Thermal infusion

Thermal infusion is the process of applying fused zinc, cadmium, or other metal coatings to a ferrous workpiece by imbuing the surface of the workpiece with metal powder or dust in the presence of heat. 

The stabilization of the PAN precursor involves preoxidation by heating the fiber in an air oven at 200°C-300°C (392°F-5722°F) for approximately one hour while controlling the shrinkage/tension of the fiber so that the PAN polymer is converted into a thermally infusible aromatic ladder-Uke structure. 

The presence of stable free radicals in the final polycondensate is supported by the observation that traces of (11) have a strong inhibiting effect on the thermal polymerization of a number of vinyl monomers. Radical polymerization was inhibited to a larger extent by a furfural resin than by typical polymerization inhibitors (34). Thermal degradative methods have been used to study the stmcture of furfural resinifted to an insoluble and infusible state, leading to proposed stmctural features (35). 

The literature of polyimines is extensive [164-173]. A number of researchers have tried to synthesize high molecular weight polymers but failed due to poor solubility in organic solvents. Polyimines are of great interest because of their high thermal stability [174-176], ability to form metal chelates [174-177], and their semiconducting properties [178-181]. Due to insolubility and infusibility, which impeded characterization of the molecular structure, the application of these polymers is very limited and of little commercial importance. 

The cationic polymerization of cardanol under acidic conditions has been referred to earlier [170,171], NMR studies [16] indicated a carbonium ion initiated mechanism for oligomerization. PCP was found to be highly reactive with aldehydes, amines, and isocyates. Highly insoluble and infusible thermoset products could be obtained. Hexamine-cured PCP showed much superior thermal stability (Fig. 12) at temperatures above 500°C to that of the unmodified cardanol-formaldehyde resins. However, it was definitely inferior to phenolic resins at all temperatures. The difference in thermal stability between phenolic and PCP resins could be understood from the presence of the libile hydrocarbon segment in PCP. 

Soluble high molecular weight infusible improved tensile strength high thermal stability to 525° C (977CF) in air film forming. 

Polyurethane materials are extremely versatile in that it is possible to produce a large variety of structures which range in properties from linear and flexible to crosslinked and rigid. The crosslinked PURs are thermosets, which are insoluble and infusible and therefore cannot be reprocessed by extrusion without suffering extensive thermal degradation. At present, the main sources of recyclable waste are flexible PUR foams and automobile waste. Waste and scraps of these materials may consist of 15-25% by weight of total PUR foam production. 

In most of the studies discussed above, except for the meta-linked diamines, when the aromatic content (dianhydride and diamine chain extender), of the copolymers were increased above a certain level, the materials became insoluble and infusible 153, i79, lsi) solution to this problem with minimum sacrifice in the thermal properties of the products has been the synthesis of siloxane-amide-imides183). In this approach pyromellitic acid chloride has been utilized instead of PMDA or BTDA and the copolymers were synthesized in two steps. The first step, which involved the formation of (siloxane-amide-amic acid) intermediate was conducted at low temperatures (0-25 °C) in THF/DMAC solution. After purification of this intermediate thin films were cast on stainless steel or glass plates and imidization was obtained in high temperature ovens between 100 and 300 °C following a similar procedure that was discussed for siloxane-imide copolymers. Copolymers obtained showed good solubility in various polar solvents. DSC studies indicated the formation of two-phase morphologies. Thermogravimetric analysis showed that the thermal stability of these siloxane-amide-imide systems were comparable to those of siloxane-imide copolymers 183>. 

Most injections are formulated as aqueous solutions, with Water for Injections BP as the vehicle. The formulation of injections depends upon several factors, namely the aqueous solubility of the active ingredient, the dose to be employed, thermal stability of the solution, the route of injection and whether the product is to be prepared as a multidose one (i.e. with a dose or doses removed on different occasions) or in a singledose form (as the term suggests, only one dose is contained in the injection). Nowadays, most injections are prepared as single-dose forms and this is mandatory for certain routes, e.g. spinal injections such as the intrathecal route and large-volume intravenous infusions (section 2.2). Multidose injections may require the inclusion of a suitable... 

Acrylonitrile Free radical polymerization similar to the above, but thermal polymerization is difficult.26 —CH,—CH— CN Infusible up to 250 Imperfectly crystalline shows oriented crystallinity in drafted fibers. Good strength. Insoluble in common solvents. Soluble in dime thy If orm amide... 

Insulin aggregation and precipitation was an impediment to the development of implantable devices for insulin delivery as noted by several investigators working with conventional insulin infusion devices [51-54]. The potential causes of the observed aggregation and precipitation are thermal effects, mechanical stress, the nature of the materials in contact with the insulin solution, formulation factors, and the purity of the insulin preparation. 

Wholly aromatic poly(azomethine)s possess remarkable thermal stability, and high strength and modulus. However, owing to their limited solubility and infusibility, it is difficult to obtain poly(azomethine)s having sufficiently high molecular weight and useful processability. 

Polybenzimidazole (PBI) is an infusible thermoplastic, perhaps the most advanced polymer from the thermal and mechanical points of view but, on the other hand, processing is the monopoly of its producer. 

The thermoset included here is derived from bisphenol-A dicya-nate. It can be thermally trimerized yielding a triazine or cyanurate network (8,9,10) as seen in the reaction scheme (Table 1). The critical molecular weight between crosslinks is relatively low, resulting in an extremely tight, brittle network. The material is usually used as a prepeg because a total cure produces a hard, infusible, and insoluble matrix. It possesses excellent adhesive properties and is currently used as a metal coupling agent. It offers many superior properties relative to conventional epoxies derived from bisphenol-A. 

Solid-state (topochemical) polymerization of cyclic disulfur dinitride to poly(sulfur nitride) (or polythiazyl), -fSN, occurs on standing at ambient temperature or higher [Banister and Gorrell, 1998 Labes et al., 1979 Ray, 1978]. Disulfur dinitride is obtained by sublimation of tetrasulfur tetranitride. Polythiazyl is a potentially useful material, since it behaves like a metal. It has an electrical conductivity at room temperature about the same order of magnitude as a metal like mercury and is a superconductor at 0.3°C. Polythiazyl also has high light reflectivity and good thermal conductivity. However, it is insoluble and infusible, which prevents its practical utilization. 

In general, polymers with heterocyclic rings as structural element show a high chemical and thermal stability. On the other hand, they are insoluble and infusible, so that they could not initially be used for practical applications in this form. 

During coal conversion, the coal structure influences both thermal and catalytic reactions. Thermal reactions of solid coals initiate the breakage of weak bonds at rates proportional to their bond dissociation energies. The radicals thus produced require stabilization by hydrogenation or addition of small molecules otherwise the radicals couple to produce much more thermally stable bonds, which eventually leads finally to the formation of infusible and insoluble coke. 

The sintered product is cut into the required shape and the active material is infused using one of a number of techniques - e.g. for the negative electrode by impregnating the sinter with concentrated aqueous cadmium nitrate, followed by thermal decomposition, or by cathodic polarization in molten Cd(NC>3)2 baths, etc. The plates are washed and the impregnation cycle is repeated up to 5-10 times until the required loading is attained. Finally the plates are formed by a sequence of carefully controlled charge/discharge cycles. Safety precautions are very important in the manufacture of cadmium-based electrodes because of the health hazards associated with this material. 

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