thread Locking Fasteners

Compared with manual liquid thread lockers, pre-applied adhesive fasteners provide:

Consistent Application

Factory-controlled coating ensures:

• Uniform adhesive thickness

• Stable locking performance

Improved Assembly Efficiency

Benefits include:

• No additional adhesive dispensing

• Reduced assembly steps

• Cleaner production process

Better Quality Control

OEM manufacturers can achieve:

• Repeatable torque performance

• Reduced assembly variation

• Improved production reliability

Thread Locking Fastener Solutions by Industry

Automotive Fasteners

Applications:

• Engine components

• Chassis systems

• Suspension systems

• Body structures

Requirements:

• Vibration resistance

• Stable preload

• Long service life

EV Battery Pack Fastening Solutions

EV battery systems require:

• High reliability

• Thermal resistance

• Vibration protection

Applications:

• Battery enclosure bolts

• Cooling system fasteners

• Electrical connections

Rail Transit Fastening Solutions

Rail applications require:

• Long-term vibration resistance

• High fatigue performance

• Safety-critical reliability

Aerospace Fastener Solutions

Aerospace requires:

• Lightweight fastening

• Precision control

• High reliability connections

Electrical Cabinet and Sheet Metal Applications

Thread locking fasteners improve reliability for:

• Control cabinets

• Electrical equipment

• Industrial enclosures

Common products:

• Pre-applied screws

• Thread locking bolts

• Rivet nuts

• Self-clinching fasteners

Machinery and Robotics Applications

Industrial automation requires fasteners that maintain performance under:

• Continuous vibration

• Repeated operation

• Dynamic loads

Why Choose Juxin Fasteners?

Juxin Fasteners provides professional OEM fastening solutions including:

✔ Pre-applied thread locking screws
✔ Microencapsulated adhesive locking bolts
✔ Anti-loosening fasteners
✔ Automotive fasteners
✔ EV battery fastening solutions
✔ Customized bolts and screws
✔ Surface treatment solutions
✔ Engineering testing support

Our solutions help customers improve:

• Connection reliability

• Production efficiency

• Product lifetime

• Maintenance cost control

Contact Juxin Fasteners

For customized thread locking adhesive fasteners and OEM fastening solutions:

Email: info@juxinfasteners.com

Website:

https://www.juxinfasteners.com/