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New semi‐aromatic bio‐based copolyamides PA 4T/4Y and PA 6T/6Y were successfully synthesized in bulk by direct solid‐state polycondensation in which hydrophobic bio‐based dicarboxylic acids sebacic acid, octadecanedioic or hydrogenated dimer fatty acid (Y = C10, C18 or C36) alternate with terephthalic acid T. The absence of a polymerization solvent and the possibility of performing the polymerization on the dicarboxylic acid make it an interesting route for future production of alternating copolyamides. A stepwise synthetic approach is taken where first terephthalic acid‐based diamide diamines of the linear C4 or C6 diamines 4T4 or 6T6 are prepared, followed by preparation of solid salts with the above aliphatic dicarboxylic acids and subjecting the salts to a solid‐state post‐condensation. The alternation is achieved by the interlocking of the 4T4 or 6T6 units in the salts with the bio‐based dicarboxylic acids and polymerizing these salts below the melt temperature of the terephthalamide‐based core. During the polycondensation, the transamidation reaction of the terephthalamide moiety is prevented and with that the randomization of the polyamide. Especially the diaminobutane‐based PA 4T/4Y copolyamides show strict alternation, leading to interesting properties like high crystallinity and high melting points of 250 to 318 °C supported by a randomness value of 2, determined using...
A new insight has been obtained relating the different structures of linear aliphatic homopolyamides to their melting points. A new equation is derived for structures based on monomers with an even number of methylene units. In this equation, the amide distribution along the polymer chain is defined by a newly introduced parameter K which indicates the lowest number of methylene units between adjacent...
It is shown that the incorporation of comonomers into polyamide (PA6) is possible below the melting temperature of the polymer. For this purpose, a nylon salt of 1,5-diamino-2-methylpentane (Dytek A) and isophthalic acid (IPA) was used and reactions were carried out via both solid-state polymerization (SSP) of the nylon salt with PA6 and melt copolymerization (MP) of the nylon salt with ε-caprolactam...
Magnetic resonance imaging (MRI), NMR relaxometry, thermal analysis and gravimetrical experiments are performed to study the water absorption by neat PA46 and copolymers of PA46 and PA4n (PA46-co-PA4n) with 4mol% n=8, 12 and 16. The observed reduction in water uptake, ingress rate and water molecular mobility with increasing value of n is explained by a combination of several physico-chemical molecular...
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