Theory of formation of the structure of closed-pore gas-filled polymers by foaming

The prototypical pillared layer MOFs, formed by a square lattice of paddle- wheel units and connected by dinitrogen pillars, can undergo a breathing phase transition by a “wine-rack” type motion of the square lattice. We studied this not yet fully understood behavior using an accurate first principles parameterized force field (MOF-FF) for larger nanocrystallites on the example of Zn 2 (bdc) 2 (dabco) [bdc: benzenedicarboxylate, dabco: (1,4-diazabicyclo[2.2.2]octane)] and found clear indi- cations for an interface between a closed and an open pore phase traveling through the system during the phase transformation [Adv. Theory Simul. 2019, 2, 11]. In conventional simulations in small supercells this mechanism is prevented by periodic boundary conditions (PBC), enforcing a synchronous transformation of the entire crystal. Here, we extend this investigation to pillared layer MOFs with flexible side-chains, attached to the linker. Such functionalized (fu-)MOFs are experimen- tally known to have different properties with the side-chains acting as fixed guest molecules. First, in order to extend the parameterization for such flexible groups, 1a new parametrization strategy for MOF-FF had to be developed, using a multi- structure force based fit method. The resulting parametrization for a library of fu-MOFs is then validated with respect to a set of reference systems and shows very good accuracy. In the second step, a series of fu-MOFs with increasing side-chain length is studied with respect to the influence of the side-chains on the breathing behavior. For small supercells in PBC a systematic trend of the closed pore volume with the chain length is observed. However, for a nanocrystallite model a distinct interface between a closed and an open pore phase is visible only for the short chain length, whereas for longer chains the interface broadens and a nearly concerted trans- formation is observed. Only by molecular dynamics simulations using accurate force fields such complex phenomena can be studied on a molecular level.

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Model Filled Polymers. 6. Determination of the Crosslink Density of Polymeric Beads by Swelling

10.21236/ada225783 ◽

1990 ◽

Author(s):

Z. Y. Ding ◽

J. J. Aklonis ◽

R. Salovey

Keyword(s):

Crosslink Density ◽

Filled Polymers ◽

Polymeric Beads

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Model Filled Polymers .11. Synthesis of Uniformly Crosslinked Polystyrene Microbeads

10.21236/ada237472 ◽

1991 ◽

Author(s):

Zheng-You Ding ◽

Shenmin Ma ◽

Dennis Kriz ◽

J. J. Aklonis ◽

R. Salovey

Keyword(s):

Filled Polymers ◽

Crosslinked Polystyrene

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Electrospun polyacrylonitrile/polyvinyl pyrrolidone composite nanofibrous membranes with high-efficiency PM2.5 filter

Journal of Polymer Engineering ◽

10.1515/polyeng-2019-0318 ◽

2020 ◽

Vol 40 (6) ◽

pp. 487-493

Author(s):

Chen Wang ◽

Kun Yan ◽

Jun Wang ◽

Siyu Chen ◽

Jiaming Cui ◽

...

Keyword(s):

Pore Structure ◽

Composite Nanofibers ◽

High Efficiency ◽

Fine Particulate Matter ◽

Polyvinyl Pyrrolidone ◽

Indoor Dust ◽

Mass Ratio ◽

Filter Efficiency ◽

Fine Particulate ◽

Closed Pore

AbstractIn this research, we successfully fabricated a novel closed pore polyacrylonitrile (PAN)/polyvinyl pyrrolidone (PVP) composite nanofibrous membrane (PCNM) on the substrate of a commercial polypropylene window mesh. First, smooth and uniform PAN/PVP composite nanofibers (PCNs) were manufactured by blending PAN and PVP with a mass ratio of 5:5 during electrospinning. Subsequently, the prepared PCNs were hot pressed in a vacuum drying oven at a given temperature of 90°C. The morphology and filter efficiency of PCN and PCNM were investigated. It was found that hot-pressing treatment significantly affected the pore structure and orientation of PCNM, which contributed to its closed pore structure and good alignment. The filter efficiency results indicated that the hot-pressed PCNMs have excellent removal efficiency of up to 96.8% of fine particulate matter. This research demonstrates that PCNMs have potential as filters for indoor dust removal and will provide a new idea for the development of air filters.

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Preparation and characterisation of closed-pore Al2O3-MgAl2O4 refractory aggregate utilising superplasticity

Advances in Applied Ceramics ◽

10.1080/17436753.2017.1405555 ◽

2017 ◽

Vol 117 (3) ◽

pp. 182-188 ◽

Cited By ~ 2

Author(s):

Lei Yuan ◽

Xiaodong Zhang ◽

Qiang Zhu ◽

Guo Wei ◽

Jingkun Yu ◽

...

Keyword(s):

Refractory Aggregate ◽

Closed Pore

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Migration and Settling of Particulates in Filled Epoxies

Volume 1: Fora, Parts A, B, C, and D ◽

10.1115/fedsm2003-45780 ◽

2003 ◽

Author(s):

Lisa Mondy ◽

Rekha Rao ◽

Eric Lindgren ◽

Amy Sun ◽

Robert Lagasse ◽

...

Keyword(s):

Particle Concentration ◽

Particle Migration ◽

Polymerization Reaction ◽

Temperature Dependent ◽

Filled Polymers ◽

Post Test ◽

Manufacturing Applications ◽

Microscopy Data ◽

Suspension Model ◽

Epoxy Systems

Manufacturing applications for filled polymers include encapsulation of microelectronics and injection molding of composite parts. Predictive tools for simulating these manufacturing processes require knowledge of time- and temperature-dependent rheology of the polymer as well as information about local particle concentration. The overall system rheology is highly dependent on the particle concentration. The local particle concentration can change due to gravity, convection and shear-induced migration. For the epoxy systems of interest, an extent of reaction can be used to track the degree of cure. We couple the curing model with a diffusive flux suspension model [Zhang and Acrivos 1994] to determine the particle migration. This results in a generalized Newtonian model that has viscosity as a function of temperature, cure and concentration. Using this model, we examine settling of the particulate phase in both flowing and quiescent curing systems. We focus on settling in molds and flow in wide-gap counter-rotating cylinders. The heat transfer, including the exothermic polymerization reaction, must be modeled to achieve accurate results. The model is validated with temperature measurements and post-test microscopy data. Particle concentration is determined with x-ray microfocus visualization or confocal microscopy. Agreement between the simulations and experimental results is fair.

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