Rubber blowing agents

Rubber Industry Vulcanization accelerator and rubber blowing agent... 

PE/PP (25 %), rubbers (including EVA) (20 %) and other thermoplastics (5 %). Physical blowing agents (PBAs) liberate gases as a result of physical processes (evaporation, desorption) at elevated temperatures or reduced pressures. PBAs are mostly volatile liquids, freons, aliphatic hydrocarbons or solid blowing agents. 

We use variants of profile extrusion to produce tubing -with diameters of less then 1 mm and pipes with diameters exceeding 1 m, Wall thicknesses can vary from a few tens of micrometers up to several centimeters. Extruded window and door frames are more complex than pipes. Such profiles are largely hollow with internal ribs and fins that reinforce and divide the interior into two or more channels. We use solid rubber profiles in applications such as door seals and windshield wipers. We can produce foamed extrudates by incorporating a blowing agent, such as butane or carbon dioxide, into the polymer in the molten state. As the polymer exits the die, its internal pressure drops and the dissolved gas expands to form bubbles within the product. Examples of foamed extrudates include pipe insulation and automobile door gaskets. 

A manufacturing method predominately used by the thermoplastic industry for the manufacture of hollow components, also used for thermosetting rubber. The polymer is forced against the inside of the mould surface by gas pressure applied either by a hollow needle or by the decomposition of a blowing agent. 

Toluol or methylbenzene a hydrocarbon of the benzene series, used as a solvent for rubbers. p-Toluene Sulphonyl Hydrazide TSH, blowing agent. o-Tolyl Biguanidine OTBG, accelerator. 

Expanded Rubber This class of product has an essentially closed cell structure. These products are most usually formed by moulding or extrusion processes and have a solid outer skin around the cell structure. Organic blowing agents are used for this type of process. 

Microcellular Rubber A product usually used for shoe soling application produced by the incorporation of a blowing agent into the high styrene resin soling compound. 

The density of chemicaUy-blown LDPE foam was altered by varying the amount of blowing agent, degree of crosslinking of the polymer, and the foam expansion temperature. A theory was proposed for the equilibrium density, based on the gas pressures in a Kelvin foam structure, and a rubber-elastic analysis of the biaxial stretching of the cell faces. 20 refs. 

MORPHOLOGY AND PHYSICAL PROPERTIES OF CLOSED CELL MICROCELLULAR ETHYLENE-PROPYLENE-DIENE TERPOLYMER(EPDM) RUBBER VULCANISATES - EFFECT OF SILICA FILLER AND BLOWING AGENT Guriy a K C Tripathy D K Indian Institute of Technology... 

Other kinds of rubber chemicals are blowing agents, peptizers, and retarders. The total market for all chemical additives for rubber is over 250 million Ib/yr. 

Until 1920, the only flexible foam available was the natural sponge, but chemically foamed rubber and mechanically foamed rubber latex were introduced before World War II. These foams may consist of discrete unit cells (unicellular, closed cell), or they may be composed of interconnecting cells (multicellular, open cells) depending on the viscosity of the system at the time the blowing agent is introduced. Over 1.5 million tons of foamed plastic is produced annually in the United States. 

Sulphur is essential in the usual processing technology of rubbers it brings about the formation of cross-links , which provide the necessary shape stability. Pentane is a blowing agent, applied in a.o. PS, to form foam. 

Ba azide has not been used as an expl, bur it has been used in the manuf of fluorescent lamps and radio tubes (Ref 12a 19)- It has also found use as a blowing agent during the vulcanization of cellular rubber (Ref 22). The expl reaction of Ba azide is prevented by adding gelatin, machine oil or Neugen (polyethylene glycol laurate)... 

The manufacture of sponge rubber products such as gaskets for heat exchangers is based on the inclusion in the compound of chemicals which cause gas formation during vulcanization and thereby produce the desired porosity. Sodium bicarbonate and ammonium bicarbonate are examples of popular blowing agents. 

Polyurethane rubber (PUR). Not only in the thermosets (and the thermoplastics), but also in the field of synthetic elastomers polyurethanes have found a position, namely as a softer type. It is, again, formed from two components and is, with a blowing agent, processed into a foam. Polyether mattresses belong to this category, but also microcellular structural foams, used in bumpers, head- and arm-rests in motorcars, etc. 

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