Charring Mechanism Of A Ferrocenyl-based Polymer And Its Application In Epoxy Resin And Polypropylene

In this paper,the latest research progres ses of fire-retarded epoxy resin and polypropylene composites are reviewed.A novel ferrocenyl-based polymeric flame retardant(PDPFDE)was synthesized by combining ferrocene,benzene rings and nitrogen together,based on the perspective of functional desi gn of molecular structure.The thermal degradation and fire behaviors of PDPFDE in epoxy resin and polypropylene were investigated,and the related flame retardant mechanism was clarified.The main work of this dissertation was illustrated as follows:1.PDPFDE was synthesized via Michael addition reaction.And its chemical structure was determined by FTIR and ~1H NMR measures.The TGA result shows that PDPFDE possessed good thermal stability.A high char residue yield of 62.9 wt%was obtained when the tempera ture up to 800 ~oC.And the possible charring mechanism of PDPFDE has been investigated by TGA,TG-FTIR,Py-GC/MS,SEM and FTIR.The results show that on the one hand PDPFDE forms iron-carbon nanotubes(Fe-CNTs)at high temperature,which increases the thermal stability of the char layer;on the other hand,Cp ring,benzene rings and some nitrogen-containing molecular chain fragments undergo ring expansion or rearrangement reactions to form a large number of aromatic cross-linked structures and nitrogen-containing aromatic cross-linked structural compounds under the catalysis of iron.And these compounds play a very good role in charring in the condensed phase.2.The EP/PDPFDE composites were prepared by adding PDPFDE as flame retardant into epoxy resin.And the influence of PDPFDE on the thermal,flame retardant and mechanical properties of the epoxy resin composites was studied.The results demonstrated that the incorporating of PDPFDE could promote the formation of char for EP,increase the limited oxygen index(LOI)of EP composites,and reduce the peak heat release rate(p HRR)and total smoke production(TSP)of epoxy resins.This is believed to be attributed to the PDPFDE catalyzed the premature degradation of the epoxy resin,and form a dense,continuous char layer,which prevent the EP matrix from exchanging heat and oxygen with the outside world,and delay the further degradation of the internal material.In addition,the impact strength and tensile strength of EP composites are enhanced by the incorporation of PDPFDE.3.PDPFDE was used as a synergist to study the synergistic flame retardant effect of PDPFDE and Intumescent Flame Retardant(IFR)in polypropylene system.The results showed that the addition of 0.5 wt%PDPFDE and 22.5 wt%IFR in PP significantly decreases the p HRR and total heat release(THR)of PP composites.The char layer that after vertical burning test was investigated by SEM and Raman.It was found that PDPFDE can promote the formation of a smooth,dense,continuous and high graphitized char layer on the surface of the PP/IFR system.And the mechanical test results show that the PDPFDE can play the role of toughening agent in the PP system.4.The flame retardant effect of PDPFDE and expandable graphite(EG)in polypropylene system was further studied.It has been found that PDPFDE can promote EG to form a good cohesive carbon layer,which solves the problem of the inability to form a strong char layer on the surface of the material and the serious?fly ash?problem.When 20 wt%EG and 5 wt%PDPFDE were added to the polypropylene,the LOI value of the composite increased to 28.8%and passed UL-94 V-0.Compared with pure PP,the peak heat release rate(p HRR)and total heat release(THR)decreased by 82.8%and 41.4%,respectively,indicating that there is a significant synergistic flame retardant effect of PDPFDE and EG in PP system.