Where Does Polyolefin Degradation Occur? Enhanced Carbonyl Detection Reveals Degradation Pathways Along the Molecular Weight Distribution

• June, 29 2026
• Category: Chemical Composition Distribution, GPC/SEC, Sample Degradation

The Need and Evolution of IR Detection for Polyolefin Analysis

The full characterization of polyolefins requires separation techniques with specific detectors that provide information about the microstructure, such as the high-temperature GPC/SEC analysis with Infrared Detection. Polymer Char, the leading company in infrared detection technology applied to polyolefins, developed and launched the polyolefin-dedicated detectors IR4 and IR5. These detectors have been extensively used in the polyolefin characterization field over the last 25 years as concentration and chemical composition detectors, to obtain the molar mass distribution and short chain branching information, or comonomer content in ethylene-alpha-olefin and in ethylene propylene copolymers (1- 2). However, there are other types of copolymers that require other bands for measuring the carbonyl groups. For example, the important class of vinyl acetate, or chemical groups as the carbonyl group generated in oxidative degradation processes, show absorption bands beyond the CH stretching band in MID-IR. This was made possible in 2018 with the development of the IR6 detector, which delivers outstanding sensitivity (the same or even better than its predecessor IR5), coupled with higher robustness. Additionally, the IR6 incorporated the capability of measuring carbonyl groups in the band of 1740 cm-1, opening the way to the development of new specialized applications.

Expanding IR Detection Capabilities for Carbonyl Analysis

Polymer Char is now launching a new filter available for the IR6 detector, centered at the band of 1780 cm-1 as an alternative to the original one, keeping the number of available bands simultaneously detected still at six, making all previous detector units compatible with this new option just by acquiring a new filter-wheel. The new band of 1780 cm-1 is proving to be a game changer in polyolefin degradation studies, considering the fact that such carbonyl groups are caused by processes such as biodegradation.

Moreover, this new band adds flexibility to the GPC-IR analysis when measuring carbonyl groups, because it allows the analysis to be performed in TCB as mobile phase, rather than in oDCB as required by the initial band of 1740 cm-1.

Validation Through Application Studies

In a research study, a series of polyolefin-based applications were tested with this new filter, proving its effectiveness and value versus the initial filter centered at 1740 cm-1. The successful results expand the power and range of the IR6 detector when coupled to the GPC-IR even further now. Read the full Application Note here.