Studies On The Preparation, Structure And Properties Of 3D Printing BIIR/PP-TPV With Low Hardness

Thermoplastic vulcanizate(TPV)is a kind of special thermoplastic elastomer(TPE),which is prepared by dynamic vulcanization at high temperature and high shear rate.It is always made up of plastic as continuous phases with(20-50 wt%)some crosslinked rubber microparticles(50-80 wt%).With the advantages of thermoplasticity as plastics and the high resilience and mechanical properties as traditional rubber,it can be used to replace thermosetting rubber in many applications.TPV,as a kind of "green" new chemical material could recycle and reproduce repeatedly.At present,various materials have bee used for TPV,including some rubbers such as EPDM and SBR and plastics such as polypropylene(PP)and polyamide(PA),so EPDM/PP-TPV is the most commercial TPV.3D printing is a rapid prototyping technology to create varied shapes and unique structures.The 3D printing equipment with Fused Deposition Molding(FDM)technology is low-cost,easy to operate and widely applied in many fields.Traditional rubbers have many disadvatanges in necessarity of high temperature vulcanization,low compatibility with 3D printing process,and processing problems with high viscosity and poor fluidity,so that they are limited in 3D printing.Therefore,it is of great significance to develop TPV with excellent strength,elasticity and 3D printing performance.TPV materials prepared from brominated butyl rubber(BIIR)and PP have attracted considerable attention in recent years due to their application in medical bottle stoppers.BIIR/PP-TPV stoppers are safer than medical stoppers prepared by traditional thermoset BIIR because the continuous PP phase prevents the migration of additives from the rubber phase to the surface contamination and reduces the formation of debris when the needle is inserted into the stopper.BIIR/PP-TPV has the disadvantages of poor fluidity and poor processing performance and cannot be used for 3D printing.Low-hardness and low-viscosity BIIR/PP-TPV with good flow properties and mechanical properties through pre-mixing process combined with oil-filled softening and interface compatibilization was prepared in this work.In order to overcome the problem of difficulty in feeding during 3D printing due to the decrease of hardness,single-screw melt feeding was used to successfully realize 3D printing.The specific work content is as follows:Firstly,the effects of formulation and process conditions on the mechanical properties and processing properties of BIIR/PP-TPV were investigated in detail,and the influence of them on the structure of BIIR/PP-TPV was studied.Comprehensive consideration of various factors,the final optim?m rubber-to-plastic ratio was 6:4,the vulcanization system was HVA-2,the temperature was 180?,and the rotational speed was 60 rpm.On the basis of the above,a low hardness BIIR/PP-TPV was prepared through pre-mixing process combined with oil-filled softening and interface compatibilization in this work.Experiments show that oil-filling and compatibilizing can not only reduce the hardness of the TPV material by improving the process,but also increase its tensile strength and elongation at break.At the same time,it can improve rheological properties of TPV.Then,the TPV with excellent mechanical properties and processing properties was obtained.By investigating the effect of maleic anhydride grafted polypropylene(PP-g-MA)compatibilization on the microstructure and properties of TPV and combining contact angle test analysis,the mechanism of PP-g-MA compatibilized BIIR/PP-T was proposed.Finally,the morphological evolution of low hardness and 3D printing BIIR/PPTPV during the preparation process was studied.The mechanism of microstructure formation ofTPV was proposed.In order to overcome the problem of difficulty in feeding during 3D printing due to the decrease of hardness,single-screw melt feeding was used to successfully realize 3D printing.The 3D-printed BIIR/PP-TPV spline has an elongation at break of 173% and a strength of 4.8 MPa,and the interlayer structure is tight,indicating that the BIIR/PP-TPV material has good adhesion.The above research shows that BIIR/PP-TPV is an ideal 3D printing material,expanding the application field of TPV.