Scalable Fabrication of Microcellular Open‐Cell Polymer Foams

Chu, Raymond; Mark, Lun Howe; Park, Chul

doi:10.1002/adem.202100985

Cited by 5 publications

(4 citation statements)

References 55 publications

(72 reference statements)

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“…As the PET nanofibrils were dispersed through the PP matrix to act as reinforcements, their presence formed a network of fibers within the PP matrix to increase the melt strength and viscosity. With a greater melt strength, the matrix is able to reduce the amount of cell coalescence after cell nucleation [ 27 ]. In addition, the PET nanofibrils will also provide increases to the cell nucleation and crystal nucleation [ 2 , 31 ].…”

Section: Resultsmentioning

confidence: 99%

“…By retracting the mold to a fixed distance, the cavity pressure rapidly drops and the polymer undergoes a strong thermodynamic instability. As the pressure falls below the solubility pressure, cells begin to nucleate and grow [ 22 , 24 , 27 ]. The spunbond webs are fed into the Arburg injection molding machine with the same processing conditions as indicated in Table 3 .…”

Section: Methodsmentioning

confidence: 99%

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Mechanical Properties of Injection Molded PP/PET-Nanofibril Composites and Foams

et al. 2022

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The creation and application of PET nanofibrils for PP composite reinforcement were studied. PET nanofibrils were fibrillated within a PP matrix using a spunbond process and then injection molded to test for the end-use properties. The nanofibril reinforcement helped to provide higher tensile and flexural performance in solid (unfoamed) injection molded parts. With foam injection molding, the nanofibrils also helped to improve and refine the microcellular morphology, which led to improved performance. Easily and effectively increasing the strength of a polymeric composite is a goal for many research endeavors. By creating nanoscale fibrils within the matrix itself, effective bonding and dispersion have already been achieved, overcoming the common pitfalls of fiber reinforcement. As blends of PP and PET are drawn in a spunbond system, the PET domains are stretched into nanoscale fibrils. By adapting the spunbonded blends for use in injection molding, both solid and foamed nanocomposites are created. The injection molded nanocomposites achieved increased in both tensile and flexural strength. The solid and foamed tensile strength increased by 50 and 100%, respectively. In addition, both the solid and foamed flexural strength increased by 100%. These increases in strength are attributed to effective PET nanofibril reinforcement.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Mechanical Properties of Injection Molded PP/PET-Nanofibril Composites and Foams

et al. 2022

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“…Pang et al reviewed in 2022 six resulting types of cell structures (60) depending on the evolution of the cell size, the cell density and the expansion ratio. It seems microcellular foams are mostly closed-cell (60), however open-cell microcellular foams have also been produced (62). Injection moulded foams have a solid skin on their surface (fig.…”

Section: Microcellular Foamsmentioning

confidence: 99%

A review on the mechanical behaviour of microcellular and nanocellular polymeric foams: What is the effect of the cell size reduction?

Le Barbenchon,

Kopp

2024

Journal of Cellular Plastics

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Research on nanocellular foams is motivated in part by the promise of physical properties, in particular mechanical properties, that can go beyond the classical mechanical framework. However, due to the difficulty in obtaining foams of a given density but different cell sizes, determining the effect of cell size on the mechanical properties of polymer foams remains a challenge. To overcome this difficulty, studies on the mechanical behaviour of mesocellular, microcellular and nanocellular polymer foams have been compiled in this review article. After describing the different cellular structures between meso-, micro- and nanocellular foams, the mechanical properties are examined as a function of relative density and cell size. It is shown that for small strains and at low strain rates, nanocellular foams exhibit mechanical behaviour predicted by the Gibson and Ashby model. Relative density remains the first important factor to be taken into account when studying the Young’s modulus and buckling stress of nanocellular foams. The focus then shifts to fracture properties, as microcellular foams have already been shown to be far superior to more conventional foams. As studies are still scarce and different methodologies have been used, no general conclusions can be drawn. However, the fracture and impact properties could be greatly improved by this change in scale. The local confinement of molecular chains in polymeric nanocellular foams or the relaxation of the triaxial stress state in front of the crack tip could explain these observations.

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“…Ishikawa 13 visualized the relationship between core-back speed, pressure drop rate as detected by pressure sensors, and cell nucleation and growth. Foamed components with high open-cell content [14][15][16] and high expansion ratios [17][18][19] can be fabricated by combining high-pressure FIM with the core-back process. Ameli 20 and Jahani 21 also used foamed components generated through the core-back process for sound insulation and thermal insulation applications.…”

Section: Introductionmentioning

confidence: 99%

Study on surface quality and cell morphology of foamed components fabricated using gas counter‐pressure with core‐back and high‐pressure foam injection molding with core‐back process

Chiu,

Yang,

Yeh

2024

Polymer Engineering & Sci

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The core‐back process has substantially increased the range of applicability of foam injection molding (FIM) by increasing the pressure drop rate and expansion ratio. However, cell nucleation and growth occur concurrently with the flow of the melt/gas mixture during the filling stage, resulting in poor surface quality and a non‐uniform cell structure. This study investigated foam injection molding with gas counter pressure (GCP) and core‐back to produce foamed components, with comparison to high‐pressure FIM with core‐back process. Through this method, the nucleation during filling is suppressed. The surface roughness was improved to 0.987 μm, a 59% reduction compared to high‐pressure injection molding foam with core‐back. In addition, the cell uniformity was improved, measured at two locations near and far from the gate, the cell density reaching 1.7 × 105 and 2.1 × 105 cells/cm3, and cell size measuring 120.88 and 129.57 μm, respectively. GCP also prevented the formation of the bubbles larger than 500 μm at the location far from the gate. Even at the lowest recommended mold temperature, the combination of GCP and core‐back enables the production of high‐quality foamed components with reduced cooling time.Highlights Preventing the simultaneous occurrence of cell nucleation, growth and melt flow. Foamed material with high surface quality produced by FIM. Improving the cell uniformity throughout the foamed component. Feasibility of GCP technology in conjunction with core‐back process.

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Scalable Fabrication of Microcellular Open‐Cell Polymer Foams

Cited by 5 publications

References 55 publications

Mechanical Properties of Injection Molded PP/PET-Nanofibril Composites and Foams

Mechanical Properties of Injection Molded PP/PET-Nanofibril Composites and Foams

A review on the mechanical behaviour of microcellular and nanocellular polymeric foams: What is the effect of the cell size reduction?

Study on surface quality and cell morphology of foamed components fabricated using gas counter‐pressure with core‐back and high‐pressure foam injection molding with core‐back process

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