Hardening process

Containerized ice cream is hardened on a stationary or continuous refrigerated plate-contact hardener or by convection air blast as the product is carried on a conveyor or through a tunnel. Air temperatures for hardening are —40 to —50° C. The temperature at the center of the container as well as the storage temperature should be <—26°C. Approximately one-half of the heat is removed at the freezer and the remainder in the hardening process. 

Lu and Pizzi [83] showed that lignocellulosic substrates have a distinct influence on the hardening behavior of PF-resins, whereby the activation energy of the hardening process is much lower than for the resin alone [84]. The reason is a catalytic activation of the PF-condensation by carbohydrates like crystalline and amorphous cellulose and hemicellulose. Covalent bonding between the PF-resin and the wood, especially lignin, does not play any role [84]. 

Case harden Process of hardening the surface of a piece of steel to a... 

TS plastic products that are injection, transfer, or compression molded combine thick and thin sections relatively easily since the hardening process is a chemical reaction (Chapter 6). Annular shapes are best made by compression to gain best dimensional control and freedom from distortion. In the compression process, the molding compound is compressed and reduced to the plastic state in the mold. During this process, portions of the material may lie in hard forms in the mold while other portions are flowing rapidly with great force. 

The insolubilization of cations and anions during the setting and hardening process is thus paralleled by that of silica. Under add conditions orthosilicic add condenses first to form polymeric silidc add and then silica gel (Her, 1979 Andersson, Dent Glasser Smith, 1982). These processes are discussed more fully in Section 6.5.4. Gelation of silica, like the formation of salt gels, is enhanced by a reduction in the acidity of solutions. 

When fully hardened, the cement is resistant to erosion provided the solution has a pH above 4. However, the glass polyalkenoate cement is susceptible to erosion immediately after set because some of the matrixforming cations and anions are still in soluble form. In fact, the hardening process is one where these cations and anions continue to precipitate. For this reason these cements have to be protected, temporarily, by a varnish. 

Sorrell Armstrong formulated cements in proportions corresponding to the 5 1 8 and 3 1 8 compositions. The initial mixtures were thick slurries with no observable tendency to separate provided a sufficiently reactive oxide was used. They tended to set within about 90 minutes, at which time samples were prepared for X-ray determination. Initially, although the preliminary hardening process was apparently complete, the only crystalline phase that could be found was MgO moreover, this material was found in amounts that approximated to the quantity in the initial mixture. 

V. P. Ovchinnikov, A. A. Shatov, N. Yu. Shulgina, and P. V. Ovchinnikov. Salt composition for regulating hardening processes of plugging agents. Neftepromysl Delo, (11-12) 32-33, November-December 1995. 

It is known that organotin compounds such as n-butyltin acid and di-n-butyltin dilaureate accelerate the hardening process of epoxy resins106) and initiate ethylene oxide polymerization 107). 

A hydraulic setting cement is incorporated as the binder additive. The green pellets are partially hardened in silos, where they remain for about 24-36 hr, and the hardening process is completed during storage in stockpiles. 

In the continuous chain model, a large part of the deformation during extension of the fibre consists of the shear deformation as a result of which the chain orientation distribution contracts. This leads to the concave shape of the tensile curve, often found for polymer fibres. Therefore, this description of the extension of the fibre implies a strain hardening process. 

P.Y.97 is also used to lend color to cast epoxy resins and to unsaturated polyester resins it considerably accelerates the hardening process in the latter (Sec. 1.8.3.7). 

P.O.34 is rarely used in polyolefins. In such media, it only withstands exposure to 200°C, and its opaque colorations show insufficient lightfastness. P.O.34 tends to bloom, especially in extrusion products made of low molecular weight LDPE types. The pigment is, however, recommended for a variety of other media. These range from aromatic polyurethane foams to cast resins of unsaturated polyester, in which the pigment slightly delays the hardening process. 

P.R.164 was also found in cast resin composed of methacrylate and unsaturated polyester. The pigment does not affect the hardening process of such media, which may be carried out, for instance, by using peroxides. An important field of application was in the coloration of various polyurethanes, for which the pigment was also sold in the form of a pigment preparation. 

Carburizing One of several thermochemical treatments involving, by heating, carbon absorption from suitable material in contact with the surface layer, and diffusion into solid (ferrous) alloys. Surface hardening processes may then be... 

Although the use of accelerators is far greater in winter, they do find application under more normal conditions to speed up the setting and hardening process for earlier finishing or mold turn round. 

CARBONITR1DING. A surface hardening process for steels involving ihe introduction of carbon and nitrogen into steels by healing in a suitable almosphere containing various combinations or hydrocarbons, ammonia, and carbon monoxide followed by a quenching to harden the case. 

The automotive industry, which turned to laser transformation hardening of engine and other drive train components, is now seriously investigating the solar hardening process,... 

The theory and practice of hydrogenation is here thoroughly reviewed. The author outlines the principal sources of raw materials, methods used to obtain and refine them, analytical methods used for classifying natural oils, the hardening process and the products of hydrogenation. 

Raffinose occurs only at low concentrations in the leaves of plants, but accumulates in the storage organs during the process of development. It has been generally observed that the level of raffinose increases as the tissue loses water this 108-1i3,u6-m js a characteristic feature of maturation of seeds and the hardening process of winter-hardy plants. The hardiness of several plants towards desiccation and elevated temperature may be compared to the property of frost resistance.125-134 When the heat resistance reaches a maximum in the summer, the frost resistance is at its minimum. 

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