Preparation And Property Study Of High-performance Damping Materials Based On Carboxylated Nitrile Rubber

With the rapid development of modern industry,vibration and noise pollution is becoming more and more serious.From an environmental protection point of view, damping materials that can reduce the vibration and noise significantly should be adopted in many cases.Polymeric damping materials are a type of newly developed materials,which can absorb vibration energy due to the characteristic viscoelastic properties of polymers.They can dissipate mechanical or acoustic energy as heat,thus to decrease the amplitude or energy of vibration.Therefore,polymeric damping materials have been widely used in numerous fields such as automobiles,industrial machinery,skyscrapers,household appliances,precision instruments,appliance industries,military equipment,etc.The development of high technology brings higher and higher requirements on damping materials and each field needs more damping materials with broad temperature region,high performance and intelligence.However, most of the damping materials are not satisfied due to their poor comprehensive properties,in particular,they can't possess both good damping and high strength at the same time.Thus,to develop damping materials with excellent comprehensive properties is extremely important.Under such a background,after comparing the advantages and disadvantages of various damping modification methods,we finally choose the recently developed organic hybrid damping modification method,through which organic hybrids with high-performance damping properties can be obtained by adding functional organic small molecules into polar polymers.Based on this novel design concept,the carboxylated nitrile rubber(XNBR) with larger polarity and good damping property was firstly chose as the matrix polymer,and selected functional organic small molecules were added into it to obtain organic hybrids with high damping factor.Then the comprehensive properties of the obtained organic hybrids were further improved by different ways to develop a series of high-performance damping material with better engineering application values.The damping mechanism of prepared materials were further discussed by using a combination of several analysis and testing means,such as dynamic mechanical thermal analysis (DMA),differential scanning thermal analysis(DSC),Fourier transform infrared spectroscopy(FT-IR) analysis,scanning electron microscopy(SEM) observation etc. to provide some theoretical reference for future research in this field.The main research contents and relevant research conclusions of this paper are as follows:1.Preparation and damping properties of binary organic hybrid damping materialsIn this paper,in order to prepare organic hybrid damping materials with high damping factor,two different functional organic small molecules 2,2'-methylenebis(6-tert-butyl-4-methylphenol)(AO-2246) and Pentaerythrityltetrakis -[β-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate](AO-1010) were screened out through some theoretical analysis and experimental tests.Then different binary XNBR/AO-2246 and XNBR/AO-1010 organic hybrid materials were thus obtained by adding them into XNBR matrix.The influence of molding condition and chemical structure of small molecules on the damping properties of binary organic hybrid material were discussed respectively.In order to discuss the influence of molding condition on the damping properties of binary organic hybrid material,unpressed and pressed XNBR/AO-2246 samples were prepared by using different molding conditions and correlations between the microstructure and damping properties of unpressed and pressed XNBR/AO-2246 samples were studied.Results showed that in the unpressed system,most of the AO-2246 molecules existed in the form of crystalline particles.They only acted like inorganic fillers thus decreased the loss tangent(tanδ) peak height of the blend system remarkably to a value lower than that of pure XNBR.Whereas,in the pressed system,AO-2246 were hybridized with XNBR due to the formation of large amounts of hydrogen bonds between them during the hot-pressing and quenching process,thus a special flower-like morphology structure were formed.The addition of AO-2246 can not only increase the tanδpeak height of the blend system significantly up to 3.5 but also shift the tanδpeak position from -21℃to 23℃by adjusting the AO-2246 content.Thus,a new type of XNBR-based high damping composite was obtained.In order to further discuss the chemical structure of small molecules on the damping properties of binary organic hybrid material,pressed XNBR/AO-1010 samples were also prepared and compared with pressed XNBR/AO-2246 samples. Results showed that in the XNBR/AO-1010 hybrid system,most of the AO-1010 molecules dispersed in the XNBR matrix in the form of crystal particles or aggregates and the system exhibited a sea(XNBR-rich matrix)-island(AO-1010-rich domain) morphology due to weak interaction between AO-1010 and XNBR.As a result,a new tanδpeak appeared besides that of XNBR.The AO-1010-rich domain,which was mainly composed of AO-1010 crystals,seemed to act like inorganic fillers thus decreased the tanδpeak of XNBR significantly.However,the tanδvalue between the two tanδpeaks increased gradually with increasing AO-1010 content,showing a broader efficient damping temperature region.Thus,we came to the conclusion that for binary organic hybrid material,different molding condition or chemical structure of small molecules leaded to differences in the number or type of the intermolecular hydrogen bonds between the two components,thus leaded to different