Abstract
The carbonyl species present in oxidized polyethylene are qualitatively and quantitatively determined through the use of infrared measurements on the polymer. The method described makes use of a carbon monoxide/ethylene copolymer wedge in the reference beam of the infrared spectro photometer to compensate the large 1720 cm^โ1^ ketone absorbance. This allows one to observe the 1710 cm^โ1^ and 1735 cm^โ1^ carbonyl absorbances as distinct peaks rather than as shoulders on the 1720 cm^โ1^ peak. This is a significant advantage over other published infrared methods for this analysis. The absorbances obtained at 1710 cm^โ1^ and 1735 ^โ1^ are then used in an equation to calculate the absorbance at 1720 cm^โ1^ due to ketonic carbonyl only. Our results confirm Cooper and Prober's assignment of both the 1710 cm^โ1^ and 1735 cm^โ1^ absorbances in the infrared spectra of oxidized polyethylene to acid functionality. Our quantitative results are comparable to those reported by Cooper and Prober, and our method represents a significant reduction in the time required for the analysis (1.5 hr vs. โผ45 days). The carbonyl distribution in a commercially oxidized polyethylene wax was determined as being โผ11.0 ketone C๏ฃพO/2000 C and โผ21.7 acid C๏ฃพO/2000 C (with a ฯ of 1.8 C๏ฃพO/2000 C and 3.0 C๏ฃพO/2000, respectively). A highโdensity polyethylene, oxidized with air in the laboratory, contained โผ1.91 ketone C๏ฃพO/2000 C and 2.19 acid C๏ฃพO/2000 C (with a ฯ of 0.08 C๏ฃพO/2000 C and 0.16 C๏ฃพO/2000 C, respectively).