Dependence of the zero shear-rate viscosity and the viscosity function of linear high-density polyethylenes on the mass-average molar mass and polydispersity

Stadler, Florian J.; Piel, C.; Kaschta, Joachim; Rulhoff, Sascha; Kaminsky, Werner; Münstedt, Helmut

doi:10.1007/s00397-005-0042-6

Cited by 126 publications

(152 citation statements)

References 21 publications

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“…This depends on the chain mobility which is dominated by the viscosity at very low shear rates close to the zero shear-rate viscosity  0 . The zero shear-rate viscosity  0 is proportional to the weight-average molar mass M w for linear molecules [27], while this relation is usually not fulfilled for long-chain branched samples [12,33,37,41]. The strong effect of the rheological behavior has been shown for example by Piel et al [12] for the crystallinity of HDPE with molar masses M w between 3,000 g/mol and 1,200,000 g/mol varying between 80% and 50% for a relatively fast cooling rate of the DSC of 20 K/min.…”

Section: Discussionmentioning

confidence: 99%

“…One parameter influencing the lattice dimensions is the weight average molar mass M w (which strongly influences the rheological properties [27] and thus the chain mobility (and also long-chain branches [12,16,34,41])). For this purpose, several HDPEs (defined by the absence of sizable numbers of short-chain branches) -some slightly long-chain branched-were characterized.…”

Section: Influence Of Molar Mass M W and The Cooling Conditions For Nmentioning

confidence: 99%

“…It was found that the chain spacing increases with molar mass. This can be explained by the higher relaxation times of the higher molecular samples -when disregarding the long-chain branches of the high molecular samples (which lengthen the characteristic relaxation times even further) -a factor of 1.2310 9 is found between the characteristic relaxation time  of the sample with the lowest and the highest molecular weight (E1: M w =6.5 kg/mol, E13: M w =1150 kg/mol) [27]. Thus, the chains of the lowest molecular sample can find the optimum structure much faster than the high molecular sample.…”

Section: Influence Of the Molecular Structure On The Amorphous Scattementioning

confidence: 99%

“…Thus, the chains of the lowest molecular sample can find the optimum structure much faster than the high molecular sample. If we assume a temperature of 120 °C and an activation energy E a =27 kJ/mol, the value of E a of linear mHDPE [38], to shift the characteristic relaxation time from 150 °C to 120 °C (the typical crystallization temperature),  is found to be approximately 2.5 minutes for E13 [27] under the assumption that the sample does not contain any long-chain branches. As E13 is long-chain branched, the characteristic relaxation time is increased further.…”

Section: Influence Of the Molecular Structure On The Amorphous Scattementioning

confidence: 99%

“…Tab. 1) was a blend of the linear mHDPE C3 [27] and the long-chain branched mHDPE D5 described elsewhere [12,28]. Additionally, several other samples were used [29], most of which were synthesized by C. Piel in a similar fashion as the samples described in [8].…”

Section: Samplesmentioning

confidence: 99%

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Lattice sizes, crystallinities, and spacing between amorphous chains - characterization of ethene-/ɑ-olefin copolymers with various comonomers and comonomer contents measured by wide angle X-ray scattering

Stadler¹,

Takahashi

Yonetake

2009

E-Polymers

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Ethene-/-olefin copolymers having a wide range of comonomer contents with comonomers between 4 and 26 carbon atoms in length were characterized by wide angle X-ray scattering (WAXS). It was found that the crystallinities matched fairly well with the crystallinities from DSC and volumetric measurements. An increase of the crystal lattice size was found with increasing comonomer content and comonomer length. Both are attributed to the formation of defects around these short-chain branches in the crystal lattice, which widen it. Increasing the cooling time will lead to a more densely packed crystal structure, if the quenched structure is distorted, i.e. if the sample contains comonomer. A higher molar mass M w widens the average space between chains in the amorphous phase as well as the addition of comonomer. The latter finding is explained by the increasing number of chain ends introduced by the comonomer which increases the free volume in the sample because of the worse amorphous packing of the chain ends.

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Section: Discussionmentioning

confidence: 99%

Section: Influence Of Molar Mass M W and The Cooling Conditions For Nmentioning

confidence: 99%

Section: Influence Of the Molecular Structure On The Amorphous Scattementioning

confidence: 99%

Section: Influence Of the Molecular Structure On The Amorphous Scattementioning

confidence: 99%

Section: Samplesmentioning

confidence: 99%

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Lattice sizes, crystallinities, and spacing between amorphous chains - characterization of ethene-/ɑ-olefin copolymers with various comonomers and comonomer contents measured by wide angle X-ray scattering

Stadler¹,

Takahashi

Yonetake

2009

E-Polymers

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Rheological Measurements

2013

Encyclopedia of Polymer Science and Technology

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Rheology is the science to study the flow and deformation of matter. It becomes an important field in material science and engineering, food, biotechnology, and so on. The objects in rheological study are not the ideal solid and ideal fluid, which can be described by the Hookean elastic model and the Newtonian viscous model, respectively. Instead, the rheological study often focuses on materials that can exhibit viscous, elastic, and plastic behavior under different flow conditions. They are often termed as complex fluids or soft matter, which include polymers, gels, suspensions, emulsions, biofluids, foods, inks (1). In contrast to hydrodynamics, which often accounts for the complex flow behavior of simple fluids, simple geometry is utilized in rheological measurements to understand the rather complicated relationship between the mechanical input and output of complex fluids. The real flow fields encountered in many applications (such as polymer extrusion, injection molding, blow molding, fiber spinning, inkjet printing, coating) are rather complicated (2). It becomes a problem whether the rheological measurements that performed under simple flow fields are useful in understanding the complicated flow behaviors of complex fluids. Fortunately, it has been proved in many examples that the properties determined from simple rheological measurements are sufficient to quantify the material parameters in various constitutive equations, which have been used widely and successfully to simulate the flow behaviors in polymer processing (3-11). The most frequently used simple flow fields are simple shear flow and simple extensional flow.The simplest geometry that defines the simple shear is two infinite parallel plates separated by a distance h. The liquid is set between two plates with one plate moving parallel to the other (Fig. 1). In reality, when the length L and the width B are much larger than the gap h, the flow in the center regime resembles the flow between two infinite plates. It means that the edge effects are ignored in most experimental shear geometries. In rheological measurements, the flow between two plates should be laminar. Moreover, it is usually assumed that the velocity across the gap satisfies a linear profile. As shown in Fig. 1, if the bottom plate is fixed and the upper plate moves horizontally with the velocity V, the fluid velocity varies linearly from 0 at the bottom plate to V at the upper plate if the no-slip boundary condition is satisfied. The linear velocity profile generates a constant velocity gradient, which is known as the shear rate. Then, the flow field between two parallel plates is homogeneous in the shear rate. The homogeneous assumption is nontrivial in the rheological tests since the actual velocity

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