Effect of the crystallinity and morphology on the microcellular foam structure of semicrystalline polymers

The paper investigates the mechanisms of microwave absorption in microcellular foamed conductive composites dedicated to protection against electromagnetic interferences (EMI). A multi-layered electromagnetic one-dimensional (1D) model mimicking the microcellular foam structure is built and validated using previous measurements carried out on various fabricated composite foams. Our model enables us to perform a parametric analysis of the absorption behaviour in a foamed composite, using as parameters the size of the hollow cell, the thickness of the cell’s walls and its conductivity, as well as the overall thickness of the composite and the frequency. Our investigations demonstrate that multiple reflections of the microwave signal between the cellular walls are not the main mechanism responsible for absorption, although they are often reported as a cause of enhanced absorption in the literature. On the contrary, our work demonstrates that the enhancement of the absorption observed in foamed conductive composite compared to unfoamed composite is mainly due to the presence of air in the microcells of the composite.

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Decoupling the Effects of the Matrix Properties and Foam Structure on the Mechanical Properties of Microcellular Foam by Sub-Tg Annealing

Journal of Reinforced Plastics and Composites ◽

10.1177/073168449501401003 ◽

1995 ◽

Vol 14 (10) ◽

pp. 1054-1068 ◽

Cited By ~ 4

Author(s):

Karl A. Seeler ◽

Vipin Kumar

Keyword(s):

Mechanical Properties ◽

Microcellular Foam ◽

Foam Structure ◽

Matrix Properties ◽

The Matrix

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3D printed polyurethane tissue engineering scaffold with hierarchical microcellular foam structure and antibacterial properties

Advanced Engineering Materials ◽

10.1002/adem.202101134 ◽

2022 ◽

Author(s):

Shuai Zhang ◽

Xuetao Shi ◽

Zhenyun Miao ◽

Haibin Zhang ◽

Xin Zhao ◽

...

Keyword(s):

Tissue Engineering ◽

Antibacterial Properties ◽

Tissue Engineering Scaffold ◽

Microcellular Foam ◽

Foam Structure ◽

3D Printed

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Semicrystalline polymers

Physics Subject Headings (PhySH) ◽

10.29172/ac47229e-a05a-48bc-aab6-b2475df16eac ◽

2018 ◽

Keyword(s):

Semicrystalline Polymers

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Study of Transcrystallization in Polymer Composites

MRS Proceedings ◽

10.1557/proc-170-117 ◽

1989 ◽

Vol 170 ◽

Cited By ~ 15

Author(s):

Benjamin S. Hsiao ◽

J. H. Eric

Keyword(s):

Thermal Conductivity ◽

Free Energy ◽

Carbon Fiber ◽

Plasma Treatment ◽

Polymer Composites ◽

High Performance ◽

Interfacial Strength ◽

Fiber Surface ◽

Semicrystalline Polymers ◽

First Case

AbstractTranscrystallization of semicrystalline polymers, such as PEEK, PEKK and PPS, in high performance composites has been investigated. It is found that PPDT aramid fiber and pitch-based carbon fiber induce a transcrystalline interphase in all three polymers, whereas in PAN-based carbon fiber and glass fiber systems, transcrystallization occurs only under specific circumstances. Epitaxy is used to explain the surface-induced transcrystalline interphase in the first case. In the latter case, transcrystallization is probably not due to epitaxy, but may be attributed to the thermal conductivity mismatch. Plasma treatment on the fiber surface showed a negligible effect on inducing transcrystallization, implying that surface-free energy was not important. A microdebonding test was adopted to evaluate the interfacial strength between the fiber and matrix. Our preliminary results did not reveal any effect on the fiber/matrix interfacial strength of transcrystallinity.

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Thin shell aerogel fabrication for FIREX-I targets using high viscosity (phloroglucinol carboxylic acid)/formaldehyde solution

Laser and Particle Beams ◽

10.1017/s0263034608000451 ◽

2008 ◽

Vol 26 (3) ◽

pp. 449-453 ◽

Cited By ~ 15

Author(s):

H. Yang ◽

K. Nagai ◽

M. Nakai ◽

T. Norimatsu

Keyword(s):

Carboxylic Acid ◽

Thin Shell ◽

Shell Thickness ◽

High Viscosity ◽

Formaldehyde Solution ◽

Resorcinol Formaldehyde ◽

Foam Structure ◽

Final Density ◽

Emulsion Process ◽

High Level

AbstractCapsules with a thin aerogel shell were prepared by the OO/W/OIemulsion process. (Phloroglucinol carboxylic acid)/formaldehyde (PF) was used as the water phase (W) solution to form the shell of the capsule. PF is a linear polymer prepared from phloroglucinol carboxylic acid. The viscosity of the PF solution can reach a high level of 9×10−5m2/s without gelation while resorcinol/formaldehyde (RF) gelates at ~3–4×10−5m2/s. Using the viscous PF solution, capsule with a 17 µm gel shell was fabricated. This thickness satisfies the specification of the first phase of Fast Ignition Realization Experiment (FIREX-I) at Osaka University. When PF gel was extracted to remove the organic solvent, shrinkage of 9% occurred. The final density of the PF aerogel was 145 mg/cm3. Both the shell thickness and density can satisfy the specification of FIREX-I. The pore size of the PF aerogel was less than 100 nm while that of RF was 200–500 nm. The SEM showed that PF had particle-like foam structure while RF had fibrous-like foam structure.

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