PU/PNIPAM semi-IPN微孔膜温度响应性研究

将聚氨酯(PU)与聚N-异丙基丙烯酰胺(PNIPAM)半互穿网络聚合物(semi-IPN)通过浸入沉淀相转化方法制备成微孔膜,并从亲水性、吸水溶胀性以及透湿性等方面对其温度响应性进行了讨论.PNIPAM的引入使膜的亲水性、吸水性和透湿性大为改善,并显著提高了膜的温度响应能力;但与此同时也使得膜的韧性降低.当PU/PNIPAM为3/1时,可获得最好的综合性能.同传统无孔致密膜相比,PU/PNIPAM semi-IPN微孔膜的透湿机理是基于微孔的开闭,在维持显著的温敏透湿性的同时可实现较高的高温透湿量.

TEMPERATURE-SENSITIVITY OF PU/PNIPAM SEMI-IPN MICROPOROUS MEMBRANES

In order to achieve fabrics with both good warmth retention at low temperature and fine sweat volatility at high temperature,a novel semi-interpenetrating polymer network(semi-IPN) based on polyurethane(PU) and poly(N-isopropylacrylamide)(PNIPAM) was synthesized via the strategy of in situ crosslinking polymerization,and the semi-IPNs were fabricated into microporous membranes by immersion precipitation phase inversion method.The relationship of the morphology and porosity of the membranes with the chemical structure of the semi-IPNs and fabrication parameters of membranes was investigated.The hydrophilicity,swelling properties and water vapor permeability of the membranes at various temperatures were then evaluated and compared.Generally,the water contact angle decreases with the introduction of PNIPAM content in the semi-IPN.Therefore,the PU/PNIPAM semi-IPN membranes have better hydrophilicity than the membranes prepared from pure PU.On the other hand,the surface hydrophilicity of the semi-IPN membranes is inhibited at high temperatures.The temperature-sensitivity was also found in the swelling properties of the semi-IPN membranes.The equilibrium swelling ratio(ESR) of PU membrane increases slightly with temperature.But with the increase of PNIPAM content,the membrane ESR decreases significantly with temperature,revealing the obvious volume contraction of the semi-IPN material at high temperatures,which is endowed by the hydrophilic-hydrophobic transition of PNIPAM with temperature.The pore diameter of the semi-IPN membranes is therefore enlarged.The enlargement could be confirmed by the results in water vapor permeability(WVP).The WVP of PU membrane at 50℃ is about 2 times of that at 25℃,which is caused by the enhancement of vaporization rate and molecular mobility of water vapor.In contrast,the WVP of semi-IPN membranes at 50℃ can reach more than 4 times of that at 25℃.These results prove that by the method proposed in this paper,membranes with fine temperature-sensitivity and high water vapor permeability can be prepared,and such membranes are highly valuable in the applications of intelligent garments.