Peptization levels

Fig. 8. Viscosity versus peptizer level for low-rotor-speed, low-ram-pressure mixing conditions, A, Renacit VII A, Pepton 44.

Fig. 9. Viscosity versus peptizer level for in batch peptization using a short, high-rotor-speed, high-ram-pressure mixing cycle. Symbols as in Fig. 8. The top two curves represent the viscosity of the masterbatch stage in each case...

Fig. 12. Effect of peptizer level on Mooney viscosity. Conditions K2A Intermix, SOrpm, 100 psi, 3 min mastication.

The initial sulfur copolymer that is formed is often high conversion and gelled. Molecular weight is reduced to the required level by cleaving some of the polysulfide Linkages, usually with tetraethylthiuram disulfide. An alkaU metal or ammonium salt (30) of the dithiocarbamate, an alkaU metal salt of mercaptobensothiasole (31), and a secondary amine (32) have all been used as catalysts. The peptization reaction results in reactive chain ends. Polymer peptized with diphenyl tetrasulfide was reported to have improved viscosity stabiUty (33). 

Nonionic cellulose ethers, hydroxyethyl(HE) and hydroxypropy1 (HP) cellulose, of variable molar substitution (M.S.) levels, were adsorbed on peptized sodium montmorillonite surfaces from fresh and saline (NaCl) aqueous solutions. The amounts adsorbed for 2 M.S. HEC and HPC and 4 M.S. HEC were insensitive to electrolyte concentration the 4 M.S. 

Exposure of proteins to heat has been shown to adversely affect peptization properties (22). The critical denaturation temperature for peanut protein in meal is above 118OC (dry heat) and above 80OC at 100% relative humidity. Although heat treatments routinely employed in a majority of peanut oil mills are insufficiently controlled to prevent denaturation of meal protein, the authors suggest that temperature and moisture control during processing can be maintained at levels sufficient to achieve oil extraction without drastic denaturation of protein. 

The fact that plasticization of rubber in the mixing mill is the result of oxidation implies that oxygen is indispensable for the same. Agents which accelerate oxidation thereby effecting plasticization to a desired mooney viscosity level are called peptizing agents. 

Bnderimatrix consists of hkfi levels of peptized alirrina... 

If filtering is done first, the filtrate is washed with successive amounts of water until a satisfactory level of impurity in the wash water is found. Again, care must be taken not to wash too much or the gel peptizes and passes through the filter paper. 

Wash the gel with S% ammonium carbonate solution, adding sufficient solution to bring the level up to the original mark. Stir the suspension for 30 min, allow the precipitate to settle, and decant again. Repeat five times or until the precipitate begins to peptize. 

Blancol . [Rhone-Poulenc Surf.] Sodium naphthalene-formaldehyde condensates thinning, dispersant, peptizing agent, dye-leveling agent used in paper industry for slime ctmtrol, improved retention of fillers or fines, improved sizing. 

Peptization will occur only if and when the concentration of colloid is sufficient to form a blanket around the particles to be solubilized. This is known as the critical concentration level. 

The polymer which is obtained when chloroprene is emulsion-polymerized in the absence of sulfur or a chain-transfer agent is a tough, insoluble non-plastic material. If sulfur is dissolved in the chloroprene prior to polymerization (at a level of 0.5-1.5 parts by mass per 100 parts by mass of monomer), the product is still a tough insoluble material which is unsuitable for use as an elastomer. However, by heating the latex obtained (still in an alkaline condition) with a thiophilic reagent, such as tetraethylthiuram disulphide (Vlll), the polymer becomes plasticized or peptized to a soft, plastic, soluble polychloroprene which is suitable for use as an elastomer. 

Peptizers such as pentachlorothiophenol are generally used at levels between 0.1 and 0.25 phr. This enables significant improvement in compound processability, reduction in energy consumption during mixing, and improvement in compound uniformity. High levels can, however, adversely... 

The amount of asphaltenes precipitated from various solvents are summarized In Table 4. Figures 2-9 show that, In general. Increase in solvent/oil ratio Increases the amount of asphaltene precipitation and levels off after certain solvent/oil ratio. Addition of solvent to oil reduces concentration of resins (which act as peptizing agents for asphaltenes) in the oil resulting in asphaltene... 

To elaborate the techniques of monoliths extrusion, the batches of powdered perovskites (up to 100 kg) were synthesized via mechanochemical route. In contrary to ceramic jierovskite powders, MA samples can be formed as rings without any addition of binder or peptizers into water-based pastes. However, after calcination at 500-900°C these rings have a rather low mechanical strength, which reaches an acceptable (ca 10 kg/cm ) level only after annealing at 1000°C. Any attempts to extrude micromonoliths without binders were imsuccessful. 

The emulsion was cooled to 20° C. A dithiocarbamate salt or secondary amine was added and the emulsion aged for 8 h to peptize the polymer. The bulk Mooney viscosity of the polymer was thus reduced to levels suitable for rubber processing. 

Increased levels of peptizers. The effect of using increased levels of peptizer (Fig. 8) was examined using Renacit VII at levels of 0 05-0 6 phr and Pepton 44 at levels of 0 05-0 5 phr. The SMR 10 blend described earlier was used with Intermix conditions as shown in Table 6, under D (low rotor speed and low ram pressure) and a... 

For this work SMR 20 was used with the two peptizers at levels of 01-0 5 phr. Mixes were processed to vulcanizates using the same formulation and conditions as before. 

The inconsistency of the batches mixed under high-speed, high ram pressure conditions can be seen clearly from Table 8, which lists the standard deviations for the six viscosity measurements made of each level. The high tack and nervy appearance of these batches are probably a result of inadequate dispersion of the peptizer before the start of chemical reaction and chain scission. This would create a blend of high and low molecular weight polymer which would then be very difficult to process. 

Fig. 11. Effect of different levels of peptizers on unaged and aged tensile strength, (a) Batches peptized for 5 min at low rotor speed and low ram pressure (b) in batch peptization. , Unaged W, aged.

Using 1-2 phr peptizer blend the viscosity can be reduced in 2 min to a level similar to that achieved in 4 min mastication (see Fig. 15). 

Relatively high levels of insoluble iron(III) and manganese(IV) frequently are found in water as colloidal material, which is difficult to remove. These metals can be associated with humic colloids or peptizing organic material that binds to colloidal metal oxides, stabilizing the colloid. 

Differences in the property profile of commercially available S-grades are caused by different combinations of sulfur level, comonomers, soap system, polymerization and peptization reactions, and staining or nonstaining stabilizers. 

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