4.1.1 Plastic Materials for Top Chains
Most Engineered Plastic Top Chains have molded parts; the pins are made of 304 stainless steel. They offer quiet operation, do not require additional lubrication, and do not scratch conveyed objects. Engineered Plastic Top Chains are divided into several types as follows:
- Standard series.
- Low-friction, wear-resistant series. In the low-friction series, the coefficient of friction (against guide rails or conveyed objects) is 15 to 45 percent lower, and wear life is 1.2 to 2 times longer than standard series.
- Heat-resistant, high-speed series. When constructed of super engineered plastic, this series can work continuously in temperatures up to 250°C, and the chains can convey objects with speeds up to 200 m/min.
- Anti-chemical series. These chains are made of super engineered plastic and resist most organic solvents, inorganic salts, acids, alkalines, and oxidizers. There is a "super anti-chemical" series with pins made of titanium.
- Electroconductive series. This series has electric resistivity of 106 Ω•cm. These chains are suitable where dust collection, electronoise, and electrosparks should be avoided.
- Plastic pin series. In this series, chains and pins are made of engineered plastic. Compared to the standard series, these chains are 15 to 25 percent lighter in weight and are easy to disassemble for recycling. A larger-diameter pin and unique design make this a very strong series. In fact, it has almost the same allowable tension as the standard series.
Table 4.1 shows the features of each type of TPU 836 chain. Coefficient of friction and maximum allowable load are under the following conditions: room temperature, non-lubricated, chain speed 10 m/min., and stainless steel rail.