M78H-41 Polyurethane Conformal Coating
Product Applications:
M78H-41 is a one-component polyurethane protective coating formulated with modified polyurethane resin, waterproofing additives, and functional auxiliaries. It is designed to form a transparent, glossy, and strongly adherent protective film on printed circuit boards (PCBs), electronic components, and metal surfaces.
The cured coating provides high electrical insulation resistance and is suitable for the protection of both high-voltage and low-voltage electrical equipment. It offers reliable resistance to moisture, water exposure, acids, alkalis, and contaminated water, helping protect sensitive electronic assemblies in demanding operating environments.
M78H-41 dries quickly at room temperature and is easy to apply, making it suitable for efficient coating operations. It is primarily used for waterproofing and moisture-proof protection of PCBs, electronic components, connectors, and metal parts.
After application, the coating creates a highly hydrophobic surface that helps repel water and reduce the risk of surface condensation in humid environments or under significant temperature changes. M78H-41 is an effective solution for electronic waterproofing, PCB moisture protection, electrical insulation, and metal surface protection.
- Description
- Technical Data
- FAQ
Description
Product Features:
· Transparent, High-Gloss Protection
· Fast, Easy Application
· Superior Waterproofing & Hydrophobicity
Physical Properties：
| Item | Specification | Test Method |
| Appearance | Yellow transparent liquid | Visual |
| Viscosity | 20-50 mPa·s | — |
| Solid Content | 40±2% | — |
| Film-Forming Time — RT, 55%RH | Surface dry: ≤30 min; full dry: 24 h | — |
| Film-Forming Time — 80℃ | Surface dry: 5-10 min; full dry: 2 h | — |
| Film Thickness | 30-50 μm | — |
| Dielectric Withstand Voltage | >1500 V | — |
| Insulation Resistance | >2.5×10¹²Ω | — |
| Moisture Resistance | ≥5×10⁹Ω | — |
| Sulfurization Resistance | PASS | — |
| Operating Range | -40 to 120℃ | — |
Process & Precautions：
· Use neat or with special thinner X-4H to adjust working viscosity and film thickness. In open containers the thinner evaporates, raising specific gravity and viscosity, causing difficult, uneven application that harms moisture protection and electrical performance — replenish X-4H regularly. For brushing, apply small amounts in multiple passes to avoid moisture absorption, gelation and caking.
· M78H-41 conformal coating must be used together with the special thinner to avoid possible adverse reactions such as precipitation, delamination or self-polymerization.
· If not used for a long time, pour it out of the open container and store it sealed to avoid excessive evaporation or gelation.
· M78H-41 can remedy defective soldering residues on circuit boards. When unsuitable rosin-free or low-solid fluxes are used, boards may show defects; in the following cases M78H-41 can be used for remediation:
· a: If post-solder residues turn white or shadowy, brush M78H-41 onto the surface; it absorbs the residues into the film, forming a thin transparent film.
· b: If post-solder residue resistance is too low, causing leakage, the previous remedy was cleaning (some fluxes are hard to clean and leave white residues).
This function requires low rosin content; if residues are too heavy, clean the board before coating to avoid uneven coating.
Packaging, Storage/Transport & Shelf Life：
· Packaging: 4 KG/pail, 20 KG/pail
· Storage & transport: flammable chemical — keep away from fire and heat; handle per regulations; store cool (RT), dark and dry.
· Shelf life: stored sealed, 6 months at 5-25℃.
Conformal Coatings：
Thinners：
Frequently Asked Questions
What is the minimum order quantity (MOQ) for M78H-41?
The standard MOQ for M78H-41 is one 4 kg pail. For trial quantities below the standard MOQ, please contact us for sample availability and a customized quotation.
What packaging options are available?
M78H-41 is available in the following standard packaging options:
- 4 kg per pail
- 20 kg per pail
Please contact us for bulk-order pricing, customized packaging, or OEM labeling requirements.
Can I request a sample before placing a bulk order?
Yes. Free samples are available for quality evaluation and application testing. Please contact us to confirm sample availability and quantity. The customer is responsible for shipping costs.
What is M78H-41 used for?
M78H-41 is a one-component polyurethane protective coating used for waterproofing, moisture-proofing, electrical insulation, and surface protection of printed circuit boards (PCBs), electronic components, connectors, and metal surfaces.
What surfaces is M78H-41 suitable for?
M78H-41 is designed for compatible PCB assemblies, electronic components, and metal surfaces. For optimum adhesion and long-term performance, surfaces should be clean, dry, and free from dust, oil, moisture, and other contaminants before application.
What protection does M78H-41 provide?
After drying, M78H-41 forms a transparent, glossy, strongly adherent, and hydrophobic protective film. It helps improve resistance to moisture, water exposure, acids, alkalis, contaminated water, and surface condensation in humid environments.
Is M78H-41 suitable for electrical equipment?
Yes. M78H-41 provides high electrical insulation resistance and can be used to protect compatible high-voltage and low-voltage electrical equipment and electronic assemblies. Please verify suitability through testing under your actual operating conditions.
How is M78H-41 applied?
M78H-41 is easy to apply and may be suitable for brushing, spraying, dipping, or other coating processes, depending on your production requirements. Please conduct application trials to determine the appropriate process and coating thickness.
How long does M78H-41 take to dry?
M78H-41 dries quickly at room temperature. Actual drying and full-curing time may vary according to coating thickness, ambient temperature, humidity, ventilation, and the application method. Please refer to the Technical Data Sheet (TDS) for verified process parameters.
How should M78H-41 be stored?
Store the product in a cool, dry, and well-ventilated place away from direct sunlight, heat sources, moisture, and ignition sources. Keep the pail tightly sealed when not in use. Please refer to the TDS and SDS for detailed storage and handling requirements.
What is the shelf life?
The shelf life is is 6 months shelf life if unopened when stored under recommended conditions. Please check the product label or contact us for batch-specific information.
Can you provide technical and compliance documents?
Yes. Available documents may include the Technical Data Sheet (TDS), Safety Data Sheet (SDS), Certificate of Analysis (COA), and applicable compliance documentation. Please contact us to request the documents required for your project.
Do you provide technical support?
Yes. Our technical team can assist with substrate compatibility testing, surface preparation, coating-process recommendations, and product selection for electronic waterproofing and moisture-protection applications.