利用奈米碳管及氮化硼增進高分子基材之導電 性導熱性及防腐蝕效果之研究

Abstract

複合材料（Composite Material）具有質量輕、高強度、質量輕、耐腐蝕等特性，已廣泛運用於、電子業、航太工業及船舶工業之中。複合材料之種類繁多，由於高分子材料普遍強度較低、導電性質不良、熱傳導性質不佳以及阻水和抗腐蝕效果不如無機材料；因此常使用無機材料增強有機高分子基材，以使高分子有機無機複合材料同時具有有機無機材料之優點。 在博士論文第一個部分，成功地利用(2,6-diaminoanthraquinone, DAAQ)與奈米碳管有優異的π-π分子間作用力，使奈米碳管不須經過化學改質，就能有效分散在聚亞醯胺，兼具好的成膜性與導電性，這原理可應用在製備其他相關的高分子/奈米碳管或各式炭材所形成的高分子複合材料。 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.