title: Molecular weight distributions of industrially-produced poly-(epsilon-caprolactams) by gel permeation chromatography.
abstract: Gel permeation chromatography with differential refractometry is used to obtain molecular weight distributions (MWD) of poly-(epsilon-caprolactams). Elution is carried out using an m-cresolchlorobenzene mixture (50:50, v/v) at 50 degrees C. MW values are obtained by a Hamielec-based calibration method, using broad-MWD poly-(epsilon-caprolactam) standards with the same chemical nature and similar MWD to the samples. Relative errors for the number-average MW (Mn) using this calibration method range from 0.4% (in the low polyamide MW range) to 20% (in the high polyamide MW range). These values are much lower than those obtained from narrow-MWD polystyrene calibration, which range from 39% to 78%. Similar values have been obtained for the other usual average MW parameters. The ability to obtain repeatability parameters for a given confidence interval and the utilization of statistical criteria for chromatogram rejection allow this method to be used in quality control for MWD of poly-(epsilon-caprolactams). Thus, production variables are related to polyamide-6 behavior in its ulterior treatment. Typical relative standard deviation percentages (for n=6) of a polyamide sample range from 1.9% (for Mn) to 3.3% (for M(z+1)).
authors.affiliation: Instituto de Carboquímica, CSIC. P.O. Box 549, 50080 Zaragoza, Spain.
authors.forename: Elena
authors.initials: E
authors.lastname: Mateos
authors.forename: Vicente L
authors.initials: VL
authors.lastname: Cebolla
authors.forename: Luis
authors.initials: L
authors.lastname: Membrado
authors.forename: Elena
authors.initials: E
authors.lastname: Piera
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Caballero