On the relationship between synthesis parameters and morphology of the anionic polycaproamide obtained in organic media. III. Macroporous powders obtained using CO2 and carbodiimides as activating compounds

Abstract

ABSTRACT:The relationship between the type of activator and the morphology of polycaproamide (PCA) powders was investigated. The powders were prepared by anionic polymerization of caprolactam in ethylbenzene using sodium caprolactamate as initiator and CO 2 , diisopropylcarbodiimide, and dicyclohexylcarbodiimide as activators. The powders were characterized by optical and scanning electron microscopy, particle size distribution, extent of the specific area, porosity, pore size, and pore size distribution. The crystalline structure of PCA powders was also investigated using X-ray diffraction technique. Formation of PCA powders during phase separation is discussed. Powders morphology is simultaneously and competitively controlled by the rates of polymerization and phase separation processes. It seems that the determining factor in the obtainment of such macroporous powders is the stepwise manner in which the growing centers are formed in the reaction medium. In addition, the effect of the site where polymerization proceeds after the occurrence of phase separation on the ultimate morphology of the PCA powders is also discussed.

Binary polyamide hybrid composites containing carbon allotropes and metal particles with radiofrequency shielding effect

“…a) are present in the form of aggregates of several, partially fused PA6 spheres with typical diameters of 5–10 μm that form final particles of 20–30 μm. This observation confirms the previously postulated effect of coalescence during the PAMC formation . Larger magnification (image 2i) shows that the empty PAMC are porous, with scaffold‐like morphology, the pores sizes being typically in the 250–500 nm range.…”

Reactive microencapsulation of carbon allotropes in polyamide shell-core structures and their transformation in hybrid composites with tailored electrical properties

“…These requirements determine the selection of the initiator DL and the commercial activator C20. As indicated in a series of previous studies on AAROP of neat lactams, without any payload, in solution [40][41][42], the growing PA6 chains form initially viscous, low molecular weight particles that upon additional propagation, coalescence and crystallization produce the final empty PAMC. It can be hypothesized that the carbon loads dispersed in the constantly stirred reaction medium will be entrapped into the viscous particles and can possibly nucleate their crystallization thus forming the loaded PAMC.…”

One‐Step In Situ Synthesis of Polyamide Microcapsules With Inorganic Payload and Their Transformation into Responsive Thermoplastic Composite Materials

“…These requirements determined the selection of the initiator DL and the activator C20 (Scheme ). As indicated in a series of studies on AAP of neat lactams in solution, the growing PA6 chains form initially viscous particles that upon additional propagation, coalescence, and crystallization produce the final empty PAMC. It can be hypothesized that any load present in the constantly stirred reaction medium will be entrapped into the viscous particles and can possibly nucleate their crystallization thus forming the loaded PAMC.…”

“…Chemical approaches are also reported for the synthesis of powdered neat n ‐polyamides such as polyamide 6 (PA6) and polyamide 12 (PA12) employing activated anionic ring‐opening polymerization (AAP) of lactams in hydrocarbon solutions. Thus, porous PA6 particles with diameters in the 5–500 μm range have been obtained . Ricco et al performed AAP of ϵ‐caprolactam (ECL) in suspension preparing smooth PA6 particles with diameters between 50 and 480 μm.…”