ABSTRACTHigh‐performance thermoplastic composites based on semiaromatic polyamides are prime candidates for metal replacement in lightweight structural applications. However, the low ductility and toughness of semiaromatic polyamides remain major obstacles to their wider industrial application. In this study, we showed that novel random copolymers were formed by the unexpectedly efficient transamidation during the melt compounding of semicrystalline semiaromatic and aliphatic polyamides. Thus, homogeneous materials with a single glass transition and a high degree of crystalline order were obtained from blends of the semiaromatic poly(hexamethylene terephthalamide‐co‐isophthalamide) (PA6TI) with poly(hexamethylene adipamide) (PA66) or poly(hexamethylene sebacoamide) (PA610). By contrast, phase segregation and a less efficient transamidation was observed for cocompounded PA6TI and polylaurolactam (PA12). We attributed this to differences in the hydrogen‐bonding patterns of the two polyamides. This study opened the way for the preparation of novel high‐performance thermoplastic polyamides and composites through simple melt compounding. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44349.

Dispersion quality has a large influence on the resulting properties of filled polymers, hybrids and nanocomposites in general. Reducing the van der Waals forces and therefore, matching the refractive index between the filler and the matrix should improve dispersion in hybrid materials. However, in this case the usual light-based techniques cannot be used to assess dispersion quality. In this work, dispersions containing silica nanoparticles and a solvent mixture of 1-butanol and benzyl alcohol were analysed by rheologica I methods. The refractive index of the solvent was changed by varying the mixing ratio, and thus the effectof index difference on the filler-matrix interaction was investigated. In agreement with theory, a stronger gel network was observed when the refractive index of filler and solvent were matched. If the difference in refractive index of the two materials became too large, particles and solvent interaction was reduced, and agglomerates were formed. This resulted in a weaker gel network.