The UV-protection provided to addition type silicone elastomers by various colorants, such as conventional dry earth pigments, as well as the so called "functional or reactive" pigments, was investigated. Moreover, the effect of a UV light absorber and a silica filler was also explored. Under the experimental parameters of this work, the exposure of silicone to UV radiation resulted in some changes of the IR absorbance, thermal decomposition after 400 degrees C, T(g) and tensile properties, whereas the storage modulus of samples was not affected. The obtained spectroscopic data, as well as the results of TGA and storage modulus, were interpreted by assuming that chain scission takes place during aging, whereas the improvement of tensile strength allows the hypothesis of a post-curing process, initiated by UV radiation. Therefore, the increase of T(g) could partly be due to the above reason and, furthermore, to the contribution of a rearrangement of chain fragments within the free volume of the elastomeric material. Regarding the evaluation of various coloring agents used in this work, the obtained results show that dry pigments are more sensitive to accelerated ageing conditions in comparison with functional liquid pigments. Moreover, the hydrophobic character of silicone matrix is enhanced, with the addition of this type pigments because of the vinyl functional silanes groups present in their chemical structure. Finally, it should be noted that the incorporation of silica nanofiller did not seem to prevent the silicone elastomer from degradation upon UV irradiation, but showed a significant reinforcing effect.
In this research, graphene nanocomposites of poly(acrylonitrile‐butadiene‐styrene)/polycarbonate (ABS/PC) and ABS/polypropylene (ABS/PP) blends were prepared by melt blending and their thermal and mechanical properties were studied. The incorporation of graphene into ABS/PC and ABS/PP blends caused a significant decrease of their melt flow index values. Although graphene led to reduction of onset degradation temperature (Tonset) and maximum degradation rate temperature (Tpeak) of ABS/PC blends, and mainly of pure PC, the obtained residue from thermogravimetric analysis showed an increase. The thermal degradation of PC phase, in PC‐rich blends, was completed at higher temperatures. In ABS/PP blends, the effect of graphene was an outstanding increase of Tonset and Tpeak in the case of pure PP, while increasing the residue at all proportions. Regarding the Young's modulus, in ABS/PC blends the result of the addition of graphene was dependent on the blend composition. In ABS/PP hybrids, the elastic modulus increased by the incorporation of graphene and this increase, reached anabout 43% in pure PP. The addition of graphene to pure ABS, pure PP and their blend 50/50 w/w resulted in an increasing trend of the dielectric constant (κ′), whereas the loss factor (tanδ) was similar in non‐reinforced and graphene‐reinforced samples, within the entire range of the examined frequencies. POLYM. COMPOS., 40:E1662–E1672, 2019. © 2018 Society of Plastics Engineers
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