Relationship in polypropylene melt between its linear viscoelasticity and its steady capillary flow properties

Abstract

synopmsIt is the object of the present study to obtain clear knowledge of the relations in the polypropylene melt between its linear viscoelasticity and its nonlinear steady capillary flow, paying particular attention to the elastic properties in its capillary flow. By representing the linear viscoelasticity numerically with zero-shear viscosity, q0, and steady-state compliance, Je0, evaluation has been made of the properties concerning the elasticity of polymer melt in the capillary flow, such as non-Newtonianity, the entrance pressure loss, the end correction, the Barus effect, and the melt fracture. The steady flow viscosity q, the entrance pressure loss Po, the critical shear stress, T~, and the critical shear rate +, at which melt fracture begins to occur are subject to 70 as follows:log $ a log qo, log P o a log 70, TC alog 70, log 9, alog $0.From the well-known relationship between $0 and the weight-average molecular weight 2,, these quantities are governed by M, . Meanwhile, for such quantities tls structural viscosity index N, end correction coefficient Y, and elastic pressure loss ratio Po/P, following correlations hold: N 0: log ($0.Jeo), log P a log ($oZ.J2), Po/P a log (qo*.J,O). As 70 and J,O are respectively determined mainly by $w and the molecular weight distribution MWD, these quantities are governed by both a, and MWD. Physical meanings of qO-Jeo and qoz-Jao are, respectively, mean relaxation time and a measure of stored energy in steady flow. The Barus effect has a positive correlation t o J,O, Y, and Po/P. (The symbol a employed here means positive correlation.)

Rheological properties of polypropylenes with different molecular weight distribution characteristics

“…As a large tendency, ν is higher as MFI is lower or the molecular weight is higher. This tendency is also generally reported for PP7, 18–21 and other polymers 12, 14, 17, 22–24. Compared at a similar MFI (molecular weight), cat.‐B PPs with generally broader molecular weight distribution tend to show higher ν.…”

Rheological properties for binary blends of i-PP and ethylene-1-hexene copolymer

“…The value of DH of i-PP was about 40 kJ/mol, which was in good agreement For the miscible i-PP/EHR57 blends, G and GЉ are proportional to v 2 and v, respectively, in with the values reported previously. 20,22,23 The DH …”

Melt Rheology and Its Role in Plastics Processing

“…In this regime, calculation of a slip velocity using Equation 8-29 gave results that were double those at the upper end of the oscillatory flow regime. TM~ behavior for polypropylene has been reported to be similar to that of polystyrene [89,99]. At higher flow rates, gross distortion is observed, with no discontinuity in the flow curve.…”