Research On Preparation And Performance Of Rubber Damping Composites Based On Chemical Modification

Damping materials can convert mechanical vibration energy(or acoustic energy,etc.)into thermal energy and dissipate it.It is a functional material that is widely used in the fields of sound absorption and noise reduction in defense equipment,vibration and noise reduction in the machinery industry,and vibration isolation in bridge buildings.Due to the special viscoelasticity,rubber materials exhibit high loss capacity,and they are important substrates for damping material products.The research on high-performance rubber damping composite materials has attracted much attention.High damping performance materials need to meet the indicators of high loss and wide temperature range(wide frequency band).However,the damping temperature range of traditional rubber materials is closely related to the glass transition temperature(Tg),generally in the low temperature region and the temperature range is narrow(about 20-30 ?),which is difficult to meet the requirements of high loss performance under normal temperature and wide temperature range of defense equipment.Therefore,the preparation of rubber composite materials with high loss factor at room temperature and wide temperature range damping is still an extremely important and challenging project.In this thesis,Eucommia ulmoides gum and butyl rubber were chemically modified,and then blending modification,nano-damping technology were employed to prepare new rubber damping composites.Then the relationship of‘structure-performance'was studied,and damping mechanism was completed,and finally a rubber damping composite material with high loss factor at room temperature and in wide temperature range was obtained.Our research provides theoretical guidance and design ideas for the development of new rubber damping composite materials.The main research work and innovative results are as follows.(1)Natural bio-based Eucommia ulmoides gum(EUG)has rubberplastic duality,but crystallization restrains the loss peak near Tg.As a result,its damping performance can be improved by adjusting its crystallinity.Epoxidation chemical modification is a powerful method.In this chapter,the emulsion one-step method was used to epoxidizedly modify EUG,and the optimal reaction conditions of epoxidation was obtained,and epoxidized eucommia gum(EEUG)with an epoxy degree of 3%-30%was prepared,and the relationship between the degree of epoxy and the damping loss peak was studied.The results show that epoxidation supress the crystallization ability of EEUG.When the degree of epoxy is higher than 15.22%(mole percentage),EEUG cannot more crystallize.As the degree of epoxy increases,the loss peak of EEUG near Tg moves significantly from the low temperature to the high temperature,and the loss peak is significantly enhanced,and also significantly improves the loss factor at room temperature.(2)Although the chemically modified EEUG can increase the loss factor at room temperature,the increase is limited,and the mechanical strength of EEUG is seriously reduced.Based on this,in this chapter,using‘rubberplastic duality'of EUG and nano-modification method increase loss factor at room temperature,and prepare new vibration damping material.In this chapter,carbon nanotubes(CNT)as nanofillers were added into EUG and EEUG,and(E)EUG/CNT nanocomposites,where CNTs aligned,were prepared by a simple mechanical stretching method.Then the effect of orientation degree and CNT content on the damping performance of composite materials was explored.Under a 200%of mechanical tensile strain,the CNTs align greatly in the matrix,which brings a significant improvement of damping performance of the composite.At the same time,in the case of good CNT dispersion,with a 3%of CNT content,the loss factor of the CNT-aligned composite is increased by 78.88%compared with neat EUG.The damping mechanism of(E)EUG/CNT nanocomposites is attributed to hybrid-shish-kebab(HSK)on CNT surface.HSK acts as an interfacial adhesion with appropriate forces,and it dissipates much energy when the HSK slips on the CNT.Both the chemically modified EEUG and(E)EUG/CNT nanocomposites have demonstrated the application potential of mechanical vibration damping at room temperature.(3)In addition to high loss factor at room temperature,wide temperature range is also important factor for rubber damping composites.Natural rubber(NR)has a narrow damping temperature range,but has excellent mechanical properties.Butyl rubber(IIR)possesses excellent damping properties and aging resistance.However,IIR suffers from poor mechanical properties,low cure reactivity,poor adhesion and compatibility with unsaturated rubber,and can not meet the needs of practical application of damping materials.In order to prepare a wide temperature range damping rubber composite material with both mechanical properties and aging resistance,firstly,IIR was modified by bromination to solve the problem of poor compatibility,co-crosslinked with NR.Then,brominated modified butyl rubber(BIIR)was blended with NR to prepare damping composites.The influence of bromine content and bonding structure of the bromine atom on the double bond reactivity of BIIR and the compatibility with NR were explored.The results have shown that the double bond reactivity and NR compatibility increased with bromine content of BIIR.The double bond reactivity of BIIR(BIIR-ENDO)with a endo-bromomethyl olefin was higher than that of BIIR(BIIR-EXO)with a predominant exo-methylene allyl,and the compatibility with NR was better than that of BIIR-ENDO.Compared with the NR,the damping temperature range of NR/BIIR-ENDO composite widened by 12.9? and the tensile strength and aging coefficient of NR/BIIR-ENDO composite only decreased by 3.59%and increased by 205.32%,respectively.NR/BIIR-ENDO composite shows excellent comprehensive performance,and it exhibitied the industrial application potential of damping in a wide temperature range.