Steam-chest molding of expanded thermoplastic polyurethane bead foams and their mechanical properties

Ge, Chengbiao; Ren, Qian; Wang, Shiping; Zheng, Wenge; Zhai, Wentao; Park, Chul

doi:10.1016/j.ces.2017.09.011

Cited by 65 publications

(60 citation statements)

References 49 publications

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“…The linear elastic region is observed at the strain less than 5% for all four samples, where stress increases linearly with deformation and the strain is recoverable. 11 With the increase in strain, a typical stress plateau region is presented, where the stress of MPEIs increases gradually with increasing strain. This phenomenon suggested that MPEIs exhibited a rigid characteristic under deformation, possibly resulting from the presence of rigid epoxy shell around EPEI beads.…”

Section: Results and Discussionmentioning

confidence: 96%

Poly(ether imide)/Epoxy Foam Composites with a Microcellular Structure and Ultralow Density: Bead Foam Fabrication, Compression Molding, Mechanical Properties, Thermal Stability, and Flame-Retardant Properties

et al. 2020

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It is challenging to prepare ultralow-density microcellular foams based on high-performance polymers due to their low gas solubility and rigid polymer matrix. In this study, by applying microcellular foaming technology using CO 2 /acetone as the blowing agent, ultralow-density poly(ether imide) (PEI) bead foams with an expansion ratio of 30–56 times and cell density of 10 7 –10 9 cells/cm 3 were fabricated, resulting from the enhanced plasticization effect of the mixed fluid. The slow diffusivity of acetone at room temperature ensured the saturated PEI beads to foam after desorption for more than 6 days, which potentially reduces the transportation cost of PEI bead foams significantly. A novel compression molding process was developed to prepare the molded PEI bead foams (MPEIs) using epoxy as a coating agent. The good infiltration character of epoxy on bead foams endowed the MPEIs with excellent mechanical properties, together with an ultralow density of 80–200 kg/m 3 , long-term dimensional stability at 160 °C, and excellent flame-retardant properties of V0 rating. These features made the MPEIs very promising for many advanced applications.

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Section: Results and Discussionmentioning

confidence: 96%

Poly(ether imide)/Epoxy Foam Composites with a Microcellular Structure and Ultralow Density: Bead Foam Fabrication, Compression Molding, Mechanical Properties, Thermal Stability, and Flame-Retardant Properties

et al. 2020

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“…The foaming temperature is clearly a very important parameter, with respect to the appearance of the foamed material's morphology in the foaming process. Usually, the foaming condition, along with the increased temperature, greatly improves the foaming ability [24,53], but too high foaming temperature will cause the collapse of foamed material as well as other structural damage [33]. As previously noted, low saturation pressures produced large cells, which could then generate a very thick perforated membrane.…”

Section: Preparation Of the Tpu Perforated Membranementioning

confidence: 95%

Preparation of Thermoplastic Polyurethane (TPU) Perforated Membrane via CO<sub>2</sub> foaming and Its Particle Separation Performance

Zhai

Park

2019

Preprint

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The way in which a perforated structure is formed has attracted much interest in the porous membrane research community. This novel structure gives materials an excellent antifouling property as well as a low operating pressure and other benefits. Unfortunately, the current membrane fabrication methods usually involve multi-step processes and the use of organic solvents or additives. Our study is the first to offer a way to prepare perforated membrane by using a physical foaming technique with CO2 as the blowing agent. We selected thermoplastic polyurethane (TPU) as the base material because it is a biocompatible elastomer with excellent tensility, high abrasion resistance, and good elastic resilience. Various processing parameters, which included the saturation pressure, the foaming temperature, and the membrane thickness, were applied to adjust the TPU membrane’s perforated morphology. We proposed a possible formation mechanism of the perforated membrane. The as-prepared TPU membrane had good mechanical properties with a tensile strength of about 5 MPa and an elongation at break above 100%. Such mechanical properties make this novel membrane usable as a self-standing filter device. In addition, its straight-through channel structure can separate particles and meet different separation requirements.

