Fabrication And Characterization Of Composite Membranes Based On Medical Polyurethane

To develop a new fine performance dressing is imperative. So the wound dressing shouldpossess the following properties: the dressing must be capable of covering the wound andabsorbing the exuded liquid from the wounded area; the dressing should no microbial transportbut allow water evaporation at a certain rate; the material should be soft and flexible to reducethe patients’ pain. Biomedical polyurethane （PU） is well-known for its outstanding propertiesdue to its segmented polymeric character. Thus, PU has been used as a potential biomaterial suchas artifical hearts, catheters etc. As a wound dressing, animal and clinical trial has been provedthat PU films non-toxic, without excitant. However, PU films are mostly used on dry or lowexudates wounds, so with. Therefore improve current PU membranes low water absorption andmoisture permeability is the focus.In this work, acetic starch （ASt） or poly （ethylene glycol）（PEG） was chosen to fill in twokinds of PU （PUa, PUb） which were different sources as raw materials according to two speciesmoisture transmission mechanism, i.e. adsorption-diffusion-desorption and permanent porestructure. The influence of different film ways to the water absorption, moisture permeability andmechanical properties of composites were discussed; variation trend of the water absorption,moisture permeability and mechanical properties with increase of the content of filling materialswas studied; discusses the filler material on blend membrane density and porosity, and theinfluence of the composite membranes microstructure and chemical structure changes; and thebacteria penetration and biodegradability were also investigated.After investigation of the influence of film forming by dry method at70℃and at roomtemperature and wet method on water absorption, moisture permeability of polyurethane filmsand so on, ultimately the wet method was choosen. The influence on the morphology feature ofPU-based composite membranes with the introduction of ASt and PEG was discussed. Theresults showed ASt make larger influence on PUa, but the effect is not evident to PUb. Thecross-section morphology of PUa/PEG membranes presented a sponge-like sublayer structurederiving from PEG solubility in water, while making the PUb’s porous structures became tight.Because of changes of the structure, the blend membrane changes in density, porosity.The resultrevealed that the water absorption and water vapor transmission rate increased significantly asthe introduction of ASt, the water absorption rate ranged from20.0%to129.3%. With the content of PEG increased, the water absorption and water vapor transmission rate of PUa/PEGcomposite membranes were improved, WVTR ranged from2830g·m^-2·day^-1to4939g·m^-2·day^-1,while the PUb’s decreased. The mechanical properties of composite membranesexhibited a descending trend with the increase of additives content, while PEG greatly increasedmechanical properties of the PUb’s mechanical properties, whereas all membranes presentedexcellent elasticity.Resistance of bacteria showed that ASt and PEG added resistance of bacteriadoes not affect the two types of polyurethane. Degradation results show that ASt and PEGintroduced to increase the speed of degradation of polyurethane membranes, and lysozymeparticipation conditions, degradation rate significantly higher than not added lysozyme.The introduction of ASt in PU can improve the water absorption and moisture permeabilityobviously. The water vapor transmission rate of composite membranes ranged from1442g·m^-2·day^-1to7396g·m^-2·day^-1, which can meet the requirements of different degrees of woundon medical dressings, with broad application prospects in the clinic.