Synthesis Of Zirconium Organophosphonate And Study On Properties And Mechanisms Of Flame Retardant And Toughened Epoxy Resin Composites

Epoxy resin(EP)has good mechanical strength,electrical insulation,chemical stability,corrosion resistance and excellent bonding properties,making it widely used in various fields.However,like general polymer materials,EP composed of C,H,and O is extremely flammable and easy to cause fires.With the release of a large amount of smoke and toxic gases,it is easy to suffocate and die,which brings great difficulties to rescuers.Moreover,the crosslinking density of EP after curing is very high,resulting in EP having high rigidity,high brittleness,and easy brittle fracture.The flammability and brittleness of EP limit its scope of application.Aiming at the flammability and brittleness of EP mentioned above,this paper uses zirconium organophosphonate with excellent thermal stability and acid-catalyzed carbon-forming ability as the flame retardant and smoke suppressant and strengthening and toughening agent of EP.The organic zirconium phosphonate nanoparticles have weak Bronsted acid sites and strong Lewis acid sites derived from P-OH and Zr4+,which have acid catalysis and can promote the carbon formation reaction of EP,and the dense carbon layer formed can act as a physical barrier,It can cut off the heat and mass exchange,and has the effect of flame retardant and smoke suppression on EP.Zirconium organophosphonate has good interface compatibility with EP,can be uniformly dispersed in the EP matrix,and has a strengthening and toughening effect on EP.The synthesis of different zirconium organophosphonates through molecular design shows that these zirconium organophosphonates have good flame retardant and smoke suppression and toughening effects on EP.The following is the main research content of this paper:1.The layered compound zirconium phenylphosphonate(ZrPP)was prepared using a monophosphonic acid phenylphosphonic acid as a raw material.XRD results show that the interlayer space of ZrPP is 1.474 nm,which is larger than α-ZrP(0.743nm).This is because a lot of phenyl groups are bonded to the layer of ZrPP,which is larger than the hydroxyl group on α-ZrP,which enlarges the space position between the sheets.The lamella characteristics of ZrPP were observed by SEM and TEM.ZrPP exhibits a lamella structure similar to α-ZrP.The lamella size is basically within 1 μm,and the lamella size is relatively dispersed.TGA results show that ZrPP has good thermal stability,and the pyrolysis mass loss is mainly due to the phenyl group.The combustion of pure EP produces a large amount of flue gas and heat.Compared with pure EP,the PHRR,THR,TSR and COPR of 3wt%ZrPP-EP composite material are reduced by 7.6%,11.2%,17.5%and 16.7%,respectively.It can be seen that ZrPP has a certain flame-retardant and smoke-suppressing effect on EP.The tensile strength of pure EP is 35.10 MPa,and the elongation at break is 3.31%.Compared with pure EP,the tensile strength of the 2wt%ZrPP-EP composite is increased to 49.49 MPa,an increase of 41.0%;the elongation at break is 4.96%,an increase of 49.8%.With the increase of ZrPP addition,the tensile strength and elongation at break of ZrPP-EP composites gradually increase,indicating that ZrPP has the dual effects of strengthening and toughening EP.The impact strength test results further confirmed the toughening effect of ZrPP on EP.2.A kind of bisphosphonate N,N-bis(phosphonate methyl)glycine(GDMP)was prepared by Mannich reaction,and complexed with zirconium oxychloride to form layered Zirconium N,N-bis(phosphonate methyl)glycine(ZrGDMP).Compared with pure EP,the tensile strength of 3wt%ZrGDMP-EP is increased to 57.65 MPa,an increase of 73.2%;the elongation at break is 5.67%,an increase of 56.6%.The impact strength of 3wt%ZrGDMP-EP reaches 24.8 kJ/m2,which is an increase of 55%compared with pure EP.It can be seen that ZrGDMP has a strengthening and toughening effect on EP.Compared with the ZrPP prepared in Chapter 2,ZrGDMP has a better flame retardant and smoke suppression effect on epoxy resin.It may be because the bisphosphonic acid structure of GDMP makes ZrGDMP have higher flame retardant efficiency.The elemental composition also proves this point(ZrPP has a P