| Rice husk ash(RHA), which is an agricultural waste, is used as filler to preparerubber materials. It has many advantages by using RHA, such as cheaper cost, savingenergy, reducing stacking for RHA, protecting environment, sustainable use ofresources. Furthermore, rubber composites filled by RHA has virtues of low density,good abrasion performance, high filling, biodegradability. However, the properties ofrubber composites are easily affected by RHA, which can agglomerate and disperdifficultly into rubber matrix due to extenal hydroxy. Many modification methodincluding preliminary modification together with in-situ interface modificationbetween NBR and RHA interface were used improving dispersibility of RHA andinteraction of NBR-RHA interface in this paper. NBR/RHA composite cured coatingsand NBR/RHA composite foamed coatings were prepare, and the effect ofmodifications mentioned above on microstructure structure, cell morphology andproperties of these coatings also were investigated. Meanwhile, NBR/RHA/ZDMAhybrid cured coatings and NBR/RHA/ZDMA hybrid foamed coatings filled by RHAand in-situ formed ZDMA were prepared and researched. Finally, the applicationexample was provided, namely preparing rubbber-metal composite sealings applied tosealing or noise reduction, playing a role in sealing, shock resistance, damping, soundabsorption, thermal insulation. The research was significant for energy saving,together with mitigating risk of environmental pollution caused by leakage of organicsolvent and fuel, and noise pollution caused by vibration of mechanical parts. Themain research contents as follows:Firstly, solubility parameter of NBR was calculate by using group contributionmethod, and the range of solvent solubility parameter was determined, Sencondly,hydrogen bond, volatile speed of solvent, environmental impact and price were takeninto account. Then, the solvent used for dissolving NBR N32was determined finally.The preparation technology of NBR foamed coatings filled by carbon black wasdiscussed. The main technological parameters, namely blowing content, blowingtemperature, curing system and cabon black content, were studied by means of toluene swelling test, axio imager test, mechanical properties test, aging resistancetest and fluid resistance test and so on, then superior process route and recipe wereacquired.NBR/RHA composite cured coatings and NBR/RHA composite foamed coatingsfilled by RHA were prepared through liquid blending process. RHA was preliminarymodified by many kinds of modifiers such as Si69, KH550, KH560, and MAH, thenthe effect of preliminary modification on dispersibility of RHA and adhesion ofNBR-RHA interface, together with microstructure, cell morphology, mechanicalproperties, heat stability, fluid resistance of NBR/RHA composite cured coatings andNBR/RHA composite foamed coatings were studied by dispersibility testing, boundrubber testing, toluene swelling testing, SEM, mechanical properties testing andTGA-DTG and so on. The result showed that by means of20%Si69, dispersibility ofRHA, and adhesion of NBR-RHA interface, together with crosslink densities, fluidresistance, mechanical properties testing and heat stability of NBR/RHA compositecured coatings and NBR/RHA composite foamed coatings were superior in genaral,meanwhile cell size and distribution were uniform for NBR/RHA composite foamedcoatings.NBR/RHA composite cured coatings and NBR/RHA composite foamed coatingswere in-situ interfacial modified using interfacial modication MAA. The effect of in-situ interfacial modification using MAA on NBR-RHA interface reaction, theevolution of crosslink network together with mechanical properties, fluid resistance,heat stability of NBR/RHA composite cured coatings and NBR/RHA compositefoamed coatings were studied. The result showed that by adding MAA intoNBR/RHA blends, NBR matrix bonded with RHA by graft copolymerization withcomplexing of in-situ formed ZDMA for one hand, and by graft copolymerizationwith hydrogen-bond interaction of MAA for another hand. Furthermore, in-situformed ZDMA polymerized as poly-ZDMA nano particle and dispersed into NBRmatrix, so as to reinfore NBR/RHA composite cured coatings and NBR/RHAcomposite foamed coatings. Finally, the dispersibility of RHA was improved due tointerreaction of RHA and MAA or RHA and ZDMA. Meanwhile, the mechanicalproperties, fluid resistance, heat stability of NBR/RHA composite cured coatings and NBR/RHA composite foamed coatings by using interfacial modifier MAA, moreover,cell average diameter, porosity, expanding ratio increased, and cell density ofNBR/RHA composite foamed coatings decreased, when MAA content was higherthan10phr, the cell was easy to break and combine.Overall consideration, when the contents of MAA were12phr and10phrrespectively, the integrated performance of NBR/RHA composite cured coatings andNBR/RHA composite foamed coatings were superior.NBR/RHA/ZDMA hybrid cured coatings and NBR/RHA/ZDMA hybrid curedcoatings which were filled by RHA and in-situ formed ZDMA were prepared byliquid blending process. The effect of in-situ formed ZDMA on NBR-RHA interfacereaction, cell Morphology and the forming and evolution of crosslink network werediscussed by the testing of total crosslink density, covalent crosslink density, ioniccrosslink density, combined with the testing of XRD, SEM, mechanical properties,fluid resistance, and TGA-DTG and so on. When researching on NBR/RHA/ZDMAhybrid cured coatings, the evolution of crosslink network during curing wasinvestigated, moreover, the model of crosslink network was obtained. The resultindicated that the fundimental rubber network formed rapidly in the initial7min, afew ionic crosslinks also appeared, and the whole crosslinked network was dominatedby covalent crosslinks. As the curing process in progress, the ionic crosslinksincreased while the covalent crosslinks only increased a little. WhenNBR/RHA/ZDMA hybrid cured coatings vulcanizated over, the covalent crosslinksand developed ionic crosslinks constituted the whole crosslink network which thecovalent crosslinks was dominant. In-situ formed ZDMA was trigger by free radicalof DCP and then reacted homopolymerization and copolymerization with NBRduring vulcanization. The copolymerization formed ionic crosslinks.When ZDMAcontent was higher than20phr, the cell was easy to break and combine, meanwhilecell size and distribution were ununiform for NBR/RHA/ZDMA hybrid foamedcoatings. Overall consideration, when the contents of ZDMA were30phr and20phrrespectively, the integrated performance of NBR/RHA/ZDMA hybrid cured coatingsand NBR/RHA/ZDMA hybrid foamed coatings were superior.Rubber-metal composites containing NBR foamed coatings filled by carbon black, together with NBR/RHA composite foamed coatings, NBR/RHA compositecured coatings, NBR/RHA/ZDMA hybrid foamed coatings, and NBR/RHA/ZDMAhybrid cured coatings filled by RHA, were prepared by liquid blending process. Theywere studied on basic properties of NBR-metal composites applying in sealing field,as well as on acoustical performance of NBR foam-metal composites containing NBRfoamed coatings filled by carbon black, together with NBR/RHA composite foamedcoatings, NBR/RHA/ZDMA hybrid foamed coatings filled by RHA. Furthermore, thecontribution of RHA filler and microcellular structure on sound absorption and noisereduction were discussed. The prepared composites mentioned aboved could be usedfor sealings, as well as damping with reducing noise in mechanical equipment andmotor vehicle, it extended orientation of management of transportation noise andindustial noise. |
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