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

With trimesinic acid as a molecular weight regulator, the hydrolytic polyme rization Of epsilon -caprolactam was carried out, and nylon-6 or polyamide- 6 with three-branched chains was obtained. Through a systematic study of th e effects of conditions such as the reaction time and concentration of trim esinic acid on the polymerization, we found that the conversion of caprolac tam was almost insensitive to the initial concentrations of the regulators, but the relative viscosity of the polymer decreased with increasing trimes inic acid. Characterization investigations showed that differential scannin g calorimetry curves changed from a single peak for normal nylon-6 to one m ain peak and one shoulder or one small peak for the branched polymer; the m elting point of the star-shaped nylon-6 decreased with an increasing amount of trimesinic acid, whereas its crystallization temperature was higher tha n that of linear-chain nylon-6. A wide-angle X-ray diffraction study indica ted that the crystal structure of the starshaped nylon-6 still belonged to the a form, and the crystallizability of the branched polymer with an eleva ted amount of trimesinic acid during polymerization did not seem to be weak ened; the characteristic absorption of infrared spectra provided indirect e vidence 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. (C) 2001 John Wiley & Sons, Inc.