Preparation And Properties Of Polyethylene Terephthalate (PET) Based Halogen-free Flame Retardant Composites

Polymeric materials are used in many fields for their excellent properties,and they are widely used in people's daily life.However,most polymers are easy to burn since their main elements are C,H,and O with a low limiting oxygen index(LOI)less than 22%.As one of the important engineering plastics,polyethylene terephthalate(PET)is mainly used in textile fibers,electronic components,automotive parts,packaging materials and many other fields.Due to its wide application and flammable characteristics,research on its flame retardancy is quite necessary.In addition,PET has good insulation and is prone to generate a large amount of static electricity during usage,which not only causes electronic components to malfunction,but also causes serious accidents such as electric shock,fire,and explosion.Therefore,studies on the flame retardancy and antistatic properties of PET have become practically important.In this paper,the research is mainly conducted on the flame retardant properties of PET,and the corresponding researches are also carried out on antistatic properties,crystallization properties,mechanical properties,etc.Firstly,PET/MCA composites were prepared by melt blending.The effects of the addition of flame retardant and particle size were studied on the thermal stability,mechanical properties,rheological properties,flame retardancy and crystallization behavior of PET composites.The research results show that the addition of MCA makes the movement of the PET macromolecular chain blocked during shearing,resulting in increased complex viscosity.Because MCA has lower thermal stability than PET,the thermal stability of the composites decreases,but MCA has the advantage of promoting the formation of carbon layers during the decomposition of the polyester,the maximum decomposition rate of the composite material decreases,and the degradation rate slows down.The decrease of MCA particle size and more uniform distribution in matrix will help to reduce the effect of filler on tensile strength and notched impact strength.The nucleation of MCA can increase the crystallinity of PET,and reduction of MCA size further improves crystallinity of PET.MCA has gas-phase flame retardant effect,which increases the LOI of the composites,reduces the total heat release(THR),and improves the flame retardant effect.Secondly,PET composites were prepared with halogen-free flame retardants MPP and ZB,and their thermal stability,mechanical properties,flame retardancy and crystallization behavior were studied.The results show that MPP has great damage to the mechanical properties of the material,and the combination of ZB and MPP can reduces the loss of mechanical properties of the composites.The addition of filler will reduce the effect of the cooling rate on the crystallization of the composite.The addition of ZB will increase the absolute crystallinity and initial crystallization temperature of the PET/MPP composites,and promote PET crystallization.According to thermal stability test,ZB and MPP can help to promote the composite material to carbon.The combination of ZB and MPP added to PET has higher thermal stability than the sole usage of MPP.In terms of flame retardancy,ZB and MPP both have flame retardant effects,but the effect is not good when ZB is used alone as the flame retardant.When ZB is used in combination with MPP,good flame retardant effect can be achieved.Last but not the least,the flame retardant ADP and conductive filler Fe powder were also added to the matrix to prepare PET composites.The mechanical properties,electrical and thermal conductivity,thermal stability,flame retardancy and crystallization behavior of PET composites were studied.The agglomeration and toughening effect of Fe powder result in a reduction of the tensile strength and an increase of the impact resistance for the PET composites.The addition of ADP decreases the thermal stability of the composites to an extent,and the addition of Fe powder can obviously improve the thermal stability of the material.The addition of ADP increases the crystallinity of the matrix,while the addition of Fe powder will hinder the movement of the polymer macromolecular segments and slow down the crystallization of the matrix.The addition of Fe powder can effectively improve the thermal conductivity of the material.The more Fe powder,the stronger the material's thermal conductivity.The dielectric test shows that the addition of Fe powder increases both dielectric constant and conductivity and reduces the insulation of the composite material,indicating that the Fe powder can improve the antistatic ability.Combustion data show that after adding ADP,both HRR and THR values of PET composites are significantly reduced with LOI reaching 36% and V-0 rating passed,indicating that ADP can effectively improve the flame retardancy of the composites.The addition of Fe powder can have a certain flame retardant effect on the material,and improve the carbon formation rate of the material.