Study On Properties Of Polypropylene Modified With Nano-Calcium Carbonate/Sodium Lignosulfonate Composite Filler

In this paper,sodium lignosulfonate(SL)and nano-calcium carbonate(CaCO3)were used to prepare composite filler sodium lignosulfonate/nano-calcium carbonate(SL/CaCO3),and then SL/CaCO3 was used for the modification of polypropylene(iPP).to study the effect of different conditions on the properties of iPP.SL and CaCO3 were prepared into composite filler SL/CaCO3 by planetary ball mill,and then modified iPP.Subsequently,the thermal stability effects of modified iPP were also studied by TG and DSC.In addition,scanning electron microscopy(SEM)was used to study the dispersion of fillers in polypropylene.Finally,the effects of fillers on the mechanical properties of polypropylene were studied under the optimal compounding ratio and addition amount.The crystallization and melting behavior of composite filler SL/CaCO3 modified iPP with different compounding ratios were studied by DSC.With single fillers SL and CaCO3,the crystallization peak temperature increased by 6℃ and 5℃,respectively(compared to pure iPP),and the crystallization peak temperature increased significantly with the addition of the composite filler.At the same time,the relative content of β crystals(Kβ)of modified Ipp was calculated by DSC method,and it was concluded that when the compound ratio of SL and CaCO3 was 1:3,the Kβ of modified iPP was the highest,and Kβ was 0.6448.On this basis,the effects of the additions of SL,CaCO3 and SL/CaCO3 on the crystallization and melting behavior of iPP were investigated.When the crystallization peak temperature of SL-modified iPP was between 121.0℃ and 123.0℃,the β-crystal content of SL-modified iPP increased first and then decreased with the increase of SL addition amount.When the addition amount of CaCO3 was 5 wt%,the β-crystal content of the modified iPP reached the maximum value of 0.4761,and it first increased and then decreased with the increase of CaCO3 addition amount.At the same time,with the addition of SL CaCO3,when the amount of SL/CaCO3 was 2 wt%,the Kβ of the modified iPP reached 0.8280,indicating that SL/CaCO3 is a highly active and selective β-crystal nucleating agent for iPP.The effect of different composite fillers on the crystal morphology of iPP was studied by XRD.After adding SL/CaCO3 modification,a new high-intensity characteristic diffraction peak was observed at 2θ=16.2°.This peak is the characteristic diffraction peak of β-iPP,which indicates that SL/CaCO3 can induce the formation of β-iPP.TG was used to test the thermal stability of different modified iPP.SL-modified iPP could not improve the thermal stability of iPP.The thermal stability is between SL and CaCO3.At the same time,in order to simulate the number of industrial thermal cycle processing,SL,CaCO3 and SL/CaCO3 modified iPP were heated for multiple times by DSC.Through comparison,it was found that the thermal stability of the three fillers in iPP was ranked as CaCO3>SL/CaCO3>SL.The dispersion state of composite fillers in iPP was observed by SEM.While no obvious agglomerates are observed on the fracture surface of SL/CaCO3 modified iPP,the surface SL/CaCO3 is relatively uniformly dispersed in iPP.In addition,the mechanical properties of SL/CaCO3 modified iPP were tested under the optimal compound ratio and the optimal addition amount.Compared with pure iPP,adding 2 wt%SL/CaCO3 to iPP can increase the impact strength and elongation at break of iPP by 62.38%and 32.27%,respectively.At the same time,the tensile strength and flexural modulus of the modified iPP decreased.But in general,it can better achieve the purpose of significantly improving the toughness of iPP,while less affecting the rigidity of iPP.