| Rubber is an important component of polymer materials. It is widely used in industrial production and our daily life, it also can be used for the preparation of shock absorber, tires, conveyor belt,defense products, et al. Natural rubber is the most widely used general rubber. However,natural rubber molecular structure feature makes it easy to burn, and the limit oxygen index is only 18%, but many industries and situations require flame retardant natural rubber products, therefore,the research and development of flame retardant natural rubber is promising.This paper firstly discussed the solubility of thermal activation APP, we found that the solubility of II-APP had remained at the lower level before and after activation, but I-APP’s solubility was greatly influenced by activation time. Then,we studied the thermal activation APP modificated by MEL and CH2 O, through analysis of the FT-IR confirmed that the modification was successed.After grafting, the water solubility of RMAPP and RCMAPP were lower than APP. And then we discussed the properties of flame retardant when added in 40 phr various kinds of flame retardants, we found that the APP had a better effect on nature rubber after thermal activation, the LOI was increased from 23.8% to 25.3%. When compounded with PER,the LOI was great increased to 26.1%. After grafting modification with CH2 O, RCMAPP improved the flame retardant effection and the LOI reached 26.3%. In the same way, after compounded with PER,the LOI reached 26.9% and could satisfied UL94V-0 level test. The results could be further verified through the cone calorimetry test, thermogravimetric experiment, scanning electron microscopy(sem) test.Secondly, we studied the vulcanization properties of natural rubber when it was directly added DOPO, we found that both peroxide vulcanization system and sulphur vulcanization system cannot made it vulcanized, the main reason is that DOPO’s acid inhibits the vulcanization. Therefore, we considered using KH-560 to modify DOPO. After the modification, natural rubber can normal vulcanization when added in DK, and peroxide vulcanizing had better effect than the sulfur curing system, but there was still a certain inhibition. We continued to explore the vulcanization properties of DK flame retardant of natural rubber after using white carbon black and active metal oxide, we found that they all can promote vulcanization and increase crosslinking. After adding 60 phr white carbon black, the tensile strength and tear strength of DK flame retardant natural rubber had increased by 81.2% and 63.2%.After adding 40 phr DK, the LOI of natural rubber can reach to 25.6%, the LOI reached 26.4% after adding 60 phr white carbon black, both of them can satisfy UL94V-0 level. Cone calorimeter results showed that, compared to add 20 phr DK, the PHRR was reduced from 559.9 k W/m-2to 519.8 k W/m-2and the THR was reduced from 108.4 MJ/m2 to 96.01MJ/m2 when adding 40 phr DK.At last,we discussed epoxy modified natural rubber by using formic acid and H2O2, through the infrared spectrum analysis, we found there were new characteristic absorption peaks of epoxy group formed in 1255cm-1and 906cm-1,which conformed that ENR had successfully prepared. We studied the vulcanization properties of ENR when directly adding DOPO, it showed that ENR could vulcanize but there still have certain restrictions, so we made some research on the mechanism of vulcanization. We discussed the flame retardant properties of ENR influenced by APP, when add 40 phr APP,the LOI was increased by 0.3% compared with NR, then added 20 phr DK and 60 phr white carbon black, the LOI of ENR had reached 26%, and could satisfy the UL94V-0 level.According the cone calorimeter test, when added in the same phr of APP and DK, flame retardant ENR had lower PHRR, MHRR, THR than NR. Thermogravimetric analysis also showed that heat resistant properties of ENR had improved, scanning electron microscopy(sem) of carbon residue structure was further confirmed the results. |
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