Study On Structural And Performance Of Polypropylene/Modifier/nano CaCO₃ Compound System

The modification of Polypropylene is an important topic in the study of high polymer material,which enjoys a wide market in industry.This paper firstly reviewed the development of CaCO3-modified Polypropylene,then proposed a series of experimental tests to improve the dispersion of nano-CaCO3 in the matrix and improve the interaction between PP and nano-CaCO3 by adding different modifiers.The PP/modifier/nano-CaCO3 composite with excellent impact strength is obtained.Firstly,the PP/nano-CaCO3 composite is prepared by melt-blending method.The impact strength of the composite can reach to a maximum value under a nano-CaCO3 content percentage of 6%,but its increamental is not obvious.Based on the 6%content of nano-CaCO3,SEBS,SEBS-g-MA and SEBS-DBM are used as modifiers for the blending modification,on which performance tests and organization representation are conducted.PP/SEBS/nano-CaCO3 composite is prepared,and the effects of SEBS content on the structure and performance of the composite are studied.Under room temperature condition,the impacted strength of the composite can reach to a maximum value under a SEBS content of 8%.Under low temperature,the impact strength increases with the increase of SEBS content below 2%,while above 2%,the impact strength tends to be stable and its tensile strength decreases.To increase the interaction between PP and nano-CaCO3,PP/SEBS-g-MA/nano-CaCO3 composite is produced.With the adding of SEBS-g-MA,it parcels the nano-CaCO3 particles,forming a core-shell structure,in which SEBS-g-MA is the shell and the ano-CaCO3 is the core.The impact strength of PP/SEBS-g-MA/nano-CaCO3 is higher than PP/SEBS/nano-CaCO3,and its decrease of tensile strength is slower than PP/SEBS/nano-CaCO3.In SEBS-g-MA,the interaction between MA and nano-CaCO3 is relatively weak,and MAH is toxic,therefore SEBS-g-DBM is prepared using melt-grafting method.The effects of DCP content and DBM on the grafting ratio and grafting efficiency are studied.The reaction temperature and screw revolution are optimized to further improve the grafting ratio of SEBS-g-DBM.DBM with two different grafting ratios are used to produce PP/SEBS-g-DBM/nano-CaCO3 composite.It is found that due to the high grafting ratio of SEBS-g-DBM,the dispersion of nano-CaCO3 in the matrix is remarkably improved.With the increase of SEBS-g-DBM,nano-CaCO3 is more uniform in the matrix,the aggregates is smaller than the ones in the SEBS system and in the SEBS-g-MA system.The interface between nano-CaCO3 and matrix is obscure,which allows the decrease of crystallization temperature and degree of crystallinity.The particle is significantly refined.Therefore,under both the room temperature and low temperature,the toughen effect of SEBS-g-DBM is obviously better than SEBS-g-MA and SEBS,and the decrease of tensile strength is remarkably slower than PP/SEBS-g-MA/nano-CaCO3 and PP/SEBS/nano-CaCO3 composite.