The Preperation And Performance Of The Natural Rubber (NR)/Nitrile Rubber (NBR)- Hindered Phenol (AO-80) Composites

As one of unpredictable natural disaster with strong burst and devastating, the earthquake affect the human life and property safety seriously. Currently, more and more modern buildings’seismic design is based on the concept of seismic isolator, and the commonly used isolation device is laminated rubber isolation bearing. The rubber isolator are made of thin rubber layers and thin steel plates, which are alternate and co-vuicanizated. The performance of the rubber material used in the rubber isolator affects its isolation effect significantly.In this study, the natural rubber and the nitrile rubber/hindered phenol hybrid material are blended through a specific mixing and dispersion process. The natural rubber is an excellent material with the ability of strain induced crystallization, at the same time, the nitrile rubber/hindered phenol hybrid material is a high damping material with the ability of strain induced orientation. The hinderd phenol used in this study is AO-80.We have studied the structure and properties of the natural rubber/nitrile rubber/hinderd phenol composites with different blending proportions, curing systems and external forces. The morphology structure of the natural rubber (NR)/nitrile rubber (NBR)/hindered phenol (AO-80) composite was tested by the atomic force microscopy (AFM), transmission electron microscopy (TEM), differential scanning calorimentry (DSC) and dynamic mechanical analyzer (DMTA). The strain induced crystallization of NR phase in the NR/NBR/AO-80 composites is analysed by the sunchrotron-WAXD, and the strain induced orientation of the NR phase and the NBR/AO-80 phase was analysed by the FT-infrared spectroscopy instrument. The damping property of the NR/NBR/AO-80 composits dependent on the temperature, frequency and shear strain was characterized by the dynamic mechanical analyzer (DMTA) and rubber processing analyzer (RPA). The mechanical properties of the NR/NBR/AO-80 composites were characterized by the electronic tensile testing machine. Also, as a compatibilizer, the epoxidized natural rubber (ENR) was added into the NR/NBR/AO-80 composites. We studied the phase structure, strain induced crystallization and orientation, damping properties, mechanical properties and the mechanism of the ENR/NR/NBR/AO-80 composites. The main work of this thesis and the results are as follows:(1) through high temperature pre-dispersing process, the hindered phenol AO-80 is mainly concentrated in the NBR phase in the NR/NBR/AO-80 composites. When raw rubber the ratio of NR:NBR are higher than 50:50, the NR is the continious phase, the NBR is the dispersed phase. When the raw rubber raito of NR:NBR are lower than 50:50, the result is on the contrary. When the raw rubber raito of NR.NBR are 50:50, the composite has shown the co-continuous state. This study mainly discussed the structure and properties of NR/NBR/AO-80 composite with NR as the continuous phase.(2) Under the effect of the tensile strain, the NR molecular chain orientation, and the infrared dichroism function (DF) increases slowly with the strain increasing. When the strain higher than 300%, the molecular chain crystallizes. At the same time, the NBR/AO-80 phace occurres orientation, the DF increases linearly with the strain increasing. The addition of NBR/AO-80 makes the onset crystallization strain of the NR phase increases, but the degree of the crystallization decreases.(3) the addition of NBR/AO-80 into NR greatly improves the damping properties of the composites at room temperature. With the increasing of the NBR/AO-80 content, the tan 5 of the NR/NBR/AO-80 composite increases between 0℃～40℃. There is an obvious influence on the damping property of the NR/NBR/AO-80 composites with the change of the frequency, shear strain and temperature. Within the range of 0～33Hz, the higher of the frequency, the greater of the tan 5. Within the range 1～260% of the shear strain, the larger of the shear strain, the greater of the tan 5. The damping property of the NR/NBR/AO-80 composite depends on the relationship between glass transition temperature of the NBR/AO-80 phase and the testing temperature, and the tan 5 becomes larger when they are closer.(4) the mechanical properties of NR/NBR/AO-80 composites are excellent. When the strain is less than 300%, the tensile is lower than 2 MPa, and when the strain is more than 400%, the stress increases rapidly with the strain increasing. With the increaing of the NBR/AO-80 content added into the NR/NBR/AO-80 composite, the rate of stress increasing become larger. The tensile strength is higher than 20MPa, and the elongation at break is higher than 650%.(5) Experiment results showed that, with ENR added, the dispersed phase size of the NR/NBR/AO-80 composite decreased significantly. ENR is in the interface between the NR phase and NBR/AO-80 phase, and forms an elastic coating to the dispersed NBR/AO-80 phase. When the addition of ENR is 7 phr, the degree of crystalliztion and mechnical property of the composite improves, but the damping performance declines. When the addition of ENR is 21 phr, the damping performance improves, but the degree of crystalliztion and mechnical property declines. When the addition of ENR is 14 phr, the comprehensive performance of the NR/NBR/AO-80 achieves the best.