Figure 2.
Effect of plasticizer (tricresyl phosphate) on Tg (a) and free volume (b) of PVC polymer [59]. (c)—The plasticization phenomenon in polymers [15]. (d)—Free volume for plasticization sources: (A) chain end motion; (B) side-chain motion, (C) main chain “Crankshaft”, (D) external plasticizer motion [59].