Processing/Structure/Properties Relationships in Polymer Blends for the Development of Functional Polymer Foams

Volume 15: Advances in Multidisciplinary Engineering ◽

10.1115/imece2015-50288 ◽

2015 ◽

Author(s):

Ali Rizvi ◽

Chul B. Park

Keyword(s):

Strain Hardening ◽

Elastic Properties ◽

Crystallization Kinetics ◽

Extensional Flow ◽

Relaxation Times ◽

Rheological Behaviour ◽

Polymer Processing ◽

Phase Morphology ◽

Dispersed Phase ◽

Carbon Dioxide Co2

In this study we present a comprehensive experimental investigation of the effect of polymer blending on the dispersed phase morphology and how the dispersed phase morphology influences the foaming behavior of the semicrystalline polymer matrix using three different material combinations: polyethylene (PE)/polypropylene (PP), PP/polyethylene terephthalate (PET) and PP/polytetrafluoroethylene (PTFE). Samples are prepared such that the dispersed phase domains exhibit either spherical or fibrillated morphologies. Measurements of the uniaxial extensional viscosity, linear viscoelastic properties and crystallization kinetics under ambient pressures and elevated pressures of carbon dioxide (CO2) are performed and the morphological features are identified with the aid of SEM. Batch foaming and lab-scale extrusion foaming experiments are performed, as a screening model for polymer processing, to show the enhancement of the foaming ability as a result of the blend morphology, taking into account the rheological behaviour and the effects of crystallization kinetics. The formation of high aspect ratio fibrils imparts unique characteristics to the semicrystalline matrix such as strain-hardening in uniaxial extensional flow, prolonged relaxation times, pronounced elastic properties and enhanced kinetics of crystallization. In contrast, the regular blends containing spherical dispersed phase domains do not exhibit such properties. Foam processing of the three blends reveals a marked broadening of the foaming window when the dispersed phase domains are fibrillated due to the concurrent increase in crystallization kinetics, improved elastic properties and strain hardening in extensional flow.

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The role of dispersed phase morphology on toughening of epoxies

Polymer ◽

10.1016/s0032-3861(96)00492-2 ◽

1997 ◽

Vol 38 (1) ◽

pp. 21-30 ◽

Cited By ~ 56

Author(s):

Julie Y. Qian ◽

Raymond A. Pearson ◽

Victoria L. Dimonie ◽

Olga L. Shaffer ◽

Mohamed S. El-Aasser

Keyword(s):

Phase Morphology ◽

Dispersed Phase

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The Self-Enforcing Starch–Gluten System—Strain–Dependent Effects of Yeast Metabolites on the Polymeric Matrix

Polymers ◽

10.3390/polym13010030 ◽

2020 ◽

Vol 13 (1) ◽

pp. 30

Author(s):

Thekla Alpers ◽

Viviane Tauscher ◽

Thomas Steglich ◽

Thomas Becker ◽

Mario Jekle

Keyword(s):

Strain Hardening ◽

Polymer System ◽

Rheological Behaviour ◽

Rate Dependency ◽

Lower Strain ◽

End Point Rate ◽

The Impact ◽

Elongational Rheometry ◽

Strain Dependent ◽

Strain Hardening Index

The rheological behaviour of dough during the breadmaking process is strongly affected by the accumulation of yeast metabolites in the dough matrix. The impact of metabolites in yeasted dough-like concentrations on the rheology of dough has not been characterised yet for process-relevant deformation types and strain rates, nor has the effect of metabolites on strain hardening behaviour of dough been analysed. We used fundamental shear and elongational rheometry to study the impact of fermentation on the dough microstructure and functionality. Evaluating the influence of the main metabolites, the strongest impact was found for the presence of expanding gas cells due to the accumulation of the yeast metabolite CO2, which was shown to have a destabilising impact on the surrounding dough matrix. Throughout the fermentation process, the polymeric and entangled gluten microstructure was found to be degraded (−37.6% average vessel length, +37.5% end point rate). These microstructural changes were successfully linked to the changing rheological behaviour towards a highly mobile polymer system. An accelerated strain hardening behaviour (+32.5% SHI for yeasted dough) was promoted by the pre-extension of the gluten strands within the lamella around the gas cells. Further, a strain rate dependency was shown, as a lower strain hardening index was observed for slow extension processes. Fast extension seemed to influence the disruption of sterically interacting fragments, leading to entanglements and hindered extensibility.

