Preparation And Properties Of Nano-enhanced Composite Phenolic Foam

Rigid phenolic foam (PF) is a kind of novel thermal-insulation material which is extensively used in various sectors including construction, chemical industry, transportation and aerospace application due to their excellent properties: light weight, high strength, low thermal conductivity, fine flame retardant and flexible processing methods as well as convenient molding to construction. As a structure material, it lacks certain strength, stiffness and toughness. In order to solve the above problems, it needs to be modified and reinforced. Nano-materials have specially physical and chemical properties, various kinds of reinforcing inorganic nano-fillers are added into PF matrix to enhance strength and toughness in-step, and then improve general property of PF dramatically.In this paper, PF of stable dimension and fine property was prepared by curing reaction of phenolic resin catalysed with acid. The main effect of foaming parameters, including amount of raw materials and assitants, temperature as well as pressure on foams properties were discussed.With continuous advantages of nano-technology, the study on the polymer nanocomposite foams has attracted many interests of researchers. In this paper, the hydrophilic A200 nano-SiO₂ and hydrophobic R805 nano-SiO₂ were dispersed into phenolic resin by ultrasonic cavitation and high speed shearing, and PF/nano-SiO₂ composites were prepared. The results of the compressive test indicate that the compressive strength of the PF samples increases with the addition of increasing amount of nano-SiO₂ in the range of 0-1.5wt%, but when the amount continuously increases, compressive properties of PF decline due to the agglomeration of the nano-particles. R805 nano-SiO₂ does not play key roles in enhancing compressive strength. From the results of thermogravimetric analysis, it is found that the initial thermal decomposition temperature of PF reinforced with A200 nano-SiO₂ is 355℃, which is 5℃higher than that of pure PF, and ratio of residual carbon of PF reinforced with R805 nano-SiO₂ is 20%. Because the hydrophilic nano-SiO₂ has good interface compatibility with phenolic matrix, suitable amount and species of nano-SiO₂ can reduce the average diameter of cells and improve compressive strength and thermal stability.Attapulgite(ATP) does not play key roles in strengthing due to bad interface compatibility with phenolic resin, which is a family of fibrous hydrous magnesium silicates. In the paper, ATP was firstly modified on the surface with silane coupling agent KH-560, and then the dispersity of ATP and Si-ATP( modified with KH-560) was investigated. In addition, phenolic nanocomposite foams were prepared with addition of ATP and Si-ATP, and the effect of Si-ATP on the compressive properties and thermal stability has been studied.The research results show that the addition of Si-ATP can improve the compressive strength and thermal stability. It strengthens interface action of organic-inorganic phases, for silane coupling agent acting as media and bonding with pheolic matrix and attapulgite. It can activate phenolic resin and enhance degree of cross link. The analysis indicates that ATP in the phenolic matrix acts as the heterogeneous nucleation agent and reduces the average diameter of cells, which depends on the effect of surface modification by silane coupling agent.