Review of developments in rheology and polymer processing

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The special issue “Rheology and polymer processing” contains the most recent discoveries in the field of rheology and polymer processing, with cutting-edge research focused on the processing of sophisticated polymers and composites.

Study: Rheology and processing of polymers. Image Credit: Image Source Trading Ltd/Shutterstock.com

Bo Lu et al. examined the fundamental and technical aspects of interface phenomena in the coextrusion of multi-micro/nanolayer polymers. Multi-layer coextrusion processing is a top-down method capable of industrially manufacturing multi-layer films, as opposed to traditional approaches such as layer-by-layer assembly and spin-coating, which have low growth.

Throughout multilayer coextrusion processing, several phenomena, such as interlayer diffusion, interlayer reaction, interfacial instabilities, and interfacial geometric confinement, generally occur at the interfaces of multilayer polymers.

More comprehensive work should be carried out in the future in academia and industry to better understand these interfacial processes in order to develop multilayer coextrusion.

In an effort to protect the surface of the stainless steel (SS304) mold substrate against wear and corrosion, Najoua Barhoumi et al. has developed a fluorinated ethylene propylene (FEP) polymer coating. A compact and uniform film was created using an air spray and curing technique, and the mechanical, adhesion and corrosion properties, among others, were examined.

The Cox-Merz rule was tested on linear high-density polyethylene (HDPE) materials of varying molecular weights by Raffael Rathner et al. The Cox-Merz rule is an empirical correlation used in research and industry to estimate shear viscosity from an oscillatory rheometry test.

However, it does not apply to all polymer melts. The shear rate-dependent viscosity of three distinct HDPE materials was determined using three different rheological evaluation methods: oscillating parallel plate, high pressure capillary, and extrusion slot rheometry.

The results demonstrated that viscosity data based on capillary pressure flow of high molecular weight HDPE accurately represented the pressure drop across the pipe head significantly better than data based on parallel plate rheometry using the rule of Cox-Merz for HDPE grades. assessed. Both measurement methodologies were in good agreement for low molecular weight HDPE.

Violette Bourg et al. developed linear and branched polybutylene succinate (PBS) mixtures to study their molecular structure and rheological behavior.

Compared to linear structures, long chain branching (LCB) structures have already proven their effectiveness in increasing melt strength. Due to the more difficult synthesis or additional reactive extrusion step required to generate LCB polymers in general, and recently developed (bio)polymers in particular, they are more expensive than linear polymers.

Angelique Avella et al. examined melt crosslinking performance between reactive water-assisted (REx) melt processing and slower PCL macroradical diffusion. The inclusion of water improved the molecular weight of PCL and the gel content compared to the dry method, from 1% to 34% with 1% by weight. percentage of peroxide, indicating that water-assisted REx is more effective for radical propagation.

From design to recycling, Géraldine Cabrera et al. has developed an innovative technique for the complex polyethylene/polypropylene (PE/PP) and polyethylene/polystyrene (PE/PS) systems often found in industrial waste streams. Going from eco-design to mechanical recycling of multilayer films by coextrusion in forced assembly is the way.

It has been established that the design of multi-micro/nanolayer films, whatever the polymer system analyzed, is a very promising solution to the industrial difficulties related to the valorization of recyclable materials without the use of compatibilizers.

In the process of spinning fluids Giesekus, Geunyeop Park et al. explained the nature of the stability curves – the initial stabilization and the subsequent destabilization pattern with respect to the average range of the material parameter.

Changes in Giesekus fluid stability curves in the uncooled isothermal spinning process have been studied using a range of theoretical strategies, including constant velocity profiles and extensional strain properties in the line of rotation, as well as kinematic waves moving along the entire line of rotation.

The experimental method for viscoelastic identification of a nanocomposite reinforced with polymethylsilsesquioxane nanoparticles (PMSQ–HDPE) was evaluated by Fouad Erchiqui et al. Two different types of experiments were used, one based on free inflation of the membrane and the other on dynamic mechanical testing (DMA).

In a hot and humid environment, Mei Fang et al. studied the aging process of carbon fiber (CF)/polycarbonate (PC) composites. During the aging process, the moisture absorption rate was recorded and determined.

The stretching results were similar to the effects of aging time on storage modulus and solid particle erosion resistance. The formation of holes on the surface of the CF/PC composites was generated by hydrothermal aging, which reduced the sand erosion resistance of the sample. In the meantime, the physical properties of CF/PC composites have been altered.

