Physical Foaming Agents

Chemical foaming agents Physical foaming agents Insulation, packaging, wood substitutes... 

Keywords Polyolefin foams Polyethylene foams Crosslinking Foaming agents Physical properties of foams... 

These essentially comprise a mixture of a skin-forming component, which comprises two distinct phases blended together, a high zero-shear viscosity material and a low zero-shear viscosity material, and a foam core-foaming component, which includes a blowing agent, physically dry blended together. The three materials are preferably selected from suitable homopolymers and copolymers of ethylene. CANADA... 

Catalysts, colorants, foaming agents, biocides, lubricants, and antistats are also used as additives for polymers. Although foaming agents reduce the specific gravity, the other cited additives, when used in moderate amounts, have little effect on the physical or thermal properties of the polymers. 

Q-1 represents the reciprocal value of the well known gas throughput number Q. Fr is the Froude number, here formed with the gas throughput and cT is the dimensionless concentration (in ppm) of the foaming agent in the liquid. S are the physical properties which affect foam stability. Because they are neither known by number (i) nor by kind, instead of S the type of the foaming agent (name and chemical structure) must be given. 

In all cases, It Is obvious that the foaming agent must not adversely effect fabric esthetic or physical properties. 

ABS with ASA and two SAN copolymers were foamed with a physical foaming agent easy formability, excellent physical properties and Freon resistance Kim and Choi, 1998... 

Anti-foam agents are almost always used in SBR latex modified cement compositions because they increase mix density by minimizing air-entrainment, thereby upgrading physical properties. Anti-foam agents may be added to the SBR latex by the manufacturer of the latex and additional amounts may be added by the formulator of the final cementitious mortar composition. The amount of anti-foam added may range from 0.1% anti-foam solids on latex solids up to 3.5%. 

If foam formation caimot be avoided, it can be destroyed mechanically by foam breakers, physically by ultrasound, heat or electrical methods, or chemically by antifoam agents [33]. In industrial production, with a few exceptions, mechanical foam breakers (e.g. steroid biotransformation [34]) are not used because of their high power input demand, which is often higher than the power input by the stirrer. Physical methods are not used either, because ultrasovmd, heat or electric treatment can impair the viabiUty of the microorganisms. Therefore, only chemical methods are considered in this review. 

Additives which alter physical properties either during processing or in the final plastic include plasticizers, fillers, lubricants and flow promoters, impact modifiers and foaming agents. 

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