sing Carbon Nanotube and Boron Nitride for Enhancing Electronic, Thermal Conductivity and Anti-corrosive Properties of Polymers
在第二個部分，本研究利用 聚亞醯胺/氮化硼 複合薄膜來提升不銹鋼304之抗腐蝕特性，並且探討不同高分子組態(configuration)對防腐蝕效果的影響；對剛硬的聚亞醯胺而言，其結晶度會因加入氮化硼而下降；反之，柔軟的聚亞醯胺則否。柔軟型的聚亞醯胺加入5wt%之氮化硼可以減低84%的水氣穿透率已達到優秀的防腐蝕效果。
第三部分則利用氮化硼水解產生大量的OH基，使之更容易在溶劑中分散並且利用OH基與 Methylene diphenyl diisocyanate (MDI) 反應，如此一來氮化硼和聚氨酯能夠有共價鍵結並且提升其機械性質及導熱性，也減少了相分離度 (degree of phase separation, DPS)。當加入50 wt%水解氮化硼後，聚氨酯/氮化硼 複合薄膜之導熱係數可提升至2.93 w/Km，相對純聚氨酯之導熱值0.27 w/Km 提升了10.8倍。|
Generally, polymers are light-weight, flexible, low-cost and easy for process. However, polymers exhibit weak mechanical strength, low thermal and electronic conductivity and poor barrier properties. Fabricating composite materials is an economic way to promote the above shortcomings of polymers. In this thesis, we imports inorganic materials (carbon nanotube and boron nitride) into polymer matrix as fillers. The researches have been reported as three parts: In the first part of this thesis, we present a valuable in situ fabrication process for synthesizing high electrical conductive polyimide/multiwalled carbon nanotube (PI/MWCNT) composite films. The success of this process was achievedthe addition of 2,6-diaminoanthraquinone (DAAQ). The DAAQ is not only an excellent dispersion agent to stably disperse pristine MWCNTs in solvent but also a monomer to directly synthesize PI. The strong interaction between DAAQ with MWCNT was verified by FTIR, UV–Vis, Raman, and fluorescence spectra. The highest value of electrical conductivity of 55.6 S/cm are achieved by the PI composite containing 40 wt.% of MWCNT. Moreover, the electrical conductivity of this film further enhanced to 106 S/cm after the thermal compression process. The MWCNT content at the percolation threshold of conductivity is 0.50 wt.% (or 0.32 vol.%) and the critical exponent is equal to 2.52. The developed in situ fabrication process through DAAQ-derived molecules can also be applied to synthesize other polymers requiring diamine structure. In the second part of this thesis, anti-corrosive polyimide/hexagonal boron nitride (PI/h-BN) compositefilms were prepared with different monomers to offer different polymer backbone rigidity: rigid and soft. In PI/h-BN composite films, different configurations of polymers show different crystallinity trends of the polymer matrix. In our study, the degree of crystallinity in rigid polymer decreases with increasing of the BN content; in flexible polymers it is independent of the BN content. It is worth noting that BN in different PI matrices can effectively enhance the protection of steel from corrosion. With a flexible PI matrix, the PI/h-BN coating exhibited better resistance to water vapor and better anti-corrosion. Only 5 wt.% of h-BN in the composite is enough to offer high anti-corrosion, a positive corrosion voltage In the third part of this thesis, we fabricated polyurethane/boron nitride (PU/BN) composites films via chemical reacting with OH group of hydrolyzed boron nitride (BN) and methylene diphenyl diisocyanate (MDI) as monomer of PU. The covalent bonding of PU and BN enhances the mechanical properties and thermal conductivities. Moreover, because of the excellent compatibility of PU and BN, the degree of phase separation (DPS) is decreasing with adding hydrolyzed BN into PU matrix. The thermal conductivity of PU/BN composite films up to 2.93 w/Km with 50 wt.% hydrolyzed BN.
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