Preparation and Characterization of Polyimide/silica-sol Hybrid Films

• Main Authors: Huang Yi-Chia, 黃奕嘉
• Other Authors: Tsai Mei-Hui
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/51770577851171549064

碩士 === 國立勤益科技大學 === 化工與材料工程系 === 99 === Part 1：A novel route to synthesize polyimide (PI)/silica-sol hybrid films with improved thermal and mechanical properties was developed. Low-molecular-weight poly(amic acid) (PAA), which is the precursor of PI, was successfully synthesized by controlling the molar ratio of monomers, [4,4′-(4,4′-isopropylidenediphenoxy) bis(phthalic anhydride)] (IDPA) and 2,2′-bis(4-(4-aminophenoxy)phenyl)propane (BAPP). The PAA with its low-molecule-weight feature showed good compatibility with silica-sol and dispersed well within the network of silica-sol. Silica nanoparticles with an average size of 20 nm were obtained without adding coupling agents and dispersed homogenously within the resulting PI/silica-sol hybrid films due to the hydrogen bonding between Si–OH groups and C=O in imide rings of PI. The improvement in the storage modulus and the coefficient of thermal expansion (CTE) by hybrid films was revealed. With the presence of 50 wt.% silica-sol in hybrid films, the storage modulus was 5857 MPa and the CTE was 18.1 ppm/°C, compared with 1620 MPa and 76.5 ppm/°C for pure PI. Most importantly, the transmission at 550 nm was 81.4% for the hybrid films with 50 wt.% silica-sol, which is close to 87.5% for pure PI. The CTE of the hybrid film dropped to the level comparable with that of copper without sacrificing its transparency, which was associated with the well-dispersed silica nanoparticles and the semi-interpenetrating polymer network (semi-IPN) structure within the PI matrix. Part 2：In this part, the effects of monomers on the properties of PI/silica-sol hybrid films were reported. Besides the monomers BAPP-IDPA used in Part 1, p-phenylene diamine (PPD) and 4,4′-Biphthalicanhydride (BPDA) were selected in preparing PAA. The difference in stiffness of monomers led dissimilar thermal and mechanical properties of PI/silica-sol hybrid films. The effect of silica-sol content on CTE of PI(BP-PD)/silica-solshows a reverse trend to that from hybrids derived from Part 1. The CTE of polyimide/silica-sol hybrid films in Part 2 increased from 5.6 ppm/°C for pure PI to 24.7 ppm/°C for polyimide/silica-sol hybrid films containing 30 wt.% silica-sol. According to the results of XRD, DMA, PL spectra, water absorption and the calculations of FFV by Bondi′s group contribution, the crystallinity of PI was decreased with the incorporation of silica-sol to PI matrix. Part 3：The polyimide /silica-sol hybrid films from Part 1 and 2 were used to prepare porous PI by etching the silica-sol in diluted HF solution. The results showed that the dielectric constant decreases from 3.2 for pure PI (ID-BA) to 2.3 for porous film (ID-BA-40-F) with the porosity of 30.3%. Moreover, the PI films containing fluorine were synthesized by using 4,4-( hexafluoroisopropylidene)- diphthalic anhydride (6FDA) and 2,2-Bis [4-(4-aminophenoxy phenyl)] hexafluoropropane (HFBAPP) as monomers. The dielectric constant of the porous PI (6F-HF-40-F) is 2.0. In addition, the peel strength of ID-BA-30-F is 1.59 kgf/cm which with the porosity 23.7%, comparing to that of pure (ID-BA) is 1.17 kgf/cm. The thermal conductivities of PI (ID-BA) and ID-BA-50-F are 0.21 and 0.11 W/m°C, respectively.