The MW averages and the MWD are important characteristics of a resin. They may be used for a variety of correlations for fundamental studies, processing, or product applications. The MW and MWD values may also be used for production quality control of resins.

Limitations—Comparison of SEC molecular weight values should be made only if the data were obtained under identical chromatographic conditions.

1.1 This practice covers the determination of apparent molecular weight (MW) averages and molecular weight distributions (MWD) for THF-soluble hydrocarbon and terpene resins by size-exclusion chromatography (SEC). This technique is not absolute; it requires calibration with standards of known molecular weight. This practice is applicable to resins containing molecular-weight components that have elution volumes falling within the elution volume range defined by polystyrene standards.

SEC is also known as gel permeation chromatography (GPC).

1.2 SEC systems employ low-volume liquid chromatography components and columns packed with relatively small (generally 3 to 20 m) microporous particles. High-performance liquid chromatography instrumentation and automated data handling systems for data acquisition and processing are also required.

1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.

This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.