Preparation And Damping Properties Of Polar Small Molecule/Nitrile-Rutadiene Rubber Hybrids

The visco-elastic properties of rubbers make them ideally suitable for applying as damping materials and finding numerous applications in the building, aircraft, automobile, and machinery industries both for the reduction of unwanted noise and the prevention of vibrational fatigue failure. In recent years, organic small molecule/polymer hybrids have attracted great interest, both in industry and in academia. Compared with conventional damping materials, they often exhibit remarkable improvement in damping properties. There has been considerable interest in theories of preparation and the relation of properties and microstructure.Two organic small molecules were studied to prepare rubber hybrids with nitrile butadiene rubber (NBR) in this paper. The NBR/polar small molecule rubber hybrids were successfully developed by applying the adopted preparation procedure/conditions. The influence of matrixes, small molecules and preparation procedure/conditions on the structural, damping and mechanical properties of hybrids were systematically investigated by using the instrumentation of DSC, SEM, XRD, FTIR, DMA and tensile tester and the mechanism of forming the hydrogen bonding network was primary expatiated. On the base of that, the effect of cabon black/silica reinforcement on the damping and mechanical properties of hybrids were tentatively explored and found some interesting results.Followed contents have been studied in this paper:A NBR/hindered phenol hybrid was successfully prepared by mixing3,9-bis[1,1-dimethyl-2{b-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy}ethyl]-2,4,8,10-tetraoxaspiro[5,5]-undecane (AO-80) into NBR (N220S with the acrylonitrile percentage of41wt%). The character band of hydrogen bonded hydroxyl group appeared in the infrared spectra of the hybrids, and the OH band shifted to the low wave number direction. NBR/AO-80hybrid showed single relaxation transitions, and the glass transition temperatures (Tg) increased prominently with an enhancing amount of AO-80in the hybrids. Associated with the results of SEM and TEM, AO-80dispersed in molecular-level and formed AO-80enriched phase in the NBR matrix when the addition of AO-80increased. The formation and uniform dispersion of AO-80particles in the NBR/AO-80hybrids were credited to the forming of the strong hydrogen bonding network between AO-80molecules and NBR.All of the NBR/AO-80hybrids had only one tan5peak. With increasing of AO-80amount in the hybrids, the tan8peak gradually shifted to higher temperatures and the peak also became broader. Particularly, when the AO-80amount in the hybrids increased from0phr to100phr, the tan8value increased from1.9to3.2. Taken together, high tan δ values and broad transition temperature ranges suggested that the NBR/AO-80hybrids could possess excellent damping properties. There was no reinforcement agent added in the hybrids, but the NBR/AO-80hybrids also showed excellent mechanical properties:greatly increasing tensile strength (2-6times for the pure NBR), very large elongation at break, very small permanent residual deformations and reasonably good stabilities. The excellent damping and improved mechanical properties of the NBR/AO-80hybrid could be attributed to the strong hydrogen bonding formed between AO-80molecules and NBR matrix.NBR/AO-80hybrids with varied mass ratios of NBR/AO-80were successfully prepared by mixing AO-80into NBR containing various acrylonitrile percentage. AO-80had the good compatibility with all types NBR and all hybrids appeared semblable structure and property with the NBR(N220S)/AO-80hybrid. However, with the decreasing of the acrylonitrile percentage of NBR, the damping and machanical properties of hybrids declined clearly.2. NBR/hindered phenol hybrids were successfully prepared by mixing tetrakis [methylene-3-(3-5-ditert-butyl-4-hydroxy phenyl) propionyloxy] methane (AO-60) into NBR with various acrylonitrile mass fraction. The character band of hydrogen bonded hydroxyl group appeared in the infrared spectra of the hybrids, and the OH band shifted to the low wave number direction. This illustrated that the strong hydrogen bonds had been formed between the hydroxyl groups of AO-60and NBR.Associated with the results of DSC, SEM and TEM, when the addition of AO-60increased, NBR (N220S)/AO-60hybrid had two phases:(1) the AO-60enriched phase and (2) the NBR enriched phase (matrix). And it appeared the corresponding Tg in the DSC curves. The NBR (N220S)/AO-80hybrids had three tan δ peaks. The peak of NBR matrix had some reduced. But two novel transitions above the Tg of NBR matrix appeared, corresponding to amorphous and ordered AO-60agglomerations respectively. All the other NBR/AO-60hybrids showed single relaxation transition, and the glass transition temperature (Tg) increased prominently with an enhancing amount of AO-60in the hybrids. Associated with the results of SEM and TEM, AO-60dispersed in molecular-level and formed AO-60enriched phase in the NBR matrix when the addition of AO-80increased. The hybrids had only one tan δ peak of NBR matrix. With increasing of AO-60amount in the hybrids, the tan δ peak gradually shifted to higher temperatures and the peak also became higher and broader. NBR/AO-60hybrids also showed excellent damping property.There was no reinforcement agent added in the hybrids, but the NBR/AO-60hybrids also showed excellent mechanical properties:greatly increasing tensile strength (2times of that of the pure NBR), very large elongation at break, very small permanent residual deformations and reasonably good stabilities. The excellent damping and improved mechanical properties of the NBR/AO-80hybrid could be attributed to the strong hydrogen bonding formed between AO-60molecules and NBR matrix.3. Comparing with the pure NBR, NBR/AO-80/nanofiller hybridss exhibited higher glass transition temperatures, a lower tan δ values, broader transition temperature ranges, and the peak location shifted to higher temperature. NBR/AO-80/nanofillers hybrids showed high peak values more than1.19(up to1.98), and the transition temperature ranges(tan δ≥0.3)broader than35℃, indicating a good damping property. Comparing with neat NBR and NBR/AO-80hybrids, NBR/AO-80/nanofillers hybrids had much higher mechanical properties with the tensile strength of28MPa and the tear resistance of44KN/m. Stress at100%and300%of the hybrids had a great increase. At the same time, NBR/AO-80/Nanofillers hybrids also had very good mechanical properties at high temperature of60℃or after aging at100℃and48hours. All of that showed carbon black or silica reinforced NBR/AO-80hybrids had excellent mechanical properties at high temperature and after thermal aging.