A novel cover layer material for flexible printed circuit (FPC) applications was developed in this work. A high molecular weight of polyimide composed of four monomers, pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 2,2'-bis(trifluoromethyl)benzidine (TFMB) and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (BisApAf) was prepared by the one-pot polycondensation in N-methyl-2-pyrrolidone (NMP) without precipitation and gelation. The polyimide (PI) was highly soluble in various common organic solvents. Interestingly, the PI film formed by simple solution-casting of the PI solution had a low CTE value close to that of copper foil, therefore almost no curling of the PI/copper laminate was observed when the PI film was directly formed on a copper foil. The PI film also exhibited other combined properties, including a low CTE, a high Tg, high thermal stability, low water absorption, comparatively good transparency, the highest levels of non-flammability, good insulation properties and sufficient film flexibility. In addition, fine positive-tone patterns could be obtained from DNQ-containing PI with a sensitivity of 238 mJ cm-2. The results revealed that the present PI system is a promising candidate as a novel cover layer material.
Collagen/poly (vinyl alcohol) (PVA) and chitosan/PVA blends were cast into films from mixed polymer solutions in aqueous acetic acid. Transition behavior of two series of binary blends was examined by DSC measurements. Composition-dependent shift in the glass transition temperature (Tg) of PVA was observed for chitosan/PVA blends and the melting point of PVA was depressed systematically with increasing chitosan content. On the other hand, the less significant shift in Tg of PVA was observed for collagen/PVA blends. These results suggest that the chitosan is compatible with PVA, while collagen is incompatible with PVA. An attempt was made to introduce crosslinks into both series of blends with the aid of glutaraldehyde. Enhancement of the compatibility was achieved for collagen/PVA blends and the mixing state was improved by the introduction of the crosslinking in consequence of the bridge formation between PVA and collagen molecules. On the other hand, chitosan/PVA blends lost their high compatibility due to the preferential crosslinking among chitosan chains. Elongation/contraction behavior of the crosslinked collagen/PVA blends during the alternate immersion in water and concentrated LiCI solution was examined. Further, the moduli of crosslinked collagen/PVA and chitosan/PVA blend hydrogels were also discussed in terms of the degree of crosslinking and the higher order structure of collagen in the hydrogel .
A novel cover layer material for flexible printed circuit (FPC) applications was developed in this work. A high molecular weight of polyimide composed of four monomers, pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 2,2'-bis(trifluoromethyl)benzidine (TFMB) and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (BisApAf) was prepared by the onepot polycondensation in N-methyl-2-pyrrolidone (NMP) without precipitation and gelation. The polyimide (PI) was highly soluble in various common organic solvents. Interestingly, the PI film formed by simple solution-casting of the PI solution had a low CTE value close to that of copper foil, therefore almost no curling of the PI/copper laminate was observed when the PI film was directly formed on a copper foil. The PI film also exhibited other combined properties, including a low CTE, a high T g , high thermal stability, low water absorption, comparatively good transparency, the highest levels of non-flammability, good insulation properties and sufficient film flexibility. In addition, fine positive-tone patterns could be obtained from DNQ-containing PI with a sensitivity of 238 mJ cm 12 . The results revealed that the present PI system is a promising candidate as a novel cover layer material.
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