Thermally expandable microspheres with high expansion ratios: Design of core and shell for largest size change

Gomez, Jasmine C.; Vishnosky, Nicholas S.; Grafstein, Jeremy; Kim, Spencer T.; Steinhardt, Rachel C.

doi:10.1002/app.52517

Cited by 4 publications

(6 citation statements)

References 36 publications

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“…As shown in Figure c(iv–vi), when the samples were kept at 150 °C for 5 min, the EM volume increased significantly, and the volume was largely maintained after expansion (Video S2 and S4, Supporting Information). The reason for this is that when exposed to heat, the low-boiling-point solvent inside the EM increases the internal pressure through phase transition, the heating temperature exceeds the glass transition temperature of the shell, and the EM expands driven by the internal pressure. , Under the elastic force binding of the cross-linked network of the rubber matrix, the material expands to the maximum value when the expansion force is balanced with the binding force to avoid rupture. , Despite the heating source being removed, the expansion structure is finely fixed, which is attributed to the plastic deformation of the shell. , …”

Section: Results and Discussionmentioning

confidence: 99%

Flexible Thermal Protection Polymeric Materials with Self-Sensing and Self-Adaptation Deformation Abilities

Chi

Cai

Yan

et al. 2023

ACS Appl. Mater. Interfaces

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Based on the strategy of killing two birds with one stone, we introduce thermally expandable microspheres into a silicone rubber matrix to fabricate temperature-responsive controllable deformation materials, which exhibit intelligent deformation properties as well as enhanced thermal protection performance, for dynamic thermal protection in the next-generation morphing aircrafts. The formation of hollow structures endows the material with intelligent thermal management ability and makes the thermal conductivity controllable, meeting the requirements of rapid deformation and excellent thermal insulation. The dimensions of the material adaptively expand with increasing temperature, and a constant 50N force can be provided to ensure reliable sealing. Moreover, benefiting from the synergistic effect of the hollow structure and zinc borate in the ceramization process of the silicone rubber, the 10 mm thick material can reduce the temperature from 2000 to 63 °C, and the mass ablation rate is only 4.8 mg/s. To broaden the application of our material, a sensor with a sandwich structure composed of different functional layers is designed. It is pleasantly surprising to observe that the sensor can provide real-time remote warning of fire and overheating sites with a response time as short as 1 s. This synergistic strategy opens a new possibility to fabricate intelligent thermal protection materials.

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Section: Results and Discussionmentioning

confidence: 99%

Flexible Thermal Protection Polymeric Materials with Self-Sensing and Self-Adaptation Deformation Abilities

Chi

Cai

Yan

et al. 2023

ACS Appl. Mater. Interfaces

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“…2 In 1970, Dow Chemical Co. 3 published the first patent on TEMs which has since been followed by an increasing number of patents and publications. [4][5][6][7][8][9][10][11] There are studies where polymerization parameters including the effect of crosslinking, 1,[12][13][14][15][16][17][18][19] structure, 20 surface modification, [21][22][23][24][25] and applications 2,[26][27][28][29] have been investigated. Traditionally, TEMs are prepared from fossil-based monomers such as acrylonitrile (AN), methacrylonitrile (MAN), various (meth)acrylates, maleimides, acrylamides, vinylidene chloride, and styrene.…”

Section: Introductionmentioning

confidence: 99%

Thermally expandable microspheres based on fully or partially bio‐based polymers

Mousa,

Jonsson,

Granbom

et al. 2024

J of Applied Polymer Sci

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Bio‐based or partially bio‐based thermally expandable microspheres (TEMs) were synthesized by suspension (co)polymerization of the bio‐based monomer α‐methylene‐γ‐valerolactone (MeMBL) together with acrylonitrile and/or methyl methacrylate to form expandable core/shell particles by encapsulating a hydrocarbon‐based blowing agent. The core/shell polymers were characterized with respect to their chemical structure, thermal expansion, and morphology. The obtained particles, TEMs, showed an increasing onset expansion temperature with increasing content of MeMBL owing to the high glass transition temperature of PMeMBL. As a result, bio‐based/partially bio‐based TEMs are achieved with high thermal stability and expansion properties which can be tailored for various applications.

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“…For the manufacture of thermally expandable microspheres, it is appropriate to enhance the solubility of swelling agents in the matrix in order to achieve high degree of particle expansion 25 . Particularly, the functionalization of these expandable particles can allow the manufacture of foams with improved mechanical and chemical properties 26,27 .…”

Section: Introductionmentioning

confidence: 99%

“…Particularly, the functionalization of these expandable particles can allow the manufacture of foams with improved mechanical and chemical properties 26,27 . In this context, it is important to consider that particles with core–shell morphology can be obtained by different polymerization techniques (miniemulsion, emulsion, suspension, and seeded suspension) 25,26,28 …”

Section: Introductionmentioning

confidence: 99%

Investigation of swelling degree of polypropylene beads with monomers and blowing agents

Everton,

Gusmão,

Oechsler

et al. 2024

Polymer Engineering & Sci

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The swelling step of polymer particles or beads with blowing agents and monomers is one of the factors that directly affect the performance properties of expandable core–shell particles, including morphology, composition, and expansion degree. In this regard, the present work investigated the effect of swelling agents on polypropylene (PP) beads. Swelling agents were used to perform swelling tests in both bulk and suspension media at different temperatures and stirring rates. Additionally, a mass transfer model was implemented to predict the swelling degree at the analyzed experimental conditions. The obtained results indicated the important effect of temperature on swelling in both bulk and suspension tests. Among the investigated swelling agents, higher rates of PP beads swelling were observed when styrene was employed (~80 wt%), when compared to methyl methacrylate (~20 wt%), vinyl acetate (~9 wt%), and acrylonitrile (~6 wt%). Moreover, it seems that the stirring rate does not exert a considerable influence on the swelling rates, indicating that swelling is controlled by thermodynamic constraints and particle properties. Finally, experimental results showed that the final saturation concentration of the swelling agent can be reached before 1 hour of swelling, indicating that the swelling kinetics can be much faster than the polymerization kinetics.Highlights The effects of non‐conventional swelling agents on PP were investigated. The swelling presented a fast dynamic behavior. The swelling dynamics was controlled by the solubility of the swelling agent. The highest swelling degree was obtained with styrene.

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Thermally expandable microspheres with high expansion ratios: Design of core and shell for largest size change

Cited by 4 publications

References 36 publications

Flexible Thermal Protection Polymeric Materials with Self-Sensing and Self-Adaptation Deformation Abilities

Flexible Thermal Protection Polymeric Materials with Self-Sensing and Self-Adaptation Deformation Abilities

Thermally expandable microspheres based on fully or partially bio‐based polymers

Investigation of swelling degree of polypropylene beads with monomers and blowing agents

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