Visualizing the elimination of sharkskin through fluoropolymer additives: Coating and polymer–polymer slippage

Novel results and potential applications of bitumen used as an additive for polyethylene

“…This is an encouraging result, since the development of sharkskin at shear rates involved in polymer extrusion (close to 100 s -1 ) limits the industrial use of metallocene catalysed LLDPEs. Nowadays it is generally accepted that sharkskin is originated by a tearing or cracking at the surface of the extrudate, caused by elongational flow at the exit of the die [7][8]. Slippage of the polymer melt along the capillary wall, provoked typically by a processing aid agent, reduces very significantly elongational flow at the exit, avoiding sharkskin [9].…”

Rheo-Particle Image Velocimetry for the Analysis of the Flow of Polymer Melts

“…In addition, slit channels are typically long and require the use of high pressures to induce flow, which limits the range of shear rates to explore. Migler et al (2001) developed a rheo-optics technique to visualize how polymer processing additives (PPA) eliminate sharkskin in a metallocene LLDPE (mLLDPE). These authors measured tracking velocity profiles near the wall and the coating process of PPA in a sapphire capillary, and showed evidence of slip in the coated die and adhesion when this was uncoated.…”

Slip at the Interface between Immiscible Polymer Melts II: Capillary Flow of Polymers with Unequal Viscosities

“…Quantitative investigations of polymer/polymer interfacial slip are typically performed using rheological [1][2][3][4][5][6][7][8] and optical [9][10][11] techniques. Almost all of the investigations that use only rheological data to determine the slip velocity at a polymer/ polymer interface are restricted to drag flows of multilayers where the parallel layers are stacked on top of each other and sandwiched between parallel plates.…”