LOCTITE EA M-31

Main features

Ultra-Clear Bonding Material
30-Minute Working Window
19.7 kV/mm Dielectric Strength

Product Description

LOCTITE EA M-31CL is a two-part, room-temperature-curing epoxy adhesive formulated to produce an ultra-clear bondline for bonding, small potting, staking, and laminating. The resin and hardener mix at 2:1 by volume or 100:46 by weight and provide a 30-minute working life. The cured material combines minimal shrinkage with impact-resistant structural performance, electrical insulation, and resistance to a range of chemicals and solvents. It bonds glass, optical fibers, ceramics, metals, and many rigid plastics, supporting clarity-sensitive and multi-material assemblies.

Key features

Ultra-clear mixed appearance: Clear colorless to slightly yellow components produce an ultra-clear mixed adhesive for clarity-sensitive bondlines.
Controlled two-part mixing: Mix 2:1 by volume or 100:46 by weight, resin to hardener.
30-minute working life: Supports application and assembly before room-temperature cure; larger quantities or higher temperatures shorten the working time.

Applications / Suitable for

Clear bonding and laminating of glass and optical fibers
Bonding ceramics, metals, and many rigid plastics
Small potting and staking where an ultra-clear insulating epoxy is required

TDS, SDS & Technical Documents

Technical Specifications

No specifications available.

Additional Information

Two-part structural epoxy adhesive

LOCTITE EA M-31CL

LOCTITE EA M-31CL is a two-part, low-viscosity epoxy adhesive that cures at room temperature to an ultra-clear bondline. It is designed for bonding, small potting, staking, and laminating applications involving glass, optical fibers, ceramics, metals, and many rigid plastics. Published data provide processing guidance plus mechanical, dielectric, substrate-specific bond strength, and environmental exposure results.

Two-part epoxy Ultra-clear mixed appearance 2:1 mix ratio by volume 30-minute working life Room-temperature cure Glass, metal, ceramic and rigid-plastic bonding

LOCTITE EA M-31CL two-part epoxy adhesive.

Material state

As-supplied and mixed properties

Typical reference data. Component state, test temperature, viscosity method, and ratio basis are preserved; the values are not guaranteed product specifications.

Property	Value	Unit	Method / condition
Resin appearance	Clear colorless to slightly yellow liquid	Not applicable	As supplied
Hardener appearance	Clear colorless to slightly yellow liquid	Not applicable	As supplied
Mixed appearance	Ultra clear	Not applicable	After mixing
Components	Two part	Resin and hardener	Room-temperature-curing epoxy system
Mix ratio by volume	2:1	Resin:hardener	Two-part system
Mix ratio by weight	100:46	Resin:hardener	Two-part system
Resin specific gravity	1.1	Not applicable	At 25 degrees C
Hardener specific gravity	1.0	Not applicable	At 25 degrees C
Mixed specific gravity	1.07	Not applicable	At 25 degrees C
Resin viscosity	9,000 to 12,000	mPa-s (cP)	Brookfield RVT, 25 degrees C, spindle 6, 20 rpm
Hardener viscosity	1,500 to 9,000	mPa-s (cP)	Brookfield RVT, 25 degrees C, spindle 5, 20 rpm
Working life	30	minutes	Typical; larger quantities or higher temperatures reduce the working time
Tack-free time	160	minutes	Low humidity
Gel time	90 to 150	seconds	At 100 degrees C

Bonding process

Mixing, application, and cure

Prepare clean bonding surfaces, meter the resin and hardener at the stated ratio, mix thoroughly, apply within the working window, and hold the assembly under contact pressure while the adhesive cures. Dual cartridges may be used with a mixing nozzle, or the components may be hand mixed.

Mix ratio: 2:1 by volume or 100:46 by weight, resin to hardener.

Application window: Apply to the substrates within 30 minutes. Larger mixed quantities and higher temperatures shorten this working time.

Cure guidance: Allow 24 hours at 25 degrees C for high strength. Heating up to 93 degrees C accelerates cure.

Recommended bonding sequence

Stage 1

Prepare the surfaces

Remove paint, oxide films, oils, dust, mold-release agents, and other surface contaminants before bonding.

Stage 2

Dispense and mix

For dual cartridges, verify that both components flow evenly before attaching the mixing nozzle. For hand mixing, mix thoroughly for about 15 seconds after a uniform color is obtained.

Stage 3

Assemble and cure

Apply adhesive evenly to both surfaces, assemble within 30 minutes, and prevent movement during cure. Contact pressure is required; maximum shear strength is reported at a 0.1 to 0.2 mm bondline.

Storage and Handling

Store unopened containers in a dry location at an optimal temperature of 8 to 21 degrees C. Storage below 8 degrees C or above 28 degrees C may adversely affect product properties. Keep containers closed, protect them from heat, ignition sources, direct sunlight, and moisture, and do not return removed material to the original container. Use adequate ventilation and appropriate protective gloves and eye or face protection, and review the current safety data for both components before use. Do not use the product in pure oxygen or oxygen-rich systems or select it as a sealant for chlorine or other strong oxidizing materials.

Final material state

Cured material properties

Tensile strength

55.2 N/mm2

Typical value by ISO 527-2; the TDS also reports 8,000 psi.

