Controllable Enhancement of Capsule‐Membrane Wrinkles by Flow Shear and Preparation of Double‐Layer Polyamide Microcapsules

Hu, Pan; Hadji, Edward Mohamed; Shi, Tingjing; Tai, Mo; Wang, Jingtao

doi:10.1002/slct.201900997

Cited by 2 publications

(2 citation statements)

References 40 publications

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“…The thickness of the shell is in both cases extremely low and cannot be observed with optical microscope. The morphology of microcapsules under the optical microscope rather resembles the one presented in 35 where the initially formed PA shell was let to reswell in water, after which the polymerization could continue and highly swollen in water stable shells clearly visible in the microscope could be observed. The thermal stability of microcapsules is similar to the one demonstrated in Mytara et al, 33 where double polymerization process has been used.…”

Section: Microcapsules Propertiesmentioning

confidence: 76%

Self‐lubricating polyamide 6 and polyamide 6.6 microcapsule‐based composites

Grünewald,

Herbig,

Heilig

et al. 2024

J of Applied Polymer Sci

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Polymeric applications with extended service life and low energy loss due to friction are of great interest in conveyor and power transmission technology. Self‐lubricating systems utilizing microcapsules hold significant potential for increasing energy efficiency and extending the operational life of these applications. This study focuses on synthesizing oil‐filled microcapsules through in situ polymerization of polyamide and their incorporation in polyamide 6 and polyamide 6.6. Microcapsules with a core made of thermally stable lubricant Food Lube, and particle diameter D90 of 50 μm were synthesized and isolated as a free‐flowing powder via spray‐drying procedure. The resulting powder demonstrated high thermal stability (loss of 5% at 350°C) due to the high thermal stability of both core and shell materials. A compounding process utilizing a twin‐screw extruder was developed to blend microcapsules into thermoplastic matrices. An injection molding machine forms tension rods. The composites' tribological properties are assessed through ball‐on‐disc tests conducted in both oscillation and rotation. The friction coefficient and wear rate of the composites experience a reduction of 79% and 56% for polyamide 6, as well as 77% and 75% for polyamide 6.6. Mechanical testing of the microcapsule composites reveals a decrease in mechanical properties.

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Section: Microcapsules Propertiesmentioning

confidence: 76%

Self‐lubricating polyamide 6 and polyamide 6.6 microcapsule‐based composites

Grünewald,

Herbig,

Heilig

et al. 2024

J of Applied Polymer Sci

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“…Here we present a general microfluidic approach for preparing nearly monodisperse PCM‐filled microcapsules, building off the work of others, [ 21–23 ] and show how these microcapsules can be used to form composites with bistable mechanical properties. The microfluidic approach enables formation of microcapsules with narrow and adjustable diameters, use of highly compatible capsule shell chemistries, and was found to be highly reproducible.…”

Section: Figurementioning

confidence: 99%

Polymer Composites Containing Phase‐Change Microcapsules Displaying Deep Undercooling Exhibit Thermal History‐Dependent Mechanical Properties

Liu

Streufert

et al. 2020

Adv Materials Technologies

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they melt into a liquid and releasing heat as they solidify into a solid. The greater the latent heat of fusion, the greater the energy absorbed/released during these phase transitions. [5,6] As various groups have shown, by encapsulating micron to millimeter diameter droplets of a PCM, functionalities ranging from temperaturedependent permeability to enhanced solar thermal energy storage efficiency can be realized. [7,8] Once encapsulated, PCMs can be embedded in a diversity of matrices, which may enable new applications in areas ranging from thermal energy storage and conversion, electronics, [9-12] smart fibers and textiles, and thermal comfort in vehicles. [13] A conventional approach to encapsulation is through shell polymerization in oil-in-water (o/w) or water-in-oil-in-water (w/o/w) double emulsions, such as those used to prepare the self-healing microcapsules first reported by Moore et al. [14] Challenges with this approach are the generally wide size distribution of the capsules prepared, compatibility between the capsule shell polymerization chemistry and the core chemistry, and control of the synthetic parameters required to enable reproducible results. [15-17] Because the thermal transitions of PCMs are sensitive to the Microencapsulated materials are receiving broad attention for applications as diverse as energy storage and conversion, biomedicine, self-healing materials, and electronics. Here, a general microfluidic approach is presented to prepare phase-change material-infilled microcapsules with unique thermal and mechanical properties. Aqueous sodium acetate solutions are encapsulated by an acrylate-based shell via a microfluidic method. To understand and optimize microcapsule formation, flow behavior during the encapsulation is numerically simulated. When the microcapsules are embedded in an acrylate matrix (same composition as the shell wall material), the microcapsules exhibit a significant 46.6 ºC difference between the crystallization and melting temperatures as determined by differential scanning calorimetry at a rate of 10 ºC per min. Variable temperature dynamic mechanical analysis over the range of 50 to-90 ºC reveals up to a 50% change in the composite's elastic modulus at a given temperature, depending on if the sample is being cooled or heated, due to significant undercooling of the core material crystallization as shown by X-ray diffraction.

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Controllable Enhancement of Capsule‐Membrane Wrinkles by Flow Shear and Preparation of Double‐Layer Polyamide Microcapsules

Cited by 2 publications

References 40 publications

Self‐lubricating polyamide 6 and polyamide 6.6 microcapsule‐based composites

Self‐lubricating polyamide 6 and polyamide 6.6 microcapsule‐based composites

Polymer Composites Containing Phase‐Change Microcapsules Displaying Deep Undercooling Exhibit Thermal History‐Dependent Mechanical Properties

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