Hot-point test

Note Care must be taken with the burning and hot-point tests as one of the early plastics (celluloid) will ignite when heated. It is marginally less dangerous to heat a scraping of the material to be tested than to stick a hot needle into the whole item. 

Burning and hot-point tests. Tortoiseshell bums at a lower temperature than horn. A sliver of either will bum with the typical small of burning hair because they are basically made of the same material. It is a destmctive test and so it is preferable to cut a minute sliver of the material from an area where it will not be noticed, rather than stick a hot needle into the item. Plastics give off a typical, acrid smell when they bum. 

Hot-point test A test involving pressing the tip of a hot needle against a specimen to judge its melting point and smell. 

The hot-point test involves pressing the heated point of a needle or pin against a hidden surface of the material - for example, inside the drill hole of a bead - to gauge the result. If the material is made of celluloid, this action can cause it to combust. The test can also damage some materials that bum easily and thereby leave a large hole in the specimen. The test caimot give definitive results, but. 

Some of the tests and criterion used to define fire resistance may be found in the Hterature (9). Additionally, the compression—ignition and hot manifold tests as defined in MIL-H-19457 and MIL-H-5606, respectively the Wick test as defined by Federal Standards 791, Method 352 flash point and fire point as defined in ASTM D92 autoignition temperature as defined in ASTM D2155 and linear flame propagation rate are defined in ASTM D5306 are used. 

The hot-ER test refers to measuring the impedance of a separator while the temperature is linearly increased this technique was first used by Laman et al. [5]. Figure 4 shows actual measurements for some Celgard membranes [20], The single-layer materials exhibit a sharp rise in impedance near their respective melting points the impedance goes back down after a maximum value has been reached. 

Installing hot work test sample points closer to the cutting location and in the higher elevations of the piping. 

Hot point. Similar to the above test, a needle is heated to red hot in a flame and touched against the surface of the item to be tested. It will make a small indent in a piece of amber, but will pass quickly into a piece of copal - the younger the resin the faster it melts. It should be noted that this can leave a very large hole in some materials. The hot needle may also affect plastics. 

Flocculation Point. Figure 4 shows that the flocculation point of a reactor effluent sample (cracked atmospheric bottom) is much lower than that of the reactor feed. Generally, the flocculation point decreases as the amount of solids in the sample increases. This has been confirmed by the Shell Hot Filtration Test IP/375/ASTM 4870 procedure. 

WARNING Do not touch the test tube. It will be hot. Use extreme caution around an open flame. Point test tubes away from you and others. 

The next article of interest is the test-tube of all sizes. In one works the lengths for the wider test-tubes are first cut out of tubing, a diamond being used to give a circular initial scratch inside. One edge of these tubes is then expanded out to form the mouth, and then the other end sealed and rounded. A special blowpipe, giving a very hot, pointed flame, is used for rapid work, and differs from the ordinary blowpipe in that the gas and air supply tubes are heated by a row of fine jets of burning gas. 

We are not aware of hot corrosion testing of precursor-derived ceramics. A prediction rests upon the argument that for those which contain boron a top scale compositions in the Na-B-Si-O-system should form, that is a classical glass forming system with low melting points and viscosities [176]. Apart from the hot corrosion degradation by itself it is completely unknown whether this will induce crystallization of the amorphous precursor-derived ceramics. 

Figure 34.23. Schematic setup of the hot tearing tests performed by Herfurth and Engler [29]. A thick plate of an A1 alloy is subjected to several heat sinks inducing a temperature distribution as indicated. After a thermal equilibrium has been estabhshed with a small hquid zone, acting as a stress concentrator, a tensile load is applied with a given crosshead speed and fracture goes from the bottom to the top. The sample is covered in the interesting area with a silica aerogel and the test is observed by an infrared camera. Note Tl means the liquidus temperature, Ts the solidus temperature, the eutectic point.

A more quantitative indication of compatibility can be obtained with solvent or hot melt cloud point tests. The solvent cloud point tests are based on the idea that resins will be compatible with elastomers of similar chemical nature. Thus aliphatic resins will be effective tackifiers for aliphatic elastomers such as natural rubber, while aromatic resins are needed for aromatic elastomers such as SBR. Some resins, e.g., rosin esters, will be compatible with many different types of elastomers. Solvent cloud point tests are carried out in three solvent systems which represent aliphatic, aromatic, and polar systems. The solvent blends used by Hercules are ... 

Add 1 ml. of the alcohol-free ether to 0-1-0-15 g. of finely-powdered anhydrous zinc chloride and 0 5 g. of pure 3 5-dinitrobenzoyl chloride (Section 111,27,1) contained in a test-tube attach a small water condenser and reflux gently for 1 hour. Treat the reaction product with 10 ml. of 1-5N sodium carbonate solution, heat and stir the mixture for 1 minute upon a boiling water bath, allow to cool, and filter at the pump. Wash the precipitate with 5 ml. of 1 5N sodium carbonate solution and twice with 6 ml. of ether. Dry on a porous tile or upon a pad of filter paper. Transfer the crude ester to a test-tube and boil it with 10 ml. of chloroform or carbon tetrachloride filter the hot solution, if necessary. If the ester does not separate on cooling, evaporate to dryness on a water bath, and recrystallise the residue from 2-3 ml. of either of the above solvents. Determine the melting point of the resulting 3 5 dinitro benzoate (Section 111,27). 

With some acids (e.g., succinic acid and sulplianilic acid) more satisfactory results are obtained by reversing the order of mixing, i.e., by adding the solution of the so um salt of the acid to the reagent. It should be pointed out that the melting points of the derivatives as determined on the electric hot plate (Fig. II, 11, 1) may differ by 2-3° from those obtained by the capillary tube method. In view of the proximity of the melting points of the derivatives of many acids, the mixed m.p. test (Section 1,17) should be applied. 

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