Sulfur foams

Foams. Sulfur can be foamed into a lightweight insulation that compares favorably with many organic foams and other insulating materials used in constmction. It has been evaluated as thermal insulation for highways and other appHcations to prevent frost damage (63) (see Eoamed plastics Insulation, thermal). 

Foamed Sulfur (15, 1 8). By using additives and simple ma-chinery, sulfur can be turned into a foam that has very useful properties. Lighter than water, foamed sulfur can be used for building insulation, subbases for pavements, and perhaps lightweight structural members for housing and other small structures. 

Figure 8. Foamed sulfur wallhoard showing acceptance of nails and screws...

One could visualize the possibility of self-bonding wood paneling to the foamed sulfur board the same way as paper. 

Figure 9 is a schematic of a proposed continuous process in which paper facings and foamed sulfur are carried on a conveyor through compression rollers, a cooling device, and a cut-off machine, ready to be packaged and shipped. 

Most phenohc foams are produced from resoles and acid catalyst suitable water-soluble acid catalysts are mineral acids (such as hydrochloric acid or sulfuric acid) and aromatic sulfonic acids (63). Phenohc foams can be produced from novolacs but with more difficulty than from resoles (59). Novolacs are thermoplastic and require a source of methylene group to permit cure. This is usually suppHed by hexamethylenetetramine (64). 

There are explosion hazards with phthahc anhydride, both as a dust or vapor in air and as a reactant. Table 11 presents explosion hazards resulting from phthahc anhydride dust or vapor (40,41). Preventative safeguards in handling sohd phthahc anhydride have been reported (15). Water, carbon dioxide, dry chemical, or foam may be used to extinguish the burning anhydride. Mixtures of phthahc anhydride with copper oxide, sodium nitrite, or nitric acid plus sulfuric acid above 80°C explode or react violently (39). 

Films deposited from compounded nitrile latices can be vulcanized with sulfur and accelerators, assisted by relatively high levels (ca 4.0—5.0 parts /100 DRC) of ziac oxide. For other uses, nitrile latices are sometimes used ia unvulcanized form. An appHcation of medium soHds nitrile latex, eg, Nitrex J-6849 and Polysar 845, has been ia preparation of oil-resistant foams for lubricants ia heavy-duty beariags, such as railroad-car journal boxes. 

These redox processes are usually appHcable for small sulfur capacities. The sulfur is typically produced as a slurry, and can be upgraded to cake or molten sulfur. At low pressures, the redox processes can replace the amine Claus and tail gas cleanup processes with a single step, yet obtain sulfur recoveries of 99%. At higher pressures, the redox processes experience sulfur plugging and foaming problems. 

Addition of up to 200 ppm sulfur dioxide to grape musts is customary. Strains of S. cerevisiae and S. bayanus grown in the presence of sulfite, become tolerant of fairly high concentrations of SO2. Cultures propagated in the winery are added in Hquid suspension, usually at 1—2% of the must volume. Many strains are available in pure culture. Factors such as flocculence, lack of foaming, fast fermentation, lack of H2S and SO2 formation, resistance to sulfur dioxide and other inhibitors, and flavor production will affect strain choice. No strain possesses all the desired properties. 

Cyclopentadiene oligomers have been formed by vapor deposition of CPD on kaolin to afford a sorbant for removal of oil from water (71). They are also employed as coatings for controlling release rates of fertilizers (72). Thermal addition of sulfur to a mixture of DCPD and CPD oligomers has led to a number of beneficial appHcations such as waste water oil adsorbant powdery foams (73), plasticized backing for carpets and artificial turfs (74), and in modified sulfur cements for encapsulating low-level radioactive wastes (75). 

As of 1992, the first specialty platable plastic, acrylonitrile—butadiene—styrene (ABS) terpolymer (see Acrylonitrile polymers, ABS resins), is used ia over 90% of POP appHcatioas. Other platable plastics iaclude poly(pheayleae ether) (see PoLYETPiERs), ayloa (see Polyamides), polysulfoae (see Polymers CONTAINING sulfur), polypropyleae, polycarboaate, pheaoHcs (see Pphenolic resins), polycarboaate—ABS alloys, polyesters (qv), foamed polystyreae (see Styrene plastics), and other foamed plastics (qv). 

Approximately 3 lb. of sodium bisulfite is required to reduce the iodine. Technical grade bisulfite may be used satisfactorily. Caution should be observed in adding the bisulfite, since evolution of sulfur dioxide can cause excessive foaming. This foaming occurs a short time after each addition and is most noticeable when the iodine is almost neutralized. Iodine and product clinging to the upper walls of the flask and in the condenser may be conveniently rinsed into the reaction mixture with a stream of water from a wash bottle. 

Fire Hazards-Fto/iPomr (deg. F) 53 OC Flammable Limits in Air (%) No data Fire Extinguishing Agents Dry chemical, alcohol foam, carbon dioxide Fire Extinguishing Agents Not To Be Used Water Special Hazards of Combustion Products Irritating sulfur dioxide Behavior in Fire Vapors... 

Fire Hazards - Flash Point (deg. F) 203 OC Flammable limits in Air (%) 3 - 6.3 Fire Extinguishing Agents Water, foam, dry chemical, or carbon dioxide Fire Extinguishing Agems Not to be Used Not pertinent Special Hazards of Combustion Products Sulfur dioxide, formaldehyde, and methyl mercaptan may form Behavior in Fire Not pertinent Ignition Temperature (deg. F) 572 Electrical Hazard Not pertinent Burning Rate 2.0 mm/min. 

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