If a power supply, LED driver or transformer needs potting and the spec also calls for flame retardancy, the H-GF-GY Thermal Conductive Silicone Encapsulant covers both with one layer: the product page lists UL 94 V-0 and a thermal conductivity of 1.0 to 3.0 W/m·K. Before ordering, check the specimen thickness behind the V-0 rating, the rating your end-product standard requires and your actual potting depth, then request the datasheet and samples.
Heat Transfer and Flame Rating Come From the Same Compound
The product page describes H-GF-GY as a high thermal conductivity, flame-retardant, two-component addition-cure silicone encapsulant. Its parameter table lists flame retardancy V-0 (UL 94) and thermal conductivity 1.0 / 3.0 W/m·K (ISO 22007-2). The heat path and the flame requirement can be checked against one part number, so qualification has one less material to compare.
V-0 Has Clear Pass Criteria You Can Map to Your Spec
NIST report NISTIR 7031 describes the UL 94 vertical burn test: a specimen of about 125 mm × 13 mm is clamped vertically, a small flame is applied for 10 seconds, the afterflame is timed, and the flame is applied a second time. For V-0, the afterflame time t1 or t2 for each individual specimen is less than 10 seconds, the total t1 + t2 for the 5 specimens is less than 50 seconds, flaming drips must not ignite the cotton below, and no specimen may burn up to the clamp (NIST NISTIR 7031).
The same report notes that the test simulates a short ignition source such as an internal electric fault and is not designed to predict full-scale fire performance. V-0 is a material rating; the finished product still goes through its own safety approval.
Conforms to Uneven Boards, Handling Heat and Insulation Together
Cured hardness is 55 ± 5 Shore A, and its flexibility lets the layer cover uneven component profiles and carry heat from the PCB or discrete devices to a metal housing. The same layer has a dielectric strength of 10 kV/mm and a volume resistivity of 1×10^13 Ω·cm; for high-voltage clearance design, see our note on potting for high-voltage insulation.
1:1 Mix and a 20-Minute Cure at 80°C Keep the Line Moving
Part A is a white fluid and Part B a gray fluid, mixed 1:1 by weight within a 3% error margin. Working time is 40 to 60 minutes at 25°C; the compound cures in about 8 hours at room temperature or in 20 minutes at 80°C. It bonds without primer and can be pried open after curing for rework, as covered in the primerless rework article.
Why Thermal Inertia Delays Ignition
NIST’s analysis of a thermally thick solid heated by a constant surface heat flux gives this relationship for ignition delay:
t_ign = C × kρc × [(T_ign − T_a) / (q_ext − q_crit)]^2
- t_ign: ignition delay time, s
- C: constant of the heat-conduction solution in eq. (2) of the source
- k, ρ, c: thermal conductivity (W/m·K), density (kg/m³) and specific heat (J/kg·K); their product kρc is the thermal inertia
- T_ign and T_a: surface ignition temperature and ambient starting temperature, K
- q_ext and q_crit: incident external heat flux and the critical heat flux for ignition, kW/m²
Higher thermal inertia slows surface heating, so the material reaches its ignition temperature later. The product page lists thermal conductivity of 1.0 to 3.0 W/m·K and a specific gravity of 3.0 g/cm³, two of the three terms in kρc; specific heat is not published, so the equation cannot give this product’s ignition time. The model assumes a thermally thick material, ignores flame-retardant chemistry, char and dripping, and does not convert into a UL 94 rating. Use it to read the trend only (source: NISTIR 7031, eq. (2)). For how fillers and char layers relate to V-0 in thermal pads, see thermal pad fire safety and char formation.
Where It Fits
The product page lists high-power LED lamps, power supplies and transformers, along with sensors and coils. These modules pack components tightly and concentrate heat; the potting layer is both the heat path and the material sitting right against the parts, which is why flame rating often appears in the purchasing spec.
What to Send With a Sample Request
- The flame rating and specimen thickness your end-product standard requires, plus a request for the V-0 test documentation
- Potting depth, cavity volume and component operating temperature
- Available cure conditions: 8 hours at room temperature or 20 minutes at 80°C
- Whether you need the higher conductivity grade; if so, vacuum degassing before pouring is recommended
Email these conditions to yw@zh-lx.com, or send a specification inquiry and sample request from the Thermal Conductive Silicone Encapsulant product page.
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