The molecules of SCF have strong permeability and powerful swelling ability, and the polymer will be swollen with time in SCF atmosphere, so that the volume of the polymer will change with time.

• 超临界流体分子具有很强的渗透能力，会对聚合物进行溶胀，聚合物的体积会发生变化，同时小分子在聚合物相中扩散系数对于浓度具有强烈的依赖性，这给扩散模型的建立带来了很大的困难。