Henkel LOCTITE EA M-31CL Medical Grade Epoxy Adhesive for Optical and Medical Assembly

LOCTITE EA M-31CL Medical Grade Epoxy Adhesive Performance

The resin and hardener are clear, colorless to slightly yellow liquids. After correct mixing, they form an ultra-clear bond line for applications where the joint must remain visually unobtrusive. Henkel specifies a 2:1 resin-to-hardener ratio by volume or 100:46 by weight. The mixed specific gravity is approximately 1.07 at 25°C.

Resin viscosity is approximately 9,000 to 12,000 mPa·s, while hardener viscosity is approximately 1,500 to 9,000 mPa·s at 25°C. This low-viscosity system wets detailed surfaces, spreads through narrow bond areas, and flows around small components more easily than a non-sag epoxy paste. Controlled dispensing, fixtures, dams, or masking may be required where migration into connectors, optical zones, or cavities must be prevented.

LOCTITE EA M-31CL Medical Grade Epoxy Adhesive Applications

Typical uses include bonding transparent windows, glass components, optical fibers, ceramic parts, metal housings, rigid plastic components, sensors, and small electronic assemblies. It can also be evaluated for localized potting, component staking, precision laminating, and electrical-insulation applications requiring a clear, rigid, impact-resistant epoxy.

Henkel states that the product is suitable for disposable medical-device assembly and has been tested under Henkel protocols based on ISO 10993 biocompatibility standards. This testing assists material selection but does not replace qualification of the completed device. Manufacturers must evaluate the final assembly according to its intended contact category, sterilization method, manufacturing process, regional regulations, and risk-management requirements.

7 Benefits of LOCTITE EA M-31CL Medical Grade Epoxy Adhesive

• Ultra-clear bond line: Supports optical, medical, sensor, and visible precision assemblies.
• Low-viscosity processing: Provides good wetting, narrow-gap flow, and small-potting capability.
• Room-temperature cure: Develops high strength without mandatory high-temperature equipment.
• Minimal shrinkage: Helps maintain dimensional accuracy around sensitive components.
• Excellent impact resistance: Produces a tough structural bond for demanding assemblies.
• Electrical insulation: Offers typical dielectric breakdown strength of approximately 19.7 kV/mm.
• Broad compatibility: Bonds glass, optical fibers, ceramics, metals, and many rigid plastics.

LOCTITE EA M-31CL Medical Grade Epoxy Adhesive Working and Cure Data

The mixed adhesive provides an approximate working life of 30 minutes. Application should be completed within this period because larger mixed quantities and higher temperatures can shorten working time. Henkel lists a low-humidity tack-free time of approximately 160 minutes and a gel time of about 90 to 150 seconds at 100°C.

For high strength, allow the assembly to cure for approximately 24 hours at 25°C. Heating up to 93°C can accelerate curing. Henkel recommends preventing part movement, maintaining contact pressure, and controlling the bond line between approximately 0.1 and 0.2 mm for maximum shear strength.

Strength, Insulation, and Environmental Resistance

Typical cured properties include tensile strength of approximately 55.2 MPa, elongation at break of about 8%, Shore D hardness of 80 to 90 after the stated cure schedule, and glass-transition temperature near 70°C. Published five-day lap-shear values include approximately 21.4 MPa on grit-blasted steel, 29.4 MPa on prepared aluminum, 13.6 MPa on stainless steel, and 13.4 MPa on polycarbonate.

Henkel laboratory data also shows resistance to motor oil, gasoline, water-glycol mixtures, humidity, water, acetone, and isopropanol after full cure. These values are reference results rather than finished-product guarantees. Users should qualify adhesion, optical clarity, sterilization, electrical insulation, chemical exposure, thermal cycling, and long-term reliability on representative assemblies.

Application, Storage, and Official Product Resources

Remove paint, oxide films, oil, dust, mold-release agents, moisture, and other contamination from both surfaces. With a dual cartridge, confirm both components flow evenly before attaching the static mixing nozzle. For manual mixing, blend thoroughly and continue for approximately 15 seconds after a uniform appearance is obtained. Apply evenly, assemble promptly, and fixture the parts until sufficient strength develops.

Store unopened containers in a dry location, ideally between 8°C and 21°C. Storage below 8°C or above 28°C may adversely affect product properties. Do not return dispensed material to the original container.

Review the official Henkel LOCTITE EA M-31CL product page and the official LOCTITE EA M-31CL technical data sheet for current specifications, processing instructions, safety documentation, and regional availability.

Explore our medical-grade epoxy adhesives and browse our clear structural adhesives for optical, electronic, medical-device, sensor, and precision assembly applications.