Thermal oxidation of polypropylene in the temperature range of 120–280°c

Abstract

SynopsisThermal oxidation of isotactic polypropylene films at 120-280OC in air was studied. Separation and identification of the volatiles formed was carried out by gas chromatography-mass spectrometry. Sixteen products were tentatively identified for the first time. Altogether, 50 compounds representing hydrocarbons, ethers, alcohols, aldehydes, ketones, and acids are reported. Oxygen deficiency is manifested in diffusion-limited products of olefines, dienes, and aromatic compounds. The relative amounts of acetaldehyde and acetone are almost temperature independent in the range of 12G28OoC. This indicates a similarity of oxidative degradation of the polymer in a broad temperature range. Addition of an antioxidant to the polymer depresses the evolution of the main volatiles by 9-10 times at 280°C. The relative amounts of the volatiles formed are, nevertheless, the same as for the polymer without an antioxidant. The mechanism of formation of the degradation products is discussed.

Analytical, occupational and toxicologic aspects of the degradation products of polypropylene plastics.

“…The electron microscopy showed that the particle size of the aerosols taken on Nuclepore filters was in general smaller than the pore size (0.2 pm) of the filters (figure 5). The aerosols resembled closely the PP aerosols (2). The mean concentration of the aerosols in our industrial measurements was 0.9 (SEM 0.7) mg/m\ During welding, the mean concentration was 2.2 mg/m3.…”

“…Samples without antioxidants were treated similarly. The thermogravimetric analysis and the gas chromatographic-mass spectrometric (GC-MS) methodology has been described elsewhere (2,3). The oxidation was performed in a reaction tube (inner diameter 22 mm) with an air flow of 34 ml/min (2).…”

The origins of volatile oxidation products in the thermal degradation of polypropylene, identified by selective isotopic labeling

“…For instance, methyl acetate could arise from acetic acid reacting to ''scavenge'' methanol that is formed. We have not identified methanol in our experiments, although a previous paper reports its formation among degradation products of PP [28,30]. From Table 2, the methyl acetate has labeling in the ''acetic acid portion'' of the molecule that is the same as in acetic acid itself [the carboxyl carbon is C(2) and the methyl is C (3)].…”

Flame-Retardancy Properties of Intumescent Ammonium Poly(Phosphate) and Mineral Filler Magnesium Hydroxide in Combination with Graphene

“…Charring of a polymer under oxygen is a complex process that involves oxidation, the formation of double bonds, cyclization and aromatization [40,41]. PP decomposes via the formation and release of CO, CO2, aldehydes, ketones, carboxylic acids, esters, alkenes, conjugated alkenes and furans [42][43][44]. The FTIR spectra of the volatile decomposition products of PP at maximum release rate are presented in Figure 2.…”