Rubber sheet thickness

Variation of midplane temperature with time for different values of the temperature of the injected rubber. Effect of rubber sheet thickness. The temperature of rubber sheet at the midplane is of... 

The increase in the state of cure in vulcanizates after removal from the mold is evaluated when the rubber sheet thickness is rather large, this thickness being of 4 cm. The other characteristics are as follows Temperature of the mold = 170°C... 

Laminated tapes In more general use now than pressure sensitive tapes are tapes consisting of polyvinyl chloride or polyethylene films in conjunction with butyl rubber. These tapes are applied with an adhesive butyl rubber primer. Thicknesses of up to 0-75 mm are in use and loose protective outer wraps of p.v.c. or polyethylene sheet are commonly applied. Tape quality control is exercised with reference to ASTM standard test methods and may include water vapour transmission rate and elongation. 

Detonation velocity of sheets containing 15% natural rubber is given in Figs 8 9 as functions of sheet thickness and density. These data are taken from Kegier Schaii (Ref 45, p 499), who show that the decrease in D produced by stretching the sheet is due to a decrease in sheet density... 

The slight curvature given to calender bowls to counteract the deflection produced when the calender is running, thus enabling a rubber sheet of uniform thickness across its width to be obtained. 

A more complex form of coating calender is the four-bowl Z or L arrangement. A four-bowl calender can simultaneously apply a rubber coating onto both sides of a fabric. In effect, the No. 1 and 2 bowls and the No. 3 and 4 bowls form pairs where two rubber sheets are produced. The sheets are then laminated to a substrate between the No. 2 and 3 bowls. Very sophisticated devices are usually incorporated into the calender design to control thickness and width of the individual sheets and the resulting laminate. 

Coating with Bulk Polybutadiene. E-glass fabric was embedded In Firestone s Diene 35 NFA using procedures very similar to those used to prepare peel test specimens. Rubber, which had been mill-mixed with 0.05% dlcumyl peroxide, was premolded between Mylar sheets to the desired thlckness(0.308, 0.151, or 0.100 cm) and size ( 30.5 X 18 cm) by molding for 1 hour at 60 C. and 40,000 lbs/5" ram. Fabric was cut so that the final size was at least one Inch smaller than the rubber sheets In all directions. A sandwich was made from the fabric and two premolded rubber sheets of the same thickness and about half the total thickness of the final sandwich. The sandwich was cured In a press for 2 hours at 150°C and 5000 lbs/5" ram. In the cured specimen the fabric was embedded In the center of the molded specimen (0.15 -0.40 In thick). Samples were Immensed In alkali before cutting to size for tensile tests. 

There is little work of a fundamental nature done that helps towards a better understanding or control of calendering of rubber. Most theoretical studies were concerned with the pressure developed when a stock of thick viscous rubber sheet material is reduced to a thinner sheet by passage between rolls. Calenders with 3, 4 or more rolls might be assembled to quite different configurations. Calenders in L shaped, F shaped, I shaped or Z shaped configurations with roll diameters of 168 mm, 250 mm and 350 mm are available on the market. 

In the manufacture of fine rubber sheets, two essential qualities are required in the finished products, namely, uniformity of texture and even thickness. When sheets of only a few thousandths of an inch thick are required, great care must be taken to ensure this result. The first essential quality is achieved in an adjusted calender with all its bearings in good condition. The rolls must be... 

The rubber inserts in the caps for the bottles can be cut from silicone rubber sheet ( 2-mm thickness). These ensure a very close fit with the Marprene tubing to maintain an airtight seal... 

Another kind of fault block mountains comes from stretching of Earth s crust. A model of this kind of mountains could be made by compacting a 6-in (15-cm) thick layer of moist sand on top of a rubber (not rubberized) sheet. When the sheet stretches, mimicking the elastic properties of the lower crust, the sand will crack along lines perpendicular to the direction the sheet is being pulled. Some of the surface will remain the same height, and some blocks will slide down the sides of the blocks which remain stable. This is particularly noticeable if the top surface of the compacted sand has been dusted with powder. This is a model of the process that formed the mountains in the Basin and Range province. 

Kr The 10.7-year half-life and 0.69 MeV E max beta particle make Kr-85 ideal for weight and thickness gauging in manufacturing process control for paper, plastic film and rubber sheet. 

The purpose o this work is to show that the values for temperatures o mold and storage bulb are important parameters in injection molding process o rubber. The study was performed by using two different thicknesses for rubber sheets and two values for the cure enthalpy. The problem was solved by applying an explicit numerical method with finite differences (6). Although rubber vulcanization consists of a complex series of reactions (8), the overall cure heat could be described by a first-order reaction with a single activation energy, as shown previously (6). 

Mathematical Treatment. The unidirectional heat flow through the rubber sheet of thickness was expressed by the general equation of transient heat conduction... 

According to our model (3) considering the section of the rubber sheet, the sheet was divided into n equal finite slices of thickness Ax. The heat balance was written on the plane n as follows ... 

Several parameters of interest were considered in this work the one concerned with the operational conditions of the rubber in the storage bulb as time and temperature, the other with the working conditions in the mold as mold temperature, cure time, thickness of rubber sheets, cure enthalpy (or % vulcanizing agent). 

The effect of the thickness of the rubber sheet is of importance. The time necessary for the midplane temperature to reach its maximum value is about proportional to the sheet thickness as shown in "Table II". 

The state of cure obtained at the midplane of rubber sheets is plotted as a function of time, for three values of the temperature of injected rubber, for a thickness of 1 cm (Figure 4) and 2 cm (Figure 5), while the mold temperature is kept constant at 180°C. 

The temperature of injected rubber and the sheet thickness are found to be parameters of interest ... 

The reduction in the cure time due to the increase in the temperature of injected rubber in the mold is found to vary largely with the thickness of rubber sheets. The interest of the use of a high temperature for the storage bulb is clearly shown in "Table III" and "Table IV", especially for thick rubber sheets. 

Silicone rubber sheet, 3/32M thick, Shore A - 40 durometer, 12Mx12" sheet McMaster Carr 8632K43 1... 

---