Preparation And Interfacial Properties Of Regenerated Protein Fiber Powder Composite Films

As a kind of natural polymer material,protein fiber has its unique and excellent performance.However,due to the requirements of textile processing,there are a lot of scraps and wastes after the processing and use of protein fiber,resulting in a serious waste of resources.It is of great significance for the development of society to realize the effective recycling of protein fiber and the sustainable development of natural resources.At present,it is an effective way to widen the application of the protein fiber by filling polymer with protein fiber powder.Polyurethane,a kind of hard and soft block copolymer,has good mechanical properties and chemical stability,and is widely used in textile,biomedical and environmental energy fields.Numerous studies have shown that polyurethane filled with unmodified powders have poor mechanical properties.Therefore,it has a vital significance to find a molding method that can regulate the interfacial forces between unmodified filler particles and polymer matrix.Combined with the DMF/Toluene binary solvent system previously studied by our research group,it can regulate the rearrangement of the polyurethane molecular chain during the molding process and improve the interface force between unmodified inorganic materials and polyurethane.In this paper,the effects of unmodified silk powder(SAA),down powder(SDP)and leather powder(LP)on the microstructure and mechanical properties of polyurethane(PU)composite film prepared by DMF/Tolunene system were studied,and the leading factors for the difference in interface strength between three different unmodified particles and polyurethane were further analyzed.The main conclusions are as follows:(1)High toughness and high filling silk fiber powder/polyurethane composite films were prepared.The unmodified SAA particles with high filling content can improve the moisture regain,moisture permeability and UV resistance of PU film,especially the barrier property of UVA.Compared with DMF system,SAA/PU films prepared by DMF/Toluene solvent system have excellent mechanical properties.When the SAA particles filling amount is up to50 wt.%,the stress,strain and toughness of SAA50%/PU film are 208.70 %,84.77 % and656.78 % higher than that of the composite film prepared by DMF solvent system.(2)High toughness and high filling down fiber powder/polyurethane composite films were prepared.The unmodified SDP particles with high filling content can improve the moisture regain of PU film.When the SDP particles filling amount is 50 wt.%,the moisture permeability and water absorption of the PU composite film are about 3 times and 20 timesthat of the pure PU film.Compared with DMF system,SDP/PU composite films prepared by DMF/Toluene solvent system have excellent mechanical properties.When the SDP particles filling amount is up to 50 wt.%,the stress,strain and toughness of SDP50%/PU film are461.80 %,83.64 % and 955.37 % higher than that of the composite film prepared by DMF solvent system.(3)High toughness and high filling leather fiber powder/polyurethane composite films were prepared.The unmodified LP particles with high filling content are beneficial to improve the moisture regain of PU film.Meanwhile,PU improves the solvent resistance of LP particles.Compared with DMF solvent system,LP/PU composite films prepared by DMF/Toluene solvent system have excellent mechanical properties.When the LP particles filling amount is up to 20 wt.%,the stress,strain and toughness of LP20%/PU composite film are 648.36 %,110.94 % and 1448.87 % higher than that of the composite film prepared by DMF solvent system.(4)The theoretical value of adhesive force between different particles and PU matrix were calculated,and the leading factors for the difference in toughening of different particles were put forward.Theoretically,according to the interface wetting action principle,the order of binding force of three packing particles and PU matrix is SAA > LP > SDP.The incomplete consistency between theoretical results and experimental results is mainly due to the differences in particle morphology and dispersion in PU matrix.Among them,the shape and size of SAA aggregates are the most orderly,and the stress is more uniform and easier to be transferred during the stress loading process.Therefore,the mechanical properties of SAA/PU composite films are optimal under the same particle filling amount.However,LP with irregular particle shape and large aggregate size is easy to form stress concentration and has the worst mechanical properties.Therefore,DMF/Toluene solvent system can improve the interfacial force between unmodified protein fiber powder and PU martix in the process of film formation,and the preparation of high-tenacity protein fiber powder/polyurethane composite material provides an effective way for the efficient recovery and utilization of waste protein fiber powder.