Performance And Characterization Of Nitrile Rubber Hybrid Damping Materials

The hybrid damping material has a very high loss factor (TanS value, much bigger than that of rubber matrix) and excellent adjustable service temperature range, etc., which has attracted the attention of many researchers. But its poor damping stability (The damping property will decrease with service time) would limit its use. This paper based upon these problems and different preparation technology were used to study the damping mechanism, damping stability, methods to improve damping stability and effect of parameters of fillers on the dynamical mechanical property of nitrile rubber hybrid damping material. The Dynamic Mechanical Analysis (DMA), Cantilever method, Scanning Electron Microscopy (SEM), Fast Fourier Infrared Spectroscopy (ITIR), X-Ray Diffraction (XRD), Differential Scanning Calorimetry (DSC), etc. were used. The main contents and conclusions are as follows:1. The dynamic mechanical properties of the nitrile rubber (NBR)/ 2,2’-methylenebis(6-tert-butyl-4-methyl-phenol) (AO-2246) blends and the NBR/AO-2246/Phenolic novolac resin (PF) blends were discussed respectively and the conclusions are as follows:(a) For binary NBR/AO-2246 blends, The basic damping capacity was determined by the internal friction of polymer. The effect of hydrogen bonds (break of hydrogen bonds) were gradually contributed to the damping property with increasing content of AO-2246 but lower than the critical value of number of hydrogen bonds. When the numbers of hydrogen bonds exceed critical value with further increasing content of AO-2246, the damping capacity of amorphous AO-2246 had a great role on the damping level of NBR/AO-2246 blends, (b) In the ternary NBR/AO-2246/PF blends, the formation of intermolecular hydrogen bonds between NBR and AO-2246 were retarded by the addition of PF. Meanwhile, a large number of interfaces in inner material which were advantageous to widen damping peak width.2. For NBR/AO-2246 blends, the disappeared hydrogen bonds was the major reason compared with crystals that had the negative influence on the damping stability. The crystals formed by means of homogeneous nucleation way, disappeared hydrogen bonds can further increase the numbers of crystals and its size. Furthermore, crystals formed easily at the internal micro-boundary regions and showed multi-crystal topography features. For NBR/AO-2246/PF blends, although the Tanδ value reduced compared with NBR/AO-2246 blends, but its damping stability was improved. The addition of PF is not conducive to the generation of intermolecular hydrogen bonds between NBR and AO-2246 as well as crystals formed from AO-2246.3. For the adverse influence of crystals on the damping properties, two methods were put forward to improve the damping stability and layered hybrid damping composite materials were prepared. The research results indicated that:(a) One-step cure and two-step cure technique were advantageous to improve damping stability. The main reason was lied in the formation of crystals to be suppressed by the cross layer. Simultaneously, two kinds of cure technique brought about decline in the damping peak, this was the result of reduction in the proportion of the middle hybrid damping layer, (b) Compared with hybrid damping material, the glass transition temperature (Tg) of one-step cure and two-step cure samples moved to the low temperature, which was the results of intermolecular migration induced by the mutual penetration and diffusion between crosslink layer and hybrid damping layer. Meanwhile, the damping peak width was effectively broadened by two-step cure technique which caused by the formation of interface between crosslink layer and hybrid damping layer.4. This paper investigated the influence of black carbon (CB), short fibers and sericite powder on the dynamic mechanic property of NBR/AO-2246 blends. The results were listed as follows:The NBR/AO-2246 blends filled with CB displayed a high Tanδ value than that of filling with short fibers which was determined by different topographies and property of fillers. The NBR/AO-2246 blends contained CB, the loss energy were produced by breakdown of carbon black networks formed in inner material as well as the CB moved along the polymer chains which were benefit to damping property. Filling bigger aspect ratio of short fibers into hybrid damping material showed a high damping peak than that of filling small aspect ratio of fibers (That was different from fiber resin based damping material). The larger particle size of CB was favorable to the damping peak width. The damping property, the dynamic storage modulus (E’) and loss modulus (E") were all improved on the condition of filling with sericite powders.5. The Tanδ of ethylene-propylene-diene rubber (EPDM)/polyvinyl chloride (PVC) and chloroprene rubber (CR)/PVC blends were studied respectively by the addition of AO-2246. The results indicated that hydrogen bonds just reacted with PVC instead of nonpolar or polar crystalline rubber. When AO-2246 added into two kinds of rubber/plastic blends, the damping peak values were decreased but improved effectively the altitude of between two damping peaks region. The above results indicated that non-polar crystalline polymer or nonpolar rubber with polar treatment could maximize the damping peak when smaller molecules were added.