| Epoxy resin is a kind of the thermosetting polymer materials which has a good performance, but its application is limited due to its flammability. Therefore, it is very important to study on the flame retarded epoxy resin. A lot of flame retardants are used for epoxy resin, but there are some shortcomings, such as the high toxicity and a greater influence on the mechanical properties of materials, and so on. Hexaanilinocyclotriphosphazene (HPACTPZ) is a new type of phosphorus-containing flame retardants which is developed at home and abroad in recent years, it has an excellent flame retardant effect in expoxy reisn and so on, but its research is still little at home and abroad, so it has not been industrialized. Therefore, the study on its synthesis and application has an important significance to the development of green flame retardants and flame retardant materials.In this paper, HPACTPZ was synthesized using hexachlorocyclotriphosphazene and aniline as starting materials, and triethylamine as an acid-binding agent. The results showed that the type and amount of solvents were key factors forthe synthesis, and chlorobenzene was an ideal solvent and the yield of the product was increased by reducing the amount of chlorobenzene. The optimum reaction conditions are as follows:n(hexachlorocyclotriphosphazene):n(aniline):n(the acid):n(triethylamine)=1: 7.2:6.6, w(hexachlorocyclotriphosphazene):w(chlorobenzene)=1:3.5, reaction tempera-ture being 90 ℃, and reaction time being 15h. Under the above conditions, the yield of the product could be up to 80.42%, the melting point was 268-270 ℃, the purity is more than 95%. The improved process has many adventages, such as simple process, mild conditions, high product yield and quality and soon. In addition, chlorobenzene has lower toxicity and cheaper, lower consumption and easy to recycle.The flame retardancy of HPACTPZ and its combinations in epoxy resin/modified alicyclic amine (E-44/DG593) was studied. The results showed that HPACTPZ had bad flame retardancy, and there was no synergistic flame retardancy between aluminium dipropylphosphinate (ADPP) and HPACTPZ and little synergistic flame retardancy between HPACTPZ and polyaminocyclotriphosphazene (PHACTPA) in E-44/DG593. With 25wt.% dosage, the LOI of the flame retarded(FR-)E-44/DG593 with HPACTPZ or PHACTPA was 24.0% and 26.6% respectively, both vertical burning rating failed, but with the combination of HPACTPZ and PHACTPA with the weight ratios of 1:4, the LOI was 27.3%, and the V-1 could be achieved. However, compared with FR-E-44/DG593 only with PHACTPA, total heat release (THR), average heat release rate (MHRR), peak heat release rate (PHRR), average effective heat of combustion (MEHC) of HPACTPZ/PHACTPA/E-44/DG593 were higher. TGA results showed that the thermal stability of the FR-E-44/DG593 was improved with HPACTPZ/PHACTPA instead of PHACTPA. The analysis of residues obtained in cone calorimeter tests revealed that HPACTPZ, PHACTPA and HPACTPZ/PHACTPA played the role of flame retardance mainly by condensed phase mechanism. They were decomposed into phosphoric acid compounds in the combustion process, which promoted the carbonization of E-44/DG593 by dehydration strongly, and CO2, NH3, N2 and other inert gases released from the decomposition of E-44/DG593 and flame retardant foamed the carbon. The intumescent layer resulted in a flame retardancy by the barrier effect on heat, air and volatile decomposition products. The conversion of HPACTPZ into phosphoric acid compounds is less, thus its ablity to promote the carbonization is more weak, so its flame retardant effect was poor, while the conversion of HPACTPZ and HPACTPZ/PHACTPA into phosphoric acid compounds is more, thus its ability to promoted the carbonization is more strong, so they have a good flame retardancy. |
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