Ananda D. Mali

Surface modification of montmorillonite (MMT) using column chromatography technique and its application in silicone rubber nanocomposites

AbstractSurface modification of montmorillonite (MMT) was done to improve the basal spacing using a column chromatography technique with quaternary long chain ammonium salt as an intercalent. An increase in d-spacing of organically modified montmorillonite (OMMT) was confirmed by X-ray diffraction and found to increase from 16 to 22 Å. The d-spacing was maximal (22 Å) due to ion exchange column of sufficient length (35 cm) and diameter (5 cm), which provides maximum retention time for proper ion exchange between MMT and ion-exchange resin. OMMT: silicone nanocomposites were prepared by solution blending and then compounded and molded on two roll mill and compression molding machines, respectively. The amount of loading of OMMT was in the range of 2–10 wt%. The rubber chains were uniformly dispersed within and between the exfoliated OMMT plates. The extent of dispersion was measured using atomic force microscopy. The mechanical, thermal, and physical properties were studied. Increased amounts of OMMT loading showed increased silicone:OMMT nanocomposite properties compared to those of pristine silicone rubber due to OMMT exfoliation and uniform dispersion with good wet ability of the rubber chains.

Effect of Mg(OH)2 nanoparticles on thermal, mechanical and morphological properties of millable polyurethane elastomer

Millable polyurethane (MPU) rubber nanocomposites were prepared on a two-roll mill and molded on a compression molding machine. The amount of loading of Mg(OH)2 nanoparticles (nMg(OH)2) was from 0.5 to 2.5 wt% followed by the addition of dicumyl peroxide (as a curing agent). The compounded matter was subjected to compression molding so as to get a cure sheet (130 × 130 × 3 mm). Mechanical (tensile strength, elongation at break (%) and abrasion resistance index), physical (hardness and swelling index), and thermal properties (flammability retardency and degradation stability) were studied. The extent of dispersion of nMg(OH)2 particles was studied using scanning electron microscope and atomic force microscope. nMg(OH)2 was synthesized using continuous ultrasonic cavitation technique. The size and shape of nMg(OH)2 was confirmed using X-ray diffraction and transmission electron microscopy, which was found to be ∼20–60 nm with quasi shape. MPU:nMg(OH)2 nanocomposites show improved mechanical, physical, and thermal properties compared to pristine MPU. This improvement was due to very fine grain size of nMg(OH)2, which facilitates uniform dispersion of nMg(OH)2 within MPU rubber matrix. However, higher loading of nMg(OH)2 shows marginal decrement in properties due to agglomeration, especially at 2.5 wt%.

Effect of surface modified montmorillonite on photo-oxidative degradation of silicone rubber composites

AbstractBasal spacing of montmorillonite (MMT) was improved through a column chromatography technique using quaternary long chain ammonium salt as an intercalent. An increase in d-spacing of organic montmorillonite (OMMT) was confirmed by XRD and found to increase from 16 to 22 Å. The d-spacing was maximum (22 Å) due to an ion exchange column of sufficient length (35 cm) and diameter (5 cm), which provides maximum retention time for the proper exchange of ions between plates of MMT and ion exchange resin packed into the column. Nanocomposites (OMMT: silicone rubber) were prepared using a solution blending method. The material was compounded on a two roll mill and molded in a compression molding machine in order to obtain a square (0.2 mm thickness) sheet. Photo-oxidative degradation of OMMT: silicone rubber composite was studied under accelerated UV irradiation (≥290 nm) at different time intervals. Prolonged exposure to UV leads to a progressive decrease in mechanical and physical properties along with the change in behavior of the filler-matrix interaction, which was due to decrease in cross-linkage density with an increase in the mobility of rubber chains. The increase in carbonyl (>CO), hydroxyl (-OH) functional groups on irradiation of OMMT: silicone rubber composites at different time intervals were studied using Fourier transform-infrared spectroscopy (FTIR). Whereas, change in morphological behavior regarding the OMMT-matrix interaction on irradiation was studied using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Overall, the study showed that the OMMT: silicone composites were affected more on irradiation than pristine silicone composites.