| Sodium bicarbonate is a green and environmentally friendly foaming agent,but due to its low decomposition temperature and wide decomposition temperature range,it cannot meet the functional and lightweight requirements of polyolefin materials,which limits its popularization and application.In this paper,the sodium bicarbonate capsules were prepared by the modification method of single coating and multiple coatings to improve the performance,and the optimal modification process was optimized.The decomposition temperature of EP@SB was increased,and its decomposition temperature range was narrowed,which was to expand the environmentally friendly sodium bicarbonate.The application of blowing agent in polyolefin materials provides theoretical and experimental guidance.The main conclusions are as follows:A new material of epoxy resin@sodium bicarbonate(EP@SB)microcapsules using SB as core and EP as shell were synthesized.It was found that too large or too small sodium bicarbonate particles were not conducive to the preparation of sodium bicarbonate micro,and when the particle size of sodium bicarbonate was 200 mesh,the mass ratio of epoxy resin to sodium bicarbonate was 1:5.The decomposition temperature of the sodium bicarbonate capsules obtained by epoxy modification was increased from 119°C to 155°C;the decomposition temperature range was reduced from 67°C to 25°C;the epoxy-modified sodium bicarbonate not only enhanced thermal stability,but also improved dispersion performance.In order to further increase the decomposition temperature of sodium bicarbonate,enhance the strength of the coating layer,and improve the insulation and barrier effect of the outer shell layer on the core sodium bicarbonate,so as to achieve the purpose of improving the decomposition temperature.EP@SB was modified with citric acid(CA),palmitic acid(PA),and stearic acid(SA)as modifiers by secondary coating to prepare SA/EP@SB and other capsules.The results showed that the introduction of organic acids could effectively improve the decomposition temperature and decomposition temperature range of sodium bicarbonate.The decomposition temperature of EP@SB capsules could be increased to 178?,when the modifier was palmitic acid,the solution p H was 2,and the mass ratio(EP@SB:PA)was 1:1.5.Successfully realized that mica(SER),hydrotalcite(LDHs),montmorillonite(MMT)and silica(Si O2)nucleating agent were loaded on the surface of EP@SB capsule.The results showed that the specific surface area(BET)of EP@SB after the loading of these four nucleating agents was large,and the dispersion performance was better,but it had little effect on the thermal performance of EP@SB.The addition of nucleating agents could slightly reduce the initial decomposition temperature of EP@SB.The single modified and multi modified sodium bicarbonate capsules were used in the foaming of polypropylene(PP)by injection molding,and explore the effect of various modifiers on the modified sodium bicarbonate foamed polypropylene impact.The results showed that the foaming effect of the modified sodium bicarbonate has been significantly improved,the cells diameter was reduced,and the cell density was significantly increased.In addition,the cells structure of foamed products prepared by multiple modified sodium bicarbonate was better than that of foamed materials prepared by single modification of SB with epoxy resin.Especially when long-chain PA was introduced into the surface of EP@SB,the cell diameter decreased from 163?m to 108?m,and the cell density increased from 8.72×105 cells/cm3 to 1.31×106cells/cm3.The EP@SB and PA/EP@SB composite nucleating agents were used to prepare foamed polypropylene materials,and the nucleating agents and foaming agents were separately added to the polypropylene foamed materials to conduct a comparative study.The results showed that the foaming behavior of EP@SB and PA/EP@SB after modification with nucleating agent in polypropylene is significantly better than that of direct mixing of traditional nucleating agents.Among them,the foamed polypropylene material with mica had better effect,regular cell morphology,high foaming ratio,cell density was increased from8.72×105 cells/cm3 to 1.07×106 cells/cm3,and cell diameter from 163?m was reduced to 94?m.The polypropylene foamed product prepared by coating the nucleating agent on the surface of the foaming agent had better impact performance than the foamed product prepared by adding the nucleating agent and the foaming agent to the polypropylene separately,and the impact strength was increased from 4.12 KJ/m2 to 6.11KJ/m2. |
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