The mechanical and flame retardant characteristics of lignin-based phenolic foams reinforced with MWCNTs by in-situ polymerization

Abstract

In this study, multi-walled carbon nanotubes (MWCNTs)/lignin-based phenolic foams (L₂₀PFs) composites were prepared by in-situ polymerization. SEM results indicated that MWCNTs act as heterogeneous nucleating agents, which reduces the average size of PFs cells and makes the cells more uniform; MWCNTs are dispersed on the pore walls of the cells and bear a certain load through the interface transfer of the foam to enhance the mechanical properties of the foam. The PFs doped with MWCNTs exhibit enhanced mechanical properties, with compressive and flexural strengths as high as 0.326 MPa and 0.483 MPa, which represent increases of 102.48% and 100.41% over those of pure PF, respectively. The incorporating of MWCNTs significantly improved the limiting oxygen index (LOI) of PFs as much as 44.2%, and decreased heat release rate (HRR), Total heat release (THR), and mass loss rate (MLR). This is due to the MWCNTs composite PFs surface can form dense and incompletely burning black carbon layer during the combustion process, which isolates the external heat and air from the composite material and plays a role of flame retardant. The incorporating of MWCNTs can slightly reduce the thermal conductivity of L₂₀PFs.

GRAPHICAL ABSTRACT

A table of contents entry

A novel MWCNTs/lignin-based phenolic foams composites were fabricated with excellent mechanical, flame retardant and combustion properties.

Keywords:

• MWCNTs
• lignin
• phenolic foams
• mechanical properties
• flame retardant

Additional information

Funding

The authors are grateful to the financial support from the Fundamental Research Funds for the Central Nonprofit Research Institution of CAF (No. CAFYBB2018MA001) and the National Natural Science Foundation of China (Grant No. 31700499).