Preparation of flame retardant hydrophobic renewable composite paperboard and its mechanical properties

The purpose of this paper is to study and prepare a kind of renewable composite paperboard with both flame retardancy and hydrophobicity, and to explore its flame retardancy, hydrophobicity and mechanical properties. The intumescent flame retardant system (IFR) was constructed with ammonium polyphosphate (APP)-carrageenan (KC), tetraethylorthosilicate(TEOS)-methyltrimethoxysilane (MTMS)@magnesium aluminum hydro-xide(MAH) as synergistic flame retardant, silane coupling agent KH550 (AEMO)@SiO₂ as hydrophobic filler. The flame retardant, hydrophobic and mechanical properties of APP-KC-(TEOS-MTMS)@MAH-(AEMO@SiO₂) composite paperboard were tested. According to the national standard, the main physical properties of corrugated board were measured. The flame retardant effect of corrugated board was tested by vertical combustion test and limiting oxygen index (LOI). The microstructure was characterized by FE-SEM. FTIR was used to study the changes of functional groups before and after combustion. Its thermal stability was analyzed by thermogravimetry (TG). Contact angle (CA) test, rolling angle (SA) test and water absorption test were used to determine its hydrophobicity. The water absorption of composite paperboard is 1.78 g·m⁻², the puncture strength is 6.4 J, the edge pressure strength is 8.3 kN·m⁻¹, and the compressive strength is 360 kPa. The optimal formula is adopted (the mass ratio of APP, KC, MTH and ATH was 3∶2∶1∶1). The limiting oxygen index (LOI) reaches 32% at the same time. After the combustion experiment, the carbonization length is 19 mm, the flame duration is 0.5 s, and the ignition time is 3 s. TG results show that the carbon residue of APP-KC-(TEOS-MTMS)@MAH-AEMO@SiO₂ composite paperboard is 37.5%. SEM results show that there is a foamed carbon layer on the surface of the composite board after combustion, and the fiber is still intact. The contact angle is 110.2°. The moisture content is 232% lower than that of base paper. APP-KC-(TEOS-MTMS)@MAH-(AEMO@SiO₂) composite paperboard has good flame retardancy, hydrophobicity and mechanical properties.