2. Dipping (Figure 38.2): Sometimes, molds or articles are dipped into solutions, dispersions, pastes, melts or powders. Later on, the adhering material on the surface is solidified by heat treatment.

For manufacturing articles such as gloves, boots etc. in which one side remains open , a ppositive mold is immersed and subsequently the casting is gelled. A series of identical molds mounted on dipping frames are used for the mass production of such articles. During the dipping process, degassed PVC paste placed in a vessel is raised and lowered. Sometimes, the dipping frame is moved, while the vessel is stationary. The immersion and removal stages are carried out slowly to allow the material to flow homogeneously from the mold and to prevent the introduction of air into the paste.

The gelation is usually carried out in circulating air oven, and during the process the paste temporarily becomes fluid. The molds containing the gelled coating are immersed in water for cooling. It is cooled to around 50°C and at this temperature, the moldings can be easily removed from the molds. Cables and wires are extensively coated using this process.

Figure38.2 .Dipping Unit.

a)Vessel; b)PVC paste; c)Dipping frame; d)Molds