In simple terms, annealing is a manufacturing process of heating a material up for a period of time before allowing it to cool down. This capability can be applied to all three types of basic materials, ceramic, metal, and polymer, but we focus on plastic material here at Elite Plastics. In the plastics industry specifically, annealing is the process of heating a plastic part up to half of the melt temperature for a moderate period of time before letting the plastic cool back down. When the part is reheated like this, the material relaxes and the molded stress is reduced. Annealing is a secondary operation, specifically a heat treatment, and isn’t typically done for all plastics parts or even in most plastic industries, but it is an important technology here at Elite Plastics.
This is an important step of the molding process because most plastic materials are poor conductors of heat which can lead to part damage. Because the plastic parts are heated up to high temperatures through annealing, the material is able to relax so that it does not react to stress caused by molding when it is in its final application or shape. These stresses typically include tension or compression (built-in stress or molded stress).
The purpose of annealing can vary for different plastic materials, but Elite Plastics uses it to ensure part stability over time. This is important for two main reasons. First, by reducing the stress, the plastic part will have better mechanical and thermal properties because there are fewer sites in the polymer that could propagate a crack or expand the part. Secondly, because most of the plastic parts that Elite Plastics produces are painted, a crack would be very visible against the paint. This is because the part material will contract and expand over time and if it has not already experienced this fluctuation at a more extreme condition through annealing, it will noticeably crack.
While the annealing process is not used in every plastic industry, Elite Plastics is committed to utilizing the technology to ensure plastic part quality over time.