Incorporation Of Fumed Silica Research Articles

Modification of polydimethylsiloxane with polyvinylpyrrolidone: Influence of reinforcing filler on physico-mechanical properties

The present article reports an approach for the modification of hydrophobic polydimethylsiloxane (PDMS) with low molecular weight hydrophilic polyvinylpyrrolidone (PVP) via solution blending method to develop new PDMS-based materials with improved mechanical performance and wettability which can be used in many biomedical applications. The influence of dimethyldichlorosilane treated fumed silica (FS) on physico-mechanical properties of PDMS–PVP blends were investigated and analyzed. There was the significant improvement in mechanical, dynamic mechanical and thermal properties of PDMS–PVP blends, whereas, transparency and contact angle were slightly decreased after incorporation of FS into PDMS–PVP blends. Scanning electron microscopy revealed that the fourfold reduction in the average domain size of the dispersed PVP in the PDMS matrix in the presence of compatibilizer (PDMS-PEO block copolymer) when compared with the uncompatibilized PDMS–PVP blend morphology. By incorporation of FS into the neat PDMS matrix, the onset of degradation (Ti), the maximum rate of degradation (Tmax) and overall thermal stabilities increased significantly. On the other hand, by the addition of FS into to PDMS–PVP blends, the Ti and Tmax remains unaffected, but overall thermal stabilities increased significantly. PDMS–PVP blends exhibited low contact angle (∼45°) which confirmed the formation of the hydrophilic surface. POLYM. ENG. SCI., 56:491–499, 2016. © 2016 Society of Plastics Engineers

In situ preparation and property investigation of polypropylene/fumed silica nanocomposites

We present the preparation of polypropylene (PP)/fumed silica (FS) nanocomposites via in situ polymerization in this article. The approach includes preparation and utilization of a bisupported Ziegler–Natta catalytic system in which magnesium ethoxide and FS are used as conjugate supports of the catalyst. Catalyst preparation and polymerization processes are carried out in the slurry phase and under argon atmosphere. Scanning electron microscopy images show a good dispersion of the FS throughout the PP matrix. Results from differential scanning calorimetry reveal that the crystallization temperature of prepared nanocomposites increases by increasing FS loading. Also, crystal content of nanocomposites increases as the FS concentration increases up to 3.48 wt%. Nanocomposites containing <3.14 wt% of nanoparticles do not show considerable change in their melting point where with more increment in filler concentration, melting temperature slightly increases. Thermogravimetric analysis shows a considerable improvement in the thermal stability of PP/FS nanocomposites compared to pure PP. Rheological studies indicate that the incorporation of FS into PP matrix results in increment in storage modulus, loss modulus, and complex viscosity of polymeric matrix, particularly in low frequency region. By increasing FS loading, the PP/FS nanocomposites show a transition from liquid‐like to solid‐like viscoelasticity behavior depicting microstructural changes in their structures. POLYM. COMPOS., 35:37–44, 2014. © 2013 Society of Plastics Engineers

Crystallinity and Stability of Poly(vinyl alcohol)‐Fumed Silica Mixed Matrix Membranes

Mixed matrix membranes (MMMs) containing poly(vinyl alcohol) (PVA) and 10–30% fumed silica (FS) were prepared using a solvent casting method. The FS particles were distributed evenly in the MMMs as revealed in the scanning electron microscopy/energy dispersive X‐ray spectroscopy (SEM/EDX) micrographs. The surface roughness increased with higher FS content. The thermogravimetric analysis (TGA) results showed that the MMM decomposition temperature was slightly improved with increasing FS content. The MMM crystallinity was determined using Fourier‐transform infrared spectroscopy (FT‐IR), X‐ray diffraction (XRD), and differential scanning calorimetry (DSC). All results indicated that the crystallinity was decreased with FS content. This was attributed to the fact that the FS particles restricted the polymer chain mobility during membrane formation. The confined chain mobility also slowed or inhibited crystal unfolding and, therefore, suppressed the membrane dissolution in water. The lower crystallinity drop of the swollen membranes with FS addition confirmed this finding. The incorporation of FS improved the thermal stability and resistance to water dissolution. These MMMs exhibit potential for use in alkaline direct methanol fuel cell applications.