Present article reports the rheological properties and network dynamics of fumed silica filled vinyl‐terminated polydimethylsiloxane suspensions. The results reveal that as filler loading increases, the span of the linear viscoelastic region with constant dynamic storage modulus is narrowed with increase in strain amplitude while the relaxation time of the compounds get shifted to longer time scales. The dynamics of filler‐network indicated significant Payne effect due to fumed silica incorporation into the PDMS matrix. Further, strain‐induced agglomeration of fumed silica particles, characterized by a peak in the dynamic loss modulus curve could also be observed. High loss‐tangent was observed for lower contents of filler in the suspension, an effect with an apparent relationship to the loosely formed filler‐network. The formation of a saturated network structure of fumed silica particles was evident from the dynamic modulus and complex viscosity data, that remained unaffected with frequency till a critical amount of fumed silica loading. Han plots (storage modulus versus loss modulus) revealed the microstructural changes for various filled systems that was attributed to build‐up of the filler‐network causing an apparent evolution of yielding phenomenon. Van Gurp‐Palmen plots (complex modulus versus phase lag) showed that flow behavior of the filled PDMS suspensions resembled to that of typical viscous fluids. POLYM. ENG. SCI., 57:973–981, 2017. © 2016 Society of Plastics Engineers

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 (T i ), the maximum rate of degradation (T max ) and overall thermal stabilities increased significantly. On the other hand, by the addition of FS into to PDMS-PVP blends, the T i and T max remains unaffected, but overall thermal stabilities increased significantly. PDMS-PVP blends exhibited low contact angle (458) which confirmed the formation of the hydrophilic surface. POLYM. ENG. SCI.,

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The surge in the usage of wireless electronics and communication devices has engendered a different form of pollution, viz. electromagnetic (EM) pollution, and yet another serious issue, EM interference (EMI). There is a legitimate need to develop strategies and materials to combat this issue, otherwise leading to dreadful consequences. Functional textiles have emerged as the modern materials to help attenuate EM waves due to the numerous advantagesflexibility being the most important. In addition to this, there is an inherent advantage of multiple interfaces in coated fabrics that can engender significant attenuation. Herein, we report a coating having multifunctional propertiescapable of blocking both UV and EM radiation (predominantly of the microwave frequencies) with flame-retarding properties. The layer described here comprises iron titanate (FT) synthesized from its sustainable precursorilmenite sand and carbon nanotubes (CNTs) dispersed in waterborne polyurethane. It is worth noting that FT's use as a multifunctional material is being reported for the first time. It was observed that a single layer of coated fabric shows an EMI shielding effectiveness of −40 dB translating to 99.99% attenuation and similarly a UV blocking of 99.99% in the wavelength range from 200 to 400 nm. The microwave shielding properties of the fabric were demonstrated using a Bluetooth module, where the coated fabric was able to block the incoming Bluetooth signals to the module from a mobile phone. Besides, the coated fabrics exhibited phenomenal enhancement in thermal stabilitya 5% increase in the limiting oxygen index was observed upon the application of the coating. Such exceptional properties tend to complement cotton fabrics' existing utility, thereby extending their use to specialty applications.