PVP在制备过程中分别呈现出成核、成球及分散稳定的作用， 从而实现了聚酰亚胺材料在微米尺度上的微球化。

PVP played roles of nucleation, balling and dispersion respectively in the whole process. The polyimide microspheres could be prepared in the micro-scale by this way.

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你也可以想象成一只水球，如果你拿个水球放在水中，把手放球上向下压，你就会得到上升的反作用力。

Also, you can think of it like water polo ball. If you take a water polo ball in the water, put your hand on it and press it down, you get pressure up against it that come up.

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