Study On The Preparation And Performance Of Modified Phenolic Foam

Phenolic foam is a type of polymer foam material developed from phenolic resin. Phenolic foam has a broad range of applications as insulating material in civil construction and military manufacturing due to its excellent flame resistant properties, including fire resistance, self-extinguishing character and low thermal conductivity as well as low smoke density and toxicity property. However, unlike most other polymer foams, phenolic foam is extremely friable and easily pulverized, which has severely restricted its application fields and service life. To promote the application of phenolic foam, the toughness and mechanical properties must be improved.In this paper, based on the research results in our laboratory in the past few years, chemical and physical modification methods were used to improve the toughness of phenolic foam. FT-IR and1H-NMR were employed to characterize the chemical structure of modified phenolic resin. The micro-fracture surface of modified foam was observed by SEM. Universal testing machine and thermal analyzer were employed to investigate the mechanical properties and thermal stability of modified foam.At first, bio-based Chinese gallnut tannin were used to partially replace phenol based on the green chemistry theory.the usage of chemical materials were reduced in the process of synthesis of phenolic foam, and the mechanical properties were improved as well. The results showed that compression strength, impact strength and flexural strength were improved compared to unreinforced foams, respectively. The thermostability of reinforced foams decreased according to thermal analysis results. Weight-loss ratios increased2-5%at the same temperature compared to unreinforced foam, but still have excellent thermostability.Second, based on the results of tannin modified phenolic foam, bio-based wood fibers were used to tough tannin-phenolic foam. Tannin-phenolic foams reinforced by xylem fiber at different fiber loadings were investigated by universal testing machine and thermal analyzer. The results showed that the mechanical properties and toughness of modified tannin-phenolic foams were inproved further and still have excellent thermostability.At last, fumed sillica was used to modify phenolic foam. Nano-SiO2particles were distributed on the bubble wall of phenolic foam to reinforce the bubbles, as a result, the toughness of modified foam was improved. Testing results suggested that reinforced phenolic foams have better impact strength and compressive strength when add2%fumed sillica into the composites, the improvement up to40%and63%compared to unreinforced foams, the thermostability have improved as well.