Color degradation

Because of the high melt viscosity of polyolefins, normal spinning melt temperatures are 240—310°C, which is 80—150°C above the crystalline melting point. Because of the high melt temperatures used for polyolefin fiber spinning, thermal stabilizers such as substituted hindered phenols are added. In the presence of pigments, the melt temperature must be carefully controlled to prevent color degradation and to obtain uniform color dispersion. 

Canned Fruits and Vegetables. The use of citric acid to bring the pH below 4.6 can reduce heat treatment requirements in caimed fmits and vegetables. In addition, citric acid chelates trace metals to prevent enzymatic oxidation and color degradation, and enhances the flavor, especially of caimed fmits. 

When formation of isomers or colored degradation prodncts occnrs, separation of snch componnds by HPLC mnst be carried ont in order to obtain correct and valnes. 

Poei-Langston, M.S. and Wrolstad, R.E., Color degradation in an ascorbic acid-anthocyanin-flavonol model system, J. Food. ScL, 46, 1218, 1981. 

Cracked gasoline FCC gasoline Composed of paraffinic, olefinic, and aromatic compounds branched compounds are present in a relatively high amount typically has a higher RON than MON high-olefin-content FCC gasoline can lead to gum formation and fuel color degradation. 

This is the breakdown of the percentage of paraffins, olefins, naphthenes and aromatics in gasoline. Fuel olefin content is closely monitored. High-olefin-content gasoline is unstable and can lead to various fuel problems such as deposit formation and color degradation. 

Although hydroprocessing will remove most of the naturally occurring antioxidants contained in fuel, other less stable, more reactive components will also be reduced. As a whole, ultra-low sulfur diesel fuel will be much less prone to color degradation and deposit formation than earlier-era diesel fuels. 

Identifying the source of a fuel color degradation problem... 

Add a distillate fuel color degradation control additive. 

Add a distillate fuel color degradation control additive at high rates before fuel enters tankage. 

The addition of fuel stabilizers can help inhibit distillate fuel color degradation... 

Furfural A colorless liquid which changes to reddish brown upon exposure to light and air. Furfural forms condensation products with many types of compounds including phenols and amines. If present in kerosene or jet fuel, furfural may lead to color degradation. 

The color of unbleached pulp ranges from cream or tan for the sulfite process to dark brown for the kraft process. Although about 75-90 percent of the lignin has been removed by the pulping process, the remainder, along with other colored degradation products, must be removed by bleaching. 

Color Degradation of Diesel Fuel in Deep Desulfurization. The color of diesel fuel is degraded in the higher reactor temperature range of deep desulfurization.2) The color bodies (fluorescence compounds) are thought to be polyaromatics which are... 

Figure 10 shows the nice fit of these catalyst deactivation results. It indicates that the reaction of color degradation decreases rapidly in the early stages of the operation. And the parameters obtained in the data fitting demonstrate that catalyst deactivation for color degradation is caused by a rapid decrease of the diffusion coefficients. 

Figure 11, the effect of temperature on color degradation, also reveals that the color degradation is strongly controlled by the diffusivity of the reactants. The apparent activation energy of used catalyst was 3/4 of that of fresh catalyst. 

Figure 8 Proposed Reaction Model Color Degradation of Diesel Fuel in Deep HDS...

Figure 9 Prediction of Color Degradation of Diesel Fuel by Proposed Model...

Figure 10 Catalyst Deactivation in Color Degradation Model for Deep HDS of Diesel Fuel...

Figure 11 Effect of Catalyst Aging on Apparent Activation Energy of K3 in Color Degradation Model...

These oils are characterized structurally by a large number of paraffinic side chains (55% min. Cp), and thus are highly saturated. They excel in initial color. Compared to naphthenic and aromatic oils they are most resistant to oxidation and color degradation by ultraviolet light. Their resistance to oxidation increases as their molecular weight increases. SONPAR oils are de-waxed to low pour points, and their volatility is quite low compared to the naphthenics and aromatics, as indicated by their higher flash points. 

A hydroxypropyl methylcellulose film of pigment was exposed in a fadeometer for 3, 6, and 12 h. The rate at which the colorant degraded was noted from tint strength calculations and placed on a scale of 0-10, with the higher numbers indicating an increased tendency to fade. AL-aluminum lake. 

Besides mixtures of polymers or copolymers, a very common procedure to improve desired characteristics of polymers is that of including additives. The additives are typically nonpolymeric molecules. Among the properties that are modified with additives are cost, mechanical properties, color, degradation rate under the influence of light or gases from atmosphere, odor, adhesion to processing equipment, etc. Some polymer properties modified with additives are shown in Table 1.5.1 [1]. 

GUNAWAN MI and BARRINGER s A (2000), Green color degradation of blanched... 

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