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Turbulent drag reduction by polymer additives in parallel-shear flows

Journal of Fluid Mechanics ◽

10.1017/jfm.2017.544 ◽

2017 ◽

Vol 827 ◽

Cited By ~ 22

Author(s):

Bayode E. Owolabi ◽

David J. C. Dennis ◽

Robert J. Poole

Keyword(s):

Drag Reduction ◽

Cross Sections ◽

Shear Flows ◽

Extensional Flow ◽

Relaxation Times ◽

Weissenberg Number ◽

Mechanical Degradation ◽

Turbulent Drag Reduction ◽

Time Resolved ◽

Turbulent Drag

In this study, we experimentally investigate the turbulent drag-reduction (DR) mechanism in flow through ducts of circular, rectangular and square cross-sections using two grades of polyacrylamide in aqueous solution having different molecular weights and various semidilute concentrations. Specifically, we explore the relationship between drag reduction and fluid elasticity, purposely exploiting the mechanical degradation of polymer molecules to vary their rheological properties. We also obtain time-resolved velocity data for various DR levels using particle image velocimetry and laser Doppler velocimetry. Elasticity is quantified via relaxation times determined from uniaxial extensional flow using a capillary breakup apparatus. A plot of DR against Weissenberg number ($Wi$) is found to approximately collapse the data, with the onset of DR occurring at $Wi\approx 0.5$ and the maximum drag-reduction asymptote being approached for $Wi\gtrsim 5$. Thus quantitative predictions of DR in a range of shear flows can be made from a single measurable material property of a polymer solution, at least for this particular flexible linear polymer.

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Effect of Epoxide Group in Thermoplastic Elastomer on the Properties of Polyamide6 and Low-Density Polyethylene Blends

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.979.143 ◽

2014 ◽

Vol 979 ◽

pp. 143-146 ◽

Cited By ~ 1

Author(s):

Surakit Tuampoemsab ◽

Saad Riyajan ◽

Thritima Sritapunya ◽

Pornsri Pakeyangkoon

Keyword(s):

Impact Strength ◽

Natural Rubber ◽

Shear Viscosity ◽

Thermoplastic Elastomer ◽

Phase Morphology ◽

Epoxidized Natural Rubber ◽

Low Density Polyethylene ◽

Dispersed Phase ◽

Low Density ◽

Epoxide Group

Studies on the effect of percentages of epoxide group in thermoplastic elastomer as a compatibilizer on properties of polyamide6 (PA6) and low-density polyethylene (LDPE) blends was successfully carried out in this study. Thermoplastic epoxidized natural rubber (TPENR), made from epoxidized natural rubber (ENR) and LDPE, prepared from 3 types of ENR, i.e., ENR-20, ENR-50 and ENR-70, with the ratio of 90/10 of LDPE/ENR by weight. TPENR was applied as a compatibilizer into the blend of PA6/LDPE/TPENR at the ratio by weight of 80/20/1 by using a twin screw extruder at 235°C. All test specimens were characterized for phase morphology, impact strength and rheological behaviour. Results exhibited that phase morphology of PA6/LDPE blend was incompatible. The addition of TPENR improved the compatibility of PA6/LDPE blends. With inclusion of TPENR-20 as a compatibilizer, the uniformity and the maximum reduction of dispersed phase sized were observed. Moreover, it was revealed that the rheological properties such as shear viscosity increased when compared with PA6/LDPE incompatible blend. In addition, it was found that the highest shear viscosity and also the highest impact strength were obtained for the blend of PA6/LDPE compatibilized by TPENR-20. This result was further supported by SEM images, which showed that the smallest dispersed phase size occurred when a TPENR-20 was used as a compatibilizer. So, it was clearly demonstrated in this study that the suitable type of TPENR, i.e., TPENR-20, has an effect on improving phase morphology and properties of PA6/LDPE blends.

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Broadband Dielectric Spectroscopy Study of Biobased Poly(alkylene 2,5-furanoate)s’ Molecular Dynamics

Polymers ◽

10.3390/polym12061355 ◽

2020 ◽

Vol 12 (6) ◽

pp. 1355 ◽

Cited By ~ 3

Author(s):

Michelina Soccio ◽

Daniel E. Martínez-Tong ◽

Giulia Guidotti ◽

Beatriz Robles-Hernández ◽

Andrea Munari ◽

...

