Two roll-mixing

The compounding of CR with fillers and vulcanization ingredients was done by a laboratory size open two-roll mixing mill. All the weights are given in parts per hundred parts of rubber and the recipe for the CR compounds is given in Table 4. 

As it is nowadays often no longer practical to use organic solvents, it is recommended to select a different technique such as roll-mixing or comilling with povidone. That this method is also capable of producing an amorphous distribution of phenytoin and many other active substances is shown in Fig. 46 and in Table 78. In which two roll-mixed preparations are corn-pared with the crystalline active substance and a solvent-coprecipitate by X-ray diffraction. 

Two-roll mixing is another traditional method of mixing which relies on somewhat primitive equipment and on the skills of the operator. It has never been possible to establish standard procedure for this process and batch-to-batch results vary widely. 

Recently, a new technology for the devulcanization of sulfur-cured scrap elastomers was reported [36] using a material termed Delink [37]. Such technique of devulcanization was designated as Delink process. In this process, 100 parts of 40-mesh or finer crumb is mixed with 2 to 6 parts of Delink reactant in an open two-roll mixing mill. Delink reactant is a proprietary material, and its nature and composition was not disclosed. 

Compounding was performed in an open two-roll mixing mill (laboratory size). NR was first masticated on the two-roll mill for about 2 3 min followed by addition of the ingredients. Cure characteristics were analysed using an oscillating disk rheometer (Monsanto R-lOO) at a temperature of 150 °C. The composites were cured at their respective cure times in a hydraulic press under a pressure of about 120 bar at 150 °C. Aged samples were prepared by keeping the samples in a hot air oven at 70 °C for 7 days. ... 

In another study, it was reported that NR gum and CB filled compounds containing nano-ZnO have been prepared on a laboratory size two-roll mixing mill at a friction ratio of 1 1.25 as per ASTM D 3184-89 and the samples were... 

The compatibility between the phases of the blends is even more needed when these phases are recovered from previously manufactured products. T6th et al. [165] made an approach in improving the adhesion between the compounds and thus the mechanical properties of the resulting materials in waste polyethylene/crumb rubber blends by using compatibiUzing additives such as olefin-maleic-anhydride copolymers the preparation method consisted of two-roll mixing at temperatures of 145-180°C followed by compression molding at 180°C. 

The first step of manufacturing a membrane is to prepare a suitable rubber compound either in a Banbury internal mixer or in an open two roll mixing mill by adding different compounding ingredients in the proper sequence during the mixing operation to get a well dispersed compound. 

Usually, elastomers are processed through extrusion, forming in matrices, mixing. The first observations on the cold degradation of rubber by two roll-mixing, in the last century, refers to the fact that, under prolonged processing, natural rubber becomes sticky [703-705],... 

Natural rubber s processing by two roll-mixing, in the presence of styrene, at temperatures ranging within the 75-130 C interval permits a rapid polymerization of the monomer. The reaction is influenced by the elastomer/styrene weight ratio, being observed that its decrease causes increase of the polymerization reaction rate, which comes to exceed the one corresponding to styrene s thermal polymerization. 

In this manner, natural rubber modified with maleic anhydride was obtained, two roll-mixing being applied as the processing method [710],... 

Mechanochemical reactions during polymer processing by two roll-mixing... 

Thus, by chemical and spectral methods, the products resulted by the simultaneous two roll-mixing of PVC with benzidine, o- or / -PhDA were proved to contain aromatic rings on the main chain [301,308], By the photocolorimetric dosage of the unreacted diamine, the percentage of the diamine reacted with PVC (with respect to the initial amount) could be estimated. Figure 3.231. 

An important effect for the practical processing of PVC is noticed in case of its two roll-mixing in the presence of benzidine which could partially substitutes the classical thermal stabilizer... 

Figure 3.232. Variation in time of molecular weight of PVC by two-roll mixing in the presence of aromatic diamines 1) m-PhDA 2) benzidine 3) p-PhDA.

The efficiency of the PVC-benzidine reaction as reflected in the tensile strength increase depends not only on the micromolecular compound concentration (CJ but also on other factors among which the concentration of the thermal stabilizer (C ) and the two roll-mixing duration and temperature are the most important. 

The mathematical modelling of the two roll-mixing process of the PVC-benzidine mixture, based on the above mentioned variables afforded the following function of tensile strength variation ... 

The influence of the two roll-mixing process parameters on the mechanical properties of the product resulting by the simultaneous processing of PVC with an elastomer, was thoroughly studied with a PU containing dibenzyl diisocyanate-ethylene glycol and adipic acid as an elastic component [712],... 

Figure 3.236. Tensile strength versus polyurethane coneentration for different two roll-mixing temperatures.

The interesting fact deserves mention that by the two roll-mixing processing of this polymer mixture the tensile strength increases concomitantly with the impact strength although these two properties are known to show an opposite variation, Figure 3.240. 

The conclusion can be drawn that due to the activation of some reactions as a consequence of formation of free radicals, the two roll-mixing process of polymers could be a simple and efficient method for performing chemical modifications of the mac-romolecular compounds as well as for synthesizing new compounds showing properties superior to the starting ones. 

The vulcanised, rubbers supposed to regeneration, by two-roll mixing, at temperatures between 50 and 60 °C, by the combination of mechanical and chemico-colloidal actions, regain the final prop-... 

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