Humiseal 1B51LU | Fast-Drying Synthetic Rubber Conformal Coating

Harmonization Code : 3208.20.90 | Paints and varnishes that are dispersed or dissolved in a non aqueous medium

Humiseal 1B51LU | Fast-Drying Synthetic Rubber Conformal Coating

Main features

Fast-drying formula
Low moisture vapor permeability
RoHS Directive 2002/95/EC Compliant

Product Description

HumiSeal® 1B51LU is a fast-drying, single-component, synthetic rubber conformal coating designed to protect printed circuit assemblies from moisture and environmental damage. Its unique base polymer provides an extremely low moisture vapor permeability. 1B51LU is also highly flexible, reduces stress on components, and is easily repaired. For quality control, the coating fluoresces under UV light, making inspection simple. HumiSeal® 1B51LU is in full compliance with the RoHS Directive 2002/95/EC

Product Key Features

Fast-drying formula
Superior environmental protection
Low moisture vapor permeability - Unique synthetic rubber base provides exceptional moisture resistance.
High flexibility - Minimizes stress on delicate electronic components.
Fluoresces under UV light for quick inspection and can be easily repaired.
RoHS Compliant

Applications

Suitable printed circuit assemblies.

Product Family
HS-1B51LU

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1-Liter Can 5-Liter Can

Catalog Product

Unlike other products we offer, the products listed on this page cannot currently be ordered directly from the website.

Shortest leadtime

Shipping in 6 - 8 weeks

Contact for Pricing

Packaging

TDS, SDS & Technical documents

Specifications
Additional Information

Technical Specifications

General Properties

Density (g)

0.89 g/cm3

Solids

22 %

Electrical Properties

Breakdown Voltage

Breakdown Voltage
Breakdown voltage is the minimum voltage necessary to force an insulator to conduct some amount of electricity.
It is the point at which a material ceases to be an insulator and becomes a resistor that conducts electricity at some proportion of the total current.

After dielectric breakdown, the material may or may not behave as an insulator any more because of the molecular structure alteration. The current flow tend to create a localised puncture that totally alters the dielectric properties of the material.

This electrical property is thickness dependent and is the maximum amount of voltage that a dielectric material can withstand before breaking down. The breakdown voltage is calculated by multiplying the dielectric strength of the material times the thickness of the film.

4900 V

Dielectric Constant

Dielectric Constant
Dielectric Constant (k), commonly known as relative permittivity, is a number relating the ability of a material to carry alternating current to the ability of vacuum to carry alternating current.

It determines the ability of an insulator to store electrical energy and is the ratio of electric permeability in vacuum against the electric permeability of a material.

The lower the dielectric constant (κ) and dissipation factor, the less energy is absorbed from an electric field, making it a much better insulator.

It is a dimensionless property that can be affected by various factors such as the thickness uniformity of a material, insufficient contact between the sample and electrodes, water adsorption and contact resistance.

Dielectric Constant @ 1000 kHz

2.5

Dissipation Factor

Dissipation Factor
Dissipation factor is commonly known as loss tangent or tan delta.

It is a ratio of the loss index and the relative permittivity and it measures the inefficiency of an insulating material to maintain energy (that otherwise dissipates in the form of heat). The lower the factor, the better the insulation.

It is the reciprocal of the quality factor and always refers to a specific temperature and frequency.

Dissipation Factor @ 25°C /1000 kHz

0.07

Mechanical Properties

Storage (DMA) Modulus
Storage (DMA) Modulus @ 25°C	35.3 N/mm2

Thermal Properties

Glass Transition Temperature (Tg)

Glass Transition Temperature (Tg)
The glass transition temperature for organic adhesives is a temperature region where the polymers change from glassy and brittle to soft and rubbery. Increasing the temperature further continues the softening process as the viscosity drops too. Temperatures between the glass transition temperature and below the decomposition point of the adhesive are the best region for bonding.

The glass-transition temperature Tg of a material characterizes the range of temperatures over which this glass transition occurs.

14 °C

Operating Temperature

-65 - 125 °C

Additional Information

Frequently Asked Questions About HumiSeal® 1B51LU

What are typical applications for HumiSeal® 1B51LU?

HumiSeal® 1B51LU is a single-component, fast-drying, synthetic rubber conformal coating that is used for protecting printed circuit board assemblies (PCBs) in various industries, including:

Aerospace systems (e.g., avionics, control modules)
Automotive electronics (e.g., engine control units, sensors)
Consumer electronics (e.g., smartphones, gaming devices)
Industrial automation (e.g., motor drives, PLCs)

Why choose HumiSeal® 1B51LU over other conformal coatings?

HumiSeal® 1B51LU is a highly flexible and fast-drying coating that is easy to apply. It provides excellent electrical insulation, fluoresces under UV for easy inspection, and is easily repairable. It is also compliant with RoHS 2002/95/EC, making it a trusted choice for demanding applications. You can learn how to select a conformal coating in our latest blog.

What is the shelf life of HumiSeal® 1B51LU?

HumiSeal® 1B51LU has a shelf life of 18 months from the date of manufacture when stored at room temperature (0 to 35°C) in tightly closed containers. Prior to use, allow the product to equilibrate for 24 hours at 18 to 32°C to ensure optimal performance.

How should I clean tools after applying HumiSeal® 1B51LU?

Tools and equipment used for applying HumiSeal® 1B51LU (e.g., spray guns, brushes, or dipping tanks) can be cleaned using HumiSeal® Thinner 521 & 535. For removing the coating from PCBs during rework, use HumiSeal® Stripper 1080. Always use a lint-free cloth and ensure proper ventilation during cleaning.

