Polymer reactions. III. Structure of polypropylene hydroperoxide

Abstract

Oxidation of polypropylene introduces hydroperoxide groups into the polymer. Infrared spectroscopy has determined that more than 90% of these groups are intramolecularly hydrogen bonded. The sequential lengths and sequence distributions of these neighboring hydroperoxides were estimated from the electronic spectra of the polyenes derived from the polypropylene hydroperoxide by two methods: (1) reduction, acetylation, and pyrolysis, and (2) reduction and dehydration. The results indicate that all the hydroperoxide groups are present in sequences of length two and greater. Intramolecular hydrogen abstraction during oxidation could account for the formation of these neighboring hydroperoxides.

Review on the thermo-oxidative degradation of polymers during processing and in service

“…With the mechanism developed in 1946 by Bolland and Gee [10,11] to explain the thermal oxidation of rubbers, the thermal oxidation of many other polymers can be described [12][13][14][15][16][17][18]. Several variations on this mechanism have been proposed [19][20][21] An example of this mechanism is shown in Scheme 1.…”

“…About the influence of tacticity on the oxidizability there is no consensus. It was shown that isotactic PP (iPP) is more susceptible to the oxidation than atactic PP(aPP), which was attributed to a more favourable backbiting reaction of peroxy radicals (as shown in Scheme 2) in the case of iPP [19,[84][85][86][87], but the opposite is shown too [45]. However, in many cases between aPP and iPP samples there are more differences than just tacticity (e.g.…”

Radiation-induced graft copolymerization of 2-vinylpyridine and styrene onto isotactic polypropylene fiber

“…Chien et al 14 observed that an intramolecular peroxy radical attack on the PP chain could lead to a sequence of neighboring hydroperoxy groups. In the intramolecular propagation [step (iv)], the peroxy radical attacks the COH bond at the ␤ position and migrates along the macromolecule, leaving behind a fence of hydroperoxy groups.…”

Molecular weight dependence and stereoselective chain cleavage during the early stages of the isotactic polypropylene pyrolysis

“…This can be checked in figure 6, where the signals of CO groups of either saturated ketones and acids (1708 cm-1) or α,β-unsaturated ketones (1688 cm-1) are more intense in the normalized spectrum of LPP. Finally, the analysis of the hydroperoxy groups by FTIR (figure 7), both associated (3410 cm -1 ) and free (3550 cm -1 ) [21], does not allow either ascribing the lower thermal stability of HPP to a higher content of these species. In fact, their contents are similar in both samples.…”