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“…Subsequently the expanded beads were stabilized at room temperature (23±2°C) for 72 h. Finally, lab-scale steam chest molding equipment (manufactured by DABO Precision (DPM-0404VS)) was used for molding the SEBS bead foams. The procedure follows filling of beads with SC N 2 , steam heating followed by surface bonding among beads, depressurization of the mold for the steam removal, water cooling for product stabilization, and ejecting of the molded product, which has been described in detail by Ge et al [47]. The specific parameter set used in this work is that a steam with a pressure of 3.9 bar and a temperature of 142.7°C was applied to heat the fully filled beads for 55 s.…”

Section: Processingmentioning

confidence: 99%

“…The surface of the beads are molten or softened using high pressure steam which leads to an inter-diffusion among the polymer chains of different beads, and resulting in cohesion of the beads [43]. This technology is applied for various polymers, such as expanded polypropylene (EPP), expanded polystyrene (EPS), expanded PLA, expanded TPU [44][45][46][47]. There are very limited studies with SEBS, very few recent activities primarily reported with SEBS/PS and SEBS/PP foams [20,48,49].…”

mentioning

confidence: 99%

A developed, eco-friendly, and flexible thermoplastic elastomeric foam from SEBS for footwear application

Zhang¹,

Dai²,

Zou³

et al. 2019

Express Polym. Lett.

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In search of new materials to develop comfortable shoe sole, nowadays the researchers have resorted to the thermoplastic elastomers (TPEs) usually used as cushioning materials for its easy processability and adorable physical properties that can meet both the comfort as well as other functional requirements (i.e. fashion, ultralight, aging, etc.). TPEs are a class of copolymers or physical mixes of polymers and have the morphology of non-miscible blends of elastomer and thermoplastic matrix simultaneously. Low or room temperature elastomeric behavior and high temperature processablitiy makes TPE as a suitable material for developing lightweight and recyclable microcellular foams [1]. Most of the commercial TPE foams for footwear application are developed either from thermoplastic polyurethane (TPU) or ethylenevinyl acetate (EVA) copolymer in which the soft matrix provides sufficient free space for gas absorption whereas the rigid matrix prevents the gas diffusion during foaming process [2][3][4][5][6]. Styrene-(ethylene-cobutylene)-styrene polymers (SEBS) derived from the hydrogenation of styrene-butadiene-styrene (SES) polymers is a typical TPE which shows a better weather resistance, lower compression set, lower density, etc., can be a potential alternative of TPU or EVA [7,8]. SEBS consists of a soft midblock of ethylene-butylene (E-co-B) and hard end-blocks of 948 Abstract. Developing eco-friendly, flexible thermoplastic elastomeric foams based on poly(styrene-(ethylene-co-butylene)styrene) (SEBS) is a challenging task because of its poor melt strength. A promising approach to overcome this challenge is the use of synergistic technologies, such as combination of irradiation, supercritical fluid foaming, and steam-chest molding technologies. Herein, foamed beads were produced from pre-crosslinked SEBS beads using supercritical nitrogen as blowing agent, followed by subsequently efficient steam-chest molding to obtain midsole part. The crosslinking was accomplished under the assistance of electron beam. The rheology properties and foaming behavior reveals that the viscosity and modulus of the matrix increase with the increase of crosslinking resulting from increasing the irradiation dose (ID). With increasing the ID, successful foaming with larger expansion and improved cell morphology was achieved. SEBS bead foams were successfully obtained from 65 kGy-derived pre-crosslinked beads through steam-chest molding which showed a specific gravity of 0.252 g·cm -3 and comparable/superior mechanical properties to/than that of commercial thermoplastic polyurethane (TPU) or ethylene-vinyl acetate copolymer (EVA) foams. Especially, the higher elasticity and resilience of SEBS foams meet well the desirable properties for footwear application which supports SEBS to be an alternative for TPU or EVA.

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Steam-chest molding of expanded thermoplastic polyurethane bead foams and their mechanical properties

Cited by 65 publications

References 49 publications

Poly(ether imide)/Epoxy Foam Composites with a Microcellular Structure and Ultralow Density: Bead Foam Fabrication, Compression Molding, Mechanical Properties, Thermal Stability, and Flame-Retardant Properties

Poly(ether imide)/Epoxy Foam Composites with a Microcellular Structure and Ultralow Density: Bead Foam Fabrication, Compression Molding, Mechanical Properties, Thermal Stability, and Flame-Retardant Properties

Preparation of Thermoplastic Polyurethane (TPU) Perforated Membrane via CO<sub>2</sub> foaming and Its Particle Separation Performance

A developed, eco-friendly, and flexible thermoplastic elastomeric foam from SEBS for footwear application

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