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Home > Research > Research Results > Research Results 2018 > Wood treated with fire-retardant coating maintains fireproof performance and color even after outdoor exposure for five years

Update:March 20, 2018

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Wood treated with fire-retardant coating maintains fireproof performance and color even after outdoor exposure for five years

 

Article title

(1) Combustibility of fire-retardant impregnated and surface-coated wood after 5 years of natural weathering
(2) Changes in color of fire-retardant-impregnated and surface-coated wood during outdoor exposure

Author (affiliation)

(1) Toshiro Harada(a), Daisuke Kamikawa(b), Yutaka Kataoka(c), Atsuko Ishikawa(b), Yuji Kameoka(d)

(2) Atsuko Ishikawa(b), Yutaka Kataoka(c), Toshiro Harada(a), Daisuke Kamikawa(b), Masahiko Kobayashi(b), Yuji Kameoka(d)
 (a) Shikoku research center, FFPRI, Kochi, Japan
 (b) Department of Wood Improvement, FFPRI, Tsukuba, Ibaraki, Japan
 (c) Public Relations Division, FFPRI, Tsukuba, Ibaraki, Japan
 (d) Marubishi Oil Chemical Co. Ltd., Osaka, Japan

Publication Journal

(1) Wood preservation 43 (6):322-327, November 2017, DOI: 10.5990/jwpa.43.322( External link )
(2) Wood preservation 44 (1):11-18, January 2018

Content introduction

Impregnation of fire retardant chemicals into wood is an effective method to improve its fire performance. Many non-combustible or quasi-non-combustible wood materials are currently being developed for interior use using this method. Recently, there has been an increasing demand to use these materials in open air in outdoor applications on building exteriors or exterior construction. When used outdoors, these materials are exposed to wind and rain. In such cases, there is concern regarding the leaching of fire retardant chemicals due to exposure to rainwater. However, few studies on changes in fire performance and weatherability of fire retardant-treated wood after long-term outdoor exposure (natural weathering) were conducted.

The Forestry and Forest Products Research Institute (FFPRI) conducted studies to address this concern, in collaboration with Marubishi Oil Chemical Co. Ltd. In these studies, fire retardant-treated and coated quasi-non-combustible wood materials (sugi sapwood; 18mm in thickness) were made and exposed to open air for five years. The results were as follows: To suppress the leaching of fire retardant chemicals, guanidine phosphate improved with phenolic additives is effective. Although leaching of the chemical cannot be completely suppressed, an appropriate coating is effective to maintain fire performance at the same level as that of quasi-non-combustible materials [note 1] (total heat release for 10 min is less than 8 MJ/m2) even after five-year outdoor exposure. Moreover, changes in the color of fire retardant-treated samples were lesser than those of untreated samples when non-coated or coated.

 

[Note 1] Quasi-non-combustible material: According to the Building Standards Law, these materials are allowed for use as interior finishing materials in places where fire performance is required, except in special locations including evacuation staircases.

Fig. 1

Figure 1. Relationships between fire-retardant chemical retention after natural weathering and total heat release for 10-minute cone calorimeter tests.
(Quasi-noncombustible material is required less than 8 MJ/m2 of total heat release.)

 

 

Fig. 2
Figure 2. Changes in color difference (ΔE*ab) of untreated and fire-retardant-treated specimens during outdoor exposure.

 

Photo. Natural weathering test of fire-retardant impregnated

Photo. Natural weathering test of fire-retardant impregnated and surface-coated woods.