Monsanto rheometer

Specifications for soHd i7j -l,4-polyisoprenes are shown in Table 5 and include analyses for volatile matter, extractables, ash, and Mooney viscosity at 100°C. Standard method ASTM D1416 includes chemical analysis methods for volatile matter, extractables, and total ash, while ASTM D1646 includes Mooney viscosity (82). The Monsanto rheometer data for vulcanizates prepared by a standard recipe may also be specified. This formulation for vulcanizate (ASTM D3403) is mixed in a Banbury mixer in two passes with all but sulfur and accelerator added in first pass ... 

Vulcanization was carried out in one and two stages with and without carbon black. In one-stage vulcanization, all the ingredients were mixed and the compound was vulcanized in the mold for optimum cure time as shown by Monsanto rheometer curves. In the two-stage vulcanization process, all the ingredients except XNBR were mixed and heated for a short time, followed by mixing with required amount of XNBR and heating for rest of the time required for optimum vulcanization. 

Vulcanization rate was determined by a Monsanto Rheometer. The Monsanto Oscillating Dii Rheometer is designed to measure the ccanplete curing characteristics of a single rubber specimen, heated and maintained utder continuous pressure during vulcanization. Sinusoidal oscillation of a conical dirir, embedded in the vul-canizable mix confined in a heated square carity, exerte a riiear strain on the speci-... 

As shown in Table 1, poly(isobutylene-co- -pinenes) containing up to 10 mole% -pinene are rubbery materials Tg< —53 ). In view of the structural similarity between our copolymer and butyl rubber, we decided to use conventional butyl rubber cure conditions (3) to prepare our vulcanizates (see Experimental). Figure 2 shows the curing rate of two copolymers containing 3 and 10 mole% fi-pi-nene units respectively, as determined by a Monsanto Rheometer at 160 C (320 F). As expected, the curing rate of the cr lymer containing 10 mole% unsaturation is several times hi r than that of the material with 3 mole% unsaturation level. 

Figure 3. Effect of cross-linker level on cure characteristics. (Monsanto rheometer curves - 307...

NOTE Tensile, tear, hardness, and flex life characteristics were determined with ASTM D412, D2240, D624, and D430, respectively. Cure time was determined with a Monsanto rheometer. Model R-100. Swelling characteristics of the elastomer were measured by weight difference after soaking the square shape (1 x 1 x 0.2 cm) In hexane for 28 hours at room temperature. 

The cure times used in 1958 for the original materials could not be derived from measurements in a curemeter as these instruments were only in the experimental stage. Hence, they were derived from a programme of curing for various times and measuring physical properties. The cure times for the new materials were derived from measurements on a Monsanto rheometer. 

Measurements were taken on two natural rubber compounds rubber A with a very short scorch time, and rubber B with a very long one. For both rubbers, experiments were conducted at 120 C, 140°C, 160°C, 180°C, and 200 C. A Monsanto rheometer and a Wallace-Shawbury curometer were used, as well as isothermal apparatuses (see Table 1.1). 

Laboratory measur ent of curing characteristics have been somewhat revolutionized by the introduction of the cure meters. There were two types of cure meter the reciprocating paddle type as in the Wallace-Shawbury curometer, and the oscillating disc type such as the Monsanto rheometer. In the oscillating disc type (ODR) a biconical disc is embedded in the rubber in a closed cavity. The disc is oscillating through constant angular displacement, and the torque required monitored. 

Two types of curemeters are in common use the reciprocating paddle type, such as the Wallace-Shawbury curometer, and the osaUating disc type, such as the Monsanto rheometer. 

Stanich, G. J.. 3M evaluation of Monsanto Rheometers (ODR lOOS. ODR 2000 and MDR 2000), July 31. 1991. Later published in Rubber World. 

This is followed by vulcanization to obtain vulcanized composite sheets using a compression moulding in hydraulic press. The cure time for the vulcanization is generally determined using a Monsanto rheometer and optimum curing times (tgo) is calculated. The sheeted rubber compounds are conditioned at a tem- perature of 25 °C for 24 h in a closed container before cure assessment. 

Rubber mixes were prepared in the Banbury mixer according to the recipes in Table 1-2. The rheological properties of all compounds were determined by using an oscillating disc Monsanto Rheometer MDR 2000 and Mosanto Viscometer VM2000. 

Particle size in water and paraffin oil were measured with Zetasizemano S90 (Malvern Instruments). Cure characteristics were measured at 160°C using a Monsanto rheometer. The robber mixes were prepared on a laboratory two-roll mill at about 30°C, with roll dimensions of D = 200 mm and L - 450 mm. The rotational speed of a front roll (Vp) was 2s ... 

Table 4 gives the various parameters derived from a Monsanto Rheometer examination of the mixes at 150°C. In general, little difference was noted among the oils at both levels. 

The remaining stock pieces, from which the Mooney viscosity samples had been taken, were blended together and mixed in a laboratory BR Banbury using the formulation detailed in Table 7. The cure behaviour of each batch was examined using a Monsanto Rheometer and test pieces for assessing vulcanizate properties were cured for 20 min at 150°C. Tensile properties were measured after ageing in an air oven. 

Fig. 1. Standard Monsanto rheometer chart for stock mixed on mill with various proportions (l-2-l-5wt%) of the sulphur/accelerator curing system. Conditions chart motor, 6 min range sel., 50 arc 1 temperature, 180°C. Parrel Bridge Ltd, 1987.

Wulcanized using recipe 2A given in ASTM D 3184-71. The vulcanization characteristics of each stock were determined on a Monsanto Rheometer at 140 C using ASTM D 2084-71T. 

Selected mechanical properties were determined by standard ASTM methods on samples prepared at optimum vulcanization time as determined using a Monsanto Rheometer at 60 cpm and three degrees of arc. Scorch time was taken at a two point rise in the curve, and cure time at 90% of the time for maximum point in the cure curve. 

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