凝固浴对湿法制备聚氨酯微孔膜结构和性能的影响

Effects of coagulation bath on the structure and property of porous PU membranes

为了探讨厚度方向上呈非对称异质结构聚氨酯(PU)微孔膜的成型条件和性能表现,采用湿法成膜方法制备了PU微孔膜,通过改变凝固浴组分及配比,观察分析其对微孔膜微观结构的影响,探讨微孔结构对薄膜透气性、吸湿率、孔隙率、力学性能的影响机制。结果表明:在水系凝固浴中,同时添加钠盐和N,N-二甲基甲酰胺(DMF)可以塑造微孔膜具备相对致密的“皮膜层”,有利于提高力学性能;仅添加DMF制得的薄膜内部虽无明显孔室,但凹凸起伏的褶皱结构能够形成贯通微细通道,透气性能突出;仅添加钠盐参与凝固的样品,膜体内呈海绵状蜂窝多孔结构,且膜皮层和底层具备尺寸相对较大的明显孔眼结构,因而吸湿率较高;乙醇凝固的样品,呈典型闭孔泡沫结构特征,透气、透湿和力学性能适中。

In order to explore the forming condition and the performance of porous PU membrane with asymmetrical heterostructure along the thickness direction,wet method was applied for preparing PU membrane.The microstructure of the as-prepared porous PU membrane was systematically studied upon the effects of the composition and the ratio of the coagulation bath.Besides,the impact of the micropores structure on the air permeability,water adsorption,porosity and mechanical property was discussed and analyzed.The main results found are as follows:When both DMF and NaCl were added into the deionized water coagulation bath,a skin layer with relatively compact structure was observed on the surface,enhancing the mechanical property of the membranes;For samples solidified with the presence of only DMF,the interior of the membrane seemed lack of obvious pores but was mainly characterized by fluctuant pleated structure,which connected together and formed microchannels for air flow,thus resulting in good air permeability;For samples solidified with the assistance of only NaCl,the interior of the membrane was presented as spongy-like honeycomb structure,and the skin and back layer were dotted with large-size pores,which leading to good water absorption.For samples solidified with ethanol,the internal structure was demonstrated as typical closed-cell foam feature,which renders the samples with moderate in air permeability,water absorption and mechanical property.