Thermal Conductivity And Flow Property Study Of Boron Nitride/Gutta Percha Nanocomposites

Two-dimensional(2D)boron nitride(BN)exhibits anisotropy and its theoretical thermal conductivity can reach 2000 W(m·K)-1.For the sake of enhancing the thermal conductivity and flow performance of the gutta percha point in the root canal treatment,BN was introduced into the gutta percha in this thesis to improve the treatment efficiency as much as possible in the process of root canal treatment and reduce the pain of patients.The thesis consists of the contents as follows:(1)The gutta percha@zinc oxide/boron nitride(GP@ZnO/BN)composites and GP@BN composites were prepared by adding different BN content into GP@ZnO composites and gutta percha(GP),respectively.The thermal conductivity(TC)of GP composites improve significantly by fillers'synergy effect and orientation.When boron nitride addition content is 50 phr,the TC of the GP@BN hybrids is 0.279 W(m·K)-1,and GP@ZnO/BN hybrids has a thermal conductivity of 1.188 W(m·K)-1,which exceeds 325.8%of the former.What's more,oriented GP@ZnO/BN hybrids shows excellent TC performance(2.24 W m-1·K-1)and the TC growth is much higher than those of unoriented GP@ZnO/BN material(88.6%)and GP@BN composite(702.9%).(2)It was found in the melt mass flow rate test that the flow performance of the GP@ZnO/1-BN composites is improved by 2.5%compared to the GP@BN composite material when BN content is 1 phr,and hence,we propose the "skateboard effect".In order to verify the"skateboard effect",boron nitride(BN),talc powder(talc)and ball milling boron nitride were used to make a contrast experiment by using capillary rheometer.It was found that while the content of BN is 5 phr,the shear viscosity of the GP@ZnO/5-BN composites was reduced by 48.9%compared to the GP@BN composites(taking average shear viscosity among four shear rate of 100 s-1,200 s-1,300 s-1,500 s-1);comparing to GP@BN composites,the shear viscosity of GP@ZnO/2-talc composites reduced by 13.05%with 2 phr talc(taking average shear viscosity as above);when ball-milling boron nitride added,there is no "skateboard effect" in GP@ZnO/5-BN-b composites.This result validates the"skateboard effect",indicating that the two-dimensional material BN and talc powder can interact with the 0-dimensional(0D)filler zinc oxide(ZnO)filler to promote the flow of polymer materials.(3)GP@ZnO/BN/P(GP@ZnO:BN:P=100:1:6)composites were prepared into gutta percha point to study its performance in vitro.The consequence exhibits that the tooth root surface temperature rise of oriented GP@ZnO/BN/P hybrids were 10.6 ?,which was excellent and better than commercial gutta percha DPP.The lateral canal filling depth of GP@ZnO/BN/P composite at the WL-3 level was 0.263 mm,which was greater than the filling depth of commercial gutta percha DPP at the WL-3 level(0.099 mm).The cytotoxicity grade of GP@ZnO/BN/P composites is bank 1(mild toxicity,qualified)and has good X-ray resistivity.