Guoliang Tao

A Percolation Model of Thermal Conductivity for Filled Polymer Composites

In view of the shape and distribution of fillers, a model predicting the effective thermal conductivity of filled polymer composites is proposed on the basis of the percolation theory. Compared to other models proposed in the literatures, theoretical results obtained with the percolation model agree better with the experimental data. Methods of determining the percolation threshold Vc and the exponent n in the percolation model are also discussed.In view of the shape and distribution of fillers, a model predicting the effective thermal conductivity of filled polymer composites is proposed on the basis of the percolation theory. Compared to other models proposed in the literatures, theoretical results obtained with the percolation model agree better with the experimental data. Methods of determining the percolation threshold Vc and the exponent n in the percolation model are also discussed.

Novel Isotropical Conductive Adhesives for Electronic Packaging Application

Isotropical conductive adhesives (ICAs) have recently received a lot of focus and attention from the researchers in electronic industry as a potential substitute to lead-bearing solders. In this paper, a novel kind of isotropical conductive adhesives was made by using silver (Ag) nanowires and nanosized silver particles as conductive fillers. These Ag nanowires with dismeters in the range of 30-50 nm and lengths of up to ~ 50 mum could be synthesized by a solution-phase method, which was proceed by reducing silver nitrate with ethylene glycol in the presence of poly(vinyl pyrrolidone) (PVP). Electrical property including bulk resistivity and mechanical property including shear strength were investigated and compared with that of conventional ICA filled with micrometer-sized Ag particles or nanometer-sized Ag particles. Our results indicated that ICA filled Ag nanowires exhibited higher conductivity, higher shear strength and low percolation threshold value than traditional ICA. Possible conductive mechanism was discussed based on theory calculation.

Preparation and kinetic characterization of attapulgite grafted with poly(methyl methacrylate) via R-supported RAFT polymerization

Poly(methyl methacrylate) brushes grafted from attapulgite nanoparticles (ATP@PMMA) were prepared by R-Supported reversible addition-fragmentation chain transfer polymerization (RAFT). ATP was firstly activated, and allowed to react with γ-aminopropyltriethoxysilane (APTES), 4,4′-azobis(4-cyanovaleric acid) (ACVA) and bis(thiobenzoyl) disulfide stepwise to afford 4-cyanopentanoic acid dithiobenzoate functionalized ATP (ATP-CPADB). Then, RAFT polymerizations of MMA mediated by the different systems were conducted and compared systemically. The grafting process was verified by FTIR, XRD, XPS, TGA and TEM data. Kinetic behavior indicated that the anchored CPADB is more effective before diffusing into the bulk phase. The grafting ratio (Gr), while Mn of grafted and free polymer increased linearly with increasing monomer conversion in presence of free CPADB, giving the hybrid particles with more homogeneous distribution of grafted polymer layer.