Preparation Of Modified MCA Phosphorus-nitrogen Synergistic Flame Retardant And Its Effect On Flame Retardancy Of PA6

The first developed engineering plastic,polyamide 6(PA6),has been widely used in various fields for its excellent performance.However,the limiting oxygen index(LOI)of PA6 is only 23,which means burninng easily.The electrical and electronic applications of PA6 are restricted because of its flammability,and so more and more researchers put forward a higher demand on the flame retardant PA6 and it gradually becomes a hot topic.Melamine cyanurate(MCA)is a nitrogen-based flame retardant and it is suitable for PA6.Nowadays,MCA take much attention by many researchers for its high flame retardant efficiency and environmental friendly on PA6.Unfortunately,MCA is an additive flame retardant and the mechanical properties of the traditional MCA flame retardant PA6 were reduced for the high addition amount of MCA to reach UL-94 V-0 level.And the traditional synthesis of MCA has some problems,such as the high viscosity,resulting in difficulty to continue this reaction.To improve the properties of MCA,four kinds of phosphorous-nitrogen synergistic flame retardants were prepared by using phosphorus-based flame retardants to modify MCA and comprehensively explored the effects of modified MCA on the thermal stability and flame retardancy of PA6.The falme retardant mechanism of PA6 was also investigated.The main contents of this paper are summarized as follows:1.MCA-P,MCA-?-ZrP,MCA-ADEPH and MCA-DOPO phosphorous-nitrogen synergistic flame retardants were prepared through self-assembly of melamine and cyaburic in the aqueous suspension of phosphorus(P),diethyl hypophosphite(ADEPH),?-zirconium phosphate(?-ZrP)and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide(DOPO),respectively.The viscosity of modified MCA reaction system was lower than MCA,and the particle size of the modified MCA was smaller,the structure and properties were characterized.2.The PA6/modified MCA composites were prepared by adding the above flame retardants into PA6.The dispersion of MCA in PA6 was observed.The flame retardancy of PA6/modified MCA were tested.The results showed that the flame retardantcy were much better and reached UL-94 V-0 level.3.The flame retardant mechanism of each flame retardant was explored,it was concluded that the four kinds of flame retardants could promote the formation of compact charred layer,increased the condensed phase flame retardant mechanism,promoted the degree of cross linking and graphitization,interrupted the chain reaction of PA6 during combustion,and effectively prevented PA6 from burning.4.The mechanical properties test showed that the tensile strength of PA6/ MCA-ADEPH composites were slightly decreased,the elongation ratio at break and the impact strength were increased and the comprehensive mechanical properties were improved.The mechanical properties of PA6/MCA-?-ZrP composite had almost no changes.The tensile strength of PA6/MCA-DOPO composites decreased while the impact strength increased,and the elongation ratio at break increased and then decreased.