Preparation And Performance Of Co-Crosslinked EVM/PVAc Composite With High Damping

With the development of society and modern industrialization,the effect of vibration and noise on people's lives is becoming more and more prominent.So noise reduction and attenuation of vibration have become not only a key of equipment but also the demand of people.Polymer is one of the most widely used damping materials to control vibration and reduce noise because of its unique ciscoelasticity,which can dissipate energy by chain segment of the movement within its glass transition temperature range.In engineering field,the effective damping?tan?>0.3?temperature range of damping material must reach at least60⁸0?and the effective damping temperature range must be consistent with the actual operating temperature as well.In general,the T_g of rubber is lower than room temperature,however the damping material is usually used at room temperature or even higher temperature.Therefore,broadening the effective damping temperature of rubber to room temperature or higher temperature becomes a goal of research.It's an effective method to broaden the effective damping temperature of rubber by rubber-plastic blending.But rubber-plastic blending materials usually exist a damping"trough".So we must improve the damping value of"trough".Ethylene-vinyl acetate rubber?EVM?is a ethylene-vinyl acetate copolymer with high content vinyl acetate?VA?chain segment.Polyvinyl acetate is a homopolymer of vinyl acetate.Although EVM and PVAc have the same VA chain segment,their compatibility is not so good because of the difference in molecular structure.In this paper,two kinds of EVM with different content of VA were used to blend with PVAc by co-vulcanization to increase the damping properties and mechanical properties of composite and the effect of blend ratio and the content of vulcanizator on the properties of composite were investigated.The results showed that BIPB could trigger EVM800 and PVAc to crosslink,with the increase of BIPB content,the crosslinking density of EVM800/PVAc increased.Although the two kinds of binary blends both had two loss peaks in the tan?-T curves,when applied the same of blend ratio,damping properties and mechanical properties of EVM800/PVAc blends were both better than those of EVM500/PVAc blends.When the blend ratio of EVM800 and PVAc was70/30,the effective damping temperature range was near 80?.In order to further improve the damping properties of EVM/PVAc composite materials,the effect of plasticiser on the damping properties of EVM/PVAc binary blends were studied.It was found that the introduction of PEG400 could improve sharply the damping properties of EVM500/PVAc binary blend and the damping mechanism were explored by DSC,FTIR,SEM and nuclear magnetic resonance spectroscopy analysis.The results showed that the compatibility between PEG400 and two polymers was much different and PEG400 mainly reduced the T_g of PVAc,which resulted in reducing the difference between T_g of the two polymers,thus improving the damping properties of composite materials,and used SBR/PVAc blends to prove this mechanism.In addition,PEG400 could form hydrogen bonds and thus also improving the damping properties of materials.When the blend ratio of EVM500 and PVAc was 80/20 and the content of PEG400 was 10 phr,its effective damping temperature range was from-35.1?to 59.1?,and the tan?_min=0.32.Plasticizer had little effect on EVM800/PVAc blends.Based on the characteristic of the polarity and the T_g of EVM increased as the increase of the content of VA chain segment in the molecule,we also designed EVMs/PVAc multi-components blends and the influence of the blend ratio and the content of carbon black were studied,and the damping stability of composite materials were also researched.The results showed that the introduction of EVM800 in EVM500/PVAc?80/20?blends containing10phr triethyl citrate could improve the damping properties of composite materials,when the blend ratio of EVM500/PVAc/EVM800 was 80/20/40,the effective damping temperature range of composite materials was 98??from-37.3?to 61.3??.The damping stability of the material was good and the change of damping properties of material was not obvious after storing for 6 months.When the blend ratio of EVM500/PVAc/EVM800/EVM900 was80/20/20/15,the effective damping temperature range of material was 98??from-37.0?to61.2??,and the composite had a excellent heat resistance stability,experienced 100?×72 h of heat treatment,the effective damping temperature range of material could increase to105??from-34.4?to 71.5??.Carbon black could enhance dramatically the mechanical properties of the above two kinds of matertials without lowering the damping properties.