Burnt marks

Troubleshooting - Problems and Solutions 143 5.2.4 Burnt Marks (Diesel Effect)... 

Problems and Troubleshooting - Injection Molding Flow chart 5.2.4 - Burnt marks (Diesel effect)... 

Flow chart 5.2.4 illustrates the schematic approach to solve the problem of burnt marks, also known as diesel effect. Overstay of the material in the barrel leads to the burnt marks. Machine size has to be considered to resolve the problem. There is a possibility of a vent getting clogged. Improve venting and in some cases the vent may be deepened. Increase in gate size may also be required in some cases. 

Cane sugar.—Melts, darkens, then chars, and finally burns, with a marked odour of burnt sugar. Typical of the changes given by mono- and di-saccharides. 

Enantiomers of the same compound may have differing threshold values. This property was observed for a new, strong and high impact, flavor compound, 3-thio-2-methylpentan-l-ol, first detected in thermally processed materials but that is actually present in raw onions.54 First of all, there is a marked concentration effect at 1 ppm in 5% saltwater, the odor is described as sulfuric, burnt gum, sweaty, onion and at 0.5 ppb as meat broth, sweaty, onion, leek . Since there are two chiral centers (both dependent on carbon) there are four stereoisomers, all of which have been prepared 18a, 18b, 19a, 19b (Scheme 7). For this compound, enantiomers have the following marked differences in odor thresholds (but apparently all have the same general odor). 

Incorporation of a 2% level of either ZnSn(OH) or ZnSnO into the resin, leads to marked differences in its thermal degradation profile. The initial decomposition comprises two distinct stages, the major step occurring at a lower temperature than that of the untreated polymer, which may be indicative of promotion of bromine volatilisation by the zinc stannates. Furthermore, the amount of residue burnt off in the char oxidation step is greatly increased in the tin-containing samples, and the temperature at which this process occurs is significantly higher than in the base resin. 

There is increasing evidence that the interaction of lipids with the Maillard reaction is relevant to the generation of flavor in many cooked foods. For instance, the removal of lipids from coconut has been shown to cause flavor changes in the roast material (12). Uncooked coconut contained significant amounts of lactones as the main aroma components on roasting pyrazines, pyrroles and furans were also found in the aroma volatiles which added a strong nut-like aroma to the sweet aroma of the unroasted coconut. When ground coconut was defatted and then roasted, the sweet aroma due to lactones disappeared and the product possessed a burnt, nut-like aroma. A marked increase in the number and amount of Maillard reaction products, in particular pyrazines, was found. 

When platinum is heated in a luminous coal-gas flame a black layer is formed. If the carbon is now burnt off in air the metal is left in a rough and brittle condition, but without having undergone any loss in weight. The action is considerably enhanced by the presence of alloyed rhodium or iron, whilst iridium has a less marked effect.8... 

When the outlet is non-reflecting, the flame is stable. The mean axial velocity and fuel mass fraction fields are displayed in Fig. 9.15 and 9.16 [320] the central recirculation zone (marked by a white line in Fig. 9.15) is filled by burnt gases which provide flame stabilization. Fuel staging is also apparent in Fig. 9.16. 

Marble from Hildesheim, having ash-coloured markings upon white ground, and smelling like burnt horn. 

The home trade quality constitutes the bulk of the exported rum. It has a full flavor, and chemically is characterized by a higher proportion of esters of higher fatty acids. It is generally accepted that these acids result from bacterial decomposition of the dead yeasts found in the distilling materials. As compared with local trade goods the home trade have a fuller and more fruity aroma and a marked spicy residual flavor is noted on dilution. Sometimes, even, an excess of the higher alcohols and esters which produce this result will also cause an objectionable cloudiness on dilution with water. On occasion home trade rums will have a noticeable burnt flavor resulting from over-distillation by direct fire. 

Toasting eliminates green wood and plank faults, while producing very pleasant vanilla and spicy aromas. Heavy toasting gives a marked burnt, toasty character, making the aroma different, but without any major faults. 

In Procedure B, the igniter flame is lowered to the end face of the specimen and also, to a depth of approximately 6 mm, to its vertical faces. The maximum duration of igniting is 30 s or until the specimen has burnt up to the first mark. During the ignition, the flame is removed momentarily every 5 seconds as in Procedure A. If a continuous burning is observed then, the ignition is stopped. 

For testing PVC films, BS 2782 Part 1 Method MOD 1980 is appropriate. A film strip 550 mm x 35 mm is mounted on a semi-circular holder (Fig. 3.49) surrounded by a triangular protective shield with a wall height of 460 mm. 13 mm below the end of the film strip, 0.1 cm of absolute ethanol is ignited. The distance from the start mark over which the specimen has burnt is recorded. 

In ISO R 1210-1982, a test specimen 120 mm long, 10 mm wide and 3 mm thick is marked by a line perpendicular to the longitudinal axis of the rod specimen, 80 mm from the end to be burnt. The specimen is ignited for 60 s by a Bunsen burner oriented at 45 deg. as shown in Figure 3.50. After removal of the burner, the burning time and the length destroyed are measured. The specimen is characterized according to the test results as follows ... 

A very similar method was described in the withdrawn DIN 53459-1981. In addition to the 95-mm mark, another mark is made 25 mm from the end to be ignited and the flame spread rate is also calculated if the specimen has burnt from one mark to the other. The test results are used for the flammability rating of the material (Table 3.11). 

Category BH 2 The flame ceases to burn before the 100-mm mark is reached by the front of the flame. The length of the burnt area is indicated (e.g. BH 2-70 mm). 

The latroscan FID scanner unit consists of a hydrogen flame jet and an ion collector. Following the sample application and solvent development, a set of ten rods are scanned and burnt, the ions are captured by the collector electrode and the signal is amplified in a similar way as in gas chromatography (GC). The more recent versions of the instrument (Mark IV and V) have an improved detector system (Oshima and Ackman, 1991) in which the collector and a circular electrode are close to the rod being scanned. These improvements minimize losses of ions and increase the sensitivity of the instrument. The reproducibility and accuracy of the TLC/FID method relies strongly on the standardization of all the operational parameters. Thus it will be useful and necessary to consider the various factors that affect the response of the flame ionization detector of the latroscan system. 

Bum marks Black or brown burnt areas on the part located at furthest Air entrapment in mold due to lack of venting... 

Laser markable materials are available that allow identification numbers to be burnt onto the surface of a package, removing the need for an ink marking process. 

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