Rubber sheets cooling

Rubber Hot rubber sheets cooling and rolling, tire testing... 

This case is practically obtained when a rubber sheet is cooled down in a stirred fluid (gas or liquid), after extraction from the mold (Figure 2.3). 

Cooling Stage of a Perfectly Cured Rubber Sheet in Motionless Fluid... 

The profiles of temperature developed through the thickness of rubber sheets heated at 160°C immersed in motionless air at 20°C are shown when the thickness is 1 cm (Figme 2.4) and 2 cm (Figme 2.5), as they are calculated numerically. Only half the thickness is drawn, because of the symmetry. Thus, it takes some time for the rubber sheets to cool down, the time being obviously longer for the thicker sheet. 

FIGURE 2.4 Profiles of temperature developed through the thickness of a rubber sheet at various times (min), when the rubber sheet initially at 160°C is cooled down in motionless air at 20°C. Thickness = 1 cm. Free convection is in laminar mode. Half the thickness is shown. 

Whatever the thickness of the rubber sheet, the cooling is far more efficient in stirred water, as shown by the profiles of tanpeiature developed through the thickness. 

FIGURE 4.28 Cooling of a rubber sheet of thickness (2L) = 4 cm and postcure in stirred water at 20°C. Cure at 170°C in such a way that the SOC = 80% at the mid-plane. Heating system on the rubber surface. Surface thermal coefhcient h = 276W/(m deg). Profiles of SOC (left) and temperature (right) during the postcure. 

By cooling the rubber sheet in stirred water at 20°C with a high coefficient of heat transfer at the rubber surface h = 276 W/(m deg) (Figure 4.28). 

By cooling the rubber sheet in motionless air kept at 20°C, with a low thermal... 

The second is made when the rubber sheet is ranoved from the mold, and let cool down in a fluid, by using Equations 4.1 or 4.T and 4.4, with the... 

When the rubber sheet is allowed to cool down in motionless air kept at 100°C [Figure 4.30], not only the rate of the decrease in temperature at the rubber surface is very low, but the tanperature at the mid-plane remains rather high over a long period of time. As a result, the state of cure increases regularly with time up to around 97% at the mid-plane. When the rubber sheet is cooled down in motionless air kept at 120°C [Figure 4.31], the rate of the decrease in tanperature throughout the rubber thickness is still lower. And obviously the consequence is a rather high increase in the state of cure, especially at the mid-plane, from 80 to nearly 98%. 

Abdul M. and J.M. Vergnaud. 1984. Vulcanization progress in rubber sheets during cooling in motionless air after extraction from the mould. Thermochim. Acta. 76 161-70. 

Uncured Tel-Tak specimens were prepared by cutting rubber sheeted out from a mill at about 1.4 mm (0.06 in) thick. They were then placed over a piece of square woven fabric and pressed between a sheet of mylar on the top and cellophane on the bottom in a mold for 5 minutes at 100 C. After cooling, specimens were cut from the fabric side to 0,25 in, X 2 in. Two rectangular specimens are required for each test. Each test piece is mounted in the Tel-Tak instrument perpendicular to the other in order to assure the same contact area for each test. 

For the determination of phosphorus and nitrogen glass bottles (Pyrex or Duran) may be used. If the glass bottles are provided with a metal screw cap, a liner must be inserted in the caps which is cut from a 2-3 mm thick colourless silicon rubber sheet. The polypropylene and polyethylene bottles must be cooled and decompressed very carefully, because they are easily deformed at elevated temperatures. 

Cooling of rubber sheet would generally utilise a festoon cooler if plant size warranted it. Only the smallest compounding plants would use a manual dip and rack cooling system. 

Thermal Expansion Mismatch. A thick die of HgCdTe or hiSb connected to a silicon readout using indium bumps and perhaps epozy tends to pull apart as the device is cooled due to the difference in thermal e an-sion between the materials. One effective solution to the thermal mismatdi problem is to thin the detector array, whidi forces the detector material to match the stronger, thicker silicon. The effect is similar to a rubber sheet attached at many points to a rigid block. The contraction difference locally is not large and there is no run-out effect of increasing mismatch with distance from the center of the array. 

Change in dimensions of an unvulcanised rubber (calendered sheet or extruded section) on cooling from the processing temperature. Also the volume contraction of a moulded rubber product on cooling from vulcanising temperature. See Coefficient of Thermal Expansion (Volumej. Shrinking... 

The apparatus was separated into two compartments(A,B) with a silicone rubber sponge sheet which had a hole in the middle to hold fish at just the back of pectoral fin. Both the head and rear parts of fish were covered with two small boxes which had many holes and were fixed to a cover plate of the apparatus. PCP-free water was supplied into the head compartment(A) at a flow rate of 1 liter/h and the overflow from (A) was reserved in an ice-cooled tank for the analysis of PCP excreted from gills. Fish urine was led by a cannula to an ice-cooled flask through... 

Several plants employ cooled-belt flakers. These consist of flexible steel belts, ca 1-m wide and up to 50-m long, that have short rubber skirting at the edges. Molten pitch flows from a thermostatically controlled tank over a weir to give a flat thin sheet on the belt, which is cooled from below by water sprays. At the end of the belt, the solid pitch is broken up by rotating tines. The pitch flakes are drained and transported to a covered storage silo by belt conveyor, during which time the surface moisture evaporates. 

Warm cautiously on a steam bath over a thin sheet of asbestos for 15 mins, breaking up any lumps by very cautious use of a rubber policeman attached to a glass rod. Cool to RT, let settle and decant the ale shellac soln through a small tared, previously ignited and cooled, 30 ml Gooch or Selas crucible. Repeat the extraction with new portions of abs ale until the shellac is completely removed(about 3 times). Transfer... 

Calender - A machine equipped with two or more heavy, internally heated or cooled rolls, used for the continuous sheeting or plying up of rubber compounds. 

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