PURF with PEPA had similar weight l

PURF with PEPA had similar weight loss process under 450 °C either in nitrogen or in air, the slightly higher weight loss between 300 and 350 °C might result from degradation of PEPA which could be accelerated by oxygen. But in the range of 500–800 °C, PURF with PEPA showed a relatively high weight loss in air, which could be attributed to the oxidation of the char. The present of oxygen has little effect on the decomposition of PU (below 450 °C), but showed obviously oxidation of char at high temperature.
Char residue was only 21% in air and about 37% of char was consumed by oxidation comparing to char residue generated in N2.
3.2. Influence of CaCO3 on char-forming property and char stability of PURFs
Calcium carbonate nanoparticles were used to improve char stability of the PEPA modified PURFs. According to previous studies [9] and [13], 1–7 wt% of CaCO3nanoparticles exhibited favorable results. Therefore, Different mass fraction of CaCO3was added to the PEPA modified PURFs.
3.2.1. Influence of CaCO3 on char residue of PEPA modified PURFs
The char-forming property of PEPA/CaCO3/PURFs was studied by TGA in nitrogen atmosphere, and the results were showed in Fig. 6 and Table 3. The CaCO3 content was 3 wt% and 6 wt% respectively.