An Experimental and Numerical Investigation on Bubble Growth in Polymeric Foams

Tammaro, Daniele; Villone, Massimiliano M.; D’Avino, Gaetano; Maffettone, Pier Luca

doi:10.3390/e24020183

Cited by 5 publications

(5 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In conclusion, we can remark that at a low printing speed, despite the small characteristic size of the nozzle compared to a standard foam extruder, the cell size and foam density can be tuned by using the same leverages that are usually used in foam extrusion, namely, the melt temperature and the blowing agent concentration [ 23 , 24 , 25 , 26 , 27 , 28 ].…”

Section: Resultsmentioning

confidence: 99%

“…The larger elastic modulus of the foamed PLA strands at a low density can be ascribed to the increase in the crystallinity due to (a) the larger plasticization effect at larger a concentration of the blowing agent and (b) the larger deformation rate due to the larger foam expansion [ 25 ]. The DSC measurements confirm that the crystallinity content increases as the density of the foamed strands decreases.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Microfoamed Strands by 3D Foam Printing

2022

Self Cite

View full text Add to dashboard Cite

We report the design, production, and characterization of microfoamed strands by means of a green and sustainable technology that makes use of CO2 to create ad-hoc innovative bubble morphologies. 3D foam-printing technology has been recently developed; thus, the foaming mechanism in the printer nozzle is not yet fully understood and controlled. We study the effects of the operating parameters of the 3D foam-printing process to control and optimize CO2 utilization through a maximization of the foaming efficiency. The strands’ mechanical properties were measured as a function of the foam density and explained by means of an innovative model that takes into consideration the polymer’s crystallinity content. The innovative microfoamed morphologies were produced using a bio-based and compostable polymer as well as polylactic acid and were then blown with CO2. The results of the extensive experimental campaigns show insightful maps of the bubble size, density, and crystallinity as a function of the process parameters, i.e., the CO2 concentration and temperature. A CO2 content of 15 wt% enables the acquirement of an incredibly low foam density of 40 kg/m3 and porosities from the macro-scale (100–900 μm) to the micro-scale (1–10 μm), depending on the temperature. The foam crystallinity content varied from 5% (using a low concentration of CO2) to 45% (using a high concentration of CO2). Indeed, we determined that the crystallinity content changes linearly with the CO2 concentration. In turn, the foamed strand’s elastic modulus is strongly affected by the crystallinity content. Hence, a corrected Egli’s equation was proposed to fit the strand mechanical properties as a function of foam density.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Microfoamed Strands by 3D Foam Printing

2022

Self Cite

View full text Add to dashboard Cite

show abstract

“…Foaming can also be controlled by the inclusion of additive fillers with a high aspect ratio [66]. The main process parameters that affect foaming are the blowing agent concentration, the pressure drop (how much and how it is carried out), and the temperature at which the thermodynamic instability promoting the cell nucleation is triggered [67]. In general, keeping constant the temperature and gas concentration, faster decompression rates yield foams with smaller cell sizes, while foaming at higher temperatures and keeping other factors constant yields foams with larger cell sizes [68].…”

Section: Basics Of Foaming Technologymentioning

confidence: 99%

Forefront Research of Foaming Strategies on Biodegradable Polymers and Their Composites by Thermal or Melt-Based Processing Technologies: Advances and Perspectives

Gonçalves,

Reis,

Fernandes

2024

Polymers

View full text Add to dashboard Cite

The last few decades have witnessed significant advances in the development of polymeric-based foam materials. These materials find several practical applications in our daily lives due to their characteristic properties such as low density, thermal insulation, and porosity, which are important in packaging, in building construction, and in biomedical applications, respectively. The first foams with practical applications used polymeric materials of petrochemical origin. However, due to growing environmental concerns, considerable efforts have been made to replace some of these materials with biodegradable polymers. Foam processing has evolved greatly in recent years due to improvements in existing techniques, such as the use of supercritical fluids in extrusion foaming and foam injection moulding, as well as the advent or adaptation of existing techniques to produce foams, as in the case of the combination between additive manufacturing and foam technology. The use of supercritical CO2 is especially advantageous in the production of porous structures for biomedical applications, as CO2 is chemically inert and non-toxic; in addition, it allows for an easy tailoring of the pore structure through processing conditions. Biodegradable polymeric materials, despite their enormous advantages over petroleum-based materials, present some difficulties regarding their potential use in foaming, such as poor melt strength, slow crystallization rate, poor processability, low service temperature, low toughness, and high brittleness, which limits their field of application. Several strategies were developed to improve the melt strength, including the change in monomer composition and the use of chemical modifiers and chain extenders to extend the chain length or create a branched molecular structure, to increase the molecular weight and the viscosity of the polymer. The use of additives or fillers is also commonly used, as fillers can improve crystallization kinetics by acting as crystal-nucleating agents. Alternatively, biodegradable polymers can be blended with other biodegradable polymers to combine certain properties and to counteract certain limitations. This work therefore aims to provide the latest advances regarding the foaming of biodegradable polymers. It covers the main foaming techniques and their advances and reviews the uses of biodegradable polymers in foaming, focusing on the chemical changes of polymers that improve their foaming ability. Finally, the challenges as well as the main opportunities presented reinforce the market potential of the biodegradable polymer foam materials.

show abstract

“…Existing ePE beads often collapse during standard steam chest molding due to a narrow melting peak. 26 It's important to note that the foaming of beads via foam extrusion diverges from autoclave foaming. In foam extrusion, the PE/gas solution traverses narrow capillaries, and beads are swiftly severed underwater by a rapid blade, potentially influencing cellular morphology.…”

Section: Introductionmentioning

confidence: 99%

“…Existing ePE beads often collapse during standard steam chest molding due to a narrow melting peak. 26…”

Section: Introductionmentioning

confidence: 99%

Expanded beads of polyethylene moldable at low steam pressure

Tammaro,

Strasser

2024

Journal of Cellular Plastics

Self Cite

View full text Add to dashboard Cite

In this study, we explored an innovative approach to extrude expanded polyethylene (ePE) bead foam by utilizing a blend of two types of polyethylene, specifically low-density and linear low-density polyethylene. The intention behind this mixture was to enhance the molding process’s flexibility during steam chest molding. The outcomes of our investigation reveal the adaptability of the devised method and formulation, enabling the production of a broad spectrum of foam densities ranging from 20 to 100 kg/m³. Additionally, we achieved successful molding at remarkably low steam pressures, below 0.6 bar. Our research focuses on the strategic adjustment of processing parameters, including temperature and pressure, along with optimized die geometry for the extrusion foam process. To comprehensively evaluate the foamed molded components, we conducted a comprehensive mechanical and optical analysis. The findings underscore the flexibility and cost-effectiveness of ePE produced through foam extrusion. This method emerges as a promising alternative to expandable polystyrene, especially in applications requiring flexible materials and convenient recyclability without contributing to microplastic pollution in the environment.

show abstract

An Experimental and Numerical Investigation on Bubble Growth in Polymeric Foams

Cited by 5 publications

References 22 publications

Microfoamed Strands by 3D Foam Printing

Microfoamed Strands by 3D Foam Printing

Forefront Research of Foaming Strategies on Biodegradable Polymers and Their Composites by Thermal or Melt-Based Processing Technologies: Advances and Perspectives

Expanded beads of polyethylene moldable at low steam pressure

Contact Info

Product

Resources

About