During sintering, PTFE particles on fiberglass fabric melt above 327°C, destroying original folded-chain lamellae and particle boundaries to form an amorphous melt. Upon cooling, PTFE recrystallizes into spherulites composed of radially oriented lamellae, with crystallinity ranging 50–70%. Cooling rate determines crystal perfection: slow cooling yields higher crystallinity, larger spherulites, greater hardness; rapid quenching gives finer spherulites and improved flexibility.