dispersion state of small molecules in the matrix and finally resulted in different additive effects on damping properties of binary systems.2.Preparation of ternary organic hybrid damping materials and studies on the damping stability of organic hybrid systemsBased on the analysis and comparison of two binary systems,AO-2246 and AO-1010 were added into XNBR matrix at same time,thus various ternary XNBR/AO-2246/AO-1010 hybrid systems were prepared to further discuss the synergistic effect of AO-1010 and AO-2246 on improving the damping property of XNBR.DMA measurements were carried out on various XNBR/AO-2246/AO-1010 ternary hybrids,results showed that the addition of a small amount of AO-1010(less than 20 wt%) into XNBR/AO-2246 hybrid leaded to not only a significant increase of the tanδpeak height but also a notable enhancement of the tanδpeak temperature, confirming that AO-1010 and AO-2246 indeed have a synergistic effect on enhancing the damping property of XNBR.Besides,it was also showed that the tanδpeak height and its position of ternary XNBR/AO-2246/AO-1010 hybrids could be controlled by varying AO-1010 content or XNBR/AO-2246 weight ratio.Thus,a series of high-performance damping materials with both high damping peak and controllable peak position suitable for different practical requirements were obtained.In order to get some information about the stability of the damping properties of prepared organic hybrid damping materials in practical applications,measurements were carried out on the damping properties of XNBR/AO-2246 hybrids which were aged in room temperature for a long time or annealed at different temperature in this paper.The damping stability of XNBR/AO-2246 hybrids was studied by comparing the changes of their damping properties before and after ageing or annealing.Results showed that after ageing or annealing treatment,the disappearance of strong intermolecular interactions between XNBR and AO-2246 leaded to the reaggregation and crystallization behavior of AO-2246.Thus the tanδpeak height of the hybrids decreased sharply and their high damping properties were nearly bankrupt.This is in accordance with the results found in similar polymer/small molecule blend systems. Nevertheless,it was also found that after reheating,the tanδpeak height of aged samples increased again and reverted to a value as high as even higher than that of the unaged samples due to the existence of reversible intermolecular hydrogen bonding interactions in XNBR/AO-2246 hybrid system.Such heat-reversible effect of the damping properties of XNBR/AO-2246 hybrids was attributed to bafflement of the reaggregation and crystallization behaviors of AO-2246 molecules by the recombination of the strong intermolecular hydrogen bonds between XNBR and AO-2246 molecules.Thus,XNBR/AO-2246 hybrids can be used as a new type of thermally recycling rubbers.Furthermore,studies on the damping stability of ternary XNBR/AO-2246/AO-1010 hybrid system during annealing process revealed that the addition of a small amount of AO-1010 into XNBR/AO-2246 hybrids obstructed the crystallization behavior of AO-2246 to some extent and finally improved the damping stability.Thus,a series of XNBR-based high-performance damping materials with high damping peak and controllable peak position as well as better damping stability can be designed by changing the composition of ternary XNBR/AO-2246/AO-1010 hybrid system.3.Preparation of high-performance damping materials by combination of fiber reinforcement and organic hybridizationAs to the low-modulus limitation of XNBR/AO-2246 organic hybrids,combination of fiber reinforcement and organic hybridization was adopted in order to develop a high-performance damping material with both high modulus and good damping property.After comparing the additive effects of Kevlar pulp(KP) and short carbon fiber(SCF) on the damping property of XNBR matrix,we finally selected SCF as the reinforcement fiber and combined its reinforcement effect with the hybridization effect of AO-2246.Thus,a series of ternary XNBR/SCF(90/10)/AO-2246 and XNBR/AO-2246(50/50)/SCF hybrid samples were prepared and measurements were made on their dynamic mechanical properties.Results showed that by the incorporation of AO-2246 into binary XNBR/SCF(90/10) system,the tanδpeak height increased remarkably while maintained a high modulus,at the same time,the tanδpeak position could be controlled by varying AO-2246 content to meet different practical requirements.Thus,a type of high-performance damping materials with both high modulus and good damping properties were obtained by adding AO-2246 into binary XNBR/SCF(90/10) system.It was also showed that by the introduction of SCF into binary XNBR/AO-2246(50/50) system,although the tanδpeak height was decreased to some extent,the tanδ_max value was maintained above 2.5,which was still much higher than that of most SFRC materials.While maintaining such a high damping factor,the modulus of ternary XNBR/AO-2246(50/50)/SCF system was improved significantly due to the reinforcement effect of SCF.Thus,a type of high-performance damping materials with both good damping properties and high modulus were obtained by adding SCF into XNBR/AO-2246 organic hybrids.These results confirm that a new type of high-performance damping material possessing both high modulus and high damping peak with controllable peak position can be obtained by combination of fiber reinforcement and organic hybridization. Therefore,combination of fiber reinforcement and organic hybridization can be considered to be a new way of developing high-performance damping materials with better engineering application values.