| Hydrogen bond forming polymers such as aliphatic polyamides and poly (vinyl alcohol) are important engineering plastics with good mechanical properties. The intermolecular hydrogen bonding between adjacent chains imparts to them a high melting point and good chemical resistance. However, any further attempt at improving their mechanical properties gets thwarted due to the inability of molecular chains to be drawn beyond a certain extent as they are tightly held together by hydrogen bonding. Many approaches have been attempted in the past to suppress hydrogen bonding in aliphatic polyamides. Plasticizers such as ammonia, iodine, salts and several spinning methods such as dry spinning, wet spinning, gel spinning, and dry-jet wet spinning have been investigated. More specialized methods for obtaining high modulus aliphatic polyamides, such as vibrational zone drawing/annealing, as well as laser heating zone drawing/annealing, have also been tried. However, they all have led to little or no success in achieving high strength and modulus in polyamides. We have employed a new technique that involves the dry-jet wet spinning and drawing of GaCl3/nylon 66 complex in this work. This new method allows traditional low draw ratios for nylon 66 to be increased by disrupting the interchain hydrogen bonded network. Fibers with a high modulus were obtained when high molecular weight nylon 66 was used. Further, we have also reviewed the concept of thermoreversible gelation and its application for gel spinning of ultra high molecular weight polyethylene fibers. We developed high strength and modulus nylon 6 and PVA fibers from the gels of these polymers in N-methyl pyrrolidinone. High molecular weight is essential for achieving more drawing of polymer chains which leads to high molecular orientation. Electrostatic spinning or electrospinning has received considerable research attention in recent years. It involves the application of an electric filed to a polymer solution or melt to facilitate production of fibers in the sub-micron down to nanometer range. The technique of electrospinning was applied to the complexes of GaCl3 with nylon 6 resulting in porous nanofibers. Pores were generated by removal of GaCl3 salt from the as spun nanofibers via dipping in water. Researchers have tried in the past using a highly volatile solvent, or selective removal of one polymer from a bicomponent nanofiber for developing pores in nanofibers. However, using a metal salt proved to be a simple and fast approach for generating pores in electrospun nanofibers. |
