Preparation Of Comb-Branched Polyolefin Thermoplastic Elastomer And Study On Rheological Properties

The comb-shaped polyolefin thermoplastic elastomer(CPOE)with crystalline side chains exhibits good mechanical properties and melt processability due to the special chain entanglement behavior.The presence of side chains allows CPOE to have a higher use temperature,and is also conducive to processing and shaping in a flow field dominated by stretching.(such as film blowing,foaming,spinning).Probing the structure-activity relationship between rheological and mechanical properties of CPOE and its chain structure has important guiding significance for its design,processing and application.However,it is difficult to synthesize CPOE materials with precise chain structure,and crystalline macromonomers cannot be fully inserted into the main chain during the preparation process,the macromonomers residues are difficult to remove from the product.Therefore,there are very few studies on the rheological and mechanical properties of CPOE,the structure-activity relationship with the chain structure is not clear,which greatly limits the design,processing and application of CPOE.To this end,we will use a high-temperature solution tandem metallocene catalyst system to customize CPOE samples with different chain structures to study the effects of macromonomer residues and macromonomer insertion on the rheological and mechanical properties of the product.The main research contents and results are as follows:(1)A tandem catalyst system is formed by FI-Zr and CGC-Ti,and CPOE is synthesized at 90℃.The conversion rate of PE macromonomer can reach up to 80%;the insertion amount of 1-octene is between 13-17 mol%;the number of crystalline side chains inserted in each main chain can reach up to 11.2.(2)Study the effect of PE macromonomer residues on the rheological and mechanical properties of POE,OBC,CPOE.PE macromonomer can play a plasticizing role.As its content increases,the melt fluidity is significantly improved;the zero-shear viscosity of the blends decreases linearly,which is consistent with the description of the logarithmic mixing rule model;the viscous flow activation energy is not affected;elongation at break and elastic recovery rate decrease,and tensile strength increases.(3)To study the effect of the number of PE macromonomers insert on the rheological and mechanical properties of CPOE.With the increase in the number of side chains in the CPOE backbone chain,firstly its zero-shear viscosity increases and then decreases below that of the linear chain;the chain conformation changes from a loosely grafted comb to a densely grafted comb;the viscous flow activation energy gradually decrease;the elongation at break and elastic recovery performance become worse,the breaking strength increases.The elongation at break and elastic recovery performance of some CPOE samples are better than the industrial samples POE 8842 and OBC 9100.