Casting treatment techniques

Low viscosity materials offer a quick and simple way of sealing porous castings and hairline cracks. Anaerobic cure follows penetration by capillary action. Other porosity treatment techniques often involve long and complicated curing cycles. 

Films or membranes of silkworm silk have been produced by air-drying aqueous solutions prepared from the concentrated salts, followed by dialysis (11,28). The films, which are water soluble, generally contain silk in the silk I conformation with a significant content of random coil. Many different treatments have been used to modify these films to decrease their water solubiUty by converting silk I to silk II in a process found usehil for enzyme entrapment (28). Silk membranes have also been cast from fibroin solutions and characterized for permeation properties. Oxygen and water vapor transmission rates were dependent on the exposure conditions to methanol to faciUtate the conversion to silk II (29). Thin monolayer films have been formed from solubilized silkworm silk using Langmuir techniques to faciUtate stmctural characterization of the protein (30). ResolubiLized silkworm cocoon silk has been spun into fibers (31), as have recombinant silkworm silks (32). 

The phases and their proportions present ia hardened amalgam are controlled by many factors. The composition of the alloy the size, shape, and size distribution of the particles the thermal history of the cast ingot and the comminuted alloy and the surface treatment of the particles are some of the factors for which the manufacturer is responsible. The tooth cavity preparation and the mixing, compacting, and finishing techniques of the dentist can make the difference between satisfactory and unsatisfactory restorations, even with the best of alloys. A minimal amount of residual mercury and porosity are needed to obtain the most serviceable restorations (138). 

Only a limited amount of information is available on specific plants within this industry. This section describes the treatment practice and wastewater composition at nine plants three that enamel on steel, three on aluminum, two on cast iron, and one on copper. The major treatment operation used is a settling technique. Treatment operations are not necessarily listed in this narrative in the same order that they are used at the plants. Wastewater composition data were obtained from verification sampling.3 6... 

In a previous section, the effect of plasma on PVA surface for pervaporation processes was also mentioned. In fact, plasma treatment is a surface-modification method to control the hydrophilicity-hydrophobicity balance of polymer materials in order to optimize their properties in various domains, such as adhesion, biocompatibility and membrane-separation techniques. Non-porous PVA membranes were prepared by the cast-evaporating method and covered with an allyl alcohol or acrylic acid plasma-polymerized layer the effect of plasma treatment on the increase of PVA membrane surface hydrophobicity was checked [37].The allyl alcohol plasma layer was weakly crosslinked, in contrast to the acrylic acid layer. The best results for the dehydration of ethanol were obtained using allyl alcohol treatment. The selectivity of treated membrane (H20 wt% in the pervaporate in the range 83-92 and a water selectivity, aH2o, of 250 at 25 °C) is higher than that of the non-treated one (aH2o = 19) as well as that of the acrylic acid treated membrane (aH2o = 22). 

In order to overcome some of the drawbacks associated with the fiber bonding preparation, a solvent-casting and particulate-leaching technique was developed [32], With appropriate thermal treatment porous constructs of synthetic biode-... 

The treatment of ethnographic artifacts like tapa cloth require an understanding of the material and its manufacture. The literature of the conservation of tapa is reviewed, and new techniques for filling voids are presented. These techniques include the use of hand-cast fills, and fills cast on the vacuum suction table. Case studies from 1980,... 

Over the past three years, the treatment of tapa cloth has re-emerged as a topic of interest to conservators of ethnographic materials, as evidenced by papers presented at meetings of the AIC (1), CCI Symposium 86 (2,3), and the Jubilee Conference at the University of London (4). While a number of questions remain as to the best way to stabilize this material, certain techniques have been proposed which have shown promise, including the use of cast fills for filling voids. 

Other Methods Examples for other methods include co-casting of a hydrophobic and a hydrophilic polymer that contains amine, imine, hydroxyl, or carboxyl groups [61,89] surface modification by oxidation with ozone or by exposure to an electron or ion-beam ultrasonic etching and UV or laser irradiation [90-92]. A variety of functional groups have been also introduced onto the membrane surfaces by applying the gas discharge techniques (plasma treatment) operated at low or ambient pressure [93,94]. 

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