Understanding Melt Rheology and Foamability of Polypropylene-based TPO Blends

Gunkel, Felix; Spörrer, Andreas; Lim, G. T.; Bangarusampath, D. S.; Altstädt, Volker

doi:10.1177/0021955x08088858

Cited by 36 publications

(31 citation statements)

References 12 publications

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“…Due to strong biaxial stretching of the matrix material in the cell walls during bubbles expansion, sufficient extensional flow properties such as high melt strength and high melt extensibility are needed [1,2,8]. On one hand, if melt strength is too low cell wall rupture and cell coalescence can occur leading to low expansion ratios and inhomogeneous foam morphologies with high content of open cells [1,9,10]. On the other hand, extensively high melt strengths can hinder cell nucleation and cell growth, resulting in heterogeneous foam morphologies, too, and leading to high densities of the foamed product [9,10].…”

Section: Introductionmentioning

confidence: 99%

Extensional Flow Properties of Externally Plasticized Cellulose Acetate: Influence of Plasticizer Content

et al. 2013

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Elongational flow properties of polymer melts are very important for numerous polymer processing technologies such as blown film extrusion or foam extrusion. Rheotens tests were conducted to investigate the influence of plasticizer content on elongational flow properties of cellulose acetate (CA). Triethyl citrate (TEC) was used as plasticizer. Melt strength decreases whereas melt extensibility increases with increasing plasticizer content. Melt strength was further studied as a function of zero shear viscosity. The typical draw resonance of the Rheotens curve shifts to higher drawdown velocity and the amplitude of the draw resonance decreases with increasing TEC content. With respect to foam extrusion, not only are melt strength and melt extensibility important but the elongational behavior at low strain rates and the area under the Rheotens curve are also significant. Therefore, elongational viscosity as well as specific energy input were calculated and investigated with respect to plasticizer content. Preliminary foam extrusion tests of externally plasticized CA using chemical blowing agents confirm the results from rheological characterization.

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Section: Introductionmentioning

confidence: 99%

Extensional Flow Properties of Externally Plasticized Cellulose Acetate: Influence of Plasticizer Content

et al. 2013

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“…The Cell structure of the linear PP has a non-homogeneous size distribution and collapsing of the cells. It is known that branched polymers has higher expandability capacity 2,3 , in the case of the blends studied in this work, higher level of uniformity as well as reduction of collapsing effect occurred. Image analysis through the software Image Tool allowed the determination of the cell size distribution of the different compositions tested 5 .…”

Section: Resultsmentioning

confidence: 55%

“…Thus, the blend with branched polymers did not increase the cell density, otherwise increased the uniformity in cell size distribution. This effect is related by the improvement of the melt strength as well as the lower nucleation rate of the LCBPP or POE in the linear PP matrix 3,6 . The results of the dynamic-mechanical analyses, α and glass transition temperatures (Tg), storage moduli (E') and respective specific stiffness are presented in Table 2.…”

Section: Resultsmentioning

confidence: 99%

“…As a result, the expanded grades of linear PP have a high amount of coalescence and open cells which decrease mechanical properties. To increase melt strength, one of the current solution is blend PP with branched polypropylene (LCBPP) as well as ethyleneoctene copolymer (POE) 2,3 . In this study to provide extensional properties and achieve uniform cellular structures of expanded linear PP, 20 parts per hundred of resin (phr) of LCBPP or POE was added into PP matrix.…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of foaming polypropylene modified with ramified polymer

Demori

Azeredo²,

Liberman

et al. 2015

AIP Conference Proceedings

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Polypropylene foams have great industrial interest because of balanced physical and mechanical properties, recyclability as well as low material cost. During the foaming process, the elongational forces applied to produce the expanded polymer are strong enough to rupture cell walls. As a result, final foam has a high amount of coalesced as well as opened cells which decreases mechanical and also physical properties. To increase melt strength and also avoid the coalescence effect, one of the current solution is blend PP with ramified polymers as well as branched polypropylene (LCBPP) or ethylene-octene copolymer (POE). In this research to provide extensional properties and achieve uniform cellular structures of expanded PP, 20 phr of LCBPP or POE was added into PP matrix. The blend of PP with ramified polymers was prepared by twin-screw extrusion. Injection molding process was used to produce PP foams using azodicarbonamide (ACA) as chemical blowing agent. The morphological results of the expanded PP displayed a non-uniform geometrical cell, apparent density of 0.48 g/cm³ and cell density of 13.9 .10 4 cell/cm³. Otherwise, the expanded PP blended with LCBPP or POE displayed a homogeneous cell structure and increased the amount of smaller cells (50-100 μm of size). The apparent density slightly increased with addition of LCBPP or POE, 0.64 and 0.57 g/cm³, respectively. Thus, the cell density reduced to 65% in PP/LCBPP 100/20 and 75% in the sample PP/POE 100/20 compared to expanded PP. The thermo-mechanical properties (DMTA) of PP showed specific stiffness of 159 MPa.cm -3 .g -1 , while the sample PP/LCBPP 100/20 increased the stiffness values of 10%. Otherwise, the expanded PP/POE 100/20 decreased the specific stiffness values at -30%, in relation to expanded PP. In summary, blending PP with ramified polymers showed increasing of the homogenous cellular structure as well as the amount of smaller cells in the expanded material.

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“…Therefore, a certain minimum melt viscosity is also necessary. If the melt viscosity is too high partial solidification of the melt during foaming can lead to insufficient foam expansion, heterogeneous foam morphologies and poor foam properties [6,8].…”

Section: Introductionmentioning

confidence: 99%