Effects of hybrid fillers based on micro- and nano-sized silver particles on the electrical performance of epoxy composites

In the present study, electrically conductive adhesives produced from hybrid fillers based on micro- and nano-sized silver (Ag) was developed. The influence of the hybrid filler composition on the electrical properties of the hybrid system was studied. The electrical conductivity of the epoxy composites filled with micro- and nano-silver was correlated with their morphologies. A positive effect was observed in the electrical conductivity result when the composition of micro- and nano-sized Ag particles reached a 50:50 weight ratio. The nano-sized Ag particles became interconnecting particles in the interstitial spaces between micro-sized particles. Micrograph scanning shows that the particles were well distributed and dispersed, the separation between lumps of Ag filler by the insulating matrix was significantly reduced, leading to the formation of continuous linkages. The increased electrical conductivity resulted in a charge around the particle distribution, which led to the high capacity. Hence, these particles increased the conductivity of the system.     

Effect of processing methods and functional groups on the properties of multi-walled carbon nanotube filled poly(dimethyl siloxane) composites

Pristine and functionalized multi-walled carbon nanotubes (MWCNTs) filled poly(dimethyl siloxane) (PDMS) composites were produced by two different methods, namely the solution mixing method and the mini-extruder method. The composites produced using the mini-extruder exhibit relatively higher tensile strength and higher thermal conductivity due to better nanotubes dispersion. On the other hand, the composites prepared via solution mixing have higher electrical conductivity and better thermal stability due to the high aspect ratio of nanotubes. Scanning electron micrographs of composites fracture surface revealed that composites produced by mini-extruder resulted shorter nanotube length, thus lowering the aspect ratio of MWCNTs. In general, functionalization of nanotubes increases the tensile strength, thermal conductivity, and thermal stability of the PDMS composites due to the improved interfacial adhesion and nanotubes dispersion.     

Silver-filled epoxy composites: effect of hybrid and silane treatment on thermal properties

The combination effects of hybrid nano–micron fillers and filler treatment on the thermal properties of silver-filled epoxy composites are experimentally evaluated. These hybrid composites are fabricated using two different sizes and shapes of silver particles, namely 80 nm with spherical shape and 4–8 μm with flaky shape. In this study, the ratio of silver flakes to silver nanoparticles was varied from 100:0, 75:25, 50:50, 25:75, and 0:100 at a fixed silver loading of 6 vol.%. The silver fillers are treated with 3-aminopropyl triethoxysilane (3AMPTES) at different concentrations of 5, 10, and 30 wt%. The hybrid micro:nano at 50:50 shows the highest storage modulus and the lowest coefficient of thermal expansion (CTE) value compared with other ratios. The silver fillers with 10 wt% of 3AMPTES show improvement in storage modulus, CTE, and thermal stability compared with untreated and further increasing of 3AMPTES at 30 wt% did not show any significant improvement.     

Effect of electron beam irradiation on the properties of ethylene‐(vinyl acetate) copolymer/natural rubber/organoclay nanocomposites

The effects of electron beam (EB) irradiation on the morphology, crosslink density, and tensile properties of EVA/SMR L (Standard Malaysian Rubber)/organoclay nanocomposites prepared by a melt‐blending technique were investigated. All the samples were irradiated by using a 3.0‐MeV EB apparatus with doses ranging from 50 to 200 kGy. Organoclay loading was varied from 0 to 10 phr (parts by weight per hundred parts of resin). X‐ray diffraction results and transmission electron microscopy images proved that the dispersion of organoclay in the nanocomposites was slightly improved by EB irradiation. The gel fraction yield for the nanocomposites increased with irradiation dose but decreased with organoclay loading. However, at 200 kGy, the gel fraction yield was almost the same at all organoclay loadings. Tensile strength and stress at 100% elongation increased proportionally with the irradiation dose. Elongation at break of the nanocomposites increased up to 100 kGy but then decreased at higher irradiation doses. The intercalation and exfoliation of the organoclay, the barrier effect, and the Hofmann degradation of the modification agent are the three major factors leading to the improvement of the properties of the irradiated nanocomposites. J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers