Photodegradation of polypropylene nanocomposites

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.

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confidence: 72%

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confidence: 99%

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

Morreale¹,

Dintcheva²,

Mantia³

2013

“…This phenomenon might be important in the burning of plastic products and flame retardancy, but not during the processing and use of such composites. Although the deteriorating effect of the components (OMMT, MAPP) was shown on the light stability of PP/layered silicate composites [35,36], very few papers were published on thermooxidative stability. However, degradation is obviously accelerated by the organoclay and probably also by the functionalized polymer shown by both series of measurements of this study.…”

Section: Comparison Discussionmentioning

confidence: 99%

Kinetics of structure formation in PP/layered silicate nanocomposites

Hári¹,

Dominkovics²,

Fekete³

et al. 2009

Abstract. Polypropylene (PP)/organophilized montmorillonite (OMMT) and polypropylene/organophilized montmorillonite/maleic anhydride grafted polypropylene (MAPP) composites were prepared in an internal mixer under a wide range of processing conditions to study the kinetics of structure formation. Structure and properties were characterized by a variety of techniques. The gallery structure of the organophilic silicate changed in spite of the fact that no compatibilizer was added to PP/OMMT composites. Silicate reflection shifted towards smaller 2θ angles, broadened and its intensity decreased indicating intercalation. Transmission electron microscopy (TEM) micrographs even showed individual platelets at long mixing times. However, the extent and direction of changes in the gallery structure of the silicate did not justify those observed in properties. The analysis of the results and additional experiments proved that the degradation of the polymer also takes place during processing leading to the formation of carbonyl and/or carboxyl groups, as well as to the decrease of molecular weight. The modification of the chain structure of the polymer influences interfacial interactions and the intercalation process. Some properties are directly determined by molecular weight (rheological properties, elongation). Both the clay and the MAPP seem to accelerate degradation. Thermooxidative degradation must have disadvantageous effect during the application of PP nanocomposites and needs further study. : nanocomposites, layered silicate, polypropylene, gallery structure, thermal degradation eXPRESS Polymer Letters Vol.3, No.11 (2009) [692][693][694][695][696][697][698][699][700][701][702] Available online at www.expresspolymlett.com DOI: 10.3144/expresspolymlett.2009.87 complicated systems containing several components like the polymer, the silicate, the surfactant, and quite often also swelling and coupling agents or other additives to help exfoliation [7][8][9][10][11][12][13][14]. The competitive interactions acting among the various groups of the components are very difficult to estimate and control, which results in a wide range of structures often with inferior properties. Similarly to the uncertainties related to the role and effect of interactions on the structure and properties of nanocomposites, the effect of kinetics, i.e. processing conditions, on structure development is also quite unclear. Some groups claim that processing conditions, or even preparation conditions do not influence the structure of the composites [15,16], while others found a strong effect of processing [17,18]. For example Yilmazer and Ozden [16] compared the effect of three preparation conditions, i.e. in situ polymerization, melt compounding and a masterbatch method, and did not find any significant difference in structure and properties of polystyrene (PS) nanocomposites. On the other hand, Paul and co-workers [19][20][21] carried out a detailed study on polyamide 6 (PA6) nanocomposites using a single and three twin-screw extruders...

“…The resistance to ultraviolet (UV) light is a key factor for most outdoor applications of polymeric materials. In the last few years, the impact of light on polymer/clay nanocomposites has been studied [11][12][13][14][15][16][17][18][19]. The clay nanocomposites show a significant reduction of the oxidation induction time (OIT).…”

Section: Introductionmentioning

confidence: 99%

Comparative study of filler influence on polylactide photooxidation

Bocchini¹,

Frache

2013

Abstract. Polylactide (PLA) based nanocomposites of organically modified montmorillonite and micro-talc based microcomposites were prepared with different compositions and were UV-light irradiated under artificial accelerated conditions representative of solar irradiation. The chemical modifications resulting from photo-oxidation were followed by infrared (IR) and ultraviolet (UV)-visible spectroscopies. The infrared analysis of PLA photooxidation shows the formation of a band at 1847 cm -1 due to the formation of anhydrides. The filler addition provokes an increase of anhydride formation rate dependent on filler nature, amount and dispersion degree on the matrix. The main factors that influence oxidation rate are the total extension of polymer/filler interfacial area and the presence of transition metal impurities of clays.