Preparation and characterization of polyamide‐6 with three‐branched chains

Abstract

ABSTRACT:With trimesinic acid as a molecular weight regulator, the hydrolytic polymerization of ⑀-caprolactam was carried out, and nylon-6 or polyamide-6 with threebranched chains was obtained. Through a systematic study of the effects of conditions such as the reaction time and concentration of trimesinic acid on the polymerization, we found that the conversion of caprolactam was almost insensitive to the initial concentrations of the regulators, but the relative viscosity of the polymer decreased with increasing trimesinic acid. Characterization investigations showed that differential scanning calorimetry curves changed from a single peak for normal nylon-6 to one main peak and one shoulder or one small peak for the branched polymer; the melting point of the star-shaped nylon-6 decreased with an increasing amount of trimesinic acid, whereas its crystallization temperature was higher than that of linear-chain nylon-6. A wide-angle X-ray diffraction study indicated that the crystal structure of the starshaped nylon-6 still belonged to the ␣ form, and the crystallizability of the branched polymer with an elevated amount of trimesinic acid during polymerization did not seem to be weakened; the characteristic absorption of infrared spectra provided indirect evidence for the existence of branched chains in the polymer. Moreover, the mechanical properties of star-shaped nylon-6 and linear-chain nylon-6 were compared.

Synthesis and characterization of star-branched polyamide 6 via anionic ring-opening polymerization with N , N′ , N″ -trimesoyltricaprolactam as a multifunctional activator

“…RV, FTIR, DSC and XRD analyses provided indirect evidence to confirm the existence of a star-branched structure according to the pioneer work about star-branched polyamide 6 [6,[10][11][12][13]19]. The direct proof such as NMR and MALDI TOF MS was still challenging due to the low solubility and high viscosity of SPA6 [23].…”

“…Therefore, the existence of a star-branched structure could be demonstrated by comparison of the properties [6,[10][11][12][13]19]. [10].…”

“…The crystallization temperature (T c ) of starbranched and linear samples demonstrated the same tendency. The decreased T m , T c and crystallinity would offer potential advantages in material processing and elucidate the existence of branched structures, which could disturb the original arrangement and hydrogen bonding interactions of the polymer chains [12,19]. The crystal structures of PA6 were determined with XRD.…”

“…Hydrolytic ROP was the main method to produce PA6 in industry. Three-arm SPA6 was generated in the presence of trimesinicacid through a hydrolytic mechanism [12,13]. However, the reaction conditions required long reaction time (>2 h), high temperature (>200 8C) and pressure (>1 MPa) for both cationic and hydrolytic polymerizations.…”

Formation of Short and Long Chain Branches during the Free Radical Functionalization of Polyamide 6 in the Melt

“…Dai obtained polyamide 6 with three branched chains by polycondensation of 6-aminoesanoic acid by using trimesinic acid as molecular weight regulator. This polyamide showed a decrease in relative viscosity with increasing trimesinic acid concentration.…”