Why is post-cured silicone important for rubber for high temperature gasket applications?

Some silicone rubber compounds utilize curing agents that require a secondary post-cure to finish the curing process. Although most silicones can pass the physical parameters of silicone specifications with a press cure at 300° to 340°F, the mechanical properties such as compression set resistance, can be enhanced using a 3-4 hour post-cure at 400°F in a hot air circulating oven. Most sheet silicone manufacturers post-cure to some extent. Further, if an application requires high temperature resistance, such as a door gasket on a high temperature chamber or oven, or high temperature testing instrument, an un-post-cured gasket may appear to smoke as it releases these trapped curing agents. Although these by-products are non-toxic; they may come across as being aesthetically non-appealing.