Investigation of linear polyamides with high aliphatic content

Carl Wayne Bennett


The research presented in this dissertation comprises of an investigation of a family of novel polyamides, also called nylons, with high aliphatic content. The overall objective was to obtain polymers that combined the advantages of nylons, good thermal properties, with the advantages of polyolefins, improved solvent resistance. The research in Chapters II and III focuses on linear nylons with high aliphatic content made using octadecanedioic acid with a variety of commercial linear diamines ranging from 2 to 12 carbons in the alkane segment (Chapter II) and a newly available 18 carbon diamine (Chapter III). It was found that resistance to organic solvents increased over commercial nylons with lower aliphatic content. The melting and crystallization temperatures decrease with an increase in aliphatic content. Chapter IV examines the copolymerization of nylon 6 with nylon 6 18 in varying molar ratios. The solubility in an organic solvent mixture of 2,2,2-trifluoroethanol and chloroform ranged from completely soluble for an 80:20 molar mixture of nylon 6:6 18, to formation of a gel (60:40 mixture), to merely swelling the sample (40:60 mixture), to being completely insoluble (80:20 mixture). In addition, differential scanning calorimetry (DSC) and solid state nuclear magnetic resonance (NMR) experiments showed that increasing incorporation of nylon 6 18 significantly broke up the crystallinity of the copolymers. Chapter V summarizes a fundamental study into the crystallization kinetics of a series of polyamides containing octadecanedioic acid and linear diamines of 6, 12, and 18 carbons in length. It was found that nylon 6 18 crystallizes in a manner typical of polyamides, while nylon 18 18 possessed a significant contribution from the extended polymethylene content in addition to the amide units. Nylon 12 18 was found to crystallize in an intermediate fashion, with a slightly hindered mechanism since the extended polymethylene contribution was not fully available. The research in Chapter VI introduces two polyamides with a degree of unsaturation incorporated directly in the polymer backbone, found in the center of the diacid segment. This additional functionality is available for reaction after polymerization, and has potential industrial applications as a comonomer in commercial nylons.