In this article, we studied the chain disentanglement process of UHMWPE by petrolatum. As a result of disentanglement of UHMWPE network, the G/G crossover frequency increased, and the plateau modulus decreased. The plateau moduli were shown to exhibit a power law dependence on the polymer volume fraction with the power law exponent of 2.7. This is in agreement with the scaling relationship in polymer solutions where the solvent is slightly better than the solvent. To further verify the disentanglement effect induced by the presence of petrolatum, biaxial drawing of gel crystallized films was performed. Scanning electron microscopy analysis on the extracted films shows that the fibrous crystal network structures holding the micropores in the membrane were closely related to the entanglement density. Rheological measurements showed high repeatability of results and upheld the validity of models. We are among the first to provide a reasonably quantitative description for the disentanglement of UHMWPE. POLYM. ENG. SCI., 55:1177-1186, 2015. (c) 2014 Society of Plastics Engineers