Anisotropy Effects in the Shape‐Memory Performance of Polymer Foams

Sauter, Tilman; Kratz, Karl; Madbouly, Samy A.; Klein, Frank; Heuchel, Matthias; Lendlein, Andreas

doi:10.1002/mame.202000730

Cited by 6 publications

(4 citation statements)

References 38 publications

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“…16,17 Elements for the mercantile growth of foams contain lightness, inexpensiveness, lower thermal conductivity, a broad domain of formulations from hard foam to elastic foam, a number of different processes, simple production of various parts, absence of pressure in several production methods, the higher strength-to-mass ratio in analogy to another polymer families and great impact. [18][19][20][21] In extrusion foaming processes, due to the high pressure, the gas injected into the polymer melt dissolves. The dissolution of the gas causes the polymer melt to plasticize, resulting in a uniform polymer-gas mixture flowing along the extruder.…”

Section: Introductionmentioning

confidence: 99%

Impacts of cellulose nanofibers on the morphological behavior and dynamic mechanical thermal properties of extruded polylactic acid/cellulose nanofibril nanocomposite foam

Sadeghi

Marfavi

et al. 2021

J of Applied Polymer Sci

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Polylactic acid (PLA) foams were introduced as a good substitute for oil-based foams. Much research has been done on the autoclave of PLA foam, but discontinuous processes are not attractive for industries. In order to reduce the distance between the PLA foaming process and industrialization, it is necessary to introduce continuous processes. In this work, two solutions to improve the foaming of PLA are presented: using the extrusion process and adding cellulose nanofibers. So, in this study, a twin screw extruder was used by blowing agent, CO 2 , and in order to better dissolve the gas, a static mixer was used before the die. The molecular weight of the original PLA after extrusion has reduced in the range from 20%-28% due to the hydrolysis of the ester bond in the PLA. With the cellulose nanofiber loading, nucleation and cell density have enhanced. Scanning electronic microscope (SEM) microscopic images for the nanocomposites containing 1.5 wt% of cellulose nanofiber showed the highest cellular expansion and for the nanocomposites containing 2.0 wt% of cellulose nanofiber showed the most uniform cell distribution and it confirmed the density results and the calculated expansion ratio. Finally, by examining the dynamic-mechanical thermal analysis, it can be stated that the composition of cellulose nanofibers improves the mechanical and dynamic properties of cellulose nanofiber-reinforced PLA.

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Section: Introductionmentioning

confidence: 99%

Impacts of cellulose nanofibers on the morphological behavior and dynamic mechanical thermal properties of extruded polylactic acid/cellulose nanofibril nanocomposite foam

Sadeghi

Marfavi

et al. 2021

J of Applied Polymer Sci

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“…The anisotropy of cells is important in designing anisotropic mechanical and thermal properties of foams. , Huber and Gibson reported that the anisotropy of mechanical properties such as the anisotropy ratio of Young’s modulus and plastic collapse could be significantly impacted by the shape of the cells . Martín-de León et al, who studied the effect of hot-bath and hot-press foaming methods, reported that hot-pressed foams show hardly any anisotropy .…”

Section: Resultsmentioning

confidence: 99%

“…16 In one study, the longitudinal (LD) compressive modulus became 4.3 times higher than the compressive modulus of the transversal direction (TD) for a foam with a shape anisotropy ratio of 1.72. 17 In addition, the anisotropic foam also demonstrated anisotropy in thermal conductivity. For example, freeze-dried aerogels and foams with tubular cellular structures exhibited thermal conductivity anisotropy and oil absorption capability.…”

Section: Introductionmentioning

confidence: 99%

“…Foams with anisotropic microcells have demonstrated significant anisotropy in the compressive modulus . In one study, the longitudinal (LD) compressive modulus became 4.3 times higher than the compressive modulus of the transversal direction (TD) for a foam with a shape anisotropy ratio of 1.72 . In addition, the anisotropic foam also demonstrated anisotropy in thermal conductivity.…”

Section: Introductionmentioning

confidence: 99%

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Scalable Fabrication of Anisotropic Nanocellular Foam by Hot-Press Foaming

Gebremedhin

Tseng

Demewoz

et al. 2022

Ind. Eng. Chem. Res.

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Nanocellular foam has raised much interest because its physical and mechanical properties are superior to those of microcellular foams. The hot-bath foaming method has been common on a laboratory scale due to its faster heat transfer rate. However, because of the nature of the free foaming process, the hot-bath foaming method may not be capable of making large, flat samples. This study uses the hot-press process to produce nanocellular foam. The results of hot-bath and hot-press foaming methods were compared with theoretical simulations. Both processes were able to produce cell sizes lower than 40 nm. The hot-press foamed samples exhibited larger cell size, higher expansion ratio, and higher aspect ratio (AR) than the hot-bath foamed samples. The hot-press foaming process demonstrated that it has the potential to create sizable and flat nanocellular samples. The AR of cells foamed in the hot-press method was as high as 1.93, creating a new manufacturing method for anisotropic nanocellular foam with a cell size of less than 100 nm.

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Approaches toward High Resilience Rubber Foams: Morphology–Mechanics–Thermodynamics Relationships

Prasopdee

Shah

Smitthipong

2021

Macro Materials & Eng

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Natural rubber foam (NRF) products are frequently required in high resilience or high shape recoverability applications, which is in contrast to the fundamental nature of NRF. This study aims to improve NRF properties, such as recovery, by increasing the amount of vulcanizing chemicals (Vc) and adding cassava starch (Cs). Interestingly, increasing the amount of Vc and Cs improves mechanical properties and shape recoverability of NRF although the morphology of NRF with various concentrations of Cs is similar. The ratio of internal energy to the compression force is almost constant with various amounts of Vc and Cs because the degree of freedom of the rubber chains remains stable. NRF possesses better compression strength and shape recoverability with increasing amount of Vc (optimum of 16 phr) and Cs (optimum of 8 phr). Cassava starch is discovered as an attractive filler in comparison to traditional NRF fillers, such as charcoal and silica, due to its relatively low density.

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Anisotropy Effects in the Shape‐Memory Performance of Polymer Foams

Cited by 6 publications

References 38 publications

Impacts of cellulose nanofibers on the morphological behavior and dynamic mechanical thermal properties of extruded polylactic acid/cellulose nanofibril nanocomposite foam

Impacts of cellulose nanofibers on the morphological behavior and dynamic mechanical thermal properties of extruded polylactic acid/cellulose nanofibril nanocomposite foam

Scalable Fabrication of Anisotropic Nanocellular Foam by Hot-Press Foaming

Approaches toward High Resilience Rubber Foams: Morphology–Mechanics–Thermodynamics Relationships

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