Preparation Of Phosphorous-containing And Bimetallic ZIFs Composites And Their Improvement On The Flame Retardancy Of EP

In modern times,due to the progress of polymer material science and technology,the functional,sustainable,environment friendly and safe polymer materials have been higher target requirements.However,as the pristine disadvantages,the poor stability and the high flammability have always been a fatal shortcoming of polymer materials,which seriously restricts its wide application in the production and life.As one of the important auxiliaries,flame retardant has been seriously considered and widely used in the consumer manufacturings,the household furnitures as well as the building constructions processes.At the begaining of this century,many researchers found that helogen-free flame retardant showed promising fireproof properties as well as smoke expression performances.However,after the careful studying of the death case of the fire accident,they found that many of the casualties were murdered by the toxic smoke producing by the combustion of some helogen-involning flame retardant,in which many of the toxic gases including dioxins was released and hurt the people as well as the environment.Therefore,the application of helogen-containing flame retardant was stricktly restricted.Based on this background,due to the good fire-preventing properties,many phosphrous,nitrogen,boron and hydroxide-containing flame retardants received much attentions.However,they also suffered from the poor compatiblity in the matrix,which would cause the agglomeration and the decrease of the mechanical properties of a material,and then affect its large-scale applications.Epoxy resin(EP)is widely used in various fields of.It is a thermosetting polymer material,which has the characteristics of convenient curing,chemical stability and mildew resistance.Unfortunately,it is also a kind of flammable material.The toxic flue gas produced during the combustion of EP possesses a serious of threats to human beings and nature.Therefore,EP composite materials should be explored in the aspects of high efficient flame retardancy,good mechanical properties and environmental friendly.In this paper,the compatibility of P-N and P-B system in the matrix material of EP was improved by the method of organic-inorganic hybrized approach.Meanwhile,the flame retardancy,smoke suppression and the mechanical properties of EPcomposites were also well improved.In addition,two new flame retardant elements of Zn and Co were introduced by inorganic coordination method during the synthesis of ZIFs-based flame retardant,which can not only improve the flame retardant ability but also reduce the smoke emission,therefore,to achieve the promising smoke suppression performance of EP composites.The main research contents are as follows:1.A new type of intrinsic flame retardant containing phosphorus was prepared with L-tryptophan(L-Trp)and 9,10-dihydro-9-oxa-10-phospho-10-oxide(DOPO)as main components.The active sites were provided by the organic reaction of 1,4-p-phenylene aldehyde and L-Trp through the formation of Schiff base structure.Then DOPO was successfully introduced into the Schiff base structure to synthesize L-Trp-DOPO flame retardant.The structure,morphology and flame retardant properties of EP/L-Trp-DOPO composites were characterized.The results showed that the value of the heat release rate(HRR)decreased by 50.8%(from 1459 k W/m²to 717 k W/m²),the value of the total heat release(THR)decreased by 64%,and the value of the limited oxygen index(LOI)increased to 22%.From the mechanism of solid phase and vapor phase flame retardant,it can be found that the presence of P and N elements can effectively reduce the heat release and the release of harmful volatiles of EP composites.In addition,the reaction between the carbonyl group of L-Trp-DOPO and the epoxyl group in EP can significantly promote the mechanical properties of EP composites.2.A functional hollow spherical-shaped B₂O₃@BPO₄-X flame retardant was designed and prepared through the grounding of B₂O₃and(NH₄)₂HPO₄in an agate mortar and then calcination of the mixed powder at different temparature in a porcelain boat in a muffle furnace.The functionalized B₂O₃@BPO₄-X flame retardant was applied to the EP matrix.Its structure and properties were characterized.The results of cone calorimetry(CCT)showed that the THR value of EP/composite was also decreased compared with that of the pure EP.The THR value of EP/B₂O₃@BPO₄-600? composites decreased by 19%,which indicated that the catalytic carbonization of the composites could be promoted when P and B elements were introduced at the same time,and the flame retardant performance of EP was simultaneously improved.3.Using dimethyl imidazole,zinc nitrate and cobalt nitrate as raw materials,through simple coordination reaction,a new ZIFs-based flame retardant of CoZn-ZIF-L with Zn and Co in the molecular skelton was prepare.The preparation of the composite material adopts a curing method so that the flame retardant is more uniformly dispersed in EP matrix.The flame retardant performance test showed that the value of the peak heat release rate(pk-HRR)of EP/CoZn-ZIF-L composites reduced to 516 k W/m²,the THR value reduced to 87.01 k W/m²,and the LOI value increased to 22%,respectively.Through the exploration of the flame-retardant mechanism,it found that the introduction of Co and Zn can significantly improve the flame-retardant performance of EP,and these two metal oxides have a certain positive effect on smoke suppression in combustion.