Preparation of bisDOPO-NH₂-POSS flame retardant and its application to plywood using modified urea-formaldehyde resin

ABSTRACT

A new type of polyhedral oligomeric silsesquioxanes bisDOPO-NH₂-POSS flame retardant consisting of one polyhedral oligomeric silsesquioxane (POSS), two units of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and reactive –NH₂ groups, was synthesized and characterized by FTIR, ¹H NMR, and ³¹P NMR. It was applied to modified conventional environmentally friendly E0 grade urea formaldehyde (UF) resin to prepare flame-retardant plywood. Two other POSS structure flame retardants were used for comparison. The results showed that the addition of bisDOPO-NH₂-POSS flame retardant to E0 UF resin improved bonding strength while lowering formaldehyde emission owing to the increase in cross-linking of the UF molecule chain in condensation. TGA curves showed that bisDOPO-NH₂-POSS-E0 UF exhibited the highest thermal stability. The flammability characteristics of the plywood were evaluated by a cone calorimeter test (CCT), and the results indicated that the heat release and smoke production of flame-retardant plywood were lower than those of the control E0-UF plywood. Moreover, compared to E0-UF plywood, the char residue remaining after the CCT test of the flame-retardant plywood with POSS structure increased. In particular, bisDOPO-NH₂-POSS-E0-plywood had a continual compact outer carbon layer, which was conducive to effectively forming a physical barrier to hinder the penetration of oxygen and heat and exhibiting the outstanding synergistic effect of phosphorous, silicon and nitrogen.

GRAPHICAL ABSTRACT

KEYWORDS:

• Polyhedral oligomeric silsesquioxane (POSS)
• phosphorus-silicon-nitrogen synergistic flame retardant
• environmental urea-formaldehyde resin
• plywood

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The authors are grateful for the support of the National Natural Science Foundation of China (31700483), International Cooperation Project of the Department of Science and Technology of Jilin Province (20220402058GH), Young and middle-aged scientific and technological innovation leading talents and team projects of the Department of science and technology of Jilin Province (20200301046RQ), and the Youth Science and Technology Innovation Team Cultivation Program of Beihua University 2020(160221203). We also thank the R&D Program for Forest Science Technology (Project No. FTIS 2022457A00-2224-AC02, FTIS 2020223A00-2222-AC02) provided by the Korea Forest Service (Korea Forestry Promotion Institute) for their support.