Biodegradable polymers: Wall slip, melt fracture, and processing aids

2015 ◽  
Author(s):  
Norhayani Othman ◽  
Nazbanoo Noroozi ◽  
Bashar Jazrawi ◽  
Parisa Mehrkhodavandi ◽  
Laurel Schafer ◽  
...  
Keyword(s):  
Biodegradable Polymers ◽  
Wall Slip ◽  
Melt Fracture ◽  
Processing Aids

Melt fracture and wall slip of thermoplastic vulcanizates

2020 ◽  
Author(s):  
Nikoo Ghahramani ◽  
Shiling Zhang ◽  
Krishnan Iyer ◽  
Antonios K. Doufas ◽  
Savvas G. Hatzikiriakos
Keyword(s):  
Wall Slip ◽  
Melt Fracture ◽  
Thermoplastic Vulcanizates

Wall slip and melt-fracture of polystyrene melts in capillary flow

Polymer ◽  
2010 ◽  
Vol 51 (10) ◽  
pp. 2221-2228 ◽  
Author(s):  
Ryohei Komuro ◽  
Koji Kobayashi ◽  
Takashi Taniguchi ◽  
Masataka Sugimoto ◽  
Kiyohito Koyama
Keyword(s):  
Capillary Flow ◽  
Wall Slip ◽  
Melt Fracture

Flow Properties and Melt Distortion in Molten Rubber Compounds under Capillary Extrusion

2013 ◽  
Vol 747 ◽  
pp. 627-630
Author(s):  
Watcharapong Chookaew ◽  
Yanichsa Sukniyom ◽  
Somjate Patcharaphun ◽  
Narongrit Sombatsompop
Keyword(s):  
Shear Rate ◽  
Rheological Properties ◽  
Apparent Viscosity ◽  
Wall Slip ◽  
Skin Layer ◽  
Rubber Compound ◽  
Melt Fracture ◽  
Extrudate Swell ◽  
Rubber Compounds ◽  
Capillary Extrusion

The influences of shear rate and vulcanizing system on the rheological properties and melt fracture of natural rubber compounds were investigated by using a rate-controlled capillary rheometer. The rheological properties of rubber compounds were characterized with respect to the apparent viscosity and extrudate swell. The measured results indicated that the apparent viscosity tended to decrease with increasing shear rate. This was due to the pseudoplastic behavior of molten rubber compound. It was evident that rubber compound using EV system showed the lowest apparent viscosity as compared to those obtained by CV and NS systems, respectively. This was due to the occurrences of premature crosslink at the skin layer and the wall slip of rubber compound during the flow in capillary die. Furthermore, the onset of smooth surface was also observed which depending on the types of crosslink at the skin layer.

Melt fracture revisited

2001 ◽  
Vol 12 (4) ◽  
pp. 465-477
Author(s):  
J. M. GREENBERG
Keyword(s):  
Viscous Fluid ◽  
Strain Rate ◽  
Flow Rate ◽  
Wall Slip ◽  
Oscillatory Behavior ◽  
Melt Fracture ◽  
Empirical Observation ◽  
Shark Skin ◽  
Slightly Compressible ◽  
Fracture Instability

In a previous paper the author and Demay advanced a model to explain the melt fracture instability observed when molten linear polymer melts are extruded in a capillary rheometer operating under the controlled condition that the inlet flow rate was held constant. The model postulated that the melts were a slightly compressible viscous fluid and allowed for slipping of the melt at the wall. The novel feature of that model was the use of an empirical switch law which governed the amount of wall slip. The model successfully accounted for the oscillatory behavior of the exit flow rate, typically referred to as the melt fracture instability, but did not simultaneously yield the fine scale spatial oscillations in the melt typically referred to as shark skin. In this note, a new model is advanced which simultaneously explains the melt fracture instability and shark skin phenomena. The model postulates that the polymer is a slightly compressible linearly viscous fluid but assumes no-slip boundary conditions at the capillary wall. In simple shear the shear stress τ and strain rate d are assumed to be related by d = Fτ, where F ranges between F2 and F1 > F2. A strain-rate dependent yield function is introduced and this function governs whether F evolves towards F2 or F1. This model accounts for the empirical observation that at high shears polymers align and slide more easily than at low shears, and explains both the melt fracture and shark skin phenomena.

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