Study On The Synergistic Performance Of ZIF-67 Modified Attapulgite On EVA Flame Retardant Composite

EVA was a kind of polyolefin with excellent performance and wide application.,However,EVA was extremely flammable and has a high fire risk during use.Therefore,it was very necessary to improve the flame retardant of EVA materials by applying flame retardants.There were many kinds of flame retardants,including:magnesium hydroxide（MH）,aluminum hydroxide（AH）,ammonium polyphosphate（APP）,intumescent flame retardant（IFR）and other additive flame retardants.However,these additive flame retardants had low flame retardant efficiency.It was necessary to solve this problem by adding flame retardant synergistic agent or surface modified flame retardant in composites.In this thesis,a flame retardant synergist（ZIF-67@ATP）was prepared by the in-situ growth of ZIF-67 on attapulgite（ATP）.It was added into EVA/MH composites by melt blending to study the flame retardant and mechanical properties of the composites.In order to further broaden the application of ZIF-67@ATP in flame retardant modification of EVA materials,a modified APP（MAPP）was prepared by combining ZIF-67@ATP and APP through the self-polymerization of dopamine,and added it into EVA/APP composites.The flame retardant properties of the composites were researched by limiting oxygen index（LOI）,vertical combustion test（UL-94）and cone calorimetry test（CCT）.The mechanical properties of the composites were explored by tensile test and unnotched impact test.The specific research contents were as follows:1 ZIF-67@ATP was prepared by in-situ growth of ZIF-67 on the surface of ATP.ZIF-67 was used to introduce cobalt that had catalytic charring performance.The results showed that the absorption peaks of C=N and C-H bonds were found at 1420 cm^-1 and 2960 cm^-1respectively in the infrared spectrums of ZIF-67@ATP;In X-ray diffraction experiment,ZIF-67@ATP had diffraction peaks at around 2θ=7.4°,12.7°and 18.06°respectively,which were assigned to（011）,（112）and（222）crystal planes of ZIF-67.The characteristic peak of cobalt appeared at 781.5 e V in XPS spectrum.According to EDS results,the cobalt was found on the surface of ZIF-67@ATP.According to TEM image the surface of ZIF-67@ATP become rough.The above experimental results show that ZIF-67@ATP was successfully synthesized.2 EVA/MH/ZIF-67@ATP composites were prepared by melt blending method,and the,flame retardancy and mechanical properties of the composites were studied.The results show that when the addition of ZIF-67@ATP was 3 wt%,the LOI of the composite reached43.0%,which passed the V-0 level in the vertical combustion test,while EVA/MH composite has no grade in the vertical combustion test.Through the mechanical property test,it was found that the tensile strength of composites did not change significantly.When the addition of ZIF-67@ATP reached 4 wt%,the elongation at break of the composite had increased from 69.53%to 522.16%compared with EVA/MH composite.3 A modified APP（MAPP）flame retardant was prepared through combining ZIF-67@ATP with APP by through the self-polymerization of dopamine and applied to EVA/APP composites.When 3 wt%MAPP replaced the unmodified APP,the limiting oxygen index of the composite increased to 25.9%,and reached the V-0 rating in UL-94 test.Compared with pure EVA,the peak heat release rate of the composites decreased by 60.8%and 12%respectively.The tensile strength and impact strength of the composites did not change significantly,and the mechanical properties did not deteriorate significantly.The ZIF-67 modified attapulgite and surface-modified ammonium polyphosphate prepared in this thesis showed good performance in the flame retardant modification of EVA composites,providing a new idea for application of attapulgite in the field of flame retardant polymer materials.