Study On Preparation And Properties Of Toughened And Flame Retardant Phenolic Foam

Phenolic foam is widely used as building insulation material because of its excellent thermal insulation,good flame retardancy,low smoke and low toxic.However,the brittleness and pulverization of phenolic foam restricts its development.Over the years,many toughening modification methods were promoted in improving the strength and toughness of phenolic foam,but it will affect the flame retardancy of phenolic foam.In order to solve these problems,modification of toughness and flame retardant were attracted attention widely.In this paper,the resole phenolic resin was synthesized base on formaldehyde and phenol using sodium hydroxide as catalyst.The optimum synthesis conditions of phenolic resin and the optimum preparation technology of phenolic foam were determined through orthogonal experiments and single factor experiments.A series of modified phenolic foams were prepared using urea and glass fiber as toughening agent and pentaerythritol phosphate as flame retardant,respectively.Afterward,the performances of modified phenolic foams were characterized.The main results of the paper are described as follows:(1)The optimum synthesis conditions of resole phenolic resin were that the molar ratio of formaldehyde and phenol was 1.8,reaction temperature was 85 ?,reaction time was 180 min,dosage of catalyst was 1 %.Under the optimum condition,the phenolic resin was dark brown viscous liquid that had the solid content of 84.2 %,viscosity of 5640mPa·s,free phenol and formaldehyde content of 2.57 % and 2.25 %,respectively.(2)The optimum preparation process of phenolic foam was that the amount of surfactant,foaming agent and curing agent were 4 %,10 %,10 %,respectively,while foaming temperature was 60 ?.(3)Compared with the pure phenolic foam,the thermal stability and flame retardancy of phenolic foam modified by pentaerythritol phosphate ester and urea greatly increased,and its mechanical properties were improved.Moreover,the pulverization rate and water absorption of modified foams were decreased,and the pore structures showed dense anduniform.(4)The compressive strength,bending strength and impact strength of phenolic foam modified by chopped glass fiber and pentaerythritol phosphate were improved obviously.The modified foam showed good thermal stability and high carbon residue.The flame retardancy of modified phenolic foam increased significantly,in which the optimum synergistic effect was obtained of filling with 3 % of pentaerythritol phosphate and 1 % of glass fiber.In addition,the foam had lower pulverization rate and water absorption with introduction of pentaerythritol phosphate.The results of scanning electron microscopy showed that modified phenolic foam was more fine and uniform bubble pore structure,compared with the pure phenolic foam.