Programming effects on thermal decomposition of shape memory polymer-based composites

To evaluate the effects of two-dimensional (2D) programming on thermal decomposition of shape memory polymer (SMP)-based composites when exposed to fire, the block specimens of SMP-based composites were first prepared and programmed. Then the phase structure and thermal decomposition properties of SMP-based composites were characterized before and after the 2D programming. Also, the released volatile constitutes were identified, and the microscopic morphology of charring layer was observed, and thermal decomposition mechanism of SMP-based composites was discussed. Results indicated that SMP-based composites had two phases, and the crystalline segments were not found in both non-programmed and programmed samples. The 2D programming disorients the hard phase and soft phase in the SMP matrix. Additionally, the 2D programmed SMP-based composites showed lower thermal stability than the non-programmed sample. Further, the released volatile constitutes of non-programmed composites were consistent with those of the programmed sample. However, the programmed composites released more volatiles during its thermal decomposition. Finally, the charring layer of non-programmed SMP-based composites was more continuous and compacted than that of programmed sample, preventing the volatiles from releasing out of SMP, and increasing the resistance of SMP-based composites to high temperature. The 2D programming facilitated both chain scission and cross-linking reactions during the thermal decomposition of SMP-based composites. The former released heat and gaseous products to sustain burning and produced smokes, while the latter caused the aromatization and condensation to form combustion residues.