¹³C‐NMR sequence analysis 8. Investigation on piperazine‐containing copolyamides

Reactive Melt Processing of Aliphatic/Aromatic Polyamide Blends: Effect on Molecular Structure, Semicrystalline Morphology, and Thermal Properties

“…High concentrations of amorphous PA 61 in the blend clearly hinder the transformation of the PA 46 crystals from a pseudohexagonal form into a monoclinic/triclinic crystal structure, and a pseudohexagonal frozen-in structure is obtained at room temperature. A similar observation is reported by Zimmerman et al, who found that increasing the concentration of PA-2Me6T (based on 2-methylhexamethylenediamine and terephthalic acid) in melt-mixed blends with PA 66 inhibits the normal transition of PA 66 from the hexagonal to the triclinic form [94].…”

“…Since the pioneering work of Kricheldorf and co-workers, it is well known that the shift differences for blends of homopolyamides, alternating copolyamides, and random copolyamides occur in the 13C carbonyl region [59][60][61][62][63][64][65][66][67]. This is possible when the polyamides are dissolved in sulfuric acid or in fluorosulfonic acid.…”

Polylactones. 1. Copolymerizations of glycolide and iε-caprolactone

“…A hypothetical mechanism which explains the intramolecular double cleavage of glycolide is outlined in eq 8-10. When the initial alcohólate group Al--RO-CO-CHg-0-Al-0-R (10) A i ch2 CO-OR has been replaced by a growing chain with an e-hydroxycaproyl unit attached to aluminum, intramolecular cleavage of the Glyc-Glyc bond may lead to the triad Cap-Glyc-Cap.…”

Transamidation in Melt-Mixed Aliphatic and Aromatic Polyamides. 1. Determination of the Degree of Randomness and Number-Average Block Length by Means of 13C NMR

“…Since the pioneering work of Kricheldorf and co-workers, [9][10][11][12][13][14][15][16] it is well known that the shift differences for blends of homopolyamides, alternating copolyamides, and random copolyamides especially occur in the carbon-13 carbonyl region. This is mainly possible when the polyamides are dissolved in sulfuric acid or in fluorosulfonic acid.…”

“…According to the literature, proton NMR has been used as a tool to identify polyamides and copolyamides, but on the basis of the investigation by Kricheldorf et al., it is concluded that proton NMR is not a general tool for discriminating between aliphatic copolyamides and blends of homopolyamides. Since the pioneering work of Kricheldorf and co-workers, − it is well known that the shift differences for blends of homopolyamides, alternating copolyamides, and random copolyamides especially occur in the carbon-13 carbonyl region. This is mainly possible when the polyamides are dissolved in sulfuric acid or in fluorosulfonic acid.…”