Examining the Influence of Production Scale on the Volume Expansion Behavior of Polyethylene Foams in Rotational Foam Molding

Emami, Maryam; Vlachopoulos, J.; Thompson, Michael R.; Maziers, E.

doi:10.1002/adv.21507

Cited by 4 publications

(6 citation statements)

References 10 publications

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“…In industrial settings though, stopping a production machine to evaluate a new foam material is reported to be not cost-effective. 10 In addition, long setup times, long cycle times, use of large amounts of material, and the health and safety risks (i.e., burns or limb entrapment) prevent the method from being widely adopted. Analyzing samples by interrupting a manufacturing process provides very little information about how the foam evolved to that point.…”

Section: Methods Involving Industrial-scale Equipmentmentioning

confidence: 99%

“…A similar technique of taking samples at regular intervals has been used in RFM studies, 8,9 where the foam is characterized after molding. In industrial settings though, stopping a production machine to evaluate a new foam material is reported to be not cost‐effective 10 . In addition, long setup times, long cycle times, use of large amounts of material, and the health and safety risks (i.e., burns or limb entrapment) prevent the method from being widely adopted.…”

Section: Review Of Experimental Approaches For Studying Foam Growthmentioning

confidence: 99%

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Characterization of polymer foam evolution in unpressurized melt systems

Pritchard,

Martin,

McCourt

et al. 2023

Polymer Engineering & Sci

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The evolution of foam in unpressurized melt processing techniques, such as rotational molding, is different from high‐pressure processes like injection foam molding, making comparisons difficult. This has driven the need for a dedicated technique for studying these systems. A unique test procedure was developed to capture and characterize foam evolution in test tubes under unpressurized conditions. A validation study found the procedure to be reliable, producing repeatable samples (height average (AVG) 39.69 ± 1.70 mm and density AVG 0.319 ± 0.012 g/cm3) and delivering comparable results to samples produced using the industrial rotational foam molding process. A study examined the effect of polymer particle size on the foam structures produced. Finer (>90 μm <106 μm) polymer powders produced more desirable structures, achieving 38.6% lower foam density and 43.8% taller peak foam height than coarser powders (>425 μm < 500 μm). Cycle times were much shorter (~15 min) in comparison with the industrial rotational molding process (>40 min) and required smaller amounts of materials, making it useful for rapid characterization. Future work is planned to apply the new procedure to investigate the effects of material and processing conditions on the foam structures produced under unpressurized conditions.Highlights Evaluation of existing unpressurized foam characterization methods. Rapid test procedure developed to characterize unpressurized foam evolution. Variability study of foam structures produced using the new procedure. Effect of rotational molding polymer powder and considerations for foaming. Results validated with industrial unpressurized rotationally molded samples.

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Section: Methods Involving Industrial-scale Equipmentmentioning

confidence: 99%

Section: Review Of Experimental Approaches For Studying Foam Growthmentioning

confidence: 99%

Characterization of polymer foam evolution in unpressurized melt systems

Pritchard,

Martin,

McCourt

et al. 2023

Polymer Engineering & Sci

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“…Increased attention has been given by researchers to studying the mechanisms of the rotational foaming process. − The foaming process consists of four distinct stages: primary nucleation, secondary nucleation, bubble growth, and bubble shrinkage. Notably, it was discovered that primary nucleation occurred in interstitial regions, which has a significant role in determining the final cellular structure.…”

Section: Introductionmentioning

confidence: 99%

Significantly Tunable Foaming Behavior of Blowing Agent for the Polyethylene Foam Resin with a Unique Designed Blowing Agent System

