Preparation And Study Of Reactive P-N Flame Retardant Based On Polyurethane

Polyurethane（PU）,the world’s fifth-largest plastic,is favored for its good handling characteristics,attractive price,and uncomplicated production engineering,which apply in aviation,construction,medical,electronics,and other industries.It’s a material constituted by polyether polyols and isocyanates in different permutation and inline segments.This structure causes the PU to have an inherent problem of fire,which badly hinders its application.Therefore,scientists began to develop suitable PU flame retardants.The current research focuses on halogen-free flame retardants because the halogen flame retardant is harmful to humans,in which phosphorus flame retardants（P-FRs）present a better compositive performance.A small number of P-FRs have begun to replace halogen flame retardants appear on the market.P-FRs are popular due to their powerful dehydrated carbonization ability that can form a protective layer on materials.However,a P-FR has its limitation with only phase flame retardant mechanism,and researchers have set their sights on the field of phosphorus-nitrogen flame retardants（P-N FRs）to build a two-phase flame retardant mechanism.Most existing P FRs contain rigid structures such as aromatic,spirocyclic structures,etc.,which are good at dehydrated carbon,but may be harmful to mechanical behavior and may affect the following reaction.In this article,a cyclic P,O,C structure was synthesized,with both strong dehydrated carbon properties and flame retardant performance.Meanwhile,the molecule structure is a flexible alkyl chain,which can reduce the effect on the polymer.Then the gas phase flame retardant molecule（N FR）,a nitrogen-containing five-membered ring,is introduced on the cyclic structure so that the prepared flame retardant has both condensed and gas phase flame retardant mechanism.The dihydroxy structure introduction can obtain the main chain containing phosphorus polymer by molecular design.At this time,the P-containing cyclic structure is at the side chain.Thus,poor mechanical behavior and easing migration caused by small-molecule FRs mixed into the polymer can be reduced or avoid,and hold the high flame retardancy.In this paper,the preparation of cyclic P-N flame retardant,PU foam,and PU elastomers are prepared separately:1、Prepared the cyclic P-containing molecule and N-containing five membered ring,and achieved the dihydroxy P-N containing structure,which is the reactive cyclic P-N flame retardant.It’s structure and thermal behavior have been characterized;2、Reactive cyclic P-N FR/polyurethane foam: the LOI value of this material up to23.7%.Through the SEM and XPS,the material surface formed a dense carbon layer with bubble holes,which indicates that the HAMPP played both gas-phase and condensed-phase FR mechanism.However,the problem of molten drop for flexible PU foam is still not well solved;3、Reactive cyclic P-N FR/expandable graphite/PU foam: To further solve the molten drop problem for flexible PU foam,we introduce an expandable flame retardant assistant——expandable graphite,reacts with HAMPP and acts on the flexible PU foam.The results show that the LOI value can reach 27.8% and pass the UL-94 V0 grade;4、Reactive cyclic P-N FR/polyurethane elastomer: To further study the HAMPP universality in PU,we choose PU elastomer as a base material and do further research.The result shows that the LOI value can reach 25.8%,indicates both good flame retardancy and positive mechanical behavior is positive.