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To enhance the photodegradability of polypropylene (PP), various carboxylates of iron, including ferric caprate (MF03), ferric laurate (MF04), ferric myristate (MF05), ferric palmitate (MF06), and ferric stearate (MF07), were synthesized. Virgin PP was blended with the synthesized prodegradants (0.2%) and blown into films. To study the photodegradation behavior of PP with and without the prodegradants under natural weathering conditions, all of the films were exposed to sunlight according to the procedure of ASTM 1435. All of the weathered films were found to degrade after a certain number of days of exposure; this was found from the steep increases in the carbonyl, hydroperoxide, hydroxyl, lactone, ester, carboxylic acid, and crystallinity indices. At the same time, a sudden decrease in the elongation at break percentages and tensile strength and surface cracks were also observed. PP containing the prodegradants degraded at a faster rate than the virgin material. The time taken for the material to lose half of the elongation at break value was taken as the halftime, and this was used to determine the effectiveness of the prodegradants. The effectiveness of the prodegradants for the photodegradation of PP was found to be in the following order: MF03 > MF04 > MF05 > MF06 > MF07. With increasing alkyl chain length of the prodegradants, the stability of the alkyl radical increased, whereas the mobility of the radical in the PP matrix decreased.

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Blends of 2,2-bis[4-(4-maleimidophenoxy phenyl)]propane [bismaleimide (BMIX)] with different proportions (1,2,3,4,5,7, and 9%) of the nanoclay Cloisite 15a were prepared with ultrasonication. Fourier transform infrared studies reveal the existence of interactions between the clay particles and the imide rings in BMIX. The difference in the melting characteristics and the decrease in the curing window caused by the incorporation of the clay particles in BMIX, as evidenced by detailed differential scanning calorimetry investigations, confirmed the existence of interactions between the nanoclay particles and BMIX molecules. The Flynn-Wall-Ozawa, Vyazovkin, and Friedman kinetics methods were used to calculate the activation energies (E a 's) for the curing of the BMIX materials. E a for the polymerization varied, depending not only on the amount of clay loaded in the BMIX but also on the extent of the curing reaction. Because of the loss of interaction between the clay platelets and the imide rings of BMIX, a decrease in E a at higher reaction extents was noted when there was lower clay loadings (1-4% Cloisite 15a) in BMIX. A reversal in the previous behavior was noted at higher clay loadings (7 and 9% Cloisite 15a) in BMIX and was attributed to the restriction of the molecular mobility due to the presence of increased concentrations of clay platelets and the decreased availability of reaction sites for polymerization. These two opposing factors played were equal at the optimum level of Cloisite 15a loading (5%) in BMIX, which was reflected in the constancy of E a variation noted with increasing reaction extent. Figure 6. SEM images of the (A) thermally cured BMIX and (B) BMIX þ 5% Cloisite 15a. ARTICLE WWW.MATERIALSVIEWS.COM WILEYONLINELIBRARY.COM/APP