The Synergistic Effect Of Rare Earth Nucleating Agent And Graphene Oxide On The Crystallization Behavior Of Isotactic Polypropylene

Isotactic polypropylene(iPP)has good physical,chemical and processing properties,is widely used in various fields such as daily life,packaging materials,and automotive interiors.However,the shortcomings of poor toughness and low temperature brittleness severely restricted the further development and application of iPP.Fortunately,the polymorphic characteristics of iPP provides a great performance controllability.Adding nucleating agent is the easiest way to change the crystal form of iPP in industrial processing,and the rare earth nucleating agent(WBG-?)is the most widely used.In order to achieve high performance and functionalization of iPP,in addition to the nucleating agent,a second phase filler(such as graphene oxide,GO)is often added to iPP.However,current researches tend to focus on the individual effects of fillers on the performance of iPP,while ignoring the interaction between fillers.The development of this work has a strong theoretical guiding significance for understanding the synergistic effect of multiphase fillers on the crystallization behavior of iPP and the high performance and functionalization of iPP.In this paper,a twin-screw extruder is used to melt-mix GO and iPP/WBG-?.Before mixing,in order to promote the dispersion of GO in iPP,a chemical grafting method was used to graft octadecylamine(ODA)onto the surface of GO.The self-assembly morphology of WBG-? and WBG-?/GO-ODA coexisting were observed with in-situ polarized light microscope,and the in-situ Fourier infrared spectroscopy(FTIR)was used to explore the influence of GO-ODA on WBG-? Self-assembly morphology mechanism.On this basis,a differential scanning calorimeter(DSC)was used to systematically study the static non-isothermal crystallization and melting behavior of iPP/WBG-?/GO-ODA composites,using a shear hot stage and in-situ wide-angle X Ray scattering(WAXS)comprehensively observes the shear-induced crystallization behavior of iPP/WBG-?/GO-ODA composites.The main findings are as follows:(1)In the self-assembly behavior of WBG-?,when the final processing temperature(Tf)is higher than 240 ?,WBG-? is completely dissolved and forms rod-like,dendritic,cluster-like and other forms during the cooling process.The addition of GO-ODA can change the morphology of WBG-? self-assembly.The morphological change is closely related to the content of Tf and GO-ODA(?_G):when Tf is 210 ?,the morphological change of WBG-? is small;when Tf is higher than at230 ?,the addition of GO-ODA will expand the density of the WBG-? aggregate structure.In situ Fourier Infrared Spectroscopy(FTIR)was used to explore the mechanism that GO-ODA affects the self-assembly of WBG-? due to the interaction with GO-ODA through hydrogen bonds during the association process of WBG-?.(2)In the static non-isothermal crystallization behavior,the crystallization onset temperature(Tc-on),crystallization max temperature(Tc-max)and half crystallization time(t1/2)of iPP by WBG-? and GO-ODA The relative crystallinity of?(K_?)shows a synergistic effect rather than a superimposed effect.The details are as follows:When Tf is lower than 220 ?,WBG-? will hardly dissolve in the iPP melt,and the change of its morphology is also very small.At this time,Tc-on,Tc-max,t1/2 and K_?will not change significantly with the change of?_G;when Tf is higher than 240 ?,Tc-on,Tc-max and K_?first decrease to the minimum as?_G increases,and start to rise when?_Gis greater than 0.2%high.(3)In the shear-induced crystallization behavior,when Tf is 210 ?,compared with iPP/WBG-?,the K_?of iPP/WBG-?/GO-ODA composites is the highest in a larger shear rate range(0?100 s^-1),The rheological test results show that the addition of GO-ODA is likely to change the orientation behavior of the molecular chain segments under the shear field,thereby affecting the content of?-iPP.The innovation of this work lies in the investigation of the self-assembly behavior of WBG-? in the presence of GO-ODA for the first time,revealing the synergistic effect of WBG-?/GO-ODA on the static crystallization of iPP,and discovering iPP/WBG-?/GO-The promoting effect of GO-ODA on the formation of shear-induced?-iPP in ODA composites provides certain theoretical guidance for the realization of the high performance and functionalization of iPP.