Synthesis Of Modified Melamine Cyanurate And Its Application In Flame Retarding Polyamide6

In this dissertation, a novel technology was established to synthesize modifiedmelamine cyanurate (MCA). Product’s properties were well promoted aftermodification and a new type of MCA flame retardant was prepared successfully.Based on it, halogen-free flame retardant polyamide6(PA6) composites with efficientflame retardancy and high comprehensive performance were prepared, and the flameretarding mechanism was studied.In view of some problem existing in traditional technology of preparing MCA,zinc borate microcrystalline was applied to control the synthesis process of MCA inthis paper. Namely, zinc sulfate, zinc oxide and borax were added in accordance withcertain proportion in the process of MA-CA aqueous hydrogen bonding compoundreaction to deposit zinc borate on the surface of MCA primary self-assembles dividingthe raction system into smaller independent reaction systems so that the viscosity ofthe reaction system was maintained in a low level from beginning to end. Moreover,the ratio of water/reactants was reduced from4:1to2:1compared with theconventional raction system. The novel preparation technique premoted the reactionrate as well as conversion rate and overcame the disadvantages of conventionaltechnique such as string trouble, huge emissions of waste water, low productionefficiency, etc. Not only the technique was optimized by viscosity measurement andcoversion calculation but also the structure and properties of modified MCA wascharacterized by the analysis of infrared spectroscopy (FT-IR), thermo-gravimetric(TG) and scanning electon microscope (SEM). The results showed that the optimumdosage of modifier zinc borate was4~5%so that the viscosity of modified reactionsystem could drope by two orders of magnitude, from2×10~6mPa·s to5×10~4mPa·sand the raction conversion rate rose from80%to94.8%at the same time. IR spectrapicture indicated that the structure of zinc borate modified MCA did not changed.Though the decomposition temperature dropped by nearly120℃as was seen fromthe results of thermal weightlessness, it’s still above the processing tempreture of PA6.As was showed in SEM pictures, MCA product granules were ultrafine particles andwere evenly dispersed in the presence of zinc borate microcrystalline.The properties of modified MCA flame retardant PA6were characterized bylimited oxygen index (LOI) test, vertical burning test, SEM analysis, TG analysis, differerential scanning calorimetry (DSC) analysis, etc. Due to the synergistic flameretardant effect of zinc borate, modified MCA showed higher flame retardancy thantraditional MCA. Flame retardant PA6reached UL94V-0level with the loading of20%modified MCA and the LOI was premoted by2~3%compared with unmodifiedMCA flame retardant PA6. The results of SEM showed that zinc borate couldimprove the dispersion state of MCA particses in PA6resin. In addition, zinc boratecould accelerate the thermal degradation process of PA6to generate compact carbonlayer in the combustion so as to improve the flame retardancy of modified MCA ascould be indicated from the results of Carbon layer morphology SEM pictures andthermal gravimetric analysis. The crystallization behavior and mechanical propertiesof modified flame retardant PA6was improved as well. Crystallinity was increasedfrom29.61%to33.33%and the tensile strength, flexural strength and izod impactstrength were inceased by15.5%,5%and10%respectively too.