Due to the inclusion of strain hardening, which stabilizes the shape of the foam, the long chain branching (LCB) of polypropylene (PP) is considered a game changer in foaming. Nick Weingart et al. carried out an extensive analysis of a Sinopec HMS20Z linear PP, a Sinopec E02ES CoPo PP/PE block copolymer and a long chain branched Borealis WB140 HMS PP in terms of rheology and crystallization properties.

Despite the fact that only LCB-PP showed strain hardening and had five times the melt strength of all other grades, it did not have the best foam quality in terms of density (140 g/L) or cellular form.

In DSC investigations, these observations were validated, with Sinopec HMS20Z crystal perfection occurring at a significantly slower rate, resulting in a longer gel-like state preceding solidification. This PP grade, again, showed no signs of work hardening.

Conclusion

Finally, contributions focus on fundamental and experimental data in a thematic range that includes both traditional and new treatment technologies, as well as materials-based macromolecular research. The objective of this special issue is to consolidate the current state of the art and to present the numerous applications.

Journal reference:

Lamnawar, K., & Maazouz, A. (2022) Rheology and polymer processing. Polymers, 14(12), p. 2327. Available online: https://www.mdpi.com/2073-4360/14/12/2327/htm

References and further reading

  1. Lu, B., et al. (2021) Interfacial phenomena in the coextrusion of multi-micro-/nanolayer polymers: review of fundamental and technical aspects. Polymers, 13(3), p. 417.doi.org/10.3390/polym13030417
  2. Barhoumi, N., et al. (2022) Fluorinated ethylene-propylene coatings deposited by a spray process: mechanical properties, scratch and wear behavior. Polymers, 14(2), p. 347.doi.org/10.3390/polym14020347
  3. Ratner, R. et al. (2021) Applicability of the Cox-Merz rule to high density polyethylene materials with various molecular weights. Polymers, 13(8), p. 1218. doi.org/10.3390/polym13081218.
  4. Bourg, V. et al. (2021) Shear and extensional rheology of linear and branched polybutylene succinate mixtures. Polymers, 13(4), p. 652.doi.org/10.3390/polym13040652.
  5. Avelle, A. et al. (2021) Substantial effect of water on free radical fusion crosslinking and rheological properties of poly(ε-caprolactone). Polymers, 13(4), p. 491.doi.org/10.3390/polym13040491.
  6. Cabrera, G. et al. (2021) Polyolefin-based multi-micro/nanolayer films: new approaches from eco-design to recycling. Polymers, 13(3), p. 413.doi.org/10.3390/polym13030413
  7. Chou, P.-Y., et al. (2021) Fabrication of drug-eluting nano-hydroxylapatite-filled polycaprolactone nanocomposites using solution extrusion 3D printing technique. Polymers, 13(3), p. 318. doi.org/10.3390/polym13030318.
  8. Park, G. et al. (2021) Effect of material parameter of Giesekus viscoelastic fluids on extension properties in spinline and draw resonance instability in isothermal melt spinning process. Polymers, 13(1), p. 139. doi.org/10.3390/polym13010139.
  9. Parres, F. et al. (2020) Study of the properties of a biodegradable polymer filled with different particles of wood flour. Polymers, 12(12), p. 2974. doi.org/10.3390/polym12122974.
  10. Erchiqui, F. et al. (2020) Reliability of free inflation and dynamic mechanics tests on predicting the behavior of polymethylsilsesquioxane-high density polyethylene nanocomposite for thermoforming applications. Polymers, 12(11), p. 2753. doi.org/10.3390/polym12112753.
  11. Wang, J. et al. (2020) Multi-scale structural evolution and its relationship to the dielectric properties of coextruded micro-/nano-layer PVDF-HFP/PC films. Polymers, 12(11), p. 2596. doi.org/10.3390/polym12112596.
  12. Feng, M. et al. (2020) Effects of Hydrothermal Aging of Carbon Fiber Reinforced Polycarbonate Composites on Mechanical Performance and Sand Erosion Resistance. Polymers, 12(11), p. 2453. doi.org/10.3390/polym12112453.
  13. Hel, CL, et al. (2020) TPV: a new insight into rubber morphology and mechanical/elastic properties. Polymers, 12(10), p. 2315. doi.org/10.3390/polym12102315.
  14. Guan, X. et al. (2020) Design and synthesis of a polysiloxane-based side-chain liquid crystal polymer to improve the processability and toughness of magnesium hydrate/linear low-density polyethylene composites. Polymers, 12(4), p. 911.doi.org/10.3390/polym12040911.
  15. Weingart, N. et al. (2020) Foamability Comparison of Linear and Long-Chain Branched Polypropylene – The Legend of Stress Hardening as a Requirement for Good Foamability. Polymers, 12(3), p. 725.doi.org/10.3390/polym12030725.
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