| In attempt to prepare and study the novel electrically conductive nanocomposites, with polyethylene (PE) served as the matrix, maleic anhydride grafted polyethylene (gPE) served as EG intercalates and expanded graphite (EG) served as a conductive filler, prepared gPE/EG, PE/gPE/EG electrically conductive composites via solution intercalation (SI), direct melt mixing (DMM) and master batch melt mixing (MMM) methods. By means of testing conductivity and mechanical property, with the measures of TEM, SEM, OM, XRD and DSC, studied the relationship between preparation method, material composition, and electrically conductive as well as mechanical property. The main outcomes never reported at home and abroad literature were obtained as follows:1 The gPE/EG electrically conductive nanocomposites were prepared via SI method. The percolation threshold at room temperature (φc) of the nanacomposites was merely 1.59vol%, far lower than the φc (3.13vol%) of general composites prepared via DMM method. At EG content(fv) of2.10vol%, the volume conductivity (σ) of the former was 2.18×10-8s/cm, and the σ of the latter was just 9.98×10-17s/cm, 8 to 9 order of magnitude lower than the former. The research by TEM, SEM, OM and XRD indicated that the composites prepared via SI method were nanocomposites, the structural feature was it possessed nanoscale interlayers of graphite, micron sheetings and quasi millimeter particles compounded with gPE forming multiple EG-gPE network structure. This was the essential reason of thenanocomposites with low φc and high σ, and also the structural reason that the electrical conductivity of general composites prepared via DMM method without such structure couldn't compare with it.2 The PE/gPE/EG (gPE/EG=3/2) electrically conductive nanocomposites were prepared via SI and MMM methods. The φc of the nanocomposites were 2.46vol% and 4.57vol% respectively, which was lower than that of general composites (5.25vol%) and PE/EG compared composites (5.89vol%) prepared via DMM method. At EG content of 4.01vol%, the σ of composites prepared via SI, MMM and DMM methods were 5.03×10-8 s/cm,5.68×10-14 s/cm and 2.36×10-16 s/cm respectively, the σ of the compared composite was 3.20×10-16s/cm at fv=4.51vol%. The research by TEM, SEM, OM and DSC indicated that the composites prepared Via SI and MMM methods were nanocomposites, which had the same structural feature of gPE/EG nanocomposites prepared via SI method, but the structural regularity of PE/gPE/EG (gPE/EG=3/2) nanocomposites prepared via SI method decreased a bit, and which of the nanocomposites prepared via MMM method decreased obviously, but general composites and PE/EG compared composites prepared via DMM method didn't have such structural regularity entirely. This was the essential reason of electrical conductivity had differentia of such composites, and also the structural reason that the electrical conductivity of PE/gPE/EG nanocomposites declined than that of gPE/EG nanocomposites prepared via SI method.3 The electrical conductivity of PE/gPE/EG nanocomposites prepared via MMM method had relationship with the compounding ratio of gPE/EG master batch. At certain EG content, using the master batch of gPE/EG (wt)>3.0 could increase the electrical conductivity more than using the master batch of gPE/EG (wt)<1.5. For example, when gPE/EG (wt) compounding ratio increased from 1.5 to 3, the σ of composites (fv=4.01vol%) prepared via MMM method increased from 5.68× 10-14s/cm to 1.50×10-5s/cm, even more than the a (5.03×10-8 s/cm) three order of magnitude of PE/gPE/EG (gPE/EG=1.5) nanocomposites prepared via SI method. Morphological structure analysis indicate that using the master batch of gPE/EG(wt)>3.0 could obtain structural regularity much good than master batch of gPE/EG (wt)<1.5, so the composites of the former had much well electrical conductivity than the latter.4 The σ-fv relation of gPE/EG, PE/gPE/EG nanocomposites and general composites accorded with conduct behavior described by p... |
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