Preparation Of Organic-Inorganic Doped Microcapsules And Tribological Properties Of Polymer Composites

In this thesis,methyl silicone oil as core material,melamine-formaldehyde(MF)and zinc oxide nanorods(ZONs)as hybrid shell materials,Melamine-formaldehyde single wall material microcapsule(SWLMs)and melamine-formaldehyde/zinc oxide binary shell microcapsule(BSLMs)were synthesized by in-situ polymerization.Epoxy resin(EP)and cyanate resin(CE)were adopted as matrix,the EP/SWLMs and EP/BSLMs 、 CE/SWLMs and CE/BSLMs composites were prepared by casting polymerization.The morphology of the SWLMs and BSLMs was characterized by scanning electron microscopy(SEM).The thermal stability of the SWLMs and BSLMs composites was measured by thermogravimetric analysis(TGA).The tribological and mechanical properties of the SWLMs and BSLMs composites were tested by MRH block-on-ring high speed friction tester and universal tensile testing machine.At the same time,the lubrication and wear mechanism of the composites were discussed as well.The results demonstrated that:By optimizing the synthesizing conditions,the best condition for the preparation of BSLMs is: the temperature of reaction was 55℃,pH=6,the stirring rate was300 rpm,the amount of ZONs accounts for 8 weight percent of MF and the optimum adding time of ZONs was 20 min after adjusting pH to 6.The as-prepared BSLMs have a novel structure and the addition of spherical regular ZnO nanorods makes the microcapsules exhibiting a "sea urchin-like" structure.The microcapsules have good compatibility with the matrix and can distribute uniformly in the matrix.The particle size is 4.0±0.5mm.The thermal mechanical properties and tribological properties of EP/SWLMs and EP/BSLMs composites were studied.The results showed that the BSLMs have a distinct structure and intact package in EP matrix;When 25% SWLMs was added,the initial decomposition temperature(IDT)of the composites decreases greatly.However,as 25% BSLMs was incorporated,the IDT of the composites was increased by 120℃;The tribological properties of EP/SWLMs and EP/BSLMs composites were measured as well.When 25% BSLMs was added,the average friction coefficient and wear rate of EP/BSLMs composites were decreased by 57.68% and 45.2% compared with the pure EP,respectively;The mechanical properties of EP/SWLMs and EP/BSLMs composites were analyzed and the results showed that the mechanical properties of EP/SWLMs composites were greatly decreased due to the low mechanical propertiesof MF shell and plasticization effect of silicone oil.When 25% BSLMs added into the EP matrix,the tensile strength and modulus of composites were increased by 7.53%and 5.92% and the flexural strength and flexural modulus increased by 5.39% and3.72%,respectively,compared with the pure EP.The results for the CE composites show that the as-synthesized BSLMs have a clear structure in CE matrix.The thermal stability of the CE/SWLMs and CE/BSLMs composites shows that: the initial decomposition temperature of pure CE is 250℃,the IDT of CE/25% SWLMs composites decreases to about 180℃.When 25% BSLMs microcapsules were incorporated,the IDT was increased ~130℃.For the friction and wear properties of CE/SWLMs and CE/BSLMs composites,it was found that the addition of BSLMs could improve the friction and wear properties of CE resin matrix.When 25% BSLMs was added,the average friction coefficient and wear rate of CE/BSLMs composites were decreased by 48.81% and 30.37%,respectively.Due to the strengthening effect of ZONs,the tensile strength/modulus and the flexural strength/modulus of CE/BSLMs composites were increased by 4.54%,3.55% and11.76%,4.54%,respectively.This indicates that zinc oxide inorganic nanoparticles can improve the mechanical properties of the composite while making the composites exhibiting excellent self-lubricating properties which greatly improved the comprehensive service efficiency of the composites.