Glass transition temperature

70 degrees C

Typical cured-material value measured by ASTM E 228.

Dielectric breakdown strength

19.7 kV/mm

Typical bulk-material result by IEC 60243-1; it is not a working-voltage rating.

Typical technical data

Detailed cured-property data

Cured-material results are typical reference values. Test method, cure condition, and state are retained where supplied.

Property	Value	Unit	Method / condition
Glass transition temperature	70	degrees C	ASTM E 228; cured at 25 degrees C except where noted
Elongation at break	8	%	ISO 527-2; cured at 25 degrees C except where noted
Tensile strength	55.2 (8,000)	N/mm2 (psi)	ISO 527-2; cured at 25 degrees C except where noted
Shore hardness	80 to 90	Durometer D	ISO 868; cured 16 to 18 hours at 22 degrees C, then 2 hours at 65 degrees C
Dielectric breakdown strength	19.7	kV/mm	IEC 60243-1; cured material

Adhesive performance

Bond strength by substrate

Typical laboratory results for the stated substrates, surface preparation, bondline, cure, and test method. Values are not universal joint-strength guarantees.

Property	Value	Unit	Method / condition
Lap shear - aluminum, etched and abraded, 0.13 mm gap	At least 6.9 (at least 1,000)	N/mm2 (psi)	ISO 4587; cured 2 hours at 65 degrees C
Lap shear - steel, grit blasted	21.4 (3,100)	N/mm2 (psi)	ISO 4587; cured 5 days at 22 degrees C
Lap shear - aluminum, etched and abraded, 0.1 to 0.2 mm gap	29.4 (4,270)	N/mm2 (psi)	ISO 4587; cured 5 days at 22 degrees C
Lap shear - aluminum, anodized	21.2 (3,070)	N/mm2 (psi)	ISO 4587; cured 5 days at 22 degrees C
Lap shear - stainless steel	13.6 (1,970)	N/mm2 (psi)	ISO 4587; cured 5 days at 22 degrees C
Lap shear - polycarbonate	13.4 (1,950)	N/mm2 (psi)	ISO 4587; cured 5 days at 22 degrees C
Lap shear - nylon	2.4 (350)	N/mm2 (psi)	ISO 4587; cured 5 days at 22 degrees C
Lap shear - fir wood	12.1 (1,750)	N/mm2 (psi)	ISO 4587; cured 5 days at 22 degrees C
Block shear - PVC	7.0 (1,010)	N/mm2 (psi)	ISO 13445; cured 5 days at 22 degrees C
Block shear - ABS	8.4 (1,220)	N/mm2 (psi)	ISO 13445; cured 5 days at 22 degrees C
Block shear - epoxy glass	20.6 (2,980)	N/mm2 (psi)	ISO 13445; cured 5 days at 22 degrees C
Block shear - acrylic	1.2 (180)	N/mm2 (psi)	ISO 13445; cured 5 days at 22 degrees C
Block shear - glass	24.4 (3,540)	N/mm2 (psi)	ISO 13445; cured 5 days at 22 degrees C

Exposure evidence

Chemical and environmental resistance

Percent of initial lap shear strength after exposure. Steel specimens were cured for 5 days at 22 degrees C, aged under the stated conditions, and tested at 22 degrees C.

Environment	Exposure temperature	Strength after 500 hours	Strength after 1,000 hours
Air	87 degrees C	155%	150%
Motor oil, 10W30	87 degrees C	160%	145%
Unleaded gasoline	87 degrees C	120%	110%
Water/glycol, 50/50	87 degrees C	145%	140%
Salt fog	22 degrees C	70%	85%
95% relative humidity	38 degrees C	105%	115%
Condensing humidity	49 degrees C	90%	90%
Water	22 degrees C	100%	90%
Acetone	22 degrees C	100%	105%
Isopropanol	22 degrees C	120%	120%

These results apply to the tested steel lap-shear configuration and exposure conditions. They do not establish universal chemical compatibility or bonded-assembly durability.

Application fit

Applications and use contexts

The product is documented for bonding, small potting, staking, and laminating where clarity and the cured epoxy's structural, mechanical, or electrical insulating properties are relevant. Application suitability should be confirmed with the actual substrates, surface preparation, bondline, cure, and service environment.

Clear glass and optical-fiber bonding assembly

Clear and optical assemblies

Use for bonding or laminating glass and optical fibers when an ultra-clear epoxy bondline is a primary selection requirement.

Metal, ceramic, glass and rigid-plastic bonded assembly

Multi-material bonding

Consider for joining glass, ceramics, metals, and many rigid plastics. Published strength values remain specific to the tested material, preparation, cure, and joint configuration.

Small-component potting and staking with clear epoxy

Small potting, staking, and laminating

Use in small-volume potting, component staking, and laminating applications where a clear cured epoxy with mechanical and electrical insulating properties is required.

Next steps

Evaluate LOCTITE EA M-31CL for your bonding process

Talk with Krayden about substrate preparation, mix and dispense options, bondline control, cure scheduling, and validation for your assembly. The technical team can help compare the published property data with your substrates, joint design, processing window, and operating environment.

Contact Krayden