Lightweight and strong gelling agent-reinforced injection-molded polypropylene composite foams fabricated using low-pressure CO2 as the foaming agent

Ren, Qian; Wu, Minghui; Weng, Zhengsheng; Wang, Long; Zheng, Wenge; Hikima, Yuta; Ohshima, Masahiro

doi:10.1016/j.jcou.2021.101530

Cited by 18 publications

(14 citation statements)

References 64 publications

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“…The influence of MD on the viscosity of HPP was investigated by temperature and frequency sweep tests. As reported previously, [32,35,36] adding MD to PP increases the viscosity and the melt strength. Because the formation of the nanofibril network of MD occurs as a phase separation phenomenon of MD from the molten polymer, [32] the complex viscosity increased at temperatures below 170 C, as shown in Figure 3.…”

Section: Rheological Propertiessupporting

confidence: 79%

“…This viscosity increase widens the foaming temperature window for suppressing bubble growth and keeping the bubble size on the micrometer scale. [ 35,36 ] Figure S3 shows the frequency‐sweep complex viscosity of HPP and HPP/LMPP with 0.3%MD addition. The temperatures of measurement were 200 and 170°C.…”

Section: Resultsmentioning

confidence: 99%

“…This is because MD reduces the crystal nuclei's size and provides more bubble nucleation sites to the polymer when foaming. [ 32,36 ]…”

Section: Resultsmentioning

confidence: 99%

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Improvement of the surface quality of foam injection molded products from a material property perspective

Lin

Hamamoto

Hikima

et al. 2022

Polymer Engineering & Sci

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Microcellular injection molding is an attractive method. However, their surface imperfections have been a major problem hindering wide industrial applications. Several methods have been proposed to improve the surface appearance of foams. In this study, we proposed a method to improve the surface appearance of polypropylene (PP) foams from the material property perspective, especially with regard to crystallization and viscosity. The basic idea of the surface improvement is to reduce the size of bubbles generated at the flow front, delay the solidification behavior of the polymer at the mold interface, squeeze the bubbles existing at the mold-polymer interface, and redissolve the bubbles into the polymer by holding pressure. Blending a low-modulus PP delays the crystallization of the polymers at the skin layer and solidification, taking enough time to squeeze the bubbles smaller. A sorbitol-based gelling agent, bis-O-([4 methylphenyl]methylene)-D-Glucitol, was used to increase the viscosity at a low strain rate to reduce the size of the bubbles generated at the flow front during the filling stage. The foam injection molding experiments demonstrated that the proposed method effectively improved the surface appearance of the foams. In particular, the surface appearance of the foams became almost equivalent to that of solid samples using low-modulus PP.

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Section: Rheological Propertiessupporting

confidence: 79%

Section: Resultsmentioning

confidence: 99%

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Improvement of the surface quality of foam injection molded products from a material property perspective

Lin

Hamamoto

Hikima

et al. 2022

Polymer Engineering & Sci

Self Cite

View full text Add to dashboard Cite

show abstract

“…[35][36][37][38] With high expansion ratios, cell-wall thickness decreases; the high degree of stretching exerted on the cell walls further promote void formation on walls to increase the open-cell content. [39][40][41] In this work, we investigated molding of recyclable monomaterial open-cell foam via a solvent/leaching-free process. Foaming of polypropylene (PP) was conducted with injection molding in conjunction with mold-opening to attain twofold expansion ratio for nucleated cells to grow and meet each other.…”

Section: Introductionmentioning

confidence: 99%

“…[ 35–38 ] With high expansion ratios, cell‐wall thickness decreases; the high degree of stretching exerted on the cell walls further promote void formation on walls to increase the open‐cell content. [ 39–41 ]…”

Section: Introductionmentioning

confidence: 99%

Scalable Fabrication of Microcellular Open‐Cell Polymer Foams

2021

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Open‐cell foams are foams with porous, interconnected cellular structure. This unique structure has given open‐cell foams the versatility to be used in different types of applications including acoustics, filtration, membranes, and bioscaffolds. Conventional open‐cell polymer foams comprise mainly thermosetting and/or crosslinked materials; such materials are difficult to process and have limited end‐product recyclability. This article presents a commercially viable molding process to fabricate open‐cell foams using noncrosslinked thermoplastic polypropylene (PP). Highly open‐cell and/or reticulated structures at an open‐cell content of 84% are attained. The strategies employed in molding of PP foam with high open‐cell degree include: 1) use of mold‐opening method to achieve high void fractions; 2) reduction of cell‐wall thickness through increasing the cell densities via controlled crystallization; and 3) use of low viscosity or low melt‐strength polymer resins to promote cell‐wall opening. The molding process proposed may be extended to other semicrystalline thermoplastic materials for fabricating recyclable open‐cell foams.

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Synergistic effect of thermoplastic polyester elastomer and polytetrafluoroethylene in situ fibrillation on the resilience and compression strength of long‐chain branched polypropylene foam

Wang,

Wang

2023

J of Applied Polymer Sci

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Excellent resilience and compression resistance are the key characteristics of cushioning and water–oil separation materials. Although polypropylene (PP) offers excellent performance and affordability of PP, it exhibits poor resilience. To address this shortcoming, polymer blends with long‐chain branched PP (LCBPP), thermoplastic polyester elastomer (TPEE), and polytetrafluoroethylene (PTFE) were prepared via melt blending, and their mechanical properties were tested. The LCBPP/TPEE/PTFE composites were subjected to physical foaming using supercritical CO2 (scCO2) as the blowing agent. The synergistic toughening mechanism of the elastomer/nanofiber and the effect of the structure and crystallization of the dispersed phase on the foam resilience and foam compression strength were investigated. The results revealed that fibrous PTFE and spherical TPEE formed a composite dispersed phase in LCBPP. The impact and tensile strengths of the unfoamed LCBPP were found to have been simultaneously optimized owing to the synergistic effect of the elastomeric toughening of TPEE and the reinforcement of the PTFE fiber–induced fibrous crystal structure. Compared with pure LCBPP, the impact strength of the LCBPP/TPEE/PTFE composite increased by 216%, whereas its tensile strength decreased by only 6%. In particular, the synergistic effect of TPEE/PTFE improved the resilience and compression strength of the LCBPP foam. Compared with the pure LCBPP foam, the permanent strain of the LCBPP/TPEE/PTFE foam was reduced by 13.8% after five cycles of compression and its compression strength increased by 27.3%. The experimental results of our study could be used to prepare LCBPP foams with exceptional resilience, high compression strength, and good application prospects.

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Lightweight and strong gelling agent-reinforced injection-molded polypropylene composite foams fabricated using low-pressure CO2 as the foaming agent

Cited by 18 publications

References 64 publications

Improvement of the surface quality of foam injection molded products from a material property perspective

Improvement of the surface quality of foam injection molded products from a material property perspective

Scalable Fabrication of Microcellular Open‐Cell Polymer Foams

Synergistic effect of thermoplastic polyester elastomer and polytetrafluoroethylene in situ fibrillation on the resilience and compression strength of long‐chain branched polypropylene foam

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