content of 10.49%,ZrGDMP has a N content of 6.93%,and a P content of 14.21%).ZrGDMP has a higher P content and P-N synergistic flame retardant effect,which reduces the fire hazard of composite materials.3.Zirconium aminotrimethylene phosphonate(ZrATMP)was prepared by a triphosphonic acid amino trimethylene phosphonic acid(ATMP),which exhibited a rod-like structure.Compared with pure EP,the PHRR,THR,TSR,COPR of EP composites with 3wt%ZrATMP decreased by 30.4%,39.2%,23.1%and 47.3%,respectively.The tensile test shows that ZrATMP can significantly increase the tensile strength and elongation at break of EP.Compared with pure EP,the tensile strength of 3wt%ZrATMP-EP is increased to 68.03 MPa,an increase of 110.7%;the elongation at break is 5.55%,an increase of 66.2%.The excellent reinforcement and toughening effect of ZrATMP on epoxy resin composites is due to the amino and methylene groups on the ZrATMP molecule,which can effectively improve its interface compatibility with the EP matrix,so that the ZrATMP molecule can be better dispersed In the EP matrix.When the EP composite material is subjected to an external force,the well-dispersed ZrATMP nanoparticals will produce a stress concentration effect,absorb energy,reduce internal stress,hinder crack propagation,and have a toughening effect.4.Based on inorganic-organic hybrid technology,a new type of organic zirconium phosphonate(CZrP)was synthesized from biomass cardanol.The interlayer spacing of CZrP increases to d=4.12 nm.This is because the long side chain of cardanol is inserted into the CZrP lamella to increase the interlayer spacing.From the TEM pictures of EP/ZrP-6%and EP/CZrP-6%,it can be seen that ZrP nanosheets are obviously agglomerated in the EP matrix,while CZrP nanosheets can be well dispersed in the EP matrix.Compared with pure EP,the PHRR of EP/CZrP-6%is reduced by 42%.When the same amount of ZrP is added to EP,PHRR is only reduced by 16%.Compared with pure EP,the THR value of EP/CZrP-6%is reduced by 21%.Compared with pure EP and EP/ZrP composites,all EP/CZrP composites have lower TSP values.The COPR of EP/CZrP composites gradually decreases,which is much lower than that of pure EP and EP/ZrP composites.Compared with pure EP and EP/ZrP composite materials,all EP/CZrP composite materials have a lower FIGRA value.The FIGRA value is greatly reduced from 13.5 kW/(m2·s)of pure EP to 7.2 kW/(m2·s)of EP/CZrP-6%.Compared with pure EP,FIGRA is reduced by 47%,which means that CZrP is obviously reduce the fire hazard of EP.The increase in tensile strength of EP/CZrP composites is attributed to the reinforcement of well-dispersed two-dimensional CZrP nanosheets,and the increase in elongation at break is attributed to the good toughening effect of the long alkyl chain of cardanol on CZrP.5.In order to solve the problem that the inorganic ZrP nanoparticles are easy to agglomerate in the EP matrix,the α-ZrP nanosheets are pre-intercalated with methylamine,and then hydrolyzed with the organic modifier KH550,and the aminopropyl component is grafted on the nanosheets.The FTIR test showed that small methylamine molecules were successfully intercalated into the ZrP layer,and KH550 was successfully grafted onto the ZrP layer.In order to further improve the UL-94 combustion test performance of EP composites,OZrP is used in combination with the intumescent flame retardant system IFR(ammonium polyphosphate/pentaerythritol).The OZrP/IFR composite system significantly reduces the release of heat,smoke,toxic gas and CO of EP composites.The LOI value of pure EP is only 25%,and the LOI value of EP composites with 20wt%IFR and 3wt%OZrP increased to 45%,reaching the UL-94 test V-0 level.Compared with EP,the PHRR,THR,TSR,COPR of EP composites with 20wt%IFR and 3wt%OZrP decreased by 79.1%,58.3%,62.8%and 80.9%,respectively.This is mainly because OZrP has an acid-catalyzed carbon-forming effect,which can catalyze the carbon-forming of EP.The IFR system can quickly form a protective carbon layer on the surface of the EP material to inhibit heat and mass exchange.Compared with inorganic ZrP,EP composites with OZrP have higher impact strength,thanks to the grafted organic molecules on OZrP and the large interlayer spacing,so that OZrP can be better dispersed in the EP matrix.