Selection of wooden door surfaces

The surface treatment of UL standard wooden fireproof doors (UL certified) must simultaneously meet the requirements of fire resistance performance (UL 10C/UL 10B), durability, environmental friendliness (EPA/LEED), and aesthetics. According to standards such as NFPA 80 and ASTM E84, the surface treatment of wooden fireproof doors includes key processes such as flame-retardant impregnation, fireproof coating, and decorative protection to ensure effective flame retardancy and maintain structural integrity in a fire.

Core Processing Technology

1. Substrate pretreatment

Wood selection:

Solid wood (such as oak, maple) or fire-resistant plywood (conforming to ANSI/HPVA HP-1 standard) is adopted.

The moisture content should be controlled at 8% to 12% (to prevent deformation and cracking).

Flame retardant treatment (key step) :

High-pressure impregnation method

Flame retardant type: Ammonium phosphate, borate or amino resin type (conforming to ASTM E84 Class A).

The impregnation depth is ≥ 5mm (to ensure the fire resistance performance of the core material).

Vacuum pressure treatment (to increase the permeability of the reagent).

After drying, it needs to pass a constant temperature and humidity test (to prevent deformation later).

• Fireproof coating

Intumescent fireproof paint

The coating thickness is 0.5 to 1.2mm (if it is too thick, it may affect the gap between the doors).

It expands 5 to 10 times when exposed to fire, forming a carbonized insulation layer (verified by UL 10C test).

Refractory putty filling

It is used to fill the pores of wood and improve the surface flatness (the fire resistance rating needs to match the overall door body).

3. Surface finishing process

High-pressure Refractory laminate (HPL)

The thickness is 0.8-1.5mm. It is resistant to high temperature and scratches (passing UL 72 test).

Applicable scenarios: high-flow areas such as hospitals and schools.

Solid wood veneer + fireproof varnish

The thickness of the veneer is 0.6 to 1.0mm, and a flame-retardant primer is applied to the bottom layer.

The topcoat adopts water-based fireproof UV paint (VOC < 100g/L, in compliance with EPA standards).

Direct spraying of fireproof coating

Suitable for industrial style, sprayed with matte/semi-matte fireproof paint (weather-resistant type).

Key Performance Requirements

Fire resistance performance:

Passed the UL 10C fire resistance test (20/45/90 minute grades).

The smoke density during combustion (ASTM E662) is ≤450, and the toxicity complies with NFPA 286.

Environmental protection compliance

The flame retardant is free of formaldehyde and heavy metals (conforming to TSCA Title VI).

The VOC content of the coating is less than 250g/L (EPA 40 CFR Part 59).

Physical durability

Wet heat resistance test (ASTM D4585) : No bubbling after 500 hours.

Abrasion resistance (Taber Abrasion) ≥500 cycles (HPL finish).

Iv. Quality Control and Inspection

Flame retardant penetration testing: Take sample slices and measure the immersion depth.

Adhesion of fireproof coating: The cross-sectional method (ASTM D3359) ≥4B grade.

After the fire resistance test, inspection was conducted: no cracking and the carbonized layer was intact.

V. Maintenance and Care

When cleaning, use a neutral cleaner (pH 6~8) to avoid solvent corrosion of the coating.

Regularly inspect the edge sealing strips to ensure they do not fall off (the gaps in the fire door affect the fire resistance performance).

Local damage should be repaired with fireproof coating of the same model to avoid performance decline.

Vi. Summary

The surface treatment of American standard wooden fireproof doors should focus on flame retardancy, taking into account both aesthetics and environmental protection. The process selection should be based on the application scenario (such as commercial buildings, industrial facilities or high-end decoration), and strictly follow UL, NFPA and ASTM standards to ensure the safety protection effect in case of fire.

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