Study On Preparation Of Microencapsulated Hyphosphites And Their Application In Flame Retardant Glass Fiber Reinforced Polyamide 6

Glass fiber reinforced polyamide 6(GFPA6)is a kind of engineering materials with good comprehensive performance,but easier to burn than polyamide 6(PA6)and burning with a lot of flame droplets due to "wick effect",which limits its application in electronic and electrical,transportation,office automation and other fields.As halogen-free and high efficient flame retardants for GFPA6,Organic phosphinates have complex synthetic routes and high cost.Hypophosphites are lower cost,have similar structure with organic phosphinates,but exist disadvantages such as less-than-ideal flame retardant efficiency,poor compatibility with PA6 and poor processing stability.To solve the problems above,the microencapsulation technology is introduced to prepare three kinds of microencapsulation hypophosphites with core-shell structure.And the products are applied to flame retardant GFPA6.The main research contents and results are listed as follows:Three kinds of cured epoxy compound microencapsulated hypophosphites flame retardants 1,3,5-triglycidyl isocyanurate microencapsulated aluminum hypophosphite(T-AlHP),1,3,5-triglycidyl isocyanurate microencapsulated calcium hypophosphite(T-CaHP)and E-51 epoxy resin microencapsulated aluminum hypophosphite(E-AlHP)are prepared.The core-shell structure and thermal stability of products are investigated by FT-IR,TEM,XPS and TG.The results show that three products have obvious core-shell structure and elevated processing stability.Temperature at 5%weight loss of three products are all above 300 ?,which can meet the requirement of GFPA6 processing.The technical conditions for preparation of three products are optimized by ATR-FTIR,and their better ratios of reactants are obtained.T-AlHP,T-CaHP and E-AlHP are compounded with melamine cyanurate(MCA),melamine polyphosphate(MPP)and 1,2-bis(dimelaminium of 1-nitro-3,5-diphospha-4-oxa-3,5-dihydroxy cyclohexane)ethane(EAPM)respectively.In addition,a small amount of silane coupling agent KH-560 is incorporated into the compounding system.Flame retardancy,thermal degradation properties,mechanical properties and compatibility of flame retardant glass fiber(30wt%)reinforced PA6 by above mentioned compounding system are investigated by the vertical combustion experiments,TG,mechanical test and SEM,respectively.The results show that at 20wt%loading of T-AlHP,lwt%loading of KH-560,the flame retardancy of the material preferably up to reach UL 94 V-0 rating(1.6 mm);meanwhile the tensile strength of material is 139.36MPa,which increases by 10.81%compared with neat GFPA6;nevertheless,the notched impact strength is decreased to 7.3 kJ/m2.Futhermore,although the material fails UL 94 rating at 20wt%loading of T-CaHP and 1wt%loading of KH-560,while its notch impact strength increases to 10.84 kJ/m.Both in air and nitrogen atmosphere,flame retardant GFPA6 by three compounding systems reduce the initial decomposition temperature while greatly improve the residual mass compared with neat GFPA6,moreover,only T-CaHP/MPP system in three compounding systems embodies a certain synergistic effect.The results of sectional SEM analysis show that all three flame retardants show no obvious agglomeration in GFPA6 after processing.The flame retardant mechanisms of flame retardant GFPA6 by microencapsulated hypophosphites are investigated by pyrolysis gas chromatography/mass spectrometry analysis,SEM and elemental analysis.The results show that the pyrolysis gas-phase products of all three flame retardant GFPA6 by microcapsulated hypophosphites does not include phosphorus-containing compound and the phosphorus almost whole retain in the residual char;certain correlation exists between the flame retardancy and the morphology of char.The mechanisms of microencapsulated hypophosphites flame retardant GFPA6 is a kind of condensed phase mechanism mainly based on char forming.By Kissinger,FWO and Starink methods,non-isothermal oxidation degradation kinetics of flame retardant materials are studied.The results show that the dosage of three microencapsulated hypophosphites can lead the change of thermal decomposition process of GFPA6,all of them play catalytic roles in GFPA6 charring.