Rubber temperature

The heat transfer coefficient from the mbber batch to the cooling water can be estimated by dividing the heat flux by the difference between the average rubber temperature and the cooling water temperature, or... 

Constant rubber temperature with which the calender is fed... 

Watson and coworkers (68,69) studied in details the mechanical reaction of systems of natural rubber plus poly(methyl methacrylate), using a laboratory masticator at 76 rpm, in a nitrogen atmosphere at 15° C. Prior to mastication, the deproteinized crepe rubber was extracted with acetone, imbibed with mdnomer and allowed to homogenize for 16 h, in the absence of light It must be underlined that, with limited mastication and reaction heat dissipation, the actual rubber temperature was much higher the maximum recorded was about 50° C and... 

The maximum values obtained by the midplane temperature are about the same when the injected rubber temperature is varied. 

Figure 2. Midplane temperature vs. time for several rubber temperatures at injection. 1 140°C 2 100°C 3 20°C...

A few experimental data were available based on SSBR (Tg-value = 197 K, three systems) and on ESBR (Tg-value = 215 K, two systems) both extended with an aromatic oil. The Tg-value of the rubber phase is in both cases lower than that of the oil phase i.e. the SSBR/ESBR rubber phases are for Tg-rubber < temperatures < Tg-oil, filled with glassy oil particles, resulting in an increased Tg-value of the rubber after the oil addition. The experimental values could be fitted again satisfactorily using the Gordon-Taylor relations ... 

These sulfur crosslinks make the rubber harder and stronger. This vulcanized riibber has a wide range of uses from tires to toys. An increase in temperature causes natural rubber to fuse individual chains together this makes the rubber sticky. Because of sulfur crosslinks in vulcanized rubber, temperature changes will not create either a fusion of separate chains or make it brittle. 

The problem was solved by using a numerical method based mainly on the Dusinberre generalization of the increment method [9] applied to one-dimensional transient conduction. In fact, the heat transfer coefficient at the steel-rubber interface is very large, the surface rubber temperature changed very quickly, and consequently the initial temperature was taken as the arithmetic mean of the original surface temperatures of the mold and rubber. 

ISO 471, Rubber—Temperatures, humidities and times for conditioning and testing, 1995. 

Cold runner systems have a similar temperature control requirement to the plasticising and injection unit, since the cold runner acts as an extension to the nozzle, controlling the rubber temperature to preclude any build up of scorched material while it awaits injection into the mould. 

The screw and barrel temperature should be set to a value of 70 °C to 80 °C for initial trials. The actual temperature of the rubber will depend on the frictional energy generated by the screw and can be controlled by adjusting the back pressure or screw speed. It is always advisable to run a small trial at this stage, to establish the relationship between these parameters and the final rubber temperature. 

Fig. 2.41. TPPy-FIMS of butadiene rubber temperature dependency of the total ion intensity and formation of butadiene monomer (m/z 54) and dimer (m/z 108), mercaptobenzothiazole (m/z 167) and TMDQ monomer, dimer, and trimer (m/z 173, 346, 519). After Schulten et al [675]. Reprinted with permission from Rubber Chem. Technol 62, 698 (1989). Copyright (1989), Rubber Division, American Chemical Society, Inc.

The temperature studies of Watson [54] and of Casale and Croci [39] confirm that it is possible to maintain the rubber temperature during mastication within a few degrees Centigrade (see Fig. 3.8). 

It became clear in succeeding years that the intermeshing internal mixer rotors did a better job of controlling the rubber temperature than F. H. Banbury s designs because of their higher metal surface areas. One was less likely to chemically damage expensive specialty elastomers with high temperature. 

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