Open-cell polymers

PolyHIPE materials possess many peculiar properties as a result of their unique cellular structure. Referring specifically to open-cell polymers (which have received the most attention in the literature), they are characterised by a very low dry bulk density, typically less than 0.1 gem-3, due to their highly porous, interconnected structure. 

FIGURE 4.67 Differential intrusion of mercury (dVp/dDp) vs. log Dp plot for a sample of a highly porous open-cell polymer [poly-(HIPE)]. 

Most slabstock foams are open-celled, that is, the walls around each cell are incomplete. Towards the end of the foaming process, the polymer migrates from the membranes between cells to the cell struts, which results in a porous structure. In some cases, cells near the surface of the foam collapse to form a continuous skin, which may be trimmed off later. 

Foamed polymers. Thermosets and thermoplastics formed into low density, cellular materials containing bubbles of gas. Rigid foams have their gas bubbles in closed cells, inhibiting flexibility flexible foams have the bubbles in open cells, permitting the gas to escape as the foam is flexed. 

Describes open cell foamed articles including silane-grafted single-site initiated polyolefin resins. The olefin polymer resin can be a polyethylene, a copolymer of ethylene, a C3-C20 alpha-olefin, or a copolymer of ethylene, a C3-20 alpha-olefin and a C4-C20 diene. The open cell foamed articles have good cushioning properties and can be non-allergenic. 

Journal of Applied Polymer Science 37,No.8,April 1989,p.2153-64 PREPARATION OF HYDROPHILIC POLYETHYLENE FOAM OF OPEN CELL TYPE BY RADIATION GRAFTING OF ACRYLIC ACID Kaji K Hatada M Yoshizawa I Kohara C Komai K JAPAN,ATOMIC ENERGY RESEARCH INSTITUTE SANWAKAKOCO. 

Open-cell PolyHIPE materials have also been prepared from hydrophilic methacrylates which, on hydrolysis, yield hydrophilic polymethacrylic acid-based species [155]. Stable HIPEs containing high levels of glycidyl methacrylate can also be formed, from which porous polymers can be made. These have considerable potential for further exploitation due to the reactive epoxide group [156],... 

This chapter introduces readers to the versatility of polyurethane polymers without spending too much time on the chemistry. The next chapter will discuss a more classical view of the molecule and how it is developed. Our point, however, is to present a functional view of this system. We have examined its physical characteristics, focusing our attention on the uniqueness of reticulated foams. All the chemical points we have made apply to all polyurethane polymers, whether they are open-celled foams, closed-cell foams, or thermoplastic elastomers. 

The properties of a foamed plastic can be related to several variables of composition and geometry often referred to as structural variables. These variables include polymer composition, density, cell structure (i.e., cell size, cell geometry, and the fraction of open cells), and gas composition. 

Foamed plastics can be classified in different ways, for instance by their nature (flexible vs. rigid), chemical composition of the matrix, density, cell size, cell structure (open-celled vs. closed-celled), processing method, and dimensions. It is the aimed combination of these properties that determines the final application of the cellular polymer. As an example, open-celled ultra-low density foams are highly desirable for acoustical insulation, while rigid foams with closed-cells and elevated densities are preferred as load-carrying core materials in composite materials. 

Microcellular foaming, bimodal cell size distributions, and high open-celled contents of molecular composites of HT-polymers were reported by Sun et al. [33], investigating blends of a rod-like polymer polybenzimidazole with an aminated PSU and poly(phenyl sulfone) by using carbon dioxide as a blowing agent. The complex foaming behavior was related to phase separation within the otherwise... 

Park CB, Padareva V, Lee PC, Naguib HE (2005) Extmded open-celled LDPE-based foams using non-homogeneous melt structure. J Polym Eng 25 239-260... 

Water-in-Monomer Polymerizations for Open-Celled Foams. Porous polymers or mixed polymers of styrene are prepared by polymerizing the... 

When plastics are foamed to low densities, containing more air than polymer, they acquire unique new properties and applications. Major uses are in crash padding and thermal insulation. Closed-cell foams are outstanding for flotation, rigidity, and insulation while open-cell foams are outstanding for softness, resilience, and comfort. 

The gas phase in a cellular polymer is usually distributed in voids or pockets called cells. If these cells are interconnected, the material is termed open-cell. If... 

In the case of cellular rubber, the ASTM uses several classifications based on the method of manufacture [11,12]. Cellular rubber is a general term covering all cellular materials that have an elastomer as the polymer phase. Sponge rubber and expanded rubber are cellular rubbers produced by expanding bulk rubber stocks, and are open-cell and closed- cell, respectively. Latex foam rubber, which is also a cellular rubber, is produced by frothing a rubber latex or liquid rubber, gelling the frothed latex, and then vulcanizing it in the expanded state. 

The acoustic properties of polymers are altered in a cellular structure. Sound transmission changes only slightly, because it depends predominantly upon the barrier density, in this case the polymer phase. Therefore, closed-cell cellular polymers by themselves are poor materials for reducing sound transmission. They are, however, effective in absorbing sound waves of certain frequencies [64]. Materials with open cells on the surface are particularly effective in this respect. The combination of other advantageous physical properties with fair acoustic properties has led to the use of plastic foams in soundproofing [65,66]. The sound absorption of a number of cellular polymers has been reported [7,64,65,67]. 

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