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Nucleating agent cell-control

Nucleating agent, cell-control These agents promote symmetrical, cohesive expansion of cells within foamed polyurethane and polystyrene plastics also to a limited extent in polyethylene and polypropylene plastics. [Pg.524]

Polyethylene. This is essentially a closed-cell insulation manufactured at 448 =t 2 K by an extrusion process. A blowing agent and nucleating agent are employed to control the cell size, and primary use is in insulating pipelines for hot and chilled water lines, air conditioning, and processing... [Pg.332]

Nucleation agents are substances that are able to initiate and control cell formation and growth. They are purposely incorporated into the polymeric structure. At their location, the blowing agent (pentane) preferably evaporates when the EPS beads are exposed to saturated steam. However, unwanted... [Pg.177]

The amount of blowing agent introduced is the primary determinant of the final density of the foam. The size and number of cells are controlled by the amount of nucleating agent. Extruded PS foams used for packaging typically have densities of 64 to 96 kg/m3 (4 to 6 Ib/ft ). [Pg.342]

The term nucleating agent is used in a different sense in the context of foam manufacture, where talc and other nucleating agents are used to promote bubble formation and control cell structure. [Pg.39]

To improve control of the formation of the foam during the process, and to achieve a uniform cell structure, other additives (called nucleating agents) are often used. It is also possible to extrude some thermoplastics in an expanded form by means of direct gassing, together with nucleating agents. [Pg.178]

In order to improve the number of cells, it is industrial practice to use nucleating agents to have a fine control of the final foam morphology (Fujimoto et al., 2003 Mitsunaga et al., 2003). Traditional nucleating agents are microsized particles, such as talc, which is cheap, efficient, easy to disperse in the polymer, and in large... [Pg.193]

Surface active agents are important components of foam formulations. They decrease the surface tension of the system and facilitate the dispersion of water in the hydrophobic resin. In addition they can aid nucleation, stabilise the foam and control cell structure. A wide range of such agents, both ionic and non-ionic, has been used at various times but the success of the one-shot process has been due in no small measure to the development of the water-soluble polyether siloxanes. These are either block or graft copolymers of a polydimethylsiloxane with a polyalkylene oxide (the latter usually an ethylene oxide-propylene oxide copolymer). Since these materials are susceptible to hydrolysis they should be used within a few days of mixing with water. [Pg.797]


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See also in sourсe #XX -- [ Pg.387 ]




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