Study Of Microcapsule-based Self-healing Cellulose Membrane

In the context of rapid development of science and technology,polymer materials have been widely used in various fields of life which demands the consuming of petrochemical resources.For the exploitation of petroleum resources has led to environmental pollution,develop and research materials that meets the strategy of sustainable development has been the focus of our society.Selfhealing technology can detect the damage initiatively in the material and repair the damage under certain conditions,which is an ideal long-term operation of polymers and owns broad development prospects.Traditional self-healing materials are mostly used in protective coating and cement,while the application in membrane industry is still limited.Cellulose membrane can be applied as packaging membrane,dialysis membrane and separation membrane.It is of great significance to apply self-healing technology in cellulose membrane to extend its life span.Notably,compared with other self-healing system,microcapsule-type self-healing systems have been extensively investigated due to its ease of preparation and applicability and ability to heal microscopic cracks.In our research,we prepared a self-healing regenerated cellulose membrane,an all-in-one photo-initiated microcapsule was fabricated and embedded into the cellulose membrane,giving an unprecedented application of self-healing technology based on microcapsules.The selfhealing procedure is environmentally friendly and avoid emission of volatile organic compounds.Microcapsules with a poly(urea-formaldehyde)shell was fabricated through two-step in situ polymerization,using aliphatic polyurethane acrylate,HDDA and photoinitiator as core material.The influence of,stirring speed,ratio of core to shell,reaction p H value on the surface morphology,particle size distribution and encapsulation percent was investigated to find the optimizing preparation condition.The optimum condition is as follows: Gum arabic as emulsifier,stirring rate at 500 rpm,ratio of core wall is 1.5:1,reaction p H value is 2.5~3.5.As-prepared microcapsule was characterized by infrared spectroscopy(FTIR)and thermogravimetric analysis(TG).The results showed that the core material was successfully encapsulated,thermal stable temperature of microcapsule is 226?.Self-healing behavior was observed by optical microscopy when microcapsules was applied to epoxy coatings.The preparing conditions of self-healing cellulose membrane were investigated.The results showed that the concentration of cellulose solution was determined to be 4wt% and the coagulating bath was determined to be anhydrous ethanol.Cellulose membrane with different mass fraction of microcapsules were prepared,and the cellulose membranes were characterized.These membranes was characterized by Scanning Electron Microscopy(SEM),Energy Dispersive Spectrometer(EDS),X-ray diffraction(XRD),Tensile strength and extension,Contact Angle(CA),Water vapor permeability(WVP)and Thermogravimetric(TG).The results demonstrated the as-prepared cellulose membrane was smooth and dense,microcapsules in cellulose membrane was integrated.The addition of microcapsules slightly increased the crystalline of cellulose membrane,the preparing process of cellulose membrane transformed its crystal form from cellulose ? into cellulose ?.With the mass faction of microcapsules increased,the extension of cellulose membrane first increased and then decreased,the tensile strength of cellulose membrane was decreased,the wettability of cellulose membrane was lowered,the WVP of cellulose membrane increased,thermal stable temperature of self-healing membrane is 226?.The self-healing behavior and chemical structure cellulose membrane containing 9wt% microcapsule was investigated by Confocal Laser Scanning Microscope(CLSM),EDS and FTIR.The results showed that the fracture crack in self-healing cellulose membrane was successfully repaired by core material after irradiated under UV light for 20 min due to the formation of hydrogen bond between the cellulose film and the polyurethane acrylate,indicated that applying this selfhealing method in cellulose membrane gained good healing effect.