Studied On Preparation And Application Of Hydrophobic Waterborne Polyurethane

Because the use of solvent-based polyurethane(PU)can cause severe solvent pollution,the development of environment-friendly PUs,especially waterborne polyurethane(WPU),has gradually become one of the main research directions in this field.However,the addtion of carboxylate during the synthesis of WPU leads to its poor water resistance and its properties have been reduced.which limits the use of the WPU.According to the requirement of the surface treatment of synthetic leather,a step-by-step polymerization method was adopted to synthesize the silicon-containing WPU suitable for the surface treatment of synthetic leather.The structure and properties of different types of silicon-containing WPU were studied.The main research contents and results are as follows:The 3-isocyanatemethylene-3,5,5-trimethylcyclohexyl isocyanate(IPDI),polyoxypropylene glycol(PPG2000)as the main raw materials,and dimethylamino propionic acid(DMPA)as the hydrophilic chain extender,1,4-butanediol(BDO)was a small molecule chain extender,andtrimethylolpropane(TMP)was used as a cross-linker.Polyether WPU(PE-WPU)was prepared by a step-by-step polymerization method and its structure and properties were studied.The experimental results show that when the R value(isocyanate index)is 1.7,the hydrophilic group content is 5%,and the amount of cross-linking agent is 0.72%,a stable and transparent PE-WPU emulsion can be obtained.Fourier transform infrared spectroscopy(FTIR)showed that the isocyanate(NCO)groups were almost completely reacted.Thermogravimetric(TGA)showed that the PE-WPU film began to decompose around 241.3?,and when it reached 434?,it was completely decomposed.X-ray diffraction(XRD)indicated that the crystalline peak of PE-WPU film appeared at 2?=18.5.and Atomic force microscopy(AFM)showed a slight phase separation of the PE-WPU film.IPDI,PPG2000,TMP,DMPA,BDO and macromolecular hydroxy silicone oil(HPDMS9950)as the main raw materials,block-type silicon-containing PE-WPU(Si-PE-WPU-1)was prepared by a step-by-step polymerization method,and the relationship between its structure and properties was studied.The experimental results show that with the increase of HPDMS9950 dosage,the particle size of Si-PE-WPU-1 emulsion increases sequentially and the stability gradually decreased,the tensile strength and elongation at break of Si-PE-WPU-1 film decreased,the hardness of Si-PE-WPU-1 film increased.The contact angle increased from 63.95?to 122.2?.The hydrophobicity increased and the transparency decreased.XRD showed that the crystallinity of the Si-PE-WPU-1 film decreased with the increase of the silicon-containing segment in the Si-PE-WPU-1 molecular.AFM indicated that Si-PE-WPU-1 film has a certain degree of phase separation.IPDI,PPG2000,TMP,DMPA,BDO and double-tailed hydroxy silicone oil(DSE)as the main raw materials,Side-chain silicon-containing PE-WPU(Si-PE-WPU-2)was prepared by step-by-step polymerization method,and studied the relationship between its structure and performance.The experimental results showed that with the increase of the DSE dosage,the particle size of the Si-PE-WPU-2 emulsion gradually increased,and the stability gradually decreased,the tensile strength and elongation at break of Si-PE-WPU-2 film increased first and then decreased,hardness and hydrophobicity increased.TGA shows that Si-PE-WPU-2 film rapidly decomposes at 230 ?,reaches the maximum decomposition rate at 371?,and completely decomposes after 432?.XRD showed that the phase separation of Si-PE-WPU-2 film was very obvious.IPDI,PPG2000,DMPA,BDO,TMP,and DSE as the main raw materials,NCO-terminated prepolymers were synthesized and then capped with siloxane-terminated polysiloxane(PDMS-PC)to prepare the Capped Silicon-Containing PE-WPU(Si-PE-WPU-3),and studied the relationship between its structure and properties.The experimental results show that with the increase of PDMS-PC dosage,the transparency of Si-PE-WPU-3 emulsion gradually and emulsion stability decreased,the emulsion particle size increased sequentially,the tensile strength and elongation at break of the Si-PE-WPU-3 films decreased gradually,and the hardness and hydrophobicity increased in order,and the transparency decreased significantly.XRD indicated that the hydrophobic PDMS-PC segment increased the degree of phase separation of the Si-PE-WPU-3 film.The research results of the paper provide technical data and theoretical basis for the preparation of silicon-containing WPU,and provide a new technical solution for the aqueous surface treatment of synthetic leather.