Keyword(s):

Molecular Dynamics ◽

Dielectric Spectroscopy ◽

Relaxation Times ◽

Barrier Properties ◽

Polymer Processing ◽

Industrial Applications ◽

Structure Property ◽

Property Relations ◽

Broadband Dielectric Spectroscopy ◽

Segmental Relaxation

Poly(2,5-alkylene furanoate)s are bio-based, smart, and innovative polymers that are considered the most promising materials to replace oil-based plastics. These polymers can be synthesized using ecofriendly approaches, starting from renewable sources, and result into final products with properties comparable and even better than those presented by their terephthalic counterparts. In this work, we present the molecular dynamics of four 100% bio-based poly(alkylene 2,5-furanoate)s, using broadband dielectric spectroscopy measurements that covered a wide temperature and frequency range. We unveiled complex local relaxations, characterized by the simultaneous presence of two components, which were dependent on thermal treatment. The segmental relaxation showed relaxation times and strengths depending on the glycolic subunit length, which were furthermore confirmed by high-frequency experiments in the molten region of the polymers. Our results allowed determining structure–property relations that are able to provide further understanding about the excellent barrier properties of poly(alkylene 2,5-furanoate)s. In addition, we provide results of high industrial interest during polymer processing for possible industrial applications of poly(alkylene furanoate)s.

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Enhanced Foamability with Shrinking Microfibers in Linear Polymer

Polymers ◽

10.3390/polym11020211 ◽

2019 ◽

Vol 11 (2) ◽

pp. 211 ◽

Cited By ~ 1

Author(s):

Eric Kim ◽

Heon Park ◽

Carlos Lopez-Barron ◽

Patrick Lee

Keyword(s):

Strain Hardening ◽

Polymer Processing ◽

Expansion Ratio ◽

Low Frequencies ◽

Extensional Rheometry ◽

Enhanced Strain ◽

Linear Viscoelastic ◽

Cost Efficient ◽

Strain Hardening Behavior

Strain hardening has important roles in understanding material structures and polymer processing methods, such as foaming, film forming, and fiber extruding. A common method to improve strain hardening behavior is to chemically branch polymer structures, which is costly, thus preventing users from controlling the degree of behavior. A smart microfiber blending technology, however, would allow cost-efficient tuning of the degree of strain hardening. In this study, we investigated the effects of compounding polymers with microfibers for both shear and extensional rheological behaviors and characteristics and thus for the final foam morphologies formed by batch physical foaming with carbon dioxide. Extensional rheometry showed that compounding of in situ shrinking microfibers significantly enhanced strain hardening compared to compounding of nonshrinking microfibers. Shear rheometry with linear viscoelastic data showed a greater increase in both the loss and storage modulus in composites with shrinking microfibers than in those with nonshrinking microfibers at low frequencies. The batch physical foaming results demonstrated a greater increase in the cell population density and expansion ratio with in situ shrinking microfibers than with nonshrinking microfibers. The enhancement due to the shrinkage of compounded microfibers decreasing with temperature implies that the strain hardening can be tailored by changing processing conditions.

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Extensional Magnetorheology as a Tool for Optimizing the Formulation of Ferrofluids in Oil-Spill Clean-Up Processes

Processes ◽

10.3390/pr8050597 ◽

2020 ◽

Vol 8 (5) ◽

pp. 597 ◽

Cited By ~ 1

Author(s):

José Hermenegildo García-Ortiz ◽

Francisco José Galindo-Rosales

Keyword(s):

Magnetic Field ◽

Oil Spill ◽

Particle Concentration ◽

Flow Direction ◽

Extensional Flow ◽

Rheological Behaviour ◽

Magnetic Saturation ◽

Parallel Configuration ◽

Thinning Process ◽

The Magnetic Field

In this study, we propose a new way of optimising the formulation of ferrofluids for oil-spill clean-up processes, based on the rheological behaviour under extensional flow and magnetic fields. Different commercial ferrofluids (FFs), consisting of a set of six ferrofluids with different magnetic saturation and particle concentration, were characterised in a Capillary Break-Up Extensional Rheometer (CaBER) equipped with two magnetorheological cells that allow imposing a homogeneous and tunable magnetic field either parallel or perpendicular to the flow direction. The filament thinning process with different intensities and orientation of the magnetic field with respect to the flow direction was analysed, and the results showed that the perpendicular configuration did not have a significant effect on the behaviour of the ferrofluids, as in shear magnetorheometry. However, the parallel configuration allowed to determine that the formulation of ferrofluids for oil-spill cleaning processes should consist of a 4% vol concentration of magnetic nanoparticles with a magnetic saturation of M s > 20 mT.

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