Polyurethane‐imide (PUI) composite foams with expandable graphite (EG) of different sizes were prepared by a polyimide prepolymer method. EG particles were treated with a silane coupling agent to improve compatibility with the foam. The effect of EG particle size on cell morphology, thermal degradation, flame‐resistance and mechanical properties of PUI foams was investigated. Results showed that the mean cellular diameter of foams with EG particle was much higher than that of foams with surface‐modified EG particle at the same filler loading. When filler particle diameter increased from 20 to 90 μm, the compressive strength, density and closed‐cell ratio of foams increased, and then decreased when filler particle diameter further increased from 90 to 150 μm. Thermal stability of foams increased with the increasing filler particle diameter from 20 to 50 μm, and decreased with the increasing filler particle diameter from 50 to 90 μm. The limited oxygen index (LOI) value of foams with surface‐modified EG increased from 24.8% to 32.1% when EG particle diameter was below 90 μm. Foams with surface‐modified EG exhibited enhanced mechanical properties, thermal stability and flame resistance than foams with neat EG at the same loading.

中文翻译：

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具有不同尺寸的可膨胀石墨的聚氨酯酰亚胺泡沫的机械性能和阻燃性能

通过聚酰亚胺预聚物方法制备了具有不同尺寸的可膨胀石墨（EG）的聚氨酯-酰亚胺（PUI）复合泡沫。用硅烷偶联剂处理EG颗粒以改善与泡沫的相容性。研究了EG粒径对PUI泡沫的泡孔形态，热降解，阻燃性和力学性能的影响。结果表明，在相同填充量下，带有EG颗粒的泡沫的平均孔直径比带有表面改性EG颗粒的泡沫的平均孔直径高得多。当填料粒径从20μm增加到90μm时，泡沫的抗压强度，密度和闭孔率增加，然后，当填料粒径进一步从90μm增加到150μm时，泡沫强度降低。泡沫的热稳定性随着填料粒径从20到50μm的增加而增加，并且随着填料粒径从50到90μm的增加而降低。当EG粒径小于90μm时，表面改性EG泡沫的极限氧指数（LOI）值从24.8％增加到32.1％。在相同的载荷下，表面改性的EG泡沫比纯EG的泡沫具有更高的机械性能，热稳定性和阻燃性。