This article describes the effect of natural Sepiolite nanofibers on the properties of polypropylene (PP) in the absence/presence of compatibilizer (maleic anhydride grafted-polypropylene (PP-g-MA)). For this purpose, PP/Sepiolite and PP/PP-g-MA/Sepiolite nanocomposites were prepared by melt blending using twin-screw extruder. The morphology and dispersion of Sepiolite in PP composites characterized using scanning electron microscope (SEM) and transmission electron microscope (TEM) revealed that the dispersion of Sepiolite in PP matrix was better in the presence of PP-g-MA. Thermogravimetric analysis (TGA) was used to study the effect of Sepiolite on the thermal stability of PP in absence/presence of PP-g-MA. X-ray diffraction (XRD) and differential scanning calorimetric (DSC) techniques were employed to assess the effect of Sepiolite on the crystallinity of PP matrix. Dynamic mechanical analysis (DMA) was used to evaluate the viscoelastic properties of PP/Sepiolite nanocomposites in solid state. Mechanical properties evaluated as per ASTM methods showed $65% increase in flexural modulus, 60-70% increase in tensile modulus and 10-20% increase in impact strength on addition of 10% Sepiolite in PP. Addition of compatibilizer has further improved the flexural modulus close to 85% when compared to neat PP without compromising other properties like impact strength and tensile strength. POLYM. COMPOS., 00:000-000, 2015.
We have investigated silicone-based hydrogels highlighting the effect of silyl comonomer, method of polymerization and nature of cross-linker on their bulk as well as surface properties. Transmission electron microscopy results showed that solution thermal polymerization mitigated phase segregation of hydrophobic siloxane components over bulk thermal polymerization.2-hydroxyethyl methacrylate cannot provide transparent hydrogels with 3-[tris (trimethylsilyloxy)silyl]propyl methacrylate alone and requires equal weight percent of N, N-dimethylacrylamide to compatibilize the comonomers to yield a silicone hydrogel network showing no microphase separation. The differentiated surface properties of silicone hydrogels containing varying amount of siloxane comonomers were also unraveled and rationally supported by surface infrared spectroscopic results. Different molecular states of water entrapped within hydrogel network were identified to understand the nature of gel-mesh functionality. The effect of silicone pendant groups on the gel elasticity was also explored.
K E Y W O R D Sapplications, biomedical applications, gels
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