Studies On Preparation And Strengthening And Toughening Mechanism Of Styrene-Butadiene Rubber With Sacrificial Domains

Styrene-butadiene rubber(SBR)is the largest general purpose synthetic rubber,which is widely used in daily life and tire industry.However,as a kind of non-polar rubber,neat SBR has poor mechanical properties,and its reinforcement is essential for its application.At present,the rubber reinforcement method is mainly nanofilling,but this method strongly depends on the dispersion of filler and the interaction between rubber and filler.The construction of weak bond as sacrificial bond in rubber network is an efficient reinforcement method independent of filling,but this method is often limited to polar rubbers or needs to be chemically modified in advance.Therefore,it is of great significance to explore a new,facile and efficient reinforcing method for non-polar rubbers.Inspired by the multiphase structure in the cuticle of mussel byssus and the mechanisms of strengthening and toughening with sacrificial domains,the author introduced a small amount of polar rubber crosslinked by dense weaker bonds,as the sacrificial domains,into SBR matrix through simple mixing process,and realized the strengthening and toughening of SBR through the deformation of sacrificial domains and energy dissipation mechanism of consistent breaking of weaker bonds.The main contents are as follows.(1)Based on the coordination interaction between nitrile butadiene rubber(NBR)and metal ions,the sacrificial domains containing NBR crosslinked by nitrile-cupric ion(II)coordinations were constructed by the processing consisting successive two-roll milling,hot pressing and two-roll milling.Compared with SBR,when 20 phr(parts of 100 parts of rubber)of NBR and 4 part of copper sulfate are incorporated,the modulus and strength of SBR are increased by 1.8 times and 3.1 times,respectively.In addition,the mechanical properties of the samples can also be tuned by changing the coordination temperature,the content of coordination bonds in the system and the content of domain.In this system,the dispersed phases act as strong but sacrificial domains.On the one hand,the modulus of the domain is higher,and the modulus of rubber is significantly increased due to the hydrodynamic effect;on the other hand,under external force,the domains can undergo forced elastic deformation,leading to the dissipation of mechanical energy,thus significantly reinforcing the rubber.(2)Based on the hydrogen bonding interaction between NBR and the hindered phenol(AO-80),the NBR crosslinked by hydrogen bonds between the nitrile and the hindered phenol was introduced into SBR as the sacrificial domains by the processing consisting of hightemperature internal mixing and two-roll milling.With the increase of hydrogen bond content,the strength and modulus of rubber increased continuously.With the incorporation of 20 phr of AO-80,the modulus and strength of the SBR/NBR(80/20)blend are increased by 59% and 73% respectively.In addition,the mechanical properties of the vulcanizate are increased further when the content of sacrificial domains increases.Under the external force,the hydrogen bonds dissociate and plastic deformation occurs in the domains,which can effectively dissipate mechanical energy.With the deformation of the dispersed phases,the SBR molecular chain is accordingly oriented,so the rubber finally achieves high strength and high modulus.(3)Acetylglycine(NAg)was blended with epoxidized natural rubber(ENR)and then blended with SBR.The sacrificial domains crosslinked by amide-based hydrogen bonds were constructed into SBR by hot pressing pretreatment.With the increase of NAg content,the strength and modulus of the rubber are increased continuously.Compared with the SBR/ENR(70/30)blend,when 4.5 phr of NAg is incorporated,the modulus and strength of the vulcanizate are increased by 535 % and 63%,respectively.The strengthening mechanism of this system is mainly due to the preferential break of hydrogen bonds in the dispersed phase,which breaks prior to the covalent bond and promotes the plastic deformation of the dispersed phase.This process can effectively dissipate the mechanical energy and promote the orientation of the SBR chains,thus obtaining high strength and high modulus.