The present study aims at cross-relating the different scales of analysis of polypropylene properties under photoaging.A conventional approach for studying polypropylene photoaging consists in measuring the carbonyl products by infrared spectroscopic analysis of UV-light exposed samples. Monitoring chemiluminescence has been also proposed many times to perform the analysis of oxidation. However, it is known [1] that a non-negligible amount of photo-products migrate to the gas phase, and are not taken into account by this kind of analysis. Moreover, chemical changes occur before the detection of carbonyl products can be detected [2]. Our investigations show that chemiluminescence has not proven to be a more sensitive technique than FTIR spectroscopy in the early stages of photo-oxidation. Those observations drove us to reconsider the relevancy of the experimental approach of photoaging only based on these measurements.We will present a critical review of the results that we obtained on the basis of a multi-scale approach, including SAXS, DSC, AFM, micro-hardness and rheology analyses, to describe phenomenon governing the loss of functional properties, such as the gloss loss. A particular attention is given to AFM experiments such as AFM Nanoscale Thermal Analysis Module (VITA) and nano-indentation. Figure 1. <img src='https://acs-archive-assets2.s3.amazonaws.com/241nm/uploads/70172_figure_1.jpg' alt='' />Our results indicate that oxidation provokes an increase of crystallinity, which can be detected very early. This plays a major role in the apparition of cracks (Figure 1) and results in a dramatic loss of gloss.[1] Philippart J-L, Posada F, Gardette J-L, Polym. Deg. Stab. 1995:49:285[2] Elvira M, Tiemblo P, Gomez-Elvira J-M, Polym. Deg. Stab. 2004:83:509

Cross relating the loss of functional properties to the modification of the chemical structure of polypropylene

248th National Meeting (2014)

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