Chen,

Huang

2024

ACS Omega

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The chemical blowing agent plays a crucial role in enhancing the performance of the polyethylene (PE) foaming resin during the rotational foaming process. Previously, the conventional blowing agent of the PE resin commonly used pure azodicarbonamide (AZ). It had the unavoidable drawbacks of releasing NH 3 and exhibiting strong reactions during the rotational foaming process. Meantime, pure AZ had a relatively high decomposition temperature, resulting in a sharp foaming process. To address the above issues, this work developed a uniquely designed blowing agent system. In this study, a novel blowing agent for the PE resin was successfully synthesized by a one-pot method. This blowing agent consisted of an activator and AZ, which exhibited a lower decomposition temperature and a milder decomposition rate than AZ. The activator was constituted of small-sized ammonium dihydrogen phosphate on the AZ surface, which could be decomposed properly and deliver phosphoric acid and H 2 O during the foaming process. Then, AZ reacted with H 2 O under phosphoric acid catalysis. Also, this reaction generated CO 2 emission while reducing the emission of NH 3 through recombination with phosphoric acid. Moreover, phosphoric acid catalysis caused a decrease in the AZ decomposition temperature. Meantime, the thermal coupling appeared during the foaming process, which could further reduce the decomposition rate. Consequently, the small activator played a key role in regulating cell formation and diffusion. Compared to AZ, the novel blowing agent system significantly reduced the cell diameter of the PE foam resin and enhanced its flexural modulus by 50%. Furthermore, the novel blowing agent facilitated better demolding performance and improved the surface morphology of the PE foam product. This research provides significant foaming behavior regulation for the PE resin during industrial applications.

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“…There are several works focused on analyzing and understanding the effect of the extensional rheological behavior of the polymeric matrix on the foaming behavior. These works are mainly focused on studying how the extensional rheological properties of the polymeric matrix affect the volume expansion ratio of the foams [84,96,155,192,193,194,195,196,197,198]. Some of these works have also qualitatively analyze the cellular structure [84,199] and in several occasions the cell size and the cell density are also quantified [96,155,193,194,196,197,198,200,201].…”

Section: Role Of Extensional Rheology In Foamingmentioning

confidence: 99%

“…In most of these works, the foamed materials are produced by extrusion foaming [84,155,195,196,199]. Only very few works have been found in which other foaming techniques, such as rotational molding [192], compression molding [201], injection molding [200] and foaming by gas dissolution in a pressure vessel [96,193,194,198], are used to produce the cellular materials. In this thesis (see chapter 4) the same polymeric matrices are foamed using two different foaming processes with the aim of verifying if the ranges of Hencky strain rates normally used to calculate S and hence, to relate the extensional behavior with the foaming behavior, are the correct ones or, by the contrary, they should be modified depending on the foaming process employed.…”

Section: Role Of Extensional Rheology In Foamingmentioning

confidence: 99%

Understanding the foamability of complex polymeric systems by using extensional

Gutiérrez¹

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Obtaining high density polyethylene (HDPE) based microcellular foams is a topic of interest due to the synergistic properties that can be obtained by the fact of achieving a microcellular structure using a polymer with a high number of interesting properties. However, due to the high crystallinity of this polymer the production of low density microcellular foams, by a physical foaming process, is not a simple task. In this work, the solution proposed to manufacture these materials consists on using crosslinked HDPEs, with different crosslinking degrees. In addition, the foaming conditions, i.e. the foaming time and the foaming temperature, have also been modified with the aim of analyzing and understanding the mechanisms taking place during the foaming process to control this process and therefore, to obtain cellular materials with low density and improved cellular structures. Results indicate that there is a time and a foaming temperature optima for which the nucleation rate and the cell growth rate prevails over other phenomena like cell coalescence and gas diffusion out the material. Therefore, with these foaming conditions the lowest densities and the best cellular structures are obtained. Moreover, when the gel content increases the amount of gas available for foaming increases and the rheological properties improve, as the polymers show strain hardening. As a consequence, the relative density decreases and the cell nucleation density increases. After this detailed study, it was concluded that cellular materials with relative densities of 0.37 and with cell sizes of approximately 2 microns can be produced using a saturation pressure of 5 MPa, a foaming time of 30 s, a foaming temperature of 160 ºC and a crosslinked HDPE with a gel content of 50 %.

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Examining the Influence of Production Scale on the Volume Expansion Behavior of Polyethylene Foams in Rotational Foam Molding

Cited by 4 publications

References 10 publications

Characterization of polymer foam evolution in unpressurized melt systems

Characterization of polymer foam evolution in unpressurized melt systems

Significantly Tunable Foaming Behavior of Blowing Agent for the Polyethylene Foam Resin with a Unique Designed Blowing Agent System

Understanding the foamability of complex polymeric systems by using extensional

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