Cured consistency

Rubber mixing processes are used to produce an elastomeric compound with ingredients sufficiently incorporated, dispersed, distributed and plasticized that it will be able to be processed and will cure consistently in subsequent secondary processing. 

Cured Consistency. The hardness of these gels can not be measured by the normal methods used for elastomeric materials. Test methods for characterizing their physical properties are in various stages of development. The most commonly used technique to describe the gel s softness is the penetration test, which is emerging as a... 

The paste for negative battery plates after curing consists of 3BS, PbO and small amounts of Pb. During formation, the basic lead sulfate is partially reduced to Pb and PbS04 forms (first formation stage). When the whole amount of basic lead sulfates is consumed, the electrode potential rises by absolute value and PbS04 is reduced to Pb (formation stage 2). 

Bismaleimide is easier to process than condensation-cured polyimide resins. The typical cure consists of several hours at 177-204 C. Generally, a postcure of 220-260°C is required for high-temperature applications. 

Epoxy pre-mixed putty sticks are well-known examples of one part sealants where epoxy in the premix is at a high cure consistency. 

UV-radiation curing consists basically of a photoinitiated polymerisation of multi-ftinctional monomers which are converted into a tridimensional polymer network according to the following reaction scheme [11] ... 

Cold Vulcanization. — The material in thin strips, or sheets, is passed through, or dipped into a solution of sulfur chloride (S2CI2) in carbon disulfide, or carbon tetrachloride. Some of the sulfur chloride remains united, physically or chemically, with the caoutchouc, and the excess is neutralized with ammonia. By this process the goods acquire a soft velvet feel, but unfortunately are liable to perish rather easily. A variation of the method, technically known as the vapor cure, consists of treating the goods with the vapors of sulfur chloride. Subsequent neutralization with ammonia is, of course, necessary. 

Microstructural features such as volume fraction of rubbery particles and the particle size distribution will depend on the initial resin/modifier compatibility and the cure scheme. From the processor s standpoint, the blend needs to be stable and produce the desired morphology upon cure consistently. Ideally, one would like the liquid rubber modifier and the unreacted resin to form a miscible blend at room temperature. Cure conditions will then control rubbery particle formation. Factors that affect phase separation include cure temperature and time to gelation, which is a function of temperature and catalyst system. 

PROCESSING. Tubers which are to be stored keep better if they are cured after harvesting. Curing consists of holding the sweet potatoes in a facility where the temperature is about 85°F (30°C) and the relative humidity is about 85%. These conditions promote the healing of small wounds in the tubers. 

Figure 7.34 Wear factor versus extended cure time at 260 C of SolvayTorlon 4301—12% graphite, 3% PTFE PAI (first 4 days of cure consisted of 1 day at each of the following temperatures 149°C, 216°C, 243°C, and 260°C) [5].

Propellants cast into rockets are commonly case-bonded to the motors to achieve maximum volumetric loading density. The interior of the motor is thoroughly cleaned, coated using an insulating material, and then lined with a composition to which the propellant binder adheres under the environmental stresses of the system. The insulation material is generally a mbber-type composition, filled with siUca, titanium dioxide, or potassium titanate. SiUca-filled nitrate mbber and vulcanizable ethylene—propylene mbber have been used. The liner generally consists of the same base polymer as is used in the propellant. It is usually appHed in a thin layer, and may be partially or fully cured before the propellant is poured into the rocket. 

Ammonia—Gas-Cured Flame Retardants. The first flame-retardant process based on curing with ammonia gas, ie, THPC—amide—NH, consisted of padding cotton with a solution containing THPC, TMM, and urea. The fabric was dried and then cured with either gaseous ammonia or ammonium hydroxide (96). There was Httle or no reaction with cellulose. A very stable polymer was deposited in situ in the cellulose matrix. Because the fire-retardant finish did not actually react with the cellulose matrix, there was generally Httle loss in fabric strength. However, the finish was very effective and quite durable to laundering. 

Urea.—Forma.IdehydeResins. Cellular urea—formaldehyde resins can be prepared in the following manner an aqueous solution containing surfactant and catalyst is made into a low density, fine-celled foam by dispersing air into it mechanically. A second aqueous solution consisting of partially cured urea—formaldehyde resin is then mixed into the foam by mechanical agitation. The catalyst in the initial foam causes the dispersed resin to cure in the cellular state. The resultant hardened foam is dried at elevated temperatures. Densities as low as 8 kg/m can be obtained by this method (117). 

Some high performance laminates consisting of carbon fiber webs and epoxy resins are cured in autoclaves. An autoclave is a pressure chamber in which the pressure is appHed hydrostatically. 

Chemical Composition. From the point of view of leathermaking, hides consist of four broad classes of proteins coUagen, elastin, albumen, and keratin (3). The fats are triglycerides and mixed esters. The hides as received in a taimery contain water and a curing agent. Salt-cured cattie hides contain 40—50% water and 10—20% ordinary salt, NaCl. Surface dirt is usuaUy about 2—5 wt %. Cattie hides have 5—15% fats depending on the breed and source. The balance of the hide is protein (1). 

Nonstabilized foams are referred to as froths froth-bonded fabrics are similar in properties to some saturation-bonded nonwovens. Typical foams used as nonwoven binder solutions have a consistency similar to shaving cream. AppHcation methods include knife-edge layering onto a horizontal web surface followed by vacuum penetration, and saturation and penetration of a vertical web surface using a horizontal-nip pad. Drying and curing is carried out in ovens, dmm dryers, or steam cans. 

The binder system of a plastic encapsulant consists of an epoxy resin, a hardener or curing agent, and an accelerating catalyst system. The conversion of epoxies from the Hquid (thermoplastic) state to tough, hard, thermoset soHds is accompHshed by the addition of chemically active compounds known as curing agents. Flame retardants (qv), usually in the form of halogens, are added to the epoxy resin backbone because epoxy resins are inherently flammable. 

Early phenoHc resins consisted of self-curing, resole-type products made with excess formaldehyde, and novolaks, which are thermoplastic in nature and require a hardener. The early products produced by General BakeHte were used in molded parts, insulating varnishes, laminated sheets, and industrial coatings. These areas stiH remain important appHcations, but have been joined by numerous others such as wood bonding, fiber bonding, and plywood adhesives. The number of producers in the 1990s is approximately 20 in the United States and over 60 worldwide. 

A mixture of PhenoHc MicrobaUoons and resin binder has a putty-like consistency. It can be molded to shape, troweUed onto surfaces, or pressed into a core. Curing gives a high strength, low density (0.144 g/cm ) foam free of voids and dense areas, and without a brittle skin. Syntactic foams are used in widely diverse appHcations, including boat flotation aids stmctural parts in aircraft, submarines, and missiles stmctural cores for waU panels and ablative heat shields for reentry vehicles and rocket test engines. 

The first commercial PPS process by Phillips synthesized a low molecular weight linear PPS that had modest mechanical properties. It was usehil in coatings and as a feedstock for a variety of cured injection-molding resins. The Phillips process for preparing low molecular weight linear PPS consists of a series of nucleophilic displacement reactions that have differing reactivities (26). 

---