The Study Of Mechanism Of Two Dimensional Fillers In Polypropylene And Thermoplastic Polyurethane

Fillers with two-dimensional structure have been increasingly used in the field of flame retardant.However,the specific mechanism and application of two-dimensional fillers have not been systematically summarized.In this paper,three different kinds of two-dimensional flame retardant fillers were selected to study their main role and mechanism in the process of flame retarding.Flame retardant composites were prepared by additive method,and the effects of the addition of two-dimensional fillers on flame retardant properties,thermal stability and mechanical properties of the materials were studied.The main research work is as follows:1.Aluminosilicate clays kaolin and halloysite nanotubes of different dimensions were mixed in different proportions and added to polypropylene containing intumescent flame retardant.The LOI,UL-94 and CCT tests showed that there was significant synergism between the two materials.The maximum oxygen limit index of composite material reached 36.9%,UL-94 reached V-0 level,and the peak heat release in CCT test decreased by 82%.The comprehensive analysis of the carbon residue by SEM and FT-IR shows that the hybrid system of kaolin and halloysite nanotubes is conducive to the formation of crosslinking network and the formation of compact carbon layer.2.The graphene microchip(GN)was prepared by using biolignin as adhesive by the combined preparation method of "stripping" of three-roller grinder and "ultrasonic" graphite sheet of cell grinder.The two-dimensional carbon material GN and one-dimensional carbon material CNTs were used as the fillers to add into the polypropylene intumescent flame retardant system.A series of tests and analyses were conducted on the influence of the flame retardant performance and thermal stability of the composites.The results showed that the addition of one-dimensional carbon material CNTs improved the thermal conductivity of the composites,accelerated the decomposition of the materials,and inhibited the IFR,so it had a great negative impact on the flame retardant performance of the composites.GN,a two-dimensional carbon material,also improves the thermal conductivity of the material and acts as a barrier for the two-dimensional material.Therefore,the flame retardant performance of the material can be improved in a small extent.The oxygen index of PP/IFR/GN reached the highest level of 27.4 and passed the V-0 level.3.APP was coated with melamine resin(MF)and graphene oxide(GO)to prepare a kind of modified ammonium polyphosphate with double shell structure.Then by adding blend,MCAPP-GO,the product of double layer coating structure,was added into thermoplastic polyurethane(TPU)matrix to prepare flame retardant composite material.The flame retardant performance of the composite was tested and analyzed,and it was found that adding only 5wt%MCAPP-GO could significantly improve the flame retardant performance of the composite.The LOI of TPU+5%(MCAPP-GO)was increased to 26.4%,reaching V-0 level.In the cone calorimeter tests,THR,PSPR and TSR were reduced to 58 MJ/m2,0.051 m2/s and 860 m2/m2 respectively,and the carbon residue was increased to 24.45wt%.It is found that the modified ammonium polyphosphate can effectively improve the flame retardant performance of the polymer by combining the mechanism of graphene oxide and melamine resin.