Mixing dump temperature

When there is insufficient chlorine available in the rubber compound to improve flame retardancy, chlorinated paraffins are sometimes added as a relatively inexpensive source of halogen. CP also functions as a plasticizer in rubber compounding. Chlorinated paraffins decompose into toxic gases at lower temperatures than other more stable chlorine donors that are commercially available. Therefore chlorinated paraffins cannot be used in rubber compound mixes that are going to be exposed to high mixing dump temperatures because they will emit toxic gases in the workplace, which pose a hazard to workers In the factory. 

The unit power to mix can be generally described as a function of the rotor surface area, the RPM used during mixing, the time required to reach dump temperature for the first pass mix, and a treatment for the type of antidegradant used. Again the discrete variable of antidegradant was treated continuously by assigning the values of 0, 1, and 2 to the conditions of Ctrl, PPD, and QDI. 

COMPOUNDING AND MIXING PRINCIPLES WITH FOCUS ON ZINC OXIDE ADDITION AND DUMP TEMPERATURE... 

The dump temperature of the compound was varied by changing the mixer s rotor speed and fill factor while keeping the other mixing conditions and the mixing time constant. Under the assumption that the final dump temperature is the main parameter influencing the degree of the sUanization reaction, the effect of the presence of ZnO on the dynamic and mechanical properties of the compound was investigated. ZnO was either added on the two-roll mill or in the mixer. 

In the presence of ZnO, the dump temperature is a parameter of paramount importance in mixing of a silica compound containing a couphng agent with a polysulfidic moiety The sulfur eliminated from the coupling agent causes premature scorch in the presence of ZnO. This problem is partially solved when ZnO is added in the productive mixing step on the two-roU mill. 

Figure 18.17. Dump temperature vs. mixing time of SBR rubber. [Adapted, by permission, from Urabe N, Takatsugi II. Ito M, Toko H, Fukui M, Tnt. Polym. Sci. Technol.. 22, No.5, 1995, T/63-7.]...

Mixing mill temperature can be 85 °C to 90 °C. In Banbury mixing the cycle will be 5 minutes. Dumping should be done before the temperature goes up to 110 °C, especially if a litharge cure is used. From a scorch safety point of view, masterbatches of litharge can... 

Qycles Similar to Other Rubbery Polymers Heat Generated During Mixing Dump at Temperatures of 280-350 F... 

To control compound cure rate and viscosity, the rubber batches should be mixed to a temperature profile with close control over machine start and dump temperatures [3]. The choice of mixing machines is usually governed by the machinery that is already being used by the factory (see Table 3.2). The addition of the ingredients is best governed by a pre-determined cycle derived from experimental optimisation. 

Improved release Lower dump temperature Reduce mix times Homogenization... 

The mixing of highly filled silica rabber is discussed with reference to the linking of a bifunctional organosilane to the sihca. The reaction mechanism is investigated for fotrr different silanes for the in-situ modification of sihca. A study is made of the silane reaction following the ethanol formation the influence of the dump temperature, the influence of silane concentration, the silica/silane reaction following the shear modulus tan tones, and consequences for compotmders. 23 refs. 

The dump temperature was measured by inserting a probe in the compound in several places. Because the dump temperature was an important parameter, it was controlled by the time allowed for the compound to cool to a certain temperatnre before recharging for the next stage of mixing. The dump temperature control was specified to be a temperatnre between 140 and 160 °C. 

The studies in the previous section indicate that the higher temperature encountered during mixing generates more gel and long branching, leading to the extrusion problem. A basic problem is whether the dump temperature of 155 °C (or even 150 °C) is necessary or not to complete the reaction between silica and TESPT. 

In another case where the twin-screw extruder was used, the rubber and plastic were melt mixed with all ingredients in a similar manner as described in blend compositions for static vulcanizations. The product was then dumped, cooled, and granulated. The premixed granules were then fed into a twin-screw extruder where a very narrow temperature profile was maintained with a relative high compression (2 1), and the screw speed was adjusted depending on the final torque and the flow behavior of the extruded stock. The stock was cured by shear force and temperature enforced by the twin-screw extruder. The dynamically crosslinked blend was taken out in the form of a strip or solid rod to determine the... 

One concept which evolved out of these field trials was a truck with a heated dump body. The bodies are totally enclosed, propane heated with double-walled steel or aluminum shells. These trucks are utilized to keep the temperature of the mix between 265 and 300°F during hauling. 

Moderately thermophilic bacteria, those with an optimum temperature for growth of between 45 and 50°C, have been isolated from a variety of sites, such as mud springs, coal piles, various mineral dumps, and drainage waters from sulfide ore deposits, dumps, and mines (22). Some examples are listed in Table I. Mixed bacterial cultures isolated from such environments have been purified by serial dilution and plating on thiosulfate or tetrathionate agar (83). Some moderate thermophiles are active over a wide temperature range. A mixed culture oxidized pyrite at 30°C as rapidly as T. ferrooxidans alone and carried out the same reactions at temperatures over 50°C (6). These properties are of considerable value in commercial operations (Section V). 

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