tailieunhanh - Conductive Polymers and Plastics in Industrial Applications Part 10

Tham khảo tài liệu 'conductive polymers and plastics in industrial applications part 10', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 186 Conductive Polymers and Plastics bulk density less than cc bird s nest structure-aggregate of tubes Because of the large L D and the tortuous structure of the tubes they are not straight tubes as depicted in the idealized diagram they are very efficient at establishing a percolation network at very low loadings. These loadings are less than those required to achieve similar levels of conductivity for carbon black and therefore have a smaller effect on physical performance. As previously alluded to bulk resistivity is a key performance measure to determine electrostatic paintability. The typical threshold for electrostatic paintability is approximately 106 ohm-cm. That is formulations designed with bulk resistivities significantly less than 106 ohm-cm ensure good paint transfer through the paint line. A comparison of bulk resistivity values for various applications is shown is Figure 7. An example of the percolation curve for a resin system containing nanotubes is shown in Figure 8. PROPERTIES Table 1. Physical properties of a typical PPE PA resin containing nanotubes for electrostatic painting Property Value Specific gravity g cm3 Heat distortion temperature 66 psi 1 4 oC 158 Notched Izod KJ m2 Flexural modulus 1 min 1 4 MPa 2400 Flexural yield 1 min 1 4 MPa 95 Tensile strength 2 min MPa 60 Tensile elongation at break 2 min 22 Bulk resistivity kQ-cm 3 Melt flow index 280oC 5 kg Typical physical properties for an example composition for this family of resins are given in Table 1. Such properties were arrived at through a rigorous statistically-based design of experiments approach. SUMMARY The benefits of conductive plastics for electrostatic painting can be summarized as follows. A significant reduction in base coat and clear coat us- age is seen when one changes from traditional painting to electrostatic painting ordinary plastics. However a conductive priming layer must first be applied. When electrostatic painting of a conductive plastic is