Study On Phase Distribution And Properties Of Eucommia Ulmoides Gum/Cis-1,4-Polybutadiene Blends

Cis-1,4-polybutadiene rubber(BR)has excellent properties,such as high elasticity,excellent wear resistance,cold resistance and fatigue resistance,low heat build-up and low rolling resistance.It can be used to develop high-performance fuel-efficient tire.But the main disadvantages of BR is it’s low mechanical strength,poor wet skid resistance and poor processing performance,generally BR is not used alone,it is always used together with other types of rubber.Eucommia ulmoides(EU)gum is a natural polymer extracted from Eucommia ulmoides Olive.It is easy to crystallize at room temperature and it has a special rubber-plastic duality.In addition,EU gum has the advantages of good wear resistance,pricking resistance and fatigue resistance.The main task of this project is to blend EU gum and BR physically,control the blending amount of EU gum,and analysis the properties and phase structure of the EU gum/BR blends.Then,EU gum was used in the traditional formula of truck tire sidewall,and the formula of sidewall compound with low heat build-up,low rolling resistance and excellent high temperature mechanical properties was obtained.In the first part,the relationship between the structure and properties of natural rubber(NR),styrene butadiene rubber(SBR),EU gum and BR and their vulcanization properties were studied.The tensile strength of BR is the lowest,only 0.9 MPa,due to the small force between molecular chains.The tensile strength and tear strength of SBR are low because there is no tensile crystallization.Because of strain induced crystallization,the tensile strength of NR is 2.7 MPa higher than that of BR and SBR.EU gum can crystallize at room temperature,its mechanical properties are the best,and its tensile strength can reach 25.6MPa,which is much higher than other rubbers.In the second part,the effect of EU gum content on the phase structure and properties of EU gum/BR blends were studied.With the increase of the content of EU gum,the mechanical properties of the blends were significantly improved.The tensile strength increased significantly after 50 phr,and can reach 10.5MPa at 70 phr.The tear strength and hardness increased rapidly after 30 phr.The tear strength reached 28.6MPa when the content of EU gum was 70 phr.With the increase of the amount of EU gum,the morphology of the interface changes from "island structure" to "continuous ridge structure"and then to "two-phase continuous structure".The thickness of the interface transition layer is about 100nm because it is not crosslinked.The hard EU gum plays a similar role as reinforcing filler in BR.In the third part,the effects of the content of EU gum on the phase structure and properties of the vulcanizates were studied.When the content of EU gum was 70 phr,the tensile strength was 13 times higher than that of pure BR vulcanizate,and finally reached 13.7 MPa,the tear strength was 54.2 MPa.The cutting resistance reached the best at 35 phr,and the heat generation increased in general.The evolution of phase structure of blend vulcanizate is similar to that of raw rubber blends,but the morphology is slightly different.The shape of island particles of vulcanizate is more regular and round,tends to be spherical,and the transition layer is not clear.The thickness of transition layer is about 200 nm.The fourth part studies the relationship between the content of EU gum and mechanical properties in EU gum/BR nanocomposite vulcanizates.For the nanocomposite vulcanizates,EU gum can improve the constant elongation stress,especially the constant elongation stress at high temperature.When the EU gum is 20 phr,the heat build up will decrease.The phase structure is not obvious because of the dispersion of carbon black.Carbon black is more dispersed in BR,and BR with poor mechanical properties can get more reinforcing filler,which can improve the mechanical strength of carbon black composites as a whole.In the fifth part,EU gum was used to replace BR in the original formula of TBR tire sidewall,and its mechanical properties were tested.The results showed that the tensile strength,tear strength and cutting resistance of EU gum decreased at room temperature,but the tensile stress increased.The mechanical properties of EU gum increased slightly at high temperature.When the content of EU gum was 10 phr,the heat generation and rolling resistance decreased.In general,controlling the amount of EU gum within 10 phr can optimize the comprehensive properties of sidewall rubber.