What happens to HumiSeal® 1B51LU after its shelf life?

Past its 24-month shelf life, HumiSeal® 1B51LU may experience changes in viscosity, which could affect application consistency and coating uniformity. Using expired product may lead to suboptimal performance, and the manufacturer will not be liable for quality or performance issues if expired material is used.

Why do curing times vary for HumiSeal® 1B51LU?

HumiSeal® 1B51LU is a fast air-drying coating. Curing times vary depending on temperature, humidity, and film thickness. Typically, the coating will be tack-free in approximately 10 minutes and fully cured in 24 hours.

What is the recommended thickness for HumiSeal® 1B51LU?

The recommended coating thickness for HumiSeal® 1B51LU is 25 to 75 microns. This range ensures optimal protection without compromising flexibility or electrical performance. The thickness can be adjusted by controlling viscosity with HumiSeal® Thinner 500/Thinner 521 during application.

What are the differences between application methods for HumiSeal® 1B51LU?

HumiSeal® 1B51LU can be applied via spraying, dipping, or brushing. Spraying and dipping are ideal for large-scale production, while brushing is suited for small repairs. Each method requires adjusting viscosity with the appropriate thinner for a uniform coating.

What is the maximum operating temperature for HumiSeal® 1B51LU?

HumiSeal® 1B51LU can withstand thermal shock from –65°C to +125°C. It is not recommended for continuous operation above 125°C, as prolonged exposure to higher temperatures may degrade its protective properties.

What safety precautions should I take when using HumiSeal® 1B51LU?

The solvents in HumiSeal® 1B51LU are flammable, so avoid open flames or sparks during application. Use in a well-ventilated area to prevent inhalation of vapors or spray mist, and avoid skin and eye contact. Always consult the Safety Data Sheet (SDS) prior to use for detailed safety guidelines.

How can I ensure proper application of HumiSeal® 1B51LU?

HumiSeal® 1B51LU fluoresces under UV light, allowing for easy inspection of coating coverage. After application, use a UV light source to check for uniform coating and ensure there are no missed areas, which is critical for high-reliability electronics manufacturing.

How does HumiSeal® 1B51LU perform in harsh environments?

HumiSeal® 1B51LU is designed for harsh conditions, with a moisture insulation resistance of 1.0 × 10¹⁰ ohms and fungus resistance per ASTM G21. It maintains performance in humid, mechanically stressful, or temperature-cycling environments, making it ideal for mission-critical systems.

Learn More About HumiSeal® 1B51LU

HumiSeal® 1B51LU is a proven solution for engineers seeking long-term protection of electronic assemblies in demanding environments. This modified alkyd conformal coating offers a unique combination of ease of use, excellent electrical insulation, and mechanical resilience—making it an industry favorite for protecting PCBs in sectors such as automotive, aerospace, consumer electronics, and industrial automation.

Key Features at a Glance

✔ Tack-free in 10 minutes at room temperature
✔ Compatible with “no-clean” flux residues
✔ Low viscosity for easy application

Versatile Application Methods 🧰

Application methods

Whether you’re using spraying, dipping, or brushing, 1B51LU offers flexibility in manufacturing workflows. It can be diluted with HumiSeal® Thinner 521 or Thinner 535 to fine-tune application characteristics based on part geometry and production scale. The coating cures at room temperature in 24 hours, allowing integration into both batch and inline processes.

Application Methods:

Spray: Dilute with HumiSeal® Thinner 521
Dip: 5–15 cm/min withdrawal rate
Brush: For touch-up applications

Cure the coating at room temperature (24 hrs) for convenience, or accelerate with thermal curing to match fast-paced production cycles.

Application Compatibility

It integrates well with lead-free processes, supports standard cleaning practices, and offers strong performance even on flux-contaminated surfaces.

Compatible With:

✔ Compatible with “no-clean” flux residues
✔ Common PCB finishes including ENIG, HASL, and OSP
✔ High-reliability applications requiring low ionic content
✔ Lead-free and RoHS-compliant manufacturing environments
✔ Cures at room temperature (24 hrs)

Additionally, its UV fluorescence ensures easy inspection, and the coating is reworkable using standard HumiSeal strippers—ideal for repairable designs and serviceable assemblies.

High-Performance Electrical Protection 🧪

1B51LU delivers a dielectric breakdown voltage of 1,500 volts and an insulation resistance exceeding 3.5 × 10¹⁴ ohms, protecting even the most sensitive circuit designs from moisture, contaminants, and voltage-induced failure. It’s also rated UL 94 HB, ensuring flame retardancy in critical applications.

Fluorescent for Inspection 💡

To simplify quality assurance, HumiSeal® 1B51LU fluoresces under UV light, making it easy to confirm proper coating coverage during post-application inspection—an essential feature for high-reliability electronics manufacturers.

Repairable and Reworkable 🔁

Unlike many conformal coatings, HumiSeal® 1B51LU is easily repairable. Should rework or component replacement be required, the coating can be selectively removed using HumiSeal® Stripper 1080 or 1080A, making it ideal for prototyping, low-volume builds, or field serviceability.

Reliable Across Environments 🌍

With a wide thermal shock range of –65°C to +125°C and resistance to fungus (ASTM G21) and moisture, 1B51LU ensures consistent performance across varied environmental conditions. It’s particularly well-suited for mission-critical systems exposed to humidity, mechanical stress, or temperature cycling.