Preparation And Characterization Of The New In-situ Synthesized Nanocomposite Foaming Material Modified With Silane Coupling Agent

Compared with the common foaming material, the microcellular foamscould result in better mechanical and thermal properties and was considered tobe the21st century new material. However, the foaming agents used in theearlier studies to prepare microcellular foams were mainly supercritical fluid.Besides, the preparation process of microcellular foams needed the extremepreparation conditions. To solve this problem, it came to our mind that wecould prepare the novel organic-inorganic nanocomposite foaming agent torefine the particle of the foaming agent and decrease the size of the cells. Thebiurea intercalated montmorillonite (LDA-MMT) was prepared via in-situsynthesis. The foaming performance of the novel foaming agent was studiedafter the surface modification. The main research achievements were asfollows:(1) Using the urea intercalated montmorillonite (Urea-MMT) as theprecursor, the novel nanocomposite foaming agent LDA-MMT was preparedvia the in-situ synthesis process when the hydrazine (HY) was introduced at a suitable condition. The influence of the concentration and the amount of theadded HY were investigated using the various characterization methods. XRDresults showed that the concentration of HY greater than40%and the ratio ofn (NH2NH2): n (CO(NH2)2)≥20was essential for the formation of thenanocomposite giving a d001spacing of1.76nm which was different from thatof Urea-MMT (d001=1.71nm). The new in-situ synthesized nanocompostieLDA-MMT was characterized by techniques such as FT-IR, NMR andTG-DSC, etc.(2) The dispersibility of the nanocompostie LDA-MMT was improvedafter the modifications by silane coupling agents KH-550, KH-560andKH-570. The SEM showed the best dispersibility of the KH-570modifiedsample. The XRD results revealed that the oligmers of KH-550wasintercalated into the interlayer space of MMT and led to the increase of d001ofthe nanocomposite from1.76nm to2.19nm. However, the KH-560andKH-570mainly modified the outer surface of LDA-MMT and had little effecton the interlayer distance.(3) The KH-570modified LDA-MMT nanocomposite was applied to theextrusion foaming experiments of the polymer including epoxy,polypropylene (PP) and high density polyethylene (HDPE). The resultssuggested that HDPE seemed suitable for foaming with LDA. Compared withthe foaming material made by pure LDA, the new nanocomposite foamingagent resulted in the much smaller cell size and highly uniform cell structure. The average cell diameter could be reduced from200μm to100μm.For the purposes of this study, it may not only widen the research andapplication fields of the organic-inorganic functional materials but alsoprovide a perspective way for preparing the microcellular foams in a mildcondition.