Brittle state

At very high and very low temperatures, material selection becomes an important design issue. At low temperatures, the material must have sufficient toughness to preclude transition of the tank material to a brittle state. At high temperatures, corrosion is accelerated, and thermal expansion and thermal stresses of the material occur. 

Air aging after 31 hours leaves the cloth in a friable and brittle state where the extent of degradation is very high. 

Harvested psilocybian mushrooms can be eaten fresh, or they can be dried, sealed and stored. The best procedure is to dry the mushrooms in a freeze-drier without heat. For most users, this is impossible, so a lamp or oven can do, as long as there is ventilation and the temperature does not exceed 90° F. in a dry atmosphere. (If you use an oven, leave the door cracked open.) A space heater can also be used. Whatever the means, the drying takes at least twenty to twenty-four hours and leaves the mushrooms in a brittle state. 

The findings of Hutson and Scott on embrittlement of inhibited polyethylene shown in Figure 7 also illustrate this point their presentation is unusual in that the point of embrittlement is indicated on the curve (26). As can be seen, this occurred before Stage III was well advanced. A similar situation can be found in the data of Wilson and Forshee the intrinsic fluidity of polymer that had degraded to a highly brittle state is indicated in Figure 6 (16). 

Class transition temperature (abbreviated Tg) A temperature or temperature range characteristic for polymers, below which they are in a hard/brittle state. Usually connected with a radical change of mechanical and physical properties of the polymers. Thermoplastics pass to the flow, respectively, melting range via plastic range. 

The compression molded polyimide comes in a powdery brittle state as it is added into the compression mold s cavity. Pressure is applied and at the processing temperature cross-linking takes place. Due to the thermal cycling of the mold, the process is not very efficient and molds are subject to a shorter life [5], All of these factors add to the cost of the part. 

In order to improve the surface gloss and appearance, thin layers of polystyrene or chromium have been applied to rubber-toughened plastics like ABS. However, these surface layers are brittle. Outdoor exposure to ultraviolet radiation (Chapter 10) can also convert the surface layer of a plastic into a brittle state. The effects of such layers are the most marked when the product is bent, with the brittle layer being in tension. The tensile failure strain of the surface layer is smaller than that of the substrate, so it fails first. A series of sharp cracks forms perpendicular to the surface tensile stress each relieves the surface stress over a limited length. The cracks start at the outer surface, and accelerate rapidly through the surface layer. If the substrate is tough, the cracks can be arrested, but if it has a... 

Polyvinylchloride (PVC) coating is widely used for its barrier function together with PET fabric. It is essentially a hard polymer, but its hardness, and thus its flexibility, may be varied by the addition of softeners. However, softeners pose a problem because they can volatilise during use, thus leaving PVC in a hard and brittle state with microcracks, where soil may collect and chemicals or water can get to the polyester. 

The classic method for evaluating the transition temperature from a ductile to a brittle state is by impact testing. The basic reasons for using such a test are the high strain rate that can be achieved by impact and its simplicity. Though there are currently many other ways to vary strain rate, those who choose to perform impact tests can enjoy the use of modem, instmmented impact machines. For most ceramics which are brittle at room temperature (henceforth RT), ductility is a high-temperature feature thus, it is more meaningfiil to discuss BDT, rather than ductile-to-brittle transition (DBT), the more common nomenclature. 

It should be pointed out that such a composition of 50 vol. % solids dried to an extremely brittle state before the last of the water is removed. In considering the behavior of fillers in plastics, for example, more than about 40% by volume gives a hard, relatively brittle mass. Likewise, less than 40% by volume of colloid in silicate should give a less brittle film as the last of the water is removed. In this case, by similar calculations it is found that this corresponds to a SiO-iNajO fatio of 3.5. Perhaps by coincidence this is near the common ratio used in adhesives. 

Unlike the traditional methods of studying plasticity, CRS technique provided the unique possibility to carry out micro-plasticity investigations, with revealing transitions and measuring creep rate spectra, for materials in their brittle and super-brittle states such as ceramics and silicone nitride [329-335], silicate glasses [286], brittle... 

At the same time, if a solid has strong initial plastic character (e.g., metal single crystal), the transition into a brittle state with reduced strength may not occur, even at low a. For example, liquid bismuth does not cause an embrittlement of copper single crystals. The grain boundaries in polycrystalline solids, while acting as a strengthening factor, can cause a reduction in plasticity due to the retardation of the dislocation movement. For this reason, for a polycrystalline solid, the reduction in 0 may be already sufficient for a transition to the brittle state to take place. Indeed, liquid bismuth is known to cause an anbrittlement of polycrystalline copper. 

Materials. At these extremely low temperatures, ferrous metals become brittle and consequently cannot resist shock loads. In a cryogenic pump, elements having a low transition from the ductile to the brittle state, must be used. Such elements are aluminum, copper, silver, lead, nickel, and beryllium. 

This is the reversible transition in amorphous materials from a hard and brittle state into a viscoelastic state. Thermodynamically speaking, it is a second-order transition (second derivative of the Gibbs free energy equation). 

Second order transition, which occurs at temperatures approaching — 45 °C, is not time dependent and is seen as a change from the rubber like state to a glassy, brittle state... 

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