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Tham khảo tài liệu 'conductive polymers and plastics in industrial applications part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 58 Conductive Polymers and Plastics Figure 1. Electrical-rheological plate fixture for Rheometrics RMS-705 rheometer. Figure 2. Effect of unmodified carbon black loading on G strain dependence. BohlinVORM 10 radians sec. 190oC. Custom rheometry plates were made to enable electrical resistivity and shear modulus to be measured simultaneously as seen in Figure 1. Ceramic plates were sandwiched between standard aluminum plates that fit in the RMS disposable plate fixture and brass plates which contact the sample. Steel screws were used to secure the plates together and make electrical contact with the leads. These screws were insulated from the disposable plate fixture by ceramic spacers. The leads were connected to a Fluke multimeter with which resistance measurements were made. RESULTS The elastic shear modulus G as a function of dynamic strain amplitude is shown for composites of 2.5 to 40v unmodified carbon black in Figure 2. Figure 3 is the corresponding graph for composites of 10v to 40v surface modified carbon black. G values for the composites with less than 17v carbon black are independent of strain up to about 5 strain and all lie within experimental error of each other. The noise seen at the lower strains was due to low torque values. Above about 18v carbon black G becomes increasingly dependent on strain amplitude as the carbon black loading increases. At the low strain limit about 0.5 strain G is at a maximum and independent of strain. Both the unmodified and modified carbon black composites show increased G low strain at about 18v carbon black which is consistent with a percolation theory.4 At 25v carbon black and Rheological Characterization 59 Figure 3. Effect of surface modified carbon black loading on G strain dependence. BohlinVORM 10radians sec. 190oC. Figure 4. Simultaneous G and resistivity measurements of 35v unmodified carbon black composite with increasing strain amplitude. RMS-705 10 radians sec. 190oC using electrical-rheological fixture. .