Rigid foam definition

The mechanical properties of rigid foams vary considerably from those of flexible foams. The tests used to characterize these two classes of foams are, therefore, quite different, and the properties of interest from an application standpoint are also quite different. In this discussion the ASTM definition of rigid and flexible foams given earlier is used. 

The properties of commercial rigid foamed plastics are presented in Table 2. The properties of commercial flexible foamed plastics are presented in Table 4. The definition of a flexible foamed plastic is that recommended by the ASTM Committee D 11. The data shown demonstrate the broad ranges of properties of commercial products rather than an accurate set of properties on a specific few materials. Specific producers of foamed plastics should be consulted for properties on a particular product (137,138,142). 

Tbe term structural foam was originally coined by Union Carbide to describe an injection moulded thermoplastic cellular material with a core of relatively low density and a high-density skin. The term has also been used to describe rigid foams that are load bearing. Today it is commonly taken to imply both of the above requirements, i.e. it should be load bearing and with a core of lower density than the skin. In this section the broader load-bearing definition will be used. Whilst structural foams are frequently made from polymers other than polystyrene, this polymer is strongly associated with such products and it is convenient to deal with the topic here. 

Definition Types include flexible, semirigid, and rigid foams, open- or closed-cell foams, and high-... 

The agents in this class are bicyclophosphates and bicyclothiophosphates. This class of agents is not specifically listed in the Chemical Weapons Convention nor is it covered by the language of the general definitions in the Schedules. Some of these chemicals have been used as fire retardants, oil lubricants, and for medicinal research. They also occur as breakdown products in some synthetic turbine engine lubricants and some rigid polyurethane foams. 

Synonyms Lactis proteinum Protein, whey Whey protein concentrate Definition Polypeptide obtained from the fluid part of milk after separation from curds Uses Cosmetic protein protein source in animal feeds source of lactose and lactic acid synthesis of riboflavin, acetone, butanol, fuel-grade ethanol cheesemaking culture medium in rigid polyurethane foams moisture retention aid, emulsifier, stabilizer, opacifier, protein fortifier, fat replacer in foods Regulatory FDA 21CFR 135.110, 135.140, 184.1979c... 

By definition the production of a foam depends on the formation and stabilisation of gas bubbles in a liquid. That is true even for polyurethane foam when the additional curing of the liquid results in an elastic or rigid solid material. One of the central questions is how the gas bubbles are generated and how long this generation takes. 

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