A study on the photo-degradation of zinc oxide (ZnO) filled polypropylene nanocomposites

The photo-oxidation of polypropylene/montmorillonite nanocomposites has been studied under irradiation at long wavelengths (λ > 300 nm) at 60 °C and in the presence of oxygen. The chemical modifications resulting from photo-oxidation were followed by IR and UV−visible spectroscopies for each component of these nanocomposites polypropylene (PP), organo-modified montmorillonite (MMt), and the compatibilizing agent (maleic anhydride-grafted-polypropylene). We have found that the mechanism of photo-oxidation of the polypropylene component was not modified in the polymer−nanocomposite, but that the rates of oxidation were modified, leading to an unexpected decrease of the durability of the material.

Photo-oxidation of Polypropylene/Montmorillonite Nanocomposites. 1. Influence of Nanoclay and Compatibilizing Agent

Drier influence on the curing of linseed oil

Due to the Covid-19 pandemic, the use of disposable face masks has been adopted worldwide as a precautionary measure to slow down the transmission of the virus. This has determined an unprecedented rise in the production of these protective equipments, and unfortunately to a new form of environmental contamination due to the improper disposal. To provide a preliminary estimation of the release of microfibers by a surgical mask dumped in the marine environment, we carried out artificial weathering experiments. Results indicated that a single surgical mask submitted to 180 hours UV-light irradiation and vigorous stirring in artificial seawater may release up to 173,000 fibers/ day. Moreover, SEM and micro-FTIR analysis carried out onto surgical masks collected from Italian beaches highlighted the same morphological and chemical degradation signature observed in the masks subjected to the artificially weathering experiments, confirming the risks of a similar microfiber release into the marine environment.

The release process of microfibers: from surgical face masks into the marine environment

Polypropylene (PP) has achieved a dominating position and hence, their consumption increases thereby littering, which lead to environmental pollution. Photodegradation seems to be a better choice because of naturally available sunlight as energy source for degradation. The present work involves the study of the variation of degradation behavior of PP film during tropical summer and winter seasons. The photodegradation is followed by Fourier transform infrared (FTIR) spectroscopic technique. Various indices like hydroxyl, carbonyl, vinylidene, lactones, ester, carboxylic acid and crystallinity are calculated and these values increased after a brief induction period. The variation in the mechanical properties like tensile strength and elongation at break percentages are determined. The scanning electron microscopic (SEM) images of weathered PP showed surface cracks when carbonyl index value increases sharply and the mechanical properties show a sudden decrease. Attempted life time prediction using mathematical models showed that the carbonyl growth is more affected by ultraviolet (UV) and cumulative total solar radiation for PP weathered during summer. The loss in tensile strength of PP weathered during summer is more dependent on the average temperature and the UV portion of the total solar radiation whereas, intensity of UV radiation has profound effect on the tensile strength of PP weathered during winter.

Natural Weathering Studies of Polypropylene

The detailed oxidation products have been identified and compared from the γ-, photo-, and thermally-initiated oxidation of unstabilized polypropylene films. Products were identified and quantified by a combination of iodometric analysis and infrared spectroscopy. Spectral resolution was enhanced by derivatization reactions which allow the quantification of primary, secondary, and tertiary hydroperoxide and alcohol groups as well as more reliable analysis of carbonyl species. In contrast to polyethylene oxidation which yields predominantly ketone with lesser amounts of secondary hydroperoxide and carboxylic acid, polypropylene oxidizes to give predominantly tertiary hydroperoxide and lesser quantities of secondary hydroperoxide and ketone. In addition carboxylic acid groups are a minor product except at high degrees of thermal and photoinitiated oxidation. © 1993 John Wiley & Sons, Inc.

Gamma-, photo-, and thermally-initiated oxidation of isotactic polypropylene†

Photo and thermal decomposition of iPP hydroperoxides

The oxidation mechanism of polypropylene: contribution of 13C-NMR spectroscopy

The efficiency of conventional Hindered Amine Stabilizers (HAS) can be significantly reduced by their adsorption on other additives or fillers present in the polymer. The present article reports on the effect of titanium dioxide, phtalocyanine blue, and talc on the thermal and the photo stabilizations of isotactic polypropylene (iPP) by HAS. The durability of iPP was measured by the length of the induction period preceding the development of carbonyl groups by FTIR spectroscopy. The adsorption of HAS on pigments and fillers was revealed by the precise analysis of the carbonyl band of the ester group of HAS.

D. Vaillant

Papers

Gamma-, photo-, and thermally-initiated oxidation of isotactic polypropylene†

Photo and thermal decomposition of iPP hydroperoxides

The oxidation mechanism of polypropylene: contribution of 13C-NMR spectroscopy

Stabilization of isotactic polypropylene. Problems bound to the interactions of stabilizers with pigments and fillers