Mechanical testing mixing procedure

Rubber compounds were made using A1 and A2 shown in Table 17.2 and using a model tire recipe shown in Table 17.4. The ingredients listed in Table 17.4 are in grams per 100 g of rubber (PHR). The mixing procedure used for the samples presented in Table 17.5. Both cured and un-cured compounds were tested and the mechanical testing results are shown in Table 17.6. 

The polymers, whose characteristics are summarized in Table 1, were melt mixed in a Brabender-like apparatus at 200 C and at two residence times 6 min, at 2 r.p.m. and further 10 min. at 32 r.p.m. The blend compositions are listed in Table 2. After premixing, cylindrical specimens were obtained directly by extrusion using a melting-elastic miniextruder (CSI max mixing extruder mod. CS-194), Thermal and tensile mechanical tests were performed on these specimens by an Instron Machine (mod. 1122) at room temperature and at cross-head speed of 10 mm/min. Also made were morphological studies by optical microscopy of sections microtomed from tensile samples and scanning electron microscopy of fractured surfaces of samples broken at liquid nitrogen temperature. Further details on the experimental procedures and on the techniques used are reported elsewhere . 

The mixing procedure, preparation conditions and cure schedule all have a profound effect on the mechanical properties of the adhesives and, consequently, will affect their durability [20, 73]. Because of this, expeditious on-site tests should be conducted to detect possible deficiencies. A number of test methods have been proposed by the CEN/TC193/SC1/WG11) in the pre-standard Adhesives for on-site assembling or restoration of timber structures — on-site acceptance testing . This... 

Goldberg and Rubin [Ind. Eng. Chem. Proce.s.s Des. Dev., 6 195 (1967)] showed in tests with a disk spinning vertically to the foam layer that most mechanical procedures, whether centrifugation, mixing, or blowing through nozzles, consist basically of the application of shear stress. Subjecting foam to an air-jet impact can also provide a source... 

Emulsions were tested by mixing an emulsifier (either caustic or commercial surfactants dissolved in water) and the crude oil, then heating the sealed container to 110°C in an oven. After heating, the sample was removed from the oven and placed in a mechanical shaker for 15 to 20 minutes, then returned to the oven. This procedure was repeated three times before the sample was left in the oven for observation. 

Haltner and Oliver found that several metallic sulphides brought about an improvement in the load-carrying capacity when mixed with molybdenum disulphide. The sulphides included stannic and stannous sulphides, lead sulphide, ferrous suiphide and cuprous and cupric sulphides, and in a standard test procedure there was up to a ten-fold increase in load-carrying capacity. They speculated that the action of the added sulphides was similar to that of extreme-pressure additives in liquid lubricants. This would imply the formation of some protective film on the substrate surface. Pardee later suggested that the effective mechanism was more likely to be oxidation inhibition. An alternative would seem to be the possibility that certain sulphides can act as an additional source of sulphur to form sulphide on the substrate surface, and thus improve adhesion of the molybdenum disulphide, as discussed in the previous chapter. 

Mixing properties and flow fields in stirred tanks are usually studied on a laboratory scale. Practical scale-up of a stirred tank cannot be performed requiring that every individual mixing and fluid mechanical parameters in the small scale tank should be maintained in the larger one. Therefore, scale-up procedures for different types of processes have been determined through experience, testing and computational fluid dynamics simulations. 

---