Accelerated weathering of PP based nanocomposites: Effect of the presence of maleic anhydryde grafted polypropylene

Abstract

The use of nanometric-scale sized fillers for the preparation of thermoplastic polymer composites is of topical interest in the academia, because of the significant improvements achievable in terms of technological properties, such as the elastic modulus, the tensile strength, the barrier properties, the flexural modulus [1][2][3][4][5][6][7][8]. These enhancements are promising and attracting also the interest from industrial world, in sight of several applications which could benefit from them. On the other hand, it is known [3] that polymer based nanocomposites have been struggling to conquer mainstream volume market shares, and this can be attributed to some weaknesses. One of these is represented by their environmental stability, especially when outdoor applications (i.e. furnishing, building, packaging, automotive) are concerned. It is known from the literature that polymer/silicate nanocomposites can show significant effects due to photo-oxidation (in particular, higher photo-oxidation rates and thus reduction of the mechanical prop- Abstract. Polymer nanocomposites are currently a topic of great interest. The increasing importance they are gaining also in the standpoint of industrial applications, is giving concerns regarding their environmental stability and, in general, their behaviour in outdoor applications, under direct solar irradiation. Papers available in the literature have highlighted the different influences of different nanosized fillers, in particular clay-based nanofillers; however, few data are available regarding other nanosized fillers. Furthermore, the research on polymer nanocomposites has clearly pointed out that the use of compatibilizers is required to improve the mechanical performance and the dispersion of polar fillers inside apolar polymer matrices, especially when complex mechanisms such as intercalation and exfoliation, typical of clay-filled nanocomposites, are involved. In this work, the photo-oxidation behaviour of polypropylene/clay and polypropylene/calcium carbonate nanocomposites containing different amounts of maleic anhydride grafted polypropylene (PPgMA) and subjected to accelerated weathering, was investigated. The results showed significant differences between the two nanofillers and different degradation behaviours in presence of the compatibilizer. In particular, PPgMA modified the dispersion of the nanofillers but, on the other hand, higher amounts proved to lead to the formation of some heterogeneities. Furthermore, PPgMA proved to positively affect the photo-oxidation behaviour by decreasing the rate of formation of the degradation products.

Novel silicon microparticles to improve sunlight stability of raw polypropylene

“…When Si microparticles were added to the coupled PP matrix, E 0 increased $85% for a 3 wt% of Si and arrived to a $115% for a 5 wt% of silicon microparticles. Those results were in agreement with other reports combining PP with particles such as zinc oxide [15], clay [26], calcium carbonate [26,47] or silica [48]. It was remarkable that this increment in modulus was not linked to the crystalline nucleation or growth induced by the presence of Si.…”

“…In order to avoid problems derived of phase separation between matrix and particles, some additives acting as coupling agents can be added to the composite. Maleic Anhydride (MAH) grafted PP has been proved to be an effective functional molecule for the reactive coupling between polypropylene (PP) and other polymers [24,25] and loadings [26][27][28][29][30][31]. Concretely, for silicon microparticles the use of MAH prevented the composites from the phase separation and conglomeration of silicon domains.…”

Mechanical and structural properties of glass fiber‐reinforced polypropylene (PPGF) composites

“…Thus, for the same contents of glass fiber, the average length values of fibers always seem to be higher and length dispersion is narrower when a compatibilizer is added. This could be ascribed to the higher interfacial strength induced by adding a compatibilizer that minimizes fiber breakage during melt processing. These results are in accordance with those of Yoo et al .…”

Pros and cons of melt annealing on the properties of MWCNT/polypropylene composites

“…In the same figure, the difference spectrum is also reported, evidencing a relevant increase of the absorption intensity in the carbonyl stretching region. In particular, bands at 1740 and 1712 cm À1 appeared after annealing due to the formation of ester and carboxylic acid groups [43,44]. Moreover, the presence of a weak absorption band centred at 1780 cm À1 , attributed to the formation of peresters or g-lactones was also revealed [20].…”