The Torah obligation of Tebilat Kelim immersing new utensils applies only to metal utensils, and the Sages extended this obligation to glass utensils. Utensils made from other materials, such as plastic, nylon, rubber and enamel, do not require immersion at all. This is the ruling of Hacham Ovadia Yosef, in Halichot Olam (vol. 7).
The Halachic authorities debate the status of a Teflon pot with respect to Tebilat Kelim. On the one hand, since the pot is made primarily of metal, and the Teflon is just a thin layer of nylon covering the pot, it seemingly should require immersion like other metal utensils. On the other hand, people who acquire Teflon pots are specifically interested in the Teflon, which prevents the food from sticking to the surface of the utensil, and thus perhaps the Teflon should be regarded as the primary material, such that the pot should not require Tebila. As mentioned, the Aharonim (later authorities) debate this question. In light of the difference of opinion in this regard, Teflon utensils should be immersed in a Mikveh, but without a Beracha.
Summary: Utensils made from materials other than metal and glass do not require Tebila. Metal utensils lined with Teflon should be immersed, but without a Beracha.
