Preparation And Property Evaluation Of Waterproof And Breathable Polyurethane Microporous Film

Waterproof and breathable polymer film and coatings are permeable to water vapour molecules and not to permit water droplets to penetrate through them. Garments coated with these film and coatings not only are waterproof but reduce the build-up of moisture vapour emitted from the body as perspiration inside the taditional foul-weather clothing, which leads to an increasing sense of discomfort. Based on the mechanism of waterproof and breathability , this kind of polymer film and coatings can be classified into three types: micropore, hydrophilicity and shape-memory polymer film and coatings. By adjusting the size of pore, microporous film and coatings can achieve waterproof and breathability. Hydrophilic ones are nonporous and can transport water vapour molecules by molecular diffusion (according to the sorption-diffusion model) through the polymer matrix. The last ones can also get the same properties through adjusting the class transition temperature of polymer. Because this kind of film and coatings can also serve as a barrier membrane to dust or pathogens, they are finding increasing use in medical field, such as wound dressing, multiple-use protective garments and medical glove and so on, which present a specially interesting challenge.Polymer used for waterproof and breathable film and coatings aremainly multiblock copolymers of AB type, Block-copolyether-ester(PEE), Block-copolyether-amide(PEBA) and Polyurethane(PU) etc.. Among them, polyurethane is more preferable.In order to achieve better breathability, blends of Polyethylene glycol (PEG) and Poly(tetrahydrofuran)(PTHF) are used to banlance physical properties. PEG is more hydrophilic, while PTHF is mechanically tougher and does not swell as much.In this paper, a series of polyether-based thermoplastic polyurethanes were synthesized with 4,4' -diphenylmethane diisocyanate(MDI), 1,4-butanediol(BDO) as hard segment and poly(tetrahydrofuran)(PTMG) and polyethleneglycol(PEG) as soft segment by the method of bulk two-step process. Fourier transform infraned spectroscopy (FTIR) and differential scanning calorimetry (DSC) are used to characterize their structure. The results show that compatibility between hard and soft segment is increased, which is helpful for improving breathability. Mechanical properties, water contact angles and water adsorption tests reveal that different soft segments have significantly efficacy to optimize the physical properties. This kind of polyurethanes not only possesses good mechanical properties but has good hydrophlicity. Blood compatibility is mainly determined by the hemolysis test and platelet adhesion test. The ratio of platelet adhesion on this material becomes lower because there are more hydrophlic groups in its composition, which contributes to its better blood compatibility.Furthermore, the preparation process of waterproof and breathable polyurethane microporous film was presented in this paper, which was based on three aspects, such as polyurethane concentration, precipitant bath composition and immersion time. Mechanical property, waterproofness and breathability of the microporous films were tested. The results indicate that the average diameter of the pore is about 2. 5 microns orIVless, and the pore is uniformly distributed. The Water Vapour Transmit rate(WVT) of microporous films is higer than the corresponding nonporous films, and the waterproofness declines correspondingly.