Preparation Of Eucommia Ulmoides Gum/natural Rubber Composites By Wet Mixing Technology

Eucommia ulmoides gum（EUG）,as a natural polymer material,combined with natural rubber（NR）,can not only improve the performance of rubber products,but also alleviate the problem of insufficient self-sufficiency rate of NR rubber in China.However,due to the limitation of extraction process,EUG has only solid rubber and no latex products,which greatly limits the application of EUG.At the same time,the trans polyisoprene molecular chain structure of EUG is more regular and easy to crystallize at room temperature.When EUG is prepared by dry mixing,it must reach its melting point.It is very different from NR mixing process,which affects the performance of EUG/NR compound.And there are also problems such as high energy consumption and difficult dispersion of filler.In this paper,Eucommia ulmoides latex was prepared and EUG/NR composites were prepared by wet mixing process,which avoided the difference between EUG and NR mixing process,improved the dispersion of filler and improved the properties of composites.In the first part（Chapter 2）of this paper from the perspective of expanding the application of Eucommia ulmoides gum and the latex used in wet mixing,Eucommia ulmoides latex was prepared by solution emulsification method.The effects of emulsifier,stirring speed and time,p H value,solvent removal and concentration method on EUG emulsification were investigated.It was found that a single emulsifier was not sufficient to emulsify EUG completely,and when three emulsifiers,Brij-52,Tween-20 and SDBS,were used in combination,EUG could be emulsified completely.Eucommia ulmoides latex was prepared by using compound emulsifier,stirring at 8000 rpm for 10 min in high speed homogenizer for emulsification,rotary evaporation to remove cyclohexane and centrifugal concentration to remove excess water.The average particle size was about 330 nm,the absolute value of Zeta potential was 57,and the solid content was up to 54%.The emulsification did not destroy the basic structure of EUG,and a large number of crystals still existed in the latex.In the second part（Chapter 3）of this paper different proportions of Eucommia ulmoides rubber/natural rubber/carbon black（EUG/NR/CB）composites were prepared by wet and dry mixing processes.The effects of mixing methods on the mechanical properties,vulcanization properties,crystallization properties and microstructure of EUG/NR/CB composites were systematically studied.The results showed that the tensile strength of EUG/NR/CB composites decreased with the addition of EUG.Compared with dry mixing,wet mixing partially improved the dispersion of CB in the composites,and the composites maintained better mechanical properties.The fatigue properties of EUG/NR/CB composites gradually improved with the addition of EUG,and reached the highest when the amount of EUG was 20phr.At the same time,the blending process has little effect on the crystallization properties of EUG/NR/CB composites.When the amount of EUG is within 30 phr,the composites have no obvious crystallization.In the third part（Chapter 4）of this paper different proportions of Eucommia ulmoides rubber/natural rubber/silica（EUG/NR/Si O₂）composites were prepared by wet and dry mixing processes.The effects of mixing methods on physical and mechanical properties,crystallization properties and microstructure of EUG/NR/Si O₂composites were systematically investigated.The results showed that,the dispersion of Si O₂in EUG/NR/Si O₂composites prepared by dry mixing process decreases sharply with the addition of EUG,the tensile strength of the composite material decreased significantly.Compared with dry mixing,wet mixing significantly improved the dispersion of Si O₂in the rubber matrix,and the mechanical properties of the composites performed well.The tensile strength,and tear strength were significantly better than those of EUG/NR/Si O₂composites prepared by dry mixing.The fatigue properties of EUG/NR/Si O₂composites increased and then decreased with the addition of EUG.And reached the highest level when the amount of EUG was 10 phr.The fatigue performance of composites prepared by wet mixing decreased less than that of dry mixing.The crystallization properties of the EUG/NR/Si O₂composites were not significantly affected by the mixing process,and no significant crystallization was observed when the amount of EUG was within 30 phr.