Development Of A New Semibatch Emulsion Polymerization Technology And Preparation Of High Performance Hydrogenated Nitrile Butadiene Rubber

Microemulsion polymerization is an effective method to prepare nanoparticles with small particle size,low surface tension and well penetration,wetting and leveling properties.However,a high surfactant is required to emulsify the relatively low content of monomers.In order to address the effect of residual surfactants in the latex on the performance of the synthesized polymers,a semibatch emulsion polymerization method was proposed.Semibatch microemulsion polymerization is a new and effective method for the preparation of nanopolymers,which has attracted a lot of attention.The present project is related to two aspects of research(i)to use a new microemulsion polymerization technique to prepare latex nanoparticles with small particle size and narrow particle size distribution(PSD).(ii)to prepare high performance hydrogenated nitrile butadiene rubber(HNBR)by increasing the hydrogenation rate while reducing the amount of catalyst used.Focusing on these objectives stated above,the following studies were carried out.Poly(methyl methacrylate)(PMMA)nanoparticles were synthesized by a semibatch emulsion polymerization method using different emulsification techniques,aiming to find a more effective and simple method to synthesize PMMA nanoparticles with acceptable particle size and conversion rate.There are five main emulsifying techniques,magnetic stirring,bath ultrasound,probe ultrasonic dismembrator,combination of magnetic stirring and probe ultrasonic dismembrator,and combination of bath ultrasound and probe ultrasonic dismembrator.The experimental results show that the probe ultrasound of appropriate intensity helps to reduce the particle size to below 20 nm with narrow PSD.At the same,the traditional magnetic stirring method cannot even convert all monomers into nano particles,which means there is always a part of MMA monomers being consumed to form rigid floating subjects during the reaction.However,experiments also reveal that a too powerful emulsifying force will lead to implosion,which significantly increases the reaction rate and the particle size.The combined emulsifying methods are much easier to cause implosion than an individual emulsifying method.For probe ultrasonic microemulsion polymerization,other aspects of the polymerization process,such as polymerization temperature,reaction time,monomer/water ratio,and surfactant/water ratio,to investigate their effects on polymerization.NBR nanoparticles were synthesized in a semibatch microemulsion polymerization system using different types and amounts of surfactants as raw materials.The microstructure and composition of the polymer nanoparticles were characterized by fourier-transformed infrared(FT-IR)spectroscopy and proton nuclear magnetic resonance(¹H NMR).The particle size,molecular weight and glass transition temperature(T_g)of NBR nanoparticles under different polymerization conditions were also researched,as well as the PSD and potential applications of NBR nanoparticles were analyzed and studied.The above prepared NBR nanoparticles were used as substrates for latex hydrogenation.The direct catalytic hydrogenation reaction of NBR latex nanoparticles was carried out under Wilkinson(Rh Cl(PPh₃)₃).The process of the experiment was additionally assisted by adding different types and amounts of surfactants without any organic solvents.In the polymerization and hydrogenation process,through the use of different types and different amounts of surfactants,a small amount of catalyst(<0.3wt%)was successfully used,and the hydrogenation conversion rate was>95.0%in 4hours.Hydrogenated nitrile butadiene rubber(HNBR)was successfully prepared,and the pathways of emulsifiers in the polymerization hydrogenation process and the catalytic pathways of Wilkinson